Sunday, January 28, 2018

Spring, winter, spring, winter... typical weather for this time of year!

After spending much of the first three weeks of the year in the deep freeze, the past week or so has been much more pleasant overall. Five of the past eight days saw average temperatures 10° or more above normal, while only one day was below average and that was just by a degree. Overall a nice recovery from a bitterly cold end to 2017 and start to 2018!

Average temperatures for the past 7 days were much above normal for everywhere east of the Rockies, especially when compared to the month-to-date average shown below! The pattern has done an about-face in the past week! (WxBell)

Today has been gorgeous - more like early March than late January! Sunshine and 60° is always welcome in the "dead" of winter. However, looking ahead things get rather tumultuous in the coming week or so, marked by a very progressive pattern that features a couple of fronts and areas of high pressure that pass by rather quickly, and roller coaster temperatures. Finally, as we get towards next weekend and the following week, a lobe of the famed "polar vortex" drops into eastern Canada and the northeast sector of the U.S. It will bring very cold air to that region, but a muted influence in the Mid-South, where a battleground may set up between the cold to the north and warmer air to the south.


A dry cold front that brings some measure of cloud cover to the region, moves quickly through during the early morning hours. This front, though dry, will bring an end to the warm weather we had today as highs don't quite reach the 50° mark. A north breeze will make it feel more like the 30s to near 40. Don't forget the coat you didn't need on Sunday when you head out in the morning!

The surface map as of 6am Monday shows the weakening front near the Mid-South as high pressure builds into the region from Canada. That high will mean much cooler temperatures to start the week. (NWS)


A cold day is in store as high pressure quickly moves through, resulting in less wind and sunny skies, but temperatures that start in the mid 20s and only reach the mid 40s. Wind becomes light under high pressure, then turns southerly Tuesday night as the high slips quickly off to the east.

By Tuesday evening, high pressure has moved through the region and is just to our east, setting up southerly flow and warmer temperatures for mid-week, as yet another system forms east of the Rockies. (NWS)


As low pressure develops in the Southern Plains and with the aforementioned high off to our east, steady south breezes and sunshine quickly warm temperatures back up from near 30 as you head to work or school well into the 50s by mid-afternoon. This will likely be the nicest day of the week if you don't count today!

Wednesday morning - total lunar eclipse!

Also of note on Wednesday, a total lunar eclipse will occur just before moonset and as the sun is about to rise. The image below provides the details, but the event will occur low on the western horizon, so if you have trees or buildings blocking your view of the horizon to the west, you likely won't see the total eclipse.

The penumbral eclipse will be very hard to notice, but the start of the partial eclipse will be visible to the naked eye (and no eye protection is needed for lunar eclipses!). The moon will be in totality for about 5 minutes before it slips below the horizon. Note that the altitude of the moon at 6:51am is just 1° - you won't see it if you don't have a clear view of the horizon! Sky conditions, however, currently appear to be excellent for viewing. It's also worth noting that this total eclipse is of a supermoon - when it's distance from earth is at its minimum - a "Total Eclipse of a Supermoon!"

Time sequence of events related to the total lunar eclipse on Wednesday morning. (


The low over the Plains moves our way as another cold front slips through during the day. Temperatures will still be near average, perhaps falling by mid-afternoon, but rain chances increase dramatically as we go through the day. As cold air dives in after dark behind the departing system, rainfall starts to push east. Computer models have been hinting at some frozen precipitation on Thursday night for the past several days, but now seem to be narrowing the chances to just a few short hours before precipitation ends, when it may get cold enough for a bit of snow. I wouldn't hold my breath, as oftentimes the precipitation departs before the "cold-enough" air arrives. Stay tuned to our forecast! It could change as we get closer.


Earlier model runs had again hinted at lingering precipitation (likely snow) early on Friday. I find very little chance of that at this point and will go with diminishing clouds and below average temperatures - likely with highs in the 40s and a cold breeze. Again, we'll watch it carefully, but for now it looks dry and cold. Morning lows will be near freezing as the groundhog - or some other flavor of rodent, if you prefer - makes his appearance to tell us about the next 6 weeks.

Super Bowl Weekend & Beyond

Saturday currently looks dry and a bit warmer as we will probably be between systems again. An average early February day is the best bet. The crystal ball gets foggy after that thanks to a wide range in computer model opinions. As the polar vortex sets up shop well to our north, the pattern locally could get active with generally below normal temperatures and perhaps above normal precipitation. The first full week will be one to keep an eye on! I make no promises.

The map above shows the American GFS model ensemble of temperature anomalies at 850 mb (about 5000', and a good proxy for above/below normal temperatures at the surface) for the period February 2-7. What stands out is very cold air in Canada, seeping down into the northern U.S. In the Mid-South, we're on the edge of that "cold air bubble," indicating a likelihood that we could be in the "battleground" between the cold/warm air to our north/south, respectively. We'll have to watch for any precipitation events that might also be borderline. (

Stay up to date with the latest local weather conditions, human-generated forecast, and precip-typed radar with the MWN mobile app! Not only do you get the best local weather information in the convenience of an app, you get to support your favorite independent weather source in the Mid-South at the same time! What a deal! You can find more info at the link below.

Erik Proseus
MWN Meteorologist

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Sunday, January 21, 2018

Memphis, TN Annual Climate Summary for 2017

2017 Annual Recap

Overall, 2017 was very warm, the sixth warmest in Memphis recorded history, and generally remained below normal precipitation-wise for the year outside of a few wet spells.

During the year, there were two major weather events. The first was the "Tom Lee Storm," a derecho that struck Memphis on Memorial Day weekend, knocking over the statue of Tom Lee on the Mississippi Riverfront and resulting in massive power outages across the metro due to wind that topped out over 100 mph.

The Tom Lee Memorial Statue lies in pieces after severe windstorm on May 27 blew through the city, less than an hour after Memphis in May's #901Fest ended. Photo credit: Joe Birch.

The second was the the passage of the remnants of Tropical Storm Harvey over the Mid-South on August 31, producing record rainfall and very gusty wind, as well as as handful of tornadoes in the region, mainly over northeast MS. Overall, the Mid-South recorded 27 tornadoes for the year, most weak, while only two occurred in the greater metro: an EF-0 in Tipton County near Covington on April 30 and an EF-0 in Marshall County near Red Banks on June 22. Neither produced any injuries or deaths.

The following represents a statistical recap of the weather for 2017 in Memphis. A more complete recap of  weather in the Mid-South for the year, produced by the National Weather Service in Memphis, can be found here.

Memphis International Airport, Memphis, TN

Average temperature: 64.7 degrees (1.6 degrees above average)
Average high temperature: 74.2 degrees (1.7 degrees above average)
Average low temperature: 55.2 degrees (1.6 degrees above average)
Warmest temperature: 99 degrees (July 21)
Coolest temperature: 13 degrees (January 7 & January 8)

Heating degree days: 2298 (667 below average)
Cooling degree days: 2302 (44 above average)
Days at or above 90 degrees: 50 (14.3 days below average)
Days at or below 32 degrees: 35 (7.8 days below average)
Last freeze/first freeze: March 24-November 12 (233 day growing season)

Records set or tied: Six warm weather records and one cold weather record were set during 2017. The daily records included: February 11 (79°, record high, and 63°, record warm minimum),  February 19 (77°, record high), February 22 (76°, record high), September 12 (66°, record cool maximum), October 9 (92°, record high), and November 5 (67°, record warm minimum).

Comments: 2017 was the 6th warmest year on record with a 64.7° average annual temperature. January was the 8th warmest on record, despite featuring the coldest temperature of the year as well. February was the warmest on record in Memphis and ended meteorological winter of 2016-'17 as the 4th warmest on record. April was the tenth warmest on record, landing the period January-April (as well as January-May and January-June) in second spot for warmest such periods recorded. 2016 finished as the sixth warmest year on record in Memphis.

Temperatures for the year (lows/highs) are plotted in dark blue against the normals (brown), record highs (red) and record lows (light blue).  Where the dark blue extends above or below the brown indicates temperatures above or below normal, respectively.

Monthly total: 51.38" (2.30" below average)
Days with measurable precipitation: 122 (14.3 days above average)
Days with 1"+ precipitation: 18 (0.6 days above average)
Wettest day: 4.40" (August 31

Total Snowfall: 2.0" (1.8" below average)
Days with a trace or more snowfall: 4
Greatest snow depth (at 6am CST): 1" (January 7)

Records set or tied: Three daily records were set in 2017: June 23 (1.63"), August 31 (4.04"), December 22 (3.33").

Comments: 2017 ended with slightly below average precipitation for the year. February was the 10th driest on record. August precipitation, particularly from the remnants of Harvey at the end of the month, netted a fourth place finish for wettest on record.

Precipitation accumulation for 2017 is plotted as the dark green line, compared with a normal year in brown. For a large part of the year, precipitation ran below average. Periodic downpours brought the total closer to average for short periods, particularly around September 1 and in mid-December, but the year ended slightly below normal. 

Peak wind gust: West/61 mph (May 27)
Average wind: 8.1 mph
Average relative humidity: 68%

Click here for monthly/daily statistical recaps for Memphis International Airport.

Cirrus Weather Solutions /, Bartlett, TN

Average temperature: 62.7 degrees
Average high temperature: degrees
Average low temperature: degrees
Warmest temperature: 98.7 degrees (July 22)
Coolest temperature: 10.8 degrees (January 8)

Heating degree days: 2704
Cooling degree days: 2138

Annual total: 49.40" (automated rain gauge), 52.46" (manual CoCoRaHS rain gauge)
Wettest date: 4.63" (Aug. 31- Sep. 1) (CoCoRaHS)

Total Snowfall: 1.5"
Days with a trace or more snowfall: 4
Greatest snow depth: 0.5" (multiple days)

Peak wind: West/38 mph (May 27)
Average relative humidity: 76%
Average barometric pressure: 30.06" Hg

Click here for monthly/daily statistical recaps for Bartlett, TN.

MWN Forecast Accuracy

Number of forecasts produced and rated in 2017: 574
MWN average temperature error: 2.08 degrees
MWN forecast temperatures within 2 degrees of actual: 67.8%
MWN average dewpoint error: 2.40 degrees
MWN forecast dewpoints within 2 degrees of actual: 61.1%

MWN's forecasts extend out five periods (2.5 days, or roughly 60 hours) and the numbers above represent the error/accuracy of the entire 2.5 day period. Historical accuracy statistics can be found here.

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Leaving Arctic cold in the rear-view mirror - warmer days ahead!

Winter weather is now behind us for a while it appears! I can hear your collective sigh of relief  (especially you parents with kids at home most, or all, week!).

Warmer temperatures are ahead, starting with this weekend's 60s. Though it won't be quite that warm all week, I think we'll take a good deal of 50s with morning lows near or above freezing. Southerly flow this weekend has done a number on the lingering ice, as have temperatures that have been above freezing since Friday mid-morning.

Interesting fact: in the approximately one-week period leading up to when we went above freezing on Friday, only 17 of the previous 173 hours were above freezing! Most of those hours were this past Monday when we had a one-day reprieve from the freezer on MLK Day. In addition, the period from Christmas Day through January 19 was the coldest such period in a century in Memphis!

Listing of the top 10 coldest average temperatures for the period Dec 25-Jan 19. This year was the coldest in 100 years!
Looking ahead, another potent cold front arrives overnight tonight. The good news with this one though is that the airmass trailing the front is of Pacific origin, not Arctic origin. That means a bit of a cool down, but no bitterly cold temperatures! The front itself will be running into a greatly-modified airmass from the one we had this past week - warmer, moister, and with a bit of instability. That means we will also have a chance of thunderstorms.

While I don't expect much in the way of severe weather, a few thunderstorms could have some gusty wind, as wind will be blowing strong at all levels of the atmosphere, including down here near the ground. Areas west of the Mississippi River are in the Marginal (category 1/5) severe weather risk for an expected line of rain and embedded thunderstorms that moves through between midnight and 6am Monday. Rainfall totals will likely be under a half inch for most, as the line will be fairly progressive.

A Marginal Risk (1/5) of severe weather exists west of the Mississippi River tonight as a few storms are possible that could contain strong wind gusts. Areas from Little Rock west have a higher risk of severe storms this evening. (SPC)

The National Weather Service forecast rainfall through Monday afternoon. The metro will likely average about a half-inch of rain with tonight's front. (NWS / WxBell)

By mid-morning Monday, the rain will be gone and some sun will be appearing, though a strong southwest wind is also likely throughout the day. Tie down the garbage cans and anything else lightweight that you don't want to lose before retiring for the night tonight! High temperatures will recover nicely on Monday with a fair amount of sunshine and the cooler air trailing the front by a ways. Look for highs again in the lower half of the 60s.

For the rest of the week, the cooler air arrives Tuesday with morning lows in the mid 30s and wind chills back into the 20s, recovering back to near 50 in the afternoon. Wednesday will be similar, then a slow warming trend commences again heading towards next weekend, when the next wet weather system arrives. Overall, a good deal of sunshine will be found across the Mid-South though this week! Enjoy the above average temperatures and don't forget you can keep up with the latest information on Memphis weather with the MWN mobile app!

Erik Proseus
MWN Meteorologist

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Sunday, January 14, 2018

Turning our eyes to Monday night - more snow??

Our first winter weather event (and "snow day") is in the rearview mirror, but impacts linger this weekend as bitterly cold air settles over the region. Most areas within the metro ended up with anywhere from 1-1.5" of sleet and snow and very light amounts of ice glaze on Friday. The sleet being the predominant precipitation type resulted in icy roadways, and pretty much everything else.

While sun on Saturday aided many areas greatly, despite temperatures remaining below freezing, areas that were wet from melting re-froze last night, with icy patches still around, especially on secondary roadways. Temperatures today will just slide in under the freezing (or melting?) point and with overcast conditions, there will be less progress made on the icy spots. In addition, an upper level wave is bringing light snow to Arkansas and some flurries could make it into the metro this afternoon. Current radar is shown below.

Current loop from StormView Radar
Monday will see additional warming that should help a great deal with the remaining ice as high temperatures head for 40° or better with partial sun and southerly wind. However, don't get used to the relative "warmth." By evening, the next significant push of Arctic air arrives thanks to an annoying Clipper.

No, not that annoying clipper... one from Alberta, Canada! But feel free to "T" this one up too if you want, as it'll bring another round of #StupidCold to the Mid-South by mid-week. (Off-topic: man, I still miss Z-Bo... go ahead, watch that loop a few more times. I digress...) The clipper will also be partially responsible for our next snow event right on its heels Monday night into Tuesday morning. Given that we are still recovering from one snow day and continued impacts, perhaps this one comes #TooSoon?

What to Expect

One the plus side: no ice and relatively minor amounts. On the negative side: very cold air results in high snow ratios as we head towards Tuesday morning rush hour.

So what do we expect with this system? Temperatures will fall below freezing Monday evening, but the roads will likely retain a little of the daytime heat as light snow begins to fall before midnight, resulting in initial melting and wet streets. As the night goes on, snow chances increase and temperatures continue to drop as Arctic air pours in. If the European and NAM models are correct, snow appears likely after midnight through about 8-9am Tuesday morning. By the time light snow ends, temperatures will likely be near or just below 20°.

High-resolution NAM model forecast temperatures at 6am Tuesday. It shows 21° in Memphis. (WxBell)
Snow totals will be strongly affected by the cold air pouring in, causing snow ratios to rise. A snow ratio is the amount of liquid for each inch of snow. Typically we see roughly 10:1 ratios, which means that for every 1" of liquid, we would receive 10" of snow (or more likely, for every 0.10" of liquid we see 1" of snow). Higher ratios occur in colder air when the snow is drier (think less "pack-able" for snowballs). As our temperatures drop down towards 20°, our snow ratio could exceed 15:1. That means that for the same 0.10" of liquid, we would get 1.5" of snow instead of 1.0".

So how much snow are we talking? Between 9pm Monday and about 9am Tuesday, I think an inch is a fairly decent bet, but with higher snow ratios, 1-2" feels like a good possibility, especially south of I-40 where I believe the slightly higher amounts could occur vs. north of I-40. (Oh, you don't like I-40 always being the dividing line? OK, I'll use Highway 70, which no one in MS knows anything about. See what I mean - you have to use an interstate. But again, I digress...)

Below, see the average from the European ensemble members (at a 10:1 snow ratio), as well as the NWS forecast:

The European model ensemble (51 Euro models run with slightly different parameters) average snowfall is shown above given a 10:1 snow ratio. Above, we talked about how it could be higher, thus snow totals could be underestimated, but only if this model is even correct. (

Road Conditions

As far as expected road conditions are concerned, once again very cold air could come into play. I can't help but look back to January 28, 2014, when Birmingham and Atlanta experienced "Snowmageddon" with only 1-2" of snow. Do you know why it was such a major event? Not because "it's the south," but because it was about  20°, the snow melted a bit on initial contact from warmth the day before and warm tires driving on it, then it essentially "flash froze," creating a massive skating rink. Our forecast conditions are nearly identical. The exception may be that their snow began around the morning rush hour when warm tires were prevalent, whereas most of our event will occur overnight with light traffic. Perhaps that limits the possibility of a devastating event like Snowmaggedon, as the light snow could stick to the ground overnight and the tires driving on it won't melt it. I simply don't know how roads will be impacted, but I raise the possibility of a treacherous commute because I have seen it before in these conditions. We won't know until it happens. Here's how an NWS forecaster in Amarillo describes this setup, borrowed from the AlabamaWx blog:

“We typically get our worst travel problems and most accidents with 1-2 inches of snow. It actually seems like we have more problems with the dry, powdery snows than the wet, slushy snows. Just from my short experience out here, air temperatures of 28 F and lower seem to be when snow and ice accretion really start developing quickly on the roads.” - NWS-Amarillo Meteorologist

Other impacts

I believe the airport will fare better than Friday's event, mainly because most of the snow falls at a low traffic time and dry snow is much easier to deice than sleet. As always, you'll want to check with your airline if you fly through Memphis on Tuesday and of course allow plenty of time to get to the airport - double your normal travel time, or more.

I still won't predict school closings, though this one feels more like a "get up in the morning and see how it looks" kind of event. Friday's was easier with ice predicted during the morning commute. This event is not the same. Road conditions Tuesday morning will likely drive the decision.

Once again, with a #StupidCold airmass in place, low temperatures could get down into the upper single digits on Wednesday morning (especially if there is snow cover), and only reach the mid 20s both Tuesday and Wednesday. We won't be back above freezing until mid-day Thursday. Impacts could be prolonged once again. Click here to check the MWN Forecast for this week's temperatures.

Forecast Bust Potential?

There always is. In this case, not all models are sold on anything more than a light dusting. In fact, the American GFS model is one of those that is not convinced. I currently favor the European model, which has been very consistent for several days, and in fact, drops more snow than we are currently forecasting (as much as double). The American-born NAM Nest model, which is much higher resolution and only available out to 60 hours, agrees with the global Euro model, but with a bit less snow. None predict ice, and all are sold on very cold air by Tuesday morning.

We'll have the latest on Monday with another blog or perhaps video on Monday night so you can plan accordingly for Tuesday morning. Perhaps a 4-day weekend turns into 5 days?? Time will tell!

In the meantime, download the MWN mobile app for radar, current conditions, human-generated forecast, and the latest from our social media feeds, which are all also linked below!

Erik Proseus
MWN Meteorologist

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Visit on the web or on your mobile phone.
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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Wednesday, January 10, 2018

Friday's winter weather event - our first call at the details

The best chance of wintry precipitation so far this year arrives this Friday. While (most) everyone looks forward to "snow days," if you end up with a change of plans from a normal day this time, it will most likely be due to ice, not snow. Snowball fights are currently not in the cards!

First a reminder that, as of this writing Friday evening, we're still about 36 hours away from the onset of winter precipitation, and while the computer models are generally coming into some alignment, we also see some "wild hairs" out there that lead to reduced confidence in some areas (which is not atypical for a southern winter event). Exact details are yet to be resolved and the situation remains fluid.

I'll start with the bullet points, based on the latest data and sound meteorological reasoning, unaffected by the wishes of any particular lobbying group. :-)

A Winter Storm Watch is in effect Friday for the blue counties, which are areas that have the greatest potential for impact to the general population. The counties under a watch, and later a warning or advisory, could change with new information.

What will fall: Besides temperatures, rain, then freezing rain, then a mix with sleet and snow, ending as light snow.
Start time: Rain transitions to freezing rain (ice) early Friday morning, probably between 3-5am
End time: Perhaps the lowest confidence portion of the forecast, but most likely by mid-day Friday
How much: Freezing rain: up to 1/4"; sleet and snow: 1" or less

Now for some details...

Despite very warm temperatures today and Thursday, a major cold front will escort our next Arctic air mass into the Mid-South Thursday late evening. This front will cause temperatures to drop rapidly towards freezing by the early morning hours on Friday on a strong and gusty north wind. Rain could occasionally be heavy along and just behind the front and a rumble of thunder can't be ruled out. Precipitation intensity should let up a bit as the temperature nears freezing. Once it drops to 32°, rain continues to fall (because the near-surface layer is cooling more rapidly than temperatures aloft) and starts freezing to objects that also drop below freezing - power lines, trees, and other exposed objects.

Forecast temperatures at midnight Friday just after the cold front passes through Memphis. Northeast MS is in the lower 60s, while north-central AR is in the upper 20s. (WxBell)

The European model from Wednesday morning shows the primary precipitation type between 12-6am Friday to be freezing rain, with some trailing snow to our west. Note that the precipitation does not extend very far to the west, indicating that it likely won't last long after 6am. This solution is one that favors an early departure to the precipitation and little snow. THis is just one of many models that are available to the meteorologist however. (WxBell)

Initially, roads should still be fine as they will be warm, but they will also cool quickly, particularly those with cold air blowing under them (think about an overpass). It won't take long for those to start feeling the effects of the freezing rain. As the air just aloft also cools, the rain (that freezes on contact) should start to change over to some sleet (frozen raindrops), and then probably light snow as precipitation rates continue to fall. This entire process will probably take 3-6 hours. So, from when the surface temperature first reaches freezing (right now, I'm saying 3-5 am) to when it's cold enough to snow will take 3-6 hours, or sometime during the morning hours. During that time, depending on how much sleet mixes in, we could see upwards of 1/4" of freezing rain.

During the course of Friday's event, we expect to see all of these precipitation types, moving from the left to right as warm air is overtaken by cold air, starting at the surface and moving up.
Models all agree on the details to this point fairly well. It's after this time that they start to diverge. There are multiple indications that once it gets cold enough to snow, the moisture moves out. Others keep a little around for a short time. Either way, the probability of more than a dusting to an inch of snow is not high. Then there is the occasional "outlier model" that keeps snow falling well into the afternoon. You can hope for that, but my hard-earned money is not on it!

Confidence Levels

Given we are still a little ways out, the models aren't in as good of agreement as I'd like, and we're in the south, confidence levels are worth a short discussion. Here is my confidence in the following events:

Onset time: Medium-High. If I'm wrong, it could be a bit later, but not by much.
End time: Medium-low. This could go either of two ways. A couple of solutions point to the precip ending not long after sunrise. An outlier from this afternoon (I'm looking at you 18Z NAM) says it'll snow all day. I'd pick the under if I were you.
Precip amounts: Medium. If I'm wrong, I am aiming high on the freezing rain total. I wouldn't be surprised to see it stop at 0.10" or so. That's still a real problem, so based on impact, it's not a big difference. I'm fairly convinced we won't see much snow. Less than an inch seems a solid (educated) guess right now.
Schools Cancelled: You thought I was going to bite on that didn't you...

What is the bust potential? There are valid model solutions that show precipitation ending not long after it gets cold enough to start causing problems. This is GOOD because nobody wants an ice storm, but it could result in minimal accumulations and no snow. If the precipitation ends early, snow will be the first sacrifice.

Impacts to Business and Commerce

Roads - Contrary to popular opinion, Memphis and surrounding jurisdictions do have the ability to salt/sand roadways, as does TDOT, which handles the interstates. However, given that these events are not frequent and the number of lane-miles in the metro, every road (even every major road) cannot be treated with current assets. Priority is given to the most critical and accident-prone areas, especially including elevated roads, such as Bill Morris Parkway and various interstate flyovers and ramps. In this event, rain will be falling prior to the arrival of the cold air, so pre-treating with salt brine would be a waste of money. It'll wash right off. Expect roads to be treated once freezing begins, and avoid known trouble spots altogether, even if you leave early for work Friday morning. If even light amounts of freezing rain occur, the elevated roadways will be slick and could be closed for treatment at times.

Airport - Believe it or not, the Airport Authority and FedEx are probably better equipped to handle winter weather events than the road crews are around here. They have plenty of equipment, and there's just not a ton of traffic. Cancellations into relatively minor events like this are lower than you think. The runways will be cleared, even if one at a time (that's all you really need), airplanes will be deiced, etc. The main concerns are: A) if freezing rain is more than forecast, more cancellations would occur, and it would be on flights heading into Memphis (which then means there is no plane to take you somewhere else), and B) weather elsewhere. This storm system will affect a lot of places on Friday. Cancellations elsewhere will ripple through the system like a boulder thrown into a pond. As always, check with your airline or your airline's website or app for the latest before your cross multiple iced up bridges and overpasses to get to the airport and find out your flight is cancelled.

Schools - Fortunately, I don't have to make this decision! However, the fact that (currently) the event is supposed to start very early in the morning COULD make their decision a bit easier. By 5am when many school decisions have to be made, we should know what we're dealing with. From experience, districts don't tend to mess around with ice. Kids - do your homework, then stick the spoon under your pillow. Hopefully you get to stay home and enjoy a four-day weekend (Monday is MLK Day)!

Bottom line it for me, Erik

Things are lining up for a potentially impactful winter weather event, particularly from the perspective of ice. At this time, I don't expect to see massive and widespread power outages or trees downed, but travel could definitely be hazardous to treacherous, especially Friday morning, and there could definitely be an impact to business and commerce. Don't be surprised at little to no snow though. Plan ahead now and exercise caution later. If not necessary to get out Friday morning and ice is on the ground, don't. I'm planning another formal update Thursday evening, hopefully via video. Stay tuned to our social channels listed below for updates prior to then, and of course during the event.

If you appreciate the service we provide, tell a friend or a few, and go get our app, also linked below. You'll find regular updates there, including radar, forecast, and social, as well as the opportunity to get personalized severe and winter weather notifications via the StormWatch+ in-app upgrade. I appreciate you checking it out!

Erik Proseus
MWN Meteorologist

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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Tuesday, January 9, 2018

December 2017 Climate Data for Memphis, TN

December Climate Recap

The month of December was marked by a series of frontal systems that brought large temperature swings and periods of wet weather. After starting very warm, multiple days of cool weather followed a front that brought about an inch of rain. Despite a couple of warmer days, temperatures were a bit below average from the 5th through 15th. Another warm and wet spell resulted in several inches of rain in the third week of the month. As Christmas approached, temperatures dropped precipitously with well below average conditions experienced through the final week of the month. That week put the nail in the coffin of a colder than average month with above normal rainfall that nearly put the year right on par for precipitation. Despite the very cold temperatures at the end of the month (the period from Christmas to New Year's Eve was the 12th coldest on record), the only record set was a daily rainfall mark, eclipsed on December 22 when over 3" of rain fell. Flash Flood Warnings were issued for portions of the metro on that day, otherwise no severe weather occurred during the month.

Memphis International Airport, Memphis, TN

Average temperature: 42.4 degrees (1.2 degrees below average)
Average high temperature: 51.2 degrees (0.9 degrees below average)
Average low temperature: 33.6 degrees (1.5 degrees below average)
Warmest temperature: 71 degrees (4th)
Coolest temperature: 14 degrees (31st)
Heating Degrees Days: 693 (28 above average)
Cooling Degree Days: 0 (2 below average)
Records set or tied: None
Comments: None

Monthly total: 7.26" (1.52" above average)
Days with measurable precipitation: 8
Wettest 24-hour period: 3.33" (22nd)
Snowfall: None
Records set or tied: Record daily precipitation of 3.33" was recorded on the 22nd.
Comments:  None

Peak wind: Northwest/37 mph (22nd)
Average wind: 7.7 mph
Average relative humidity: 66%
Average sky cover: 60%

Click here for a daily statistical recap for Memphis International Airport.

Cirrus Weather Solutions /, Bartlett, TN

Average temperature: 41.3 degrees
Average high temperature: 51.4 degrees
Average low temperature: 31.4 degrees
Warmest temperature: 72.0 degrees (4th)
Coolest temperature: 13.2 degrees (31st)
Comments: None

Monthly total: 7.18" (automated rain gauge), 7.96" (manual CoCoRaHS rain gauge)
Days with measurable precipitation: 9
Wettest date: 3.26" (22nd) (via automated gauge)
Snowfall: None
Comments: None

Peak wind: South/21 mph (13th)
Average relative humidity: 73%
Average barometric pressure: 30.21 in. Hg
Comments: None

Click here for a daily statistical recap for Bartlett, TN.

MWN Forecast Accuracy

MWN average temperature error: 2.70 degrees
MWN forecast temperatures within 2 degrees of actual: 50%
MWN average dewpoint error: 2.38 degrees
MWN forecast dewpoints within 2 degrees of actual: 59%

MWN's forecasts extend out five periods (2.5 days, or roughly 60 hours). Historical accuracy statistics can be found here.

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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Monday, January 8, 2018

"The Elephant in the Room" - Friday Snow Potential

Questions are starting, and since we're about four days out, I thought I would take a few minutes to address this...

It's the Big Snowy Elephant in the Room! (If the room were large enough to hold a mountain!)

Forecasts you see from multiple sources are starting to include the potential for snow in the forecast Friday and Friday night. Some of you may have even been lucky enough to see the snow map from the "vastly-superior" European model this morning. Well, I'm here to bring some reality and level-headedness to the situation. And that doesn't necessarily mean "no snow." In fact, before you go any further, check my official MWN Forecast. There are a few things that need explaining though...

1. Any map that shows snow totals in the south that are multiple times larger than the average annual snowfall beyond three days in advance of the event need to cause your "Fake News" meter to spring to life. That doesn't mean that solution is wrong, it just means that there is still a good deal of uncertainty and there are likely a number of other solutions that would discount it.

Enter this morning's European model, which believe it or not is sometimes incorrect! I'm not showing the map, but I will tell you it showed snow falling Friday night that was closer to a foot than a toe. What people haven't shared is the American version of the medium-range model, which brings the cold air in much quicker and produces a treacherous ice event Friday morning!

Do I believe one or the other is absolutely correct? Nope! Could they be? Perhaps. But both will change their minds multiple times over the next 72 hours and likely will end up somewhere removed from either end of the spectrum.

2. Ensembles rule the day in these scenarios. What are ensembles (don't answer, music friends!)? Most models are run multiple times with slightly different parameters. These parameter tweaks can produce different results from the same model. The ensembles provide the forecaster a level of confidence in that model. For example, if the main model output is in line with all of the various ensemble members, confidence is high in the solution.

Let's look at that European model from this morning. Here is the ensemble output for snowfall:

European model ensemble output for accumulated snowfall from this morning's model run. Description below. (WxBell)
The European model has a 51-member ensemble (it's run 51 times with various slight parameter tweaks). The top graph shows the snowfall from each of the 51 members in a separate row, with time going from left to right. You'll notice that most rows have some color in them in the red box that represents Friday into Friday night. Some of them turn blue in that box, meaning 2" or more. Many are gray, which is less than 2".

In the bottom graph, the snow map that some of you have seen is the "deterministic" run of the model and you can see that it peaks at 8" in the red box (yikes!). You'll also notice that the "ensemble mean" (or the average of the other 51 members) is about 1". So the snow map referenced earlier is showing about EIGHT TIMES the total that the average of the ensemble members are showing. And only 1 of those 51 members produces an amount similar to the deterministic run. In statistics, we call that a 2% chance of occurrence.

What the European ensembles tell me is that there is a pretty high probability of seeing some snow, but that totals will almost certainly be closer to 1" than 8". Let's looks at the same thing for the American GFS model:

GFS model ensemble output for accumulated snowfall from this morning's model run. Description below. (WxBell)
The GFS model only has 20 ensemble members, not 51, but the graph shows the same thing. During the period in question, many of the members produce snow. A couple show totals of 9-12", but the ensemble mean (bottom row in this graph) is about 1". Another ensemble that says an inch. Hmmm...

Ensembles bring the reality back to outrageous snow maps, which is the responsible way to forecast. We attempt to excel in that area. :-)  

(BTW - the Tuesday areas that are highlighted in the boxes above - disregard those for now. Too far out to give any credence to. But it'll definitely be very cold between Friday and Tuesday, so we'll address that as we get closer.)

3. Consider all valid sources. Here's another one - a new product from a branch of the National Weather Service that (on an experimental basis) predicts the probability of "impactful" winter weather in the 4-7 day range. The forecast is a probability of 0.25" of liquid equivalent snow or sleet. What does that mean? Assume that snowfall generally melts down to about 0.10" of liquid for every 1" of snow (a 10:1 ratio, which is very close to average). So 0.25" of liquid is roughly 2.5" of snow. The forecast below, issued today, says that we have about a 10% (or a little higher) chance of reaching that 0.25" threshold. That means it's not likely - at this point given the available data - that we'll see 2-3" of snow. But the fact that we're in the area of interest indicates that we should prepare for the possibility that we could get something.

So there is your lesson on snow forecasting in the south! Beware the share - if it seems to good to be true, it probably is and shouldn't be shared on your timeline. Besides, you hate fake news anyway, so throw crazy snow maps in that bucket.

What do I really think? 

After reaching the 60s Wednesday and Thursday, I believe we have a decent shot at seeing some winter precipitation on Friday and/or Friday night. We could see some ice mix in as rain transitions to snow, but I don't know when that would occur just yet. I do NOT know how it will affect schools - depends on the timing of the transition and individual school district decisions. And if we DO get more than an inch or so, it'll likely happen Friday night. I'll get more into the setup in a couple days, but for now, just know the answer is...


Erik Proseus
MWN Meteorologist

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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder