Monday, February 29, 2016

Leap Day update on Super Tuesday thunderstorms

In yesterday's blog about the weather this week, we discussed the probability of severe storms on Tuesday, indicating that the likelihood of severe weather was rather low. While this update isn't a complete "180," today's forecast data caused me to pause for a closer look. First let me say that another Super Tuesday severe weather outbreak (i.e., 2008) is NOT expected. However, a few severe storms cannot be ruled out.

Here are the two graphics worth sharing today. First our impact graphic produced at mid-day that contains the high-level overview:

...and next a reminder of what the various risk levels mean. For now, we're in a category 2 of 5 (Slight Risk) for Tuesday, meaning some storms could become severe, but not a lot.

Description of the outlook categories used by SPC. Click for larger image.
The details are that a strong upper level system and associated cold front will be moving through the region. These systems will tap into increasing levels of moisture and modest instability. There will also be a good deal of wind energy with this system, at the surface and especially aloft. These factors will combine to produce a large area of rain and thunderstorms, starting early Tuesday as noted above, and moving east of the metro by mid-afternoon. A few morning storms could become severe with damaging wind the primary threat. The wind energy will be borderline for producing tornadoes, so we'll have to keep a close eye out. In addition, any storms will be capable of brief heavy downpours and the wind will be blowing strong until after the front has passed in the mid-afternoon.

Tomorrow is Super Tuesday, which means many of you will be voting (we highly recommend it, but please go through the line once, even if you really like your candidate...).

While there may be some showers around during the pre-work voting hours, the best chance of strong storms will be after rush hour through the lunch hour. By the afternoon rush hour, it'll be over. If you have a choice when to vote, we recommend getting off work a little early and doing it in the late afternoon/early evening. Then expect a wait, because most everyone else will wait too.

Regarding preparation, we suggest that as well. We'll even help you with it. Tonight at 8:30pm, live via the magic of video chat, we'll convene a panel of guests to talk about severe weather preparation, and maybe a controversial topic or two, because it's Severe Weather Awareness Week. We may even have a giveaway of some sort, because we appreciate all of you. You can participate by watching on YouTube (desktop or mobile) or on our Hangout webpage and asking your questions on Twitter using the #wxchat tag or in the chat we have set up for you on the Hangout page linked. I hope you'll join us!

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

Sunday, February 28, 2016

Warm weekend gives way to spring rain. Is winter over?

The past week ended cool, but just like last weekend, beautiful spring weather arrived just in time for the weekend! We've certainly enjoyed temperatures in the 60s the past couple days with a breezy south wind.

Early week forecast

A weak front arrives tonight, bringing a slight chance of showers mainly in the late evening hours, before stalling and basically washing out over north Mississippi on Monday. Temperatures remain above normal tonight in the mid to upper 40s then rise well back into the 60s on Monday with sky conditions no worse than partly cloudy on average.

High-resolution model simulated reflectivity indicates a few showers will pass through early this evening ahead of a cold front. Graphic courtesy WxBell.

The next major weather system arrives on Tuesday. Strong southerly wind help to "reload" the atmosphere, but March won't exactly come in like a ferocious, hungry lion. Low pressure going by to our north will push a front into the region Tuesday afternoon. Some instability will be available and moisture levels will be high for this time of year, meaning thunderstorms are probable, but wind shear will be at moderate levels so severe weather is expected to be limited at best.

Tuesday afternoon instability values, as measured by Convective Available Potential Energy (CAPE), will be sufficient for thunder, but the upper level dynamics will be insufficient for much severe weather. Graphic courtesy WxBell.

The severe weather risk Tuesday is Marginal (category 1 of 5), indicating no widespread severe storms are anticipated. A few storms could have gusty wind. 

With the high atmospheric moisture content (about two times normal for early March), rainfall could be heavy on Tuesday though, even though it won't be prolonged. Some areas could see up to an inch during the afternoon and early evening hours.

Total precipitation early this week could be near 1", especially across northern portions of the Mid-South, according to the NWS. Graphic courtesy WxBell.

Extended forecast

Following the front, a couple of days of cool weather is anticipated with another decent chance of rain on Thursday as yet another low pressure system moves through the region. The good news is that the weekend trend continues with temperatures rebounding back towards the 60s by the first weekend in March. This is a trend I certainly don't mind!

OK, so is winter over?

This is the question I've been getting of late. Last year, our biggest snow storm of the year came on March 4-5. Given that no snow is expected for the first week in March, we'll be back in the 60s next weekend, and the week 2 outlook for the second week in March forecasts above normal temperatures (as average highs climb close to 60°), I am fairly confident that measurable snowfall is done for this year. That doesn't mean we won't still see a cold snap, more frost, or even a sub-freezing low over the next couple of weeks, as that is possible well into March, but chances of any more snow are dropping by the day. With one near-miss of a big snow storm, this winter will go down with very little measurable snow in a strong El Nino season.

There is a high probability that temperatures will be above normal across much of the eastern U.S. for the second week of March according to NOAA.

Severe Weather Awareness Week

This week is Severe Weather Awareness Week in Tennessee. Check out our SWAW website for details on topics that will be covered. We'll also have a few giveaways this week and host a preparedness chat Monday night at 8:30pm via Google+ Hangout. Check out our social media feeds for the latest details.

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

Saturday, February 27, 2016

Long-time west TN meteorologist retires from broadcast TV

Earlier this morning, broadcast meteorologist Eddie Holmes signed off of his last show on WBBJ-TV in Jackson, TN.

Eddie has spent 39 years in the broadcast industry, dating back to the late 1970s when he started in radio in western KY. In 1999, Eddie moved to west TN and built a loyal following at WBBJ. For the past few years, he has delivered the Saturday morning forecasts for Good Morning West Tennessee and filled in on occasion when co-workers that were on vacation. Eddie's full-time career is in the ministry, pastoring Northside Baptist Church in Milan, TN.

Eddie and I go back many years, to early in my weather career shortly after he arrived in west TN. We have had many conversations about west TN weather, family, and life in general over that time. I have trusted Eddie enough to bounce some "hair-brained" ideas off of him and I always appreciated his support, sincerity, and true friendship, as well as a deep faith that provided the underlying current for who Eddie is as a person.

In 2009, Eddie asked me if I would be interested in assuming ownership and responsibility for his very popular weather website,, pairing it with to serve all of west TN. He was unable to devote the continuing time and effort that it required, but also knew that it served a large audience in west TN. He wanted to know that the people it served would continue to have a reliable source of weather information. I was honored that he asked me to continue the service and gladly took the reins. The site lives on, largely serving the audience Eddie built.

While Eddie retires from broadcast TV, I have no doubt that his favorite hobby, the weather, will live on through his forecasts via West Tennessee Weather Online. Eddie's dedication and commitment are unfailing. Congratulations, dear friend! I look forward to sitting down with you again soon and talking shop and life and all the best in your "partial" retirement!

Erik Proseus
MWN Meteorologist

Click through to the story in the post below for WBBJ's tribute to Eddie.

Long-time friend of and a personal friend of mine, WBBJ-TV (Jackson, TN) and West Tennessee Weather...
Posted by on Saturday, February 27, 2016

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

Sunday, February 21, 2016

Warmth departs, low pressure brings a weather variety mid-week

A warm few days comes to an end tonight as a cold front moves through the metro this evening. Showers and a few thunderstorms will depart to our south by late evening. No more 60s and 70s in the forecast for the foreseeable future!

Monday will be a "tweener" day as the front sinks further south in to Mississippi and weak high pressure builds in on the back side of the front. Temperatures will be in the mid to upper 50s in the afternoon, which is very near normal, with mainly overcast conditions.

By Tuesday, the front will pull back to the north as low pressure develops in east Texas and moves northeast across AR. This will spread rain back into the region by the afternoon hours as temperatures climb to similar levels as Monday. Tuesday night will see widespread rainfall and increasing wind as the low tracks somewhere very close to the metro. Computer models still have some variation with respect to the ultimate track, and strength, of the low, but it will be close enough to bring gusty wind and periods of heavy rain as temperatures remain in the 40s. The NAM model shown below indicates the low nearly over Memphis at midnight Tuesday night.

The NAM model depicting low pressure nearly over Memphis at midnight Tuesday night. Snow is wrapping in on the northwest side of the system from MO into western AR while strong storms are possible southeast of the metro. (WxBell)
The track of the low pressure system is important for a couple of reasons. Due to its strength, it will draw unstable, warm air north from the Gulf ahead of the track. Strong wind aloft will aid in the potential for severe storms in the southeast quadrant of the storm system. Given the current storm track, that potential will be south of the metro as shown by the current severe weather outlook from the Storm Prediction Center below. A shift in that track to the north would bring the warm sector further north, as well as the threat for severe storms.

The best chance of severe weather will be to our south on Tuesday as the most unstable air is pulled north by the developing low pressure. (SPC)
In addition, the strength of the low will mean it will draw cold air around the backside of the system. The "wrap-around" precipitation in the northwest quadrant will move across Arkansas and the metro Wednesday as that cold air wraps in. Rain is expected to change to snow in northern AR and possibly the Missouri Bootheel as the system pulls out to the northeast. The NAM model depicts temperatures falling into the 30s as far south as northwest Mississippi Wednesday (see image below). This aspect of the forecast will need to be closely monitored as well. A deeper system that tracks further south could pull enough cold air in to cause a changeover in precip further south.

The NAM model predicts temperatures falling into the 30s Wednesday morning. (WxBell)
Given the current forecast model scenario, the probabilities of accumulating snow are highest in a swath northwest of the metro as shown by the Weather Prediction Center in the graphic below. For now, I expect temperatures will stay warm enough for all rain Wednesday as precip ends from west to east during the day, but don't be surprised if temperatures fall into the upper half of the 30s Wednesday afternoon.

Snowfall probabilities are minimal in the metro, but much higher not far to our northwest. (WPC)
Once the mid-week system moves out, a dry, mainly sunny, and seasonal few days are expected, which could take us right through the end of the month. A couple of long-range solutions are hinting at some shenanigans again next weekend, but are inconsistent and misleading at best and foolish at worst (for now).

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

Friday, February 12, 2016

A blast of cold, then Valentine's Day precip - but what type?

A very cold start to the week gave way to slightly warmer temperatures to end it, but another Arctic blast is diving south today and will reach the Mid-South tonight. No precipitation is forecast with this Arctic front, but you'll definitely notice it tomorrow as the "feels like" temperatures will be some 30° colder at mid-day than they were today (low 50s vs. low 20s)!

Morning lows will be in the lower 20s with brisk north wind producing wind chills in the lower half of the teens. If you are getting up for an early run... let's just say you won't see me passing you! That's  certainly cold for here, but check out these wind chills to our north at 6am tomorrow:

Wind chill values from the GFS (American) model at 6am CST Saturday. Graphic courtesy WxBell.
Despite sun, temperatures will remain in the mid 30s tomorrow afternoon with wind chills getting no higher than the 20s. That sets the stage for a cold night Saturday night with lows again in the 20s, although the approach of our next weather-maker will throw clouds over the area, acting like a blanket and keeping the mercury from completely bottoming out. This will be key in the forecast for Sunday. That weather-maker will bring precipitation into the region on Valentines's Day. You can already see where this has the potential to go...

You guessed it, we're looking closely at temperatures and timing of precipitation on Sunday. It appears the earliest precipitation will fall across northeast AR and west TN and that it could arrive during the morning hours, when it's still pretty cold.

Points to consider

  1. Precip during the day Sunday will be light, in fact very light in the morning.
  2. There is lots of dry air to overcome near the surface thanks to the very cold high pressure that will be over us prior to the precip arriving. This will serve to evaporate the initial precip as it falls.
  3. Temperatures a few thousand feet up will be warmer than they are at the surface - in fact, above freezing most likely over the metro. That means no snow. The concern is light icing.
  4. Southerly wind will help to push temperatures up in the morning ,despite cloud cover and evaporating precip. The key is, how quickly do they get above freezing?
Here are a couple of models we look at to show you just how close they think the transition from rain to ice will be to the metro during the morning. The red line is the 32° line and the blue line is 35°, both valid at noon. First the mid-day (18Z) GFS model:

Precipitation forecast Sunday morning and noon temperatures from the GFS model. Graphic courtesy WxBell.

And here's the mid-day NAM model, which specializes in short-term forecasts:

Precipitation forecast Sunday morning and noon temperatures from the NAM model. Graphic courtesy WxBell
Too close to call!

What we expect

*IF* we get any icing in the metro, it'll be more likely north (Tipton County) than south (DeSoto County), it will be very light (but it doesn't take much to foul up a flyover), and it will most likely be freezing rain, which produces a light glaze on exposed surfaces. Our official forecast calls for a slight chance of freezing rain or rain Sunday morning. By late morning, temperatures are expected to be warm enough for rain.

Sunday evening into the overnight will be wet. Could be some frog-stranglers and gully-washers out there. Rain will likely continue on President's Day before moving out Monday night. Find some indoor activities for the children. Here are the totals expected from this system over the next 5 days from the NWS Weather Prediction Center:

After moderate temperatures early next week, the good news is that strong southerly flow re-establishes itself and the pattern favors well above normal temperatures to return by mid-week and last at least a few days. Does that mean winter is over? Did it snow on March 5th last year? I'm not calling it just yet...

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

Sunday, February 7, 2016

Eastern U.S. trough is bringin' winter back (yeah)

A SUPER day in the weather department today as temperatures push towards the 60° mark thanks to a warm southwest breeze and a good deal of sunshine. A big shift in the upper level pattern takes place this week though, transitioning overnight tonight as an Arctic cold front moves through the Mid-South. Yep, it's bringin' sexy winter back!

On Monday morning, you'll likely notice the difference immediately, even though temperatures won't be any colder than the past few mornings (mid 30s). A strong northwest wind will be in place and keep temperatures from climbing much at all Monday as clouds circulate around a large trough of low pressure that builds south at the upper levels of the atmosphere.

A large upper level trough is depicted in blues in the map above valid at 6pm Monday. Air over the Mid-South will have origins in Canada, meaning a very cold pattern. Under the trough, upper level disturbances will rotate around the low bringing scattered snow showers. The Mid-South will be on the edge of these systems with borderline temperatures to support light snow. Graphic courtesy Pivotal Weather.
Under the trough, scattered snow showers are expected for much of the Midwest, Ohio and Tennessee Valleys, and northeast U.S. The Mid-South will be on the periphery of the coldest air, which in this case is both good and bad. Areas under the deeper cold air will have the best chances of light, but accumulating, snow, but they'll also be bitterly cold, while we'll only be "coat-and-gloves" cold.

Simulated radar from the NAM model valid at 6pm Monday shows the potential for very light precipitation. With temperatures falling to the mid 30s by this time, sprinkles or flurries could result. The blue narrow line is the forecast freezing line. Graphic courtesy Pivotal Weather.

Upper level flow around the main low over the Great Lakes will drive pieces of energy around it like spokes on a wheel. For us, northwest flow will mean fairly dry, cold air, but also low precip chances late Monday into early Tuesday. Most snowfall will occur to our northeast closer to the main low. Graphic courtesy Pivotal Weather.
A forecast sounding (conditions aloft over Memphis) at 3pm Monday shows the temperature (red line) falling below the freezing level (blue line) at about 1200' above the ground with a surface temperatures in the lower 40s. This means that precip would fall from the clouds as snow but would likely melt in the lowest 1000' to rain. Once the surface temperature drops into the mid 30s by sunset, there is a better chance the snow survives the lowest several hundred feet without completely melting.
The trough will hang around for the first half of the week, keeping colder than normal conditions around through that period.

Average surface temperatures from Monday night through Saturday night will be well below normal across the eastern half of the country and well above normal out west, reflecting the upper level pattern of a large trough of low pressure in the east and ridge of high pressure in the west. Graphic courtesy WeatherBell.
Once the trough moves east, upper level ridging will move in, bringing temperatures back to near or above normal by the end of the week into next weekend. Other than the Monday to early Tuesday threat of very light precipitation, the pattern supports a dry forecast until late next weekend.

Trends indicate a warming trend back to near or slightly above normal temperatures by next weekend, according to the American Ensemble model system. Graphic courtesy WeatherBell.
Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

Saturday, February 6, 2016

January 2016 Climate Data and Forecast Accuracy

January Recap

After a very warm end to 2015, the pattern shifted to start the new year and January temperatures ended up almost exactly "average" for the month. However, by daily averages, a relatively cold month was actually offset by about a week's worth of well above average days spread throughout the month. Precipitation was well below normal with one significant winter threat on the 22nd that ended up producing a coating of snow and freezing rain across the southern metro and up to 3" in the far northern metro. Thunderstorms rumbled through the metro on the 9th, which was the wettest day of the month and produced a couple of small hail and high wind reports, and on the 21st.

Graphic produced by NWS-Memphis showing approximate snowfall amounts on January 22.

Memphis International Airport, Memphis, TN

Average temperature: 41.1 degrees (0.1 degrees below average)
Average high temperature: 50.4 degrees (0.6 degrees above average)
Average low temperature: 31.8 degrees (0.8 degrees below average)
Warmest temperature: 73 degrees (31st)
Coolest temperature: 18 degrees (11th)
Records set or tied: Tied record warm minimum temperature: 61 degrees (January 31).
Comments: None.

Monthly total: 2.27" (1.71" below average)
Days with measurable precipitation: 7 (2.5 days below normal)
Wettest 24-hour period: 1.31" (9th)
Total Snowfall: 0.3"
Records set or tied: None
Comments: Despite only 0.3" of snow at the airport, surrounding areas, especially in Tipton County, received nearly 3" of snow on the 22nd.

Peak wind: Southwest/40 mph (31st)
Average wind: 8.8 mph
Average relative humidity: 64%
Average sky cover: 50%

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

Cirrus Weather Solutions /, Bartlett, TN

Average temperature: 39.8 degrees
Average high temperature: 49.7 degrees
Average low temperature: 29.8 degrees
Warmest temperature: 72.0 degrees (31st)
Coolest temperature: 17.4 degrees (11th)
Comments: None.

Monthly total: 2.58" (automated rain gauge), 2.73" (manual CoCoRaHS rain gauge)
Days with measurable precipitation: 7
Wettest date: 1.24" (9th) (via automated gauge)
Total Snowfall: 0.9" (22nd)
Comments: None

Peak wind: South/30 mph (31st)
Average relative humidity: 76%

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

MWN Forecast Accuracy

MWN average temperature error: 2.82 degrees
MWN forecast temperatures within 2 degrees of actual: 58%
MWN average dewpoint error: 2.32 degrees
MWN forecast dewpoints within 2 degrees of actual: 63%

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

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

Monday, February 1, 2016

Monday afternoon update on Groundhog Day storm potential

I've dissected this storm and possible scenarios daily since late last week and, in fact, started raising the awareness flag last Wednesday on social media. So hopefully by now, the fact that we could get severe weather tomorrow isn't a surprise. From that perspective, nothing has changed.

The scenarios mentioned yesterday are, in fact, still plausible. After studying the overnight and morning data and considering the analogs (past events with a similar setup to this one) and how they turned out, I think we'll see a mix of discrete (individual) storms and mini-lines of storms, primarily during the afternoon hours. As mentioned yesterday, these discrete cells are the most worrisome, as they won't compete with other nearby cells for atmospheric fuel like a line of storms does.

Wind fields from the surface to the jet stream level favor severe weather, including possible tornadoes.

Low level and mid-level moisture fields favor severe weather, including possible tornadoes.

Instability - the rising air, or fuel, that causes growing storms to get bigger - will be sufficient for strong to severe storms. The amount of instability, which may end up determining just how severe storms get, is still TBD. There are definitely indications that it could be sufficient to produce large, rotating storms. There are other solutions that favor a more tempered approach.

The lid on the atmosphere that we call a "cap" will, in all likelihood, erode by mid-day, meaning storms won't be stopped by a layer of warm air aloft.

In other words, all ingredients appear to be in place for severe weather, especially east of the Mississippi River. The pot is sweetened the further east you go from the river, but there's enough "atmospheric juice" in the metro to warrant preparation. Thus the latest update from the Storm Prediction Center (below) has shifted the Enhanced (category 3 of 5) risk to the far eastern metro and lowered the risk to Slight (category 2 of 5) for most of us. However, it doesn't matter if the line between the higher and lower risk areas is 30 miles west or 30 miles east of you! The threat is not gone, it's just being refined. And it could be raised again tomorrow morning if the parent storm slows just a tiny bit...

The bottom line, as of 1:30pm: 

  • Scattered morning showers will gradually strengthen into thunderstorms as the cold front and attendant severe weather ingredients draw closer by lunchtime and as temps head towards 70°. 
  • Some of these storms are likely to form into supercell storms capable of damaging wind and possibly tornadoes sometime after noon, mainly in west TN and MS where the airmass will be most favorable for severe weather. 
  • By mid-afternoon (say 3pm), the radar will likely be seeing scattered supercells, some of which may "cluster" into lines or mini-line segments. Any of these will be capable of severe weather. By rush hour, the storms should be east of the metro. 
  • There is a chance that we could see one last line of storms along the cold front around rush hour/early evening. Most models think the energy along the front will be waning and focused well ahead of it, but a line of storms with some strong wind gusts is possible along the front. 
  • By evening, it's all to our east and the threat is over.

Below you'll find safety tips that you should be reading and  putting into action. Not only do individuals need to review their safety plans, but if you are in charge of an office, retail establishment, school, or other large facility, know what you will do with those who rely on you for guidance if a warning is issued.

It's possible that some places may get no rain, while others nearby get a strong thunderstorm! That is the nature of this type of system. The forecast isn't a bust if you don't get a storm - just be grateful.

Finally, a word on warnings. I expect there will be severe thunderstorm and probably tornado warnings somewhere in the region, maybe nearby. You need multiple ways to get warnings. Please don't rely on sirens to know when to take shelter! If you're inside, you may not hear them. (In fact, you're not supposed to.) Think about where you'll be during the threat hours and how you'll get info.

We highly recommend adding StormWatch+ to our mobile app as one way of getting that warning alert. You can set it for your office, home, kid's school, or even have it follow you as you travel, and get the warnings that apply to your specific location. It is more precise than sirens and weather radios from a location perspective and will alert you well before the media source you are watching or listening to will mention your town or area. Set the types of warnings you want and you'll only get bothered if you want to be. Download links are at the bottom of this blog.

Plan ahead, stay safe, keep up with the latest information, and be prepared, not scared.

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!