Thursday, March 30, 2023

Another Friday night, another elevated severe weather threat...

One week ago - last Thursday - we were preparing for a Friday night special, a Moderate Risk zone that extended from Memphis into Mississippi. While Memphis escaped the worst of that system, many in north Mississippi cannot say the same. It's Thursday again, and like last week, another severe weather event is lining up for Friday night. This time it appears to be aiming a bit further north. While no two weather events are alike (and this one is a different scenario than last week), it does serve to remind us that we are now into the grips of "The Pollening" season, a.k.a. spring severe weather season. So let's chat about tomorrow night.

Overview of Friday's severe weather threat

The potential for severe weather tomorrow night has been monitored by the Storm Prediction Center and local meteorologists since Monday. As of today, the event has come into better focus and the more general global models have "handed off" the details to the higher resolution models that provide additional clarity. The risk level has accordingly increased to the point where the Memphis metro is now in a level 4 (of 5) Moderate Risk for severe weather. This means that severe weather somewhere in the area is likely, not necessarily in your neighborhood, but probably within the greater metro somewhere. The timeframe of most concern for big storms is 4pm-midnight Friday. A few thunderstorms of the more general variety, and more than likely some showers, are possible during the day. These may play a role in the ultimate outcome in the evening in fact.

Tornado threat

The Moderate Risk can be broken down by severe weather type to provide additional information on the probability of specific threats. Starting with the tornado threat, we have a 15% risk of tornadoes within 25 miles of any location in the metro. In addition, there is a 10% chance of a strong tornado (EF-2+) within 25 miles. This threat level drives the overall Moderate Risk for the event, as it is certainly elevated and worth preparing for... just in case. There will be plenty of strong wind and "spin" (or shear) in the atmosphere to support rotating storms if they can get going. However, as the Memphis NWS stated this morning in their discussion, "...this system is not a slam dunk. One potential area for failure is the presence and duration of Friday morning showers." As mentioned in the paragraph above, early-day precip could limit the storm fuel available later in the day, reducing the severe weather risk locally. This will bear watching, as it certainly contributed to a reduction in instability last Friday night north of the MS/TN state line.

Damaging wind threat

In addition to the tornado threat, the more likely scenario is a damaging wind event. As mentioned, there will be a LOT of wind energy with this system, from the surface up. Wind gusts outside of storms tomorrow afternoon and evening could easily top 40 mph and the winds aloft will also be screaming, contributing to storms moving at highway speeds once they form. The wind risk is 30%, which is the chance of 60 mph or higher wind gusts within 25 miles. In addition, there is a 10% risk of 75 or greater mph wind. I would expect that any storm will be capable of damaging wind, and it's likely that we will have a broken to solid line of storms move through in the evening hours, which could lead to widespread power outages and wind damage. If it's outside and not very secure, you risk losing it in the storms.

Hail threat

Most severe storms are capable of hail, and that risk also exists tomorrow night, though it is not as elevated of a risk as wind, at 15% chance within 25 miles. While large hail is not a major threat, it is also something to keep in mind. Rainfall for the event is also expected to be in the 1-2" range. Minor flash, urban, or stream flooding is possible during the evening hours. As always, you know to turn around and don't drown. Avoid the low-lying areas and roadways that are prone to holding water during and immediately after heavy rain.

Timing: 5pm-11pm Friday
Overall Threat: Moderate Risk (level 4 of 5)
Tornado Risk: 15% (10% chance of an EF-2+) (level 4 equivalent)
Wind Risk: 30% (10% chance of 75+ mph) (level 3 equivalent)
Hail Risk: 15% (level 2 equivalent)
Flooding Risk: 15% (Slight Risk - level 2 of 4)


Be prepared to execute your severe weather plans anytime after 5pm Friday. That includes being ready to use your safe place if necessary, having outdoor stuff secured, and having multiple ways of receiving weather warnings, including LOCAL TV/radio, NOAA Weather Radio, Wireless Emergency Alerts on your phone, and a reliable weather warning app such as StormWatch+ that is programmed ahead of time. Storms will be moving quickly so lead time could be reduced. 

Once the final line of storms moves through late in the evening, the severe weather risk ends. Fortunately it won't be too deep into the night when that occurs. We'll provide routine updates via our social media channels shown below throughout the event to keep you informed and safe!

Also, once this threat passes, know that there is another severe weather risk next Tuesday. We'll take them one at a time!

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook and Twitter for routine updates and the latest info!
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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Friday, March 24, 2023

Details on severe weather threat for Friday evening (March 24)

A severe weather  outbreak is expected late this afternoon and evening across the Lower Mississippi Valley. The Memphis metro is on the northern edge of where the strongest storms will be possible. This blog post will go into the details, and is effective as of 11:30am Friday. Note that the severe weather outlook graphic (embedded in the slide above) will be updated a couple more times today. This blog will likely not. I don't expect a lot of change, and even if the "lines" on the outlook move a bit. The threats and your response should really not change.

Atmospheric setup

The setup for this event is a developing low pressure system that will move southwest to northeast across Arkansas this afternoon and evening, dragging a cold front with it. Very strong wind fields will result in plenty of energy for this system to tap into. Turning of those winds with height will mean there will also be plenty of wind shear to result in strengthening and maintenance of storms once they develop. Instability, particularly once you get north into west TN, will be a factor to watch. It will not be as high as areas to our south where better chances of tornadoes exist. All of these factors will be maximized during the evening hours (6pm-midnight or so). Let's look at the individual storm threats.

Damaging wind

This will be our main threat tonight. There is a 30% chance of severe wind (roughly 55 mph or higher) within 25 miles of you location. There is also at least a 10% chance of 75 mph wind, shown by the black hatched area in the graphic below. We WILL get a squall line that will move through the metro. That is most likely in the 8-10pm timeframe for Memphis (earlier west, later east). High wind will be likely, some gusts could reach hurricane force.


Tornadoes will be a secondary threat. There are two areas these could develop. First, in supercells that form ahead of the line (after 6pm). These are most likely in MS and northern LA, but they'll move rapidly northeast, towards southwest TN. The threat for these is higher to our south, in the MS Delta, where instability is expected to be highest. Secondly, in the squall line itself, where tornadoes could "spin-up" within the line. There is more than enough shear for this to happen, and they could also be strong, but would not likely last very long. The chance of occurrence in 10% for west TN and northeast AR and 15% in the southern metro and further south. The entire area also has a 10% chance of an EF-2 or stronger tornado due to the strong wind shear expected.

Large Hail

Large hail is the least of the the three main threats. There is about a 10% chance of occurrence for all of us. Hail would be most likely in any supercells that form (again, mainly in north MS), thus there is also a 10% risk that hail could be 2" in diameter or larger in the more unstable air south of Memphis (black hatched area below).

Flash or urban flooding

There will be a LOT of water falling in a short period of time this evening. Atmospheric moisture levels are very high. So, flash flooding is possible, small creeks and streams will rise, and low-lying areas in the concrete jungle will likely become hazardous. The NWS has placed the northern half of the Mid-South in a moderate risk (3 of 4) for excessive rainfall that could lead to flash flooding, while the southern half is in a Slight Risk (2 of 4). Rainfall amounts will easily exceed an inch in a few hours, and could approach 2-3" north of I-40. Turn around, don't drown!

Limiting factors

We've had questions about whether the morning rain that dropped south to about the state line, along with a cooling north breeze and lower dewpoints, would limit the severe potential this evening. I say "probably not." 

Radar loop from 9:30am Friday, showing the rain-cooled air dropping south. The warm/moist air is poised just to the south of that area where rain fell and will move back north this afternoon.

The strong southerly wind and higher dewpoints are only a couple counties south of us. As the low forms and starts moving northeast, it will drag that warmer and more unstable air back to the north. By this evening, we'll likely be right back where we were forecast to be by the models, which leads to the setup described above. The northern areas of the metro and places north already had a slightly lower risk of severe storms, and especially supercell storms, than places to the south. That really doesn't change. So I think the current severe weather outlook from SPC (first image above) factors all of that in. It will definitely be something we watch though! If instability does not rise as expected in west TN, perhaps it will slightly limit the severe threat. Let's prepare for the worst and hope for the best though!


It's time to finalize your plans for this evening. Be where you know you can get to shelter if need be and be ready to act quickly. Storms will be fast-moving. Expect a line of storms with high wind between about 8-10pm. Make sure stuff outside is tied down. Know the counties around you and stay weather aware so you know when it is getting close. Finally, have multiple ways to get warning information, as any one could fail in severe weather. We recommend a NOAA Weather Radio, local TV outlets, Wireless Emergency Alerts on your smartphone, and a more customizable app option, such as our StormWatch+ app for Android and iOS. Of course, keep those devices charged today! Power outages are expected tonight.

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook and Twitter for routine updates and the latest info!
Complete MWN Forecast: on the mobile web or via the MWN mobile app
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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Friday, March 10, 2023

One more round of rain, then an early spring freeze for some

As we sit here on the tenth of March, most are tired of rain. Despite February actually ending a bit below average for precipitation, more than 1 of every 3 days of the month saw rain fall. January recorded more than double the usual rainfall for the month. And for the first third of March, rainfall has reached 75% of the usual amount for the entire month... and the next system this weekend could push us to near 100% of normal before the month is half over! 

We've also gotten used to above average temperatures. December-February (meteorological winter) was the 7th warmest on record, and not a single day in March has been below average, though the past couple have been right at it. Trailing the rain this weekend, a cold snap is also coming. Let's dive in... first a reminder that you lose an hour Sunday morning, but at least the sun remains up past 7pm next week! 

First, more rain, and a few storms

Today is a nice break from the rain the past few days, but it is temporary (so enjoy it!). Temperatures are cool in the 50s, and will be that way tomorrow too. But at least we do have some sunshine between the clouds today. Clouds return early tomorrow and we'll start the day in the upper 30s - the coolest morning in about three weeks! Rain showers return ahead of an approaching cold front by Saturday afternoon. Not a washout, but scattered throughout the afternoon with an isolated thunderstorm also possible. 

The Friday morning run of the high-resolution NAM model forecasts rain to begin Saturday afternoon and continue through mid-morning Sunday, at least. A few storms are also likely in the pre-dawn hours Sunday.  (WeatherBell)

By Saturday night, rain and thunderstorm chances quickly ramp up with the front due in early Sunday morning. A few storms ahead of the front early Sunday morning (pre-dawn, but after midnight) could sport gusty wind and hail, mainly in the Mississippi Delta. The city of Memphis is currently in a level 1 (Marginal) severe weather risk, but a level 2 (Slight) risk is posted just south of the city along the Mississippi River.

Overnight rain transitions to scattered showers Sunday morning into the early afternoon, mainly in north MS. Forecast rainfall is around an inch, a bit more in north MS. Clouds stick around in the afternoon before clearing out late in the day or evening. 

After the rain, prep for a potential late-season freeze

Behind Sunday's front, cold high pressure begins to build into the central and eastern U.S. for the coming week. We'll be on the southern fringes of this Canadian airmass, but it is cold enough that we'll feel its effects for multiple days! 

The Friday morning European model forecast for mid-day Tuesday shows cold high pressure sprawled across the Midwest with an influence all the way to the Gulf Coast. An active pattern continues on the west coast while a Nor'Easter brings snow to the major metros in the Northeast. (WeatherBell)

Sunshine will be abundant to start the week but look for highs to only reach around 50 degrees Monday and Tuesday. Low temperatures Monday through Wednesday mornings will be in the 30s throughout the metro. The potential for damage to early season foliage will be highest Tuesday morning when skies are clear and wind dies down, allowing temperatures to drop below freezing for a few hours outside the city (especially in west TN and northeast AR), and possibly touch freezing inside the city limits. Widespread frost is likely in all but the warmest locations. Wednesday morning could see another freeze mainly east of the city in west TN, but likely frost for all once again. 

The European model ensemble shows the probability of below freezing temperatures on Tuesday morning - near certain for areas surrounding Memphis in all directions except south, and not to be discounted in Memphis proper. (WeatherBell)

As the Canadian high shifts east, temperatures will warm on southerly wind Wednesday afternoon, back to near 60. Of course, with a few days of dry weather, you have to know more rain is not far off! At this time, we're monitoring Thursday night into St. Patrick's Day for the next cold front and rainmaker. Behind this one? NOAA's Climate Prediction Center believes there remains a decent chance of below average temperatures. Perhaps March will be the counterweight to the warmth of the past few months?

The temperature outlook for March 18-24, following the cold front late next week. It is fairly rare to see below average temperatures predicted for nearly all of the CONUS. (Not shown, precipitation is also favored to be slightly above average locally.) (CPC/Pivotal Weather)

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, March 7, 2023

February 2023 Climate Report for Memphis, TN

February Climate Recap

Temperatures for the month of February in Memphis averaged over 5 degrees above normal.  The month started out cold with highs in the low 30's due to freezing rain on the 1st, but by the 5th highs were back to the 60's.  Highs climbed to the low 70's on the 7th, but a cold front moving in on the 9th dropped high temperatures back to the 50's for the next few days.  A warmup back to the 70's happened on the 15th and 16th, before another cold front dropped the low temperature below freezing on the 17th and 18th.  Temperatures quickly rebounded to the upper 70's on the 22nd and 23rd, before yet another cold front caused the high on the 24th to occur at midnight, only reaching 47 the following day.  Highs climbed to the upper 70's to end the month.

February's precipitation was just below average, almost 1 inch below normal - with 11 days in the month receiving precipitation.  The 1st-14th had less than 1" of precipitation, with nearly 1/4 registering as freezing rain on the 1st and 2nd.  The 15th thru the 28th saw over 3" of rain, with the heaviest falling on the 16th (1.02" at the airport and 1.51" at MWN in Bartlett) as thunderstorms rolled thru the metro. The heavy rain was accompanied by strong to severe thunderstorms on the evening of the 15th, producing multiple Severe Thunderstorm Warnings, hail reports of up to ping pong ball size, and a few wind damage reports. There was also one Tornado Warning for a severe cell that traveled from near Sardis Lake into Marshall County. 

Memphis International Airport, Memphis, TN

Average temperature: 51.5 degrees (5.4 degrees above average) 
Average high temperature: 60.9 degrees (5.4 degrees below average) 
Average low temperature: 42.2 degrees (5.5 degrees above average) 
Warmest temperature: 78 degrees (23rd) 
Coolest temperature: 25 degrees (1st) 
Heating Degrees Days: 381 (151 below average)
Cooling Degree Days: 9 (7 above average) 
Records set or tied: Daily high maximum (77 degrees on 22nd)
Comments: For the period of meteorological winter (December-February), temperatures averaged 48.2 degrees,7th warmest on record.

Monthly total: 3.84" (0.71" below average) 
Days with measurable precipitation: 11 (1.1 days above average) 
Wettest 24-hour period: 1.23" (15th-16th) 
Snowfall: None
Records set or tied: None
Comments: 0.24" of freezing rain fell on the 1st/2nd. For the period of meteorological winter (December-February), a total of 18.92" of precipitation fell, ranking 22nd wettest in over 150 years of records.

Peak wind: Southwest/46 mph (22nd) 
Average wind: 9.2 mph 
Average relative humidity: 72%
Average sky cover: 63%

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

Cirrus Weather Solutions /, Bartlett, TN

Average temperature: 50.6 degrees 
Average high temperature: 61.0 degrees 
Average low temperature: 40.2 degrees 
Warmest temperature: 80.0 degrees (28th) 
Coolest temperature: 22.5 degrees (4th) 
Comments: None 

Monthly total: 4.05" (automated rain gauge), 3.95" (manual CoCoRaHS rain gauge) 
Days with measurable precipitation: 10
Wettest date: 1.51" (16th) (via automated gauge) 
Snowfall: None
Comments: 0.21" of freezing rain fell on the 1st/2nd

Peak wind: West/42 mph (27th)
Average relative humidity: 74% 
Average barometric pressure: 30.09 in. Hg
Comments: None

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

MWN Forecast Accuracy

MWN average temperature error: 2.36 degrees 
MWN forecast temperatures within 2 degrees of actual: 62% 
MWN average dewpoint error: 3.12 degrees 
MWN forecast dewpoints within 2 degrees of actual: 50% 

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

Richard Hoseney
MWN Meteorologist

Follow MWN on Facebook and Twitter for routine updates and the latest info!
Complete MWN Forecast: on the mobile web or via the MWN mobile app
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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder