Tuesday, February 24, 2015

UPDATED -- Our call on Wednesday's snow potential

UPDATE - 9:00pm Tuesday

The event looks to be pretty much on track, so please see the post below from this afternoon for details left out here. The models have come into decent agreement with the "outliers" a little more in line. Confidence is increasing in the forecast made below, which includes about an inch of snow for Memphis and Shelby County, more south, less north.

A few additional notes:

  1. Temperatures should recover into the 36-37° range during the morning hours. I wouldn't be surprised to see the precipitation onset as rain or a rain/snow mix for a couple of hours. Rain should arrive from the south by about noon in the I-40 corridor (earlier south). During this time, no accumulation
  2. That means that we should be all snow by 2pm or so with temps at 32-33°. The best time for snow that could accumulate will be 2-6pm for just about everybody. Flurries could last into the evening. Forecast accumulation remains as indicated in the map below (1" in the I-40 corridor).
  3. There will be "haves" and "have-not's" as a tight gradient in the snowfall accumulation is expected. As an EXAMPLE, we might see very little accumulation in northern Shelby County and 2-3" in southern DeSoto Co. (I'm not good enough to know where this gradient will set up.)
  4. Roads should be fine through mid-afternoon, but after 2pm, elevated roadways and exposed surfaces could start seeing accumulation and/or become slick, especially in north MS where snow could come down a little heavier. 
  5. The winners from tomorrow's snow will be south of the metro, somewhere in an area from Clarksdale to Oxford to Tupelo where 4-6" is expected.

We'll keep you updated tomorrow. I have meetings at work all day, but Mississippi State has cancelled classes, so the social media posts will continue unabated! Thanks #TeamMWN! Get our latest forecast on the MWN mobile apps or mobile web.

A Winter Storm Warning has been hoisted for all of north MS and a Winter Weather Advisory for southern west TN and east-central AR as yet another (I think this makes 5th in under two weeks? I've lost count...) winter storm moves through the Mid-South on Wednesday. This system once again moves along the southern stream - with the arctic jet stream to our south. In fact, of all the weather systems the past few weeks, this one seems to have the most "classic" setup for southern snow. In this case, it appears the I-40 corridor will be on the northern edge of this one!

Event setup

Low pressure will move along the Gulf coast with Arctic air in place on its north side. As moisture rides up and around the low into the southern U.S., it will fall into cold air which has seeped as far south as the I-20 corridor in MS and AL. North of that area, snow will fall. The greatest combination of moisture and dynamics, with sufficient cold air, will reside across southern AR into northern MS and AL, where the heaviest snow is expected.

Wednesday's surface map shows low pressure in the Gulf and snow (and some freezing rain) across a wide area of the interior southeast and Mid-Atlantic.

This map from NOAA shows the probabilities of an area receiving 2" of snow Wednesday. Note the best chance of significant snow will be across north MS and AL with decreasing chances north.

Details for the metro

Temperatures will rise into the mid 30s by noon Wednesday as precip approaches from the southwest. Precipitation will likely start as a rain/snow mix but quickly transition to all snow as temperatures fall back towards the low 30s after precip starts. The snow should taper off by early evening, ending as flurries during the evening hours. We are not expecting any ice accumulation with this event. Snowfall totals by Wednesday evening should look something like we have shown below.

Bottom line

What: About an inch of snow across far southern west TN to 2-3" across the southern metro (north MS)
When: Starting after 9am in Tunica/Tate Co and after 12pm in the I-40 corridor. Ending by 6-8pm.
Impacts: Roads coated with snow in north MS and possibly parts of the metro. Slick areas expected on elevated roadways in the I-40 corridor (including Memphis/Shelby County).
Bust potential: Moderate. One typically believable model (and its offshoots) have up to 4"+ along I-40. Almost everything else says about 1", or even a bit less, in the same area. For now, it's an outlier, but it makes the 1" forecast a little more plausible. On the other hand, the northern edge of the snow may not make it north to I-40, in which case we'll just root for spring!

After this system, another couple of cold days are expected, as you can see in our MWN Forecast, but then it appears we have a warm-up for the weekend and a RAIN event to start March! That's a good thing because it's much easier on me (and you!) and the roads and vehicles could use a good washing down. Plus north MS will be ready for the snow to disappear!

We'll keep you updated as the even unfolds.

Erik Proseus
MWN Meteorologist

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Kathy Hannings said...

Thanks Erik! Keep us posted!

Beverly said...

What's the connection with Mississippi State? You mentioned their canceling classes keeping the social media posts coming. I'm an alumnus and am curious.

Thanks for your great work. I appreciate having a no drama source for weather. I believe we were in band at Bartlett high school together many moons ago. Thanks again.

Meteorologist Erik Proseus said...

Hi Beverly,

We might have been, I seem to remember a Beverly! #TeamMWN includes 3 met interns that assist greatly with our social media posts. Since their classes are cancelled for the winter storm (they'll get more snow than us!) they will be able to keep info flowing to you all while I attend meetings. :-)