Valentine’s Day update on the President’s Day winter storm

It’s Valentine’s Day morning, the sun is shining, it’s in the 50s, and I’m typing a blog on the upcoming winter storm. To my wife: I love you and thank you for your patience and understanding! (She’s awesome y’all…)  Now on to what you came here for!

Watches/Advisories

The NWS has issued a Winter Storm Watch for the entire area from 6pm Sunday to 6pm Monday. In addition, a Wind Chill Advisory is in effect Sunday morning for Tipton County in the metro and points north as wind chills drop below zero. The rest of the metro can expect single digit wind chills if you’re out early Sunday.

 NWS Watch/Warning/Advisory map valid 10:30am Saturday.

Saturday through Sunday afternoon

Get outside today and enjoy a perfectly glorious late winter day. Temps are well into the 50s with mostly sunny skies through mid-afternoon. An Arctic cold front, that sets the stage for the next 3 days, arrives late this afternoon. Clouds move in with it, as does a stiff north wind. Temperatures will fall quickly this evening, so if you have reservations, take a coat. It could drop 15 degrees while you’re eating.

Tonight, temps free-fall and wind continues gusting. You might have guessed by the nearby Wind Chill Advisory. We’ll hit 20 for a low Sunday morning with wind chills in the single digits for most. Tipton County could see sub-zero chills. Gross. The good news is it will be dry.

Sunday just looks raw. Some sun is possible but expect more clouds. Wind continues from the northeast at 10-15 mph with temps struggling to the freezing mark and dewpoints in the single digits – both are important numbers for Sunday night. Wind chills don’t get above 20-25. If a spit of sleet comes down Sunday afternoon, I wouldn’t be shocked.

Sunday night-Monday

This is where it gets messy. Low pressure tracks by to our south – a favorable track for winter weather. I know the use of the “I-40 corridor” term propagates myths, but in this case, it’s once again accurate. I use it because it’s a landmark that most people know the location of. (By the way, “corridor” doesn’t mean “one block north or south,” it means “the counties surrounding…”) The I-40 corridor appears like it could be a significant transition zone. During precipitation in the metro, it appears we’ll be dealing with sub-freezing air at the surface, a warm layer (above freezing – 33-40°) a few thousand feet up, cold air above that, and significant dry air at precipitation onset in the lowest few thousand feet (recall the importance of dewpoint mentioned above).

If the latest trends in the models are correct, the elevated warm layer will be most prominent along and south of the I-40 corridor. This would lend itself to a better chance of snow to the north (Tipton), freezing rain to the south (north MS), and a snow/sleet mix for Crittenden, Shelby, and Fayette Co. THIS COULD CHANGE.

GFS model precipitation valid at 6am Monday, which are forecast is most closely aligned with. Precipitation amounts are for midnight-6am and precip type is valid at 6am. The gold star is over Shelby County. Graphic courtesy WxBell.
Total liquid/melted precipitation through noon Monday from the morning GFS model. The heaviest precip will fall south of  I-40, but with the colder air north, the highest snow totals would be north of I-40. Graphic courtesy WxBell.

Taken together, I am much more concerned about accumulating ice than snow for the majority of the event. This is a change from yesterday. The other significant change is that it now appears that instead of the precip pushing well to our south Monday, it could hang around longer. I am most concerned about north MS in this regard.

Our prediction, for now…

The Winter Storm Watch was a good move by the NWS. I think we start off Sunday evening, after about 9pm, with a light icy mix – freezing rain and/or sleet. That should start the bridges to getting slippery. After midnight and through mid-morning Monday will be the period of heaviest precipitation. Snow/sleet to the north (roughly north of I-40), perhaps mostly sleet with periods of snow through the heart of the metro, and freezing rain/sleet across north MS. It’s fortunate that Monday is a federal holiday and most schools are out. The commute Monday morning could be treacherous. After mid-morning, the threat shifts to north MS where continuing freezing rain/sleet could last into the afternoon. Significant icing is possible in these areas. Temperatures likely won’t get above freezing.

As for precipitation totals, they are highly dependent on all of the above factors. I’d say 2-4″ of snow/sleet is realistic for Tipton and northern Crittenden Counties. Along the I-40 corridor (including West Memphis, Shelby and Fayette County), the most likely scenario is minor icing (up to 0.10″) by midnight, 1-3″ of sleet/snow overnight into early Monday with sleet more predominant than snow. For north MS (DeSoto, Marshall, Tunica, Tate Co.’s), sleet (mostly) and freezing rain are most likely scenario, with totals of 1-2″ mixed with a dusting of snow. THIS COULD CHANGE.

MWN’s forecast winter weather totals through Monday, as of 10:30am Saturday.
Snow probabilities are highest north of I-40, but 2″+ is possible across northern portions of the area.

Monday night-Tuesday

Models diverge even more Monday night, but if the latest trends continue, we could be looking at a wave along the front to our south pushing precip back north over the I-40 corridor. Again, ice or snow would occur in this scenario and additional accumulations would result. THIS IS HIGHLY UNCERTAIN and not in our forecast for now. The upper-level trough and reinforcing shot of cold air that pushes this all out arrives Tuesday. For now, we only have a slight chance of snow with its passage. Beyond Tuesday, it gets very cold. Expect teens for lows Wednesday and Thursday and 30s for highs.

Closing remarks

So far, we have not had good agreement from run to run with the models. New data is coming in as I type. If the low tracks further north across north Mississippi, more icing is possible in the metro. If it tracks further south, more snow would result. Even if things don’t change, amounts could vary significantly from one place to another in small areas. Winter weather forecasts are always tricky and highly variable.

I’ll remind you again – beware the share! If it doesn’t pass the eye test, or isn’t from a trusted source, don’t share it. Snow accumulation maps from models are the worst – most people don’t know that they take into account ice – multiply the ice amount by 10 and show it as snow (5″ snow is actually 0.5″ ice). That’s why I don’t post those maps in ice scenarios – they’re misleading.

We’ll keep you posted throughout the weekend. The latest is always on Twitter and Facebook. Follow us there. We also conducted a Google+/YouTube video Hangout (4pm Saturday). You can watch here: https://www.youtube.com/watch?v=cDLXQzVAzsQ

Stay warm and plan ahead in a reasonable manner.

Erik Proseus
MWN Meteorologist

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