THE TROUBLE WITH SNOW...
Tuesday was chilly but otherwise a fine day with lots of sunshine and melting snow with highs in the mid to upper 30s. Readings would have easily reached the 40s if it weren't for that little issue of "snow cover". It reflects the suns energy and keeps readings a good 5-10 degrees cooler than they would be otherwise. Here's the hi-res satellite image vividly showing the snow pack thanks to nice clear skies. You can also see how the area from the the Quad Cities northeast has less snow on the ground being missed by two bands of heavier snows, one northwest and the other southeast.
What you can't see on the satellite is a cold front pressing southeast towards the northern Iowa border. By early Wednesday morning it will be in central Illinois bringing a fresh surge of colder air to the central Midwest. The front will be a dry one and sunshine will be back with us Wednesday but temperatures will be a good 5 degrees colder with highs in the low to mid 30s.
WHO NEEDS THE SHOVEL...
That leads us into Thursday and what will be our next chance of snow. It's far from a classic storm with minimal surface reflection. However, upper level energy will work on some moisture laid out along the stalled cold front in Missouri and Illinois. As the energy ripples along the stationary boundary it will generate a band of over-running snow to the north. The question is where?
Models through Tuesday remain in very poor agreement with the evolution of the system and where the snow will fall. The southward trend of Monday has continued Tuesday with the GFS and EURO painting a scenario where it appears most of the snow is confined to far southeast Iowa and WC Illinois. The EURO shows 1-2 inches near or south of HWY 34.
The GFS is even further south with the 1 inch line completely out of my area in Missouri and southern Illinois.
The differences grow far more significant when one considers the hi-resolution CAMs (convective allowing models) such as the 12K NAM, 3K NAM, and HRRR. They are massively different with 3 inch totals all the way to Dubuque and amounts as high as 7 or 8 inches in far southeastern Iowa. Here's what they indicate for accumulations.
The 12K NAM
The 3k NAM
The issue driving all this wild variance is dry air and the impact it has on the amount of moisture available to produce snow. Dry air really gives models fits and it seems the hi-res CAMS have difficulty resolving its depth during winter events, especially beyond 48 hours. I suspect they will get in step with the GFS and EURO at some point in the next 24 hours. I am currently in the camp of the EURO and its idea of the 1 inch line ending up well south of I-80 just clipping HWY 34 and areas south. Little if any snow is likely north of I-80. We'll have a definitive answer to how this plays out later Wednesday but to me it looks like a nothing burger for all but the far south. Even there it could end up a non event if the GFS verifies.
BIG CHILL TO START THE WEEKEND
What may end up being a bigger story than the snow is the cold that follows. A late season Arctic front is set to spear the region Friday afternoon and by Saturday morning lows are likely to be in the single digits. The GFS shows numbers that look like this. (Fortunately this was not 2 months ago or we could easily be down in the 10 to 15 below range with just a minimal snow cover).
As you can see, lows like the GFS depicts are 20-25 degrees below normal.
Unfortunately, there will be a good breeze and wind chills will end of 5 to 15 below zero Saturday morning. Hopefully we won't see them that low again for at least 9 months.
The high pressure center quickly moves east and return flow begins in earnest Saturday night as winds rev up from the southwest. Come Sunday the strong winds should have temperatures soaring into the 50s. A fast moving cold front cuts the warmth off Monday but by Wednesday and Thursday readings are on the way up again and highs in the 60s look likely. Here's the 5 day temperature departures on the EURO Sunday March 13th to Thursday March 18th. We're into that time of year where these big temperature swings become quite common. Hopefully we see more of the warm ones than cold!
Well, that's the long and short of it for now. It will be interesting to see how the Thursday snow situation pans out. I'm counting on the dry air to keep troubles at a minimum. Have a nice day and roll weather...TS
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