Cold, squally end to the week in the upper Midwest and Lakes

[PurdueWx80]

The Plains and Upper Midwest are about to go well below normal for an extended period the way it looks (a continuation of below normal for some places since the superfront came through on Monday). Light snow should spread south-southeastwards from northern MN towards Chicago and then east from there towards the mid-Atlantic on Thursday. The snow will mostly be driven by strong warm air advection over top the very cold air at the surface, so I believe snowfall rates will be a bit higher than average (perhaps 15 or even 20:1 in places), which means parts of MN and WI could see 2-4" with local amounts to 5 in lake-enhanced bands. Parts of the Lakes could see some healthy lake effect this weekend as very cold pockets of air traverse the relatively warmer lakes. Synoptic moisture may limit lake effect snow at first, but moisture from the ATLANTIC will cross around the backside of the polar vortex (from the strong storm that just came up the east coast) acting to enhance precipitation once it gets there. There could be some very squally weather in the northern Plains and Lakes as mini vort maxes dig into the mean trough, particularly on Friday and perhaps into the entire weekend, with extremely cold air above the March-sun warmed surface layer (enhancing lapse rates). When the sun peaks out it may melt snow on concrete/paved surfaces, but snow should add up given that surface temperatures will struggle into the teens and 20s.

With the polar vortex splitting a bit and a piece backing west towards the northern Plains and even into the Northwest, it may be a very cold period in much of the northern tier of the country through next week. Even the central Plains and midwest should get in on the below normal temps for a bit. Jer's ideas about more zonal flow are right on as well...looks like some Gulf moisture should eventually get involved, and a big storm is in the works later next week.

[PurdueWx80]

Meanwhile, to the west of today's "Manitoba Mauler" (which has produced 1 to 3", which a few 4" amts recorded so far) winds are gusting close to 65 mph in places as very dry air is mixed down to the surface. Tomorrow's system looks very impressive, and may even cause a few claps of thunder (the SPC even has a general storm risk in parts of the Midwest) as very cold air in the low/mid/upper levels overrides the warmer boundary layer. I wouldn't be surprised to hear numerous reports of graupel and small hail tomorrow afternoon somewhere in the upper or mid Mississippi Valley.

[PurdueWx80]

Very heavy convective snows have broken out in parts of MN, WI and MI as I mentioned would happen a few days ago. Cloud-to-ground lightning has recently been reported near Eau Claire, WI and snow rates are likely up to 2" per hour in some of these heavy bands. The actual lightning appears to be right along the strong arctic front, as Eau Claire reported gusts over 30mph within this band with a windshift just behind it. AMAZING! This should continue into the evening, with a few locations seeing up to 6" of snow, especially in MI where the Lake will add some mesoscale moisture into the mix!! I love thundersnow!!