Widespread accumulating snow along with a wintry mix of snow, sleet, and freezing rain at times, will spread across the area from late Friday morning through Saturday morning. Snow accumulations of 2-6 inches are likely, along with ice accumulations of up to 1/4 of an inch. Warnings or advisories are in effect for the whole area.
The majority of the ice is expected to occur south of HWY 20, especially near and south of HWY 30 where the highest accumulations are anticipated. This is what the EURO has for ice amounts.
The ice and mixed precipitation cuts into snow totals across the south. Even so snow will fall there before transitioning to a mix of freezing rain or even all rain in the far south. From I-80 south snow totals look to be more in the range of 2 to perhaps 4", with the 3-4" amounts more common near I-80.
Across the northern half (HWY 30 north) more of the precipitation falls as snow and here 4-6" amounts are likely. If the EURO is right a few spots could hit the 7" mark, especially NW of a line from Guttenburg to the SW of Waterloo where snow duration and ratios are higher.
Strong winds gusting up to 30 mph Friday afternoon and evening along with falling snow will reduce visibility and and cause treacherous travel conditions. The winds will diminish significantly for a time overnight. Then an arctic front hits toward daybreak and up come the winds again. Gusts of 45 mph along with snow showers will cause some blowing snow. In those areas that do not see a glaze from sleet or freezing rain, significant drifting along with low visibility is possible, particularly in the open country.
These are the peak 10 meter wind gusts during the day Saturday. All of the Midwest very gusty 40-50 mph
Another big issue Saturday will be a surge of arctic air that races across the region behind a cold front. Temperatures that start near or a bit above freezing will rapidly fall and by evening are expected to be about 30 degrees colder. Wind chills will plunge into the range of 10-20 below. By Sunday even worse with some of my area looking a chills of 30 below.
These are the projected lows Sunday...sub-zero most areas.
Notice the 24 hour drop in temperature from Saturday morning to Sunday morning. As much as 45 degrees in spots! Going the wrong way there.
Now, on to the latest snowfall forecasts off the models. These are not the official forecasts (strictly raw data) but it shows you the range that exists even at this late juncture. This is also the data used to make the forecasts and issue the warnings. I have also posted the Kuchera snow totals which are based in snow ratios that are greater than 10:1, which more than half of this event will achieve. The traditional ratios of 10:1 yield amounts that at 1 to 1.5" lower.
The 12K NAM
The 3K NAM
Last but not least, the official NWS forecast. I think it is too high in the south, especially from I-80 south. For example, that 5" total in Washington could easily be 2-3". Same for Burlington which could be a good 2" lower. That's not a certainty but as of late Thursday night that is the trend.
Snow is expected to develop by mid-day and spread rapidly northeast before making the transition to mixed precipitation from south to north. Most of the heavier snow will be over with by evening in the south and mid to late evening in the north.
Not much to do now but get a last look at final data in the morning and let it all unfold. I'll be in it. Roll weather...TS
LAST THING, STILL 2 SPOTS AVAILABLE FOR WEATHER SCHOOL. A GREAT BUNCH OF FOLKS COMING ALONG WITH SOME TERRIFIC CASE STUDIES YOU WILL ENJOY, ESPECIALLY 2011, THE YEAR OF THE TORNADO. AN IN DEPTH LOOK AT THE SUPER OUTBREAK OF APRIL 27TH IN ALABAMA AND THE JOPLIN TORNADO WHICH TOOK THE LIVES OF 160. YOU WANT TO LEARN WEATHER, YOU WANT TO BE HERE. GET THE DETAILS BELOW...
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WEATHER SCHOOL AGENDA:
WELCOME AND INTRODUCTION
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Simulated model driven forecast of a severe weather event/tornado outbreak
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How to forecast the rain snow line.
How to forecast snow totals from QPF
Determining totals from snow ratios.
What to look for at the surface and at upper levels (500 and 850mb)
Model bias and determining the storm track
Simulated model driven forecast of a significant Midwest winter storm
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Some final words of inspiration from the events headliners
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