Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 313 PM EST Mon Dec 21 2020 Valid 00Z Tue Dec 22 2020 - 00Z Thu Dec 24 2020 ...Pacific storm system to cross the northern tier states and then reach the Great Lakes region by Wednesday evening... The strong Pacific storm system that is currently making its way inland across Washington state is expected to be the next big weather maker for the north-central U.S. through the middle of this week. This is expected to produce widespread snow for the northern Rockies and then the northern Plains, with several inches of accumulation likely for many areas. Given the strength of the surface low, strong and gusty winds are likely for portions of Montana and extending eastward across the Dakotas, and high wind watches are now in effect for eastern Montana. Secondary cyclogenesis is expected to evolve by Tuesday afternoon across South Dakota and this will become the dominant low going through midweek. A strong cold front will accompany this low pressure system, with a corridor of showers ahead of it from the Gulf Coast to Michigan on Wednesday, and potentially blizzard conditions across northern Minnesota and the eastern Dakotas as the surface low intensifies. Another low pressure system, albeit weaker, is forecast to move across the Great Lakes tonight, accompanied by light rain, mixed precipitation, and snow across portions of the Great Lakes region, upper Ohio Valley, the central Appalachians, and the Northeast. The highest snowfall totals are likely to be realized across the higher terrain of the central Appalachians, where 3 to 6 inches of snow will be possible. In terms of temperatures, readings are expected to be well above normal ahead of the front across the central and northern Plains on Tuesday, with highs well into the 40s and even low-mid 50s. Much colder temperatures will become reality by Wednesday across much of the West and across the Plains in the wake of the departing storm system, with highs below freezing from Nebraska and points northward. It will still be mild ahead of the front across the eastern third of the nation on Wednesday. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php