Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EST Thu Jan 18 2024 Valid 12Z Thu Jan 18 2024 - 12Z Sat Jan 20 2024 ...Heavy mountain snows for the Northwest/Rockies; additional ice over the Columbia Basin... ...Bands of heavy lake-effect snow continue for the Great Lakes with hazardous snow across the Midwest and Mid-Atlantic by Friday... ...Another Arctic blast expected late this week... Yet another swath of freezing rain and heavy mountain snowfall will overtake portions of the Pacific Northwest as another storm system skirts the coastline with stubborn cold air in place. The next round of heavy freezing rain is forecast to develop later today and persist into Friday over portions of the Cascades and Lower Columbia Basin, where upwards of a quarter to half inch of ice is possible through Saturday morning with this next wave. Accordingly, moderate to major potential winter storm impacts are expected, including dangerous travel and power outages. This could exasperate earlier damage from the significant icing over the last week. Around the same time freezing rain creeps into the lower elevations, another round of heavy mountain snowfall can also be expected higher up in the Cascades, with snowfall rates exceeding 1" an hour leading to snowfall totals of 1-3 feet Saturday. Mountain passes (particularly in the Cascades), will likely see a messy mix of heavy snow, rain, and freezing rain through Friday which will make travel especially dangerous in these areas. Along the immediate coastline in northwest Oregon and Washington, precipitation will remain as rain, which could lead to localized flash flooding as soils in the area are very saturated. By tomorrow, the excessive rainfall threat will shift southward into northern California with additional isolated flash flooding possible. Lake effect snow bands will continue downwind of the Great Lakes, particularly Lakes Erie and Ontario where an additional foot is possible through tomorrow morning. The focus for winter precipitation will shift westward however as the next winter weather maker will spin up today over the Mid-Mississippi Valley, with snow likely to spread from the north-central Plains to the Midwest/Lower Great Lakes and the Mid-Atlantic by Friday. Freezing rain is also a concern over this afternoon portions of the Tennessee Valley today with shallow Arctic air on the heels of this frontal system. Winter Storm Watches are also in effect across portions of the central Appalachians in advance of the heavy snow and gusty winds expected to arrive early Friday. Although in general significant accumulations are not expected, the snow and freezing rain could still create hazardous driving conditions, and a stretch of Winter Weather Advisories are noted over the Mid-Mississippi Valley eastward into the Mid-Atlantic. The Southern Plains and Gulf Coast can enjoy a short lived break from the cold on today as temperatures rebound into the 60s and 70s south and west of the ArkLaTex. This will be short lived however as another frigid Arctic airmass will once again overspread the eastern half of the Lower 48 through this weekend. Although not as extreme as the first wave early this week, daytime highs on Friday across the Plains into the Mississippi Valley could be 20-30 degrees below normal with a few low temperature records possible, aside from the wind making it feel even colder. Asherman/Santorelli Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php