Subj : HVYSNOW: Probabilistic He To : All From : Mike Powell Date : Tue Dec 16 2025 08:40:03 FOUS11 KWBC 160835 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 335 AM EST Tue Dec 16 2025 Valid 12Z Tue Dec 16 2025 - 12Z Fri Dec 19 2025 ....Cascades and Northern Rockies... Days 1-3... Snow levels on the WA Cascades rise from 4000ft to 5500ft through this evening under brief ridging until a sharp shortwave trough axis pushes across the Cascades by 12Z Wednesday on the head of a 170ft WNWly jet. This potent cold front brings a sharp drop in snow levels tonight, reaching 2000ft in WA and 4000ft in OR early Wednesday. The precip rates rapidly drop with the snow levels, but there should be impactful snow at pass levels including Snoqualmie. Low snow levels and moderate precip rates persist into Thursday before an intense push of moisture and height rises move in, particularly into Oregon. The latest WPC probabilities remain high for snowfall accumulations >8" (particularly for the Washington Cascades) each of days 1-3, with 72-hour probabilities through Thursday remaining high for accumulations >24". Moisture and windy conditions will progress eastward over the Northern Rockies today, followed more surges tonight and Thursday, with falling snow levels. The latest WPC probabilities for snowfall >8" are moderate to high (40-80%) for the highest elevations of central and northern ID and western MT Day 1, expanding south through western Wyoming with 40-80% probs on Day 2, and then an increase over similar areas of MD/ID/WY on Day 3 with to 50-90%. ....Northern Plains, Upper Midwest, Great Lakes... Day 3... Strong low pressure tracks eastward along the U.S./Canada border roughly from Montana to Lake Superior Wednesday through Thursday. A wintry mix is possible in the warm air advection ahead of the system over the Upper Midwest Wednesday night, but the main concern is the leading axis of heavy snow on the cold conveyor belt that connects to a wrap around deformation band with an intense pressure gradient and high wind/blizzard threat. Fairly fast forward motion and the likelihood that most of the leading bands should be north of the border limits the overall snowfall for the U.S. That said, Day 2.5 WPC probabilities for snowfall >4" remain moderate (40-70%) from northeast ND through far northern Minnesota, with 10-30% for >8" in the northern Arrowhead. In general, the wind field should be worst south of the new snow, but over the Dakotas and Minnesota which has a decent snowpack that could be driven into ground blizzard conditions. Please stay tuned on this wind-whipped forecast. The probability of significant icing is less than 10 percent. Jackson $$ --- SBBSecho 3.28-Linux * Origin: Capitol City Online (618:250/1) .