Subj : HVYSNOW: Probabilistic He To : All From : Mike Powell Date : Sun Dec 14 2025 08:29:30 FOUS11 KWBC 140851 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 351 AM EST Sun Dec 14 2025 Valid 12Z Sun Dec 14 2025 - 12Z Wed Dec 17 2025 ....Mid-Atlantic through Southern New England... Day 1... Positive tilt to the trough rounding the mid-level low centered over Lake Huron this morning will continue to dig southeast as it shifts across the Northeast through this evening. Surface low development is underway along the Delmarva coast with rapid strengthening today as it shifts northeast out to sea. Decent fgen driven snow banding with rates around 1"/hr will continue to shift south over the Mid-Atlantic as they begin to wrap around the sfc low. These bands have reached the southeast Mass Cape and Islands where they will pivot through the day and become ocean/bay enhanced this evening as the low begins to pull away. This should result in around 0.75" QPF which will be all snow with totals tempered a bit from still warm waters. Day 1 PWPF for >4" after 12Z is generally limited to Cape Cod and the Islands with probabilities of 40-70%. Day 1 PWPF for an additional 2" after 12Z are generally 40-70% from Rhode Island across Long Island, down the Jersey shore through lower Delaware with 30% probs into the Northern Neck of VA and the southern Delmarva. Upslope snow rates west of the Allegheny Front dwindle through sunrise with Day 1 PWPF for an additional 2" after 12Z are generally 30-70% for elevations in central WV above 2500ft. ....Great Lakes... Days 1-2... Aforementioned low pressure system ejecting southeast from Lake Huron today will activate Nly flow snow belts into the east-central U.P. where Day 1 PWPF for >4" are 40-70%. WNWly flow over the eastern Great Lakes this morning will veer NNWly by this evening with pivoting bands from Erie and Ontario. Day 1 PWPF for >4" are 30% inland from Erie, PA and 50-80% just north of Syracuse. Lull in LES expected tonight as low level ridging shifts east over the Lakes. But a shortwave clipper approaches from the northwest late tonight and crosses Monday with a decent, but transient swath of lake enhanced snow over the northern Lakes before prompting singl-band LES over the Eastern Great Lakes Monday night with the DGZ centered on 850mb. Day 2 PWPF for >2" is 40-70% from the Keweenaw Peninsula through the eastern U.P. and Tip of the Mitt while there are 30% probs for >6" south of Buffalo and 60-80% for the Tug Hill Plateau. A return of ridging cuts off the eastern LES early Tuesday. ....Cascades and Northern Rockies... Days 2-3... Potent atmospheric river arrives early Monday morning to western WA/OR with snow levels skyrocketing up to 9000ft over the Cascades. A shortwave trough passage over WA late Monday quickly brings snow levels on the North Cascades back down to 5000ft by the evening, reaching 4000ft overnight. Lower precip rates are expected behind the trough passage, with Day 2 PWPF for >6" limited to the higher WA Cascades. However, snow levels rise only a little Tuesday ahead of the next wave that arrives Wednesday night. Precip rates increase as snow levels remains around 4500 to 6000ft on the WA/OR Cascades. Day 3 PWPF for >8" is over 80% across the higher WA Cascades. Moisture surges inland TUesday night with snow levels of 5000 to 6000ft over the ID/MT ranges where Day 3 PWPF for >6" are 40-80%. The probability of significant icing is less than 10 percent. Jackson ....Extreme Cold Key Messages are in effect and linked below... https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png $$ --- SBBSecho 3.28-Linux * Origin: ILink: CCO - capitolcityonline.net (454:3/105) .