Subj : HVYSNOW: Probabilistic Heavy Snow And Icing Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Nov 26 2025 07:56:52 FOUS11 KWBC 260756 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 256 AM EST Wed Nov 26 2025 Valid 12Z Wed Nov 26 2025 - 12Z Sat Nov 29 2025 ....Significant winter storm with localized blizzard conditions=20 will continue to impact parts of the Upper Midwest/Great Lakes=20 through Wednesday as lake effect snow intensifies into Thanksgiving and Friday for the eastern Great Lakes... ....Confidence increasing on a second winter storm to affect the=20 Northern Plains Friday and the Midwest/Great Lakes Friday night=20 into Sunday... ....Key Messages for both systems are in effect and linked below... ....Upper Midwest/Great Lakes...=20 Days 1-3... Deepening area of low pressure over the U.P. of Michigan will=20 reach peak intensity today as it moves eastward into Canada.=20 Northerly flow on its northwest side will continue to wrap in=20 moisture all the way around from the Northeast US with additional=20 infusion from Lake Superior. Lake enhanced snow will transition to=20 lake effect snow over northern WI and the U.P. of Michigan this=20 afternoon/evening and continue through Thursday and into Friday as=20 upper troughing will be slow to move out. NW flow across Lake=20 Michigan will signal the start of lake effect snow into the Lower=20 Peninsula as well, starting overnight. Lastly, after the cold front clears through western NYS today, the lake machine will pick up=20 off of Lakes Erie and Ontario and continue through Friday and into=20 Saturday morning as additional height falls and PVA flow out of=20 Ontario across the Great Lakes. Winds will remain blustery to=20 strong at times (especially along lake shores), creating blowing=20 and drifting snow. The snow bands off of the eastern lakes will=20 start as single bands on SW to WSW flow before transitioning to=20 more multi-bands off at least Lake Erie as the flow veers to W then WNW and NW on Friday.=20 Snow will accumulate rapidly under the more intense lake bands=20 that remain over the same area. The most favored locations for this will be over the western to central U.P. of Michigan where the=20 multi- banded flow can still be quite intense. WPC probabilities=20 for an additional 8 inches of snow after 12Z today are at least 50% over northern WI, most of the U.P. of Michigan (except for areas=20 closer to Lake Michigan), northwest Lower Michigan, northeastern=20 Ohio, northwestern PA, southwestern NY, and around the Tug Hill=20 Plateau. Within these regions, there is a smaller but still=20 significant area of probabilities >50% for 18 inches of snow.=20 Isolated totals could exceed 30 inches, including what has already=20 fallen.=20 Travel will be difficult and perhaps impossible at times due to=20 snow- covered roads, blowing snow, and low visibility.=20 ....Northern Rockies...=20 Day 1... Pacific system moving through WA/OR this morning will weaken but=20 retain its moisture through the northern Rockies. Generally lighter snow is expected with moderate (30-60%) probabilities of at least=20 6 inches of snow for parts of the Absarokas and south central MT=20 ranges.=20 ....Cascades, Northern Rockies/Plains to the Corn Belt... Days 2-3... The next Pacific system will approach the coast late tonight with=20 some light WAA-driven snow to the WA Cascades. Bulk of the=20 precipitation comes in on Thursday with high snow levels around=20 5000ft (north) to 7000ft (south), limiting accumulations to the=20 higher mountains. However, the mid-level shortwave will maintain=20 its identity as it crosses the Divide and is joined by an incoming=20 shortwave out of western Canada Friday. This combined longwave=20 trough will then digs through the Rockies as lee-side surface=20 cyclogenesis occurs over eastern WY/CO Friday afternoon. High=20 pressure following from Canada will help support some lower-level=20 upslope-enhanced snow over western MT where snow could be heavy at=20 times over the Lewis Range around Glacier NP. WPC probabilities for at least 8 inches of snow are >50% over the northwestern MT=20 ranges. Over the valley floors, WPC probabilities for at least 4=20 inches of snow are generally >50% east of the Divide and including=20 the Absarokas and Bighorns. Farther east, north of the developing surface low, sfc-850=20 troughing and WAA will enhance snow as well over=20 northern/northeastern MT that will eventually stretch=20 eastward/southeastward onto the Northern Plains Friday afternoon.=20 The addition of Gulf moisture from the south will help the snow=20 quickly expand ESE from the Plains to the Corn Belt by Friday=20 evening and continue into early Saturday, driven by 850-700 WAA and surface convergence near/north of the warm front. By early=20 Saturday, the upper jet will sharpen along 100W and help to=20 continue to deepen the surface low over the central Plains. Light=20 to moderate snow will continue across the Corn Belt and become=20 heavier by the end of this forecast period (to continue into the=20 medium range). Through 12Z Saturday, WPC probabilities for at least 4 inches of snow are >30% from along the ND/SD border=20 southeastward through southwestern MN into Iowa. There (northern=20 Iowa), low chances (10-30%) of at least 6 inches of snow are shown=20 with more to come. The probability of significant ice across the CONUS is less than=20 10 percent. Fracasso ....Winter Storm Key Messages are in effect. Please see current Key Messages below... Ongoing storm: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!67bOiLvMYtS1-WWIqNX8W1wwqqjbRDhtwJhwysHg9qQnP= olnpwJlNXfvYYUApTN3uV-YUEATpPITnOvf32225fCX0SA$=20 Next system: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!67bOiLvMYtS1-WWIqNX8W1wwqqjbRDhtwJhwysHg9qQnP= olnpwJlNXfvYYUApTN3uV-YUEATpPITnOvf3222AR5asso$=20 $$ =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. 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