BBS: TELESC.NET.BR Assunto: HVYSNOW: Probabilistic Heavy Snow And Icing Discussion De: COD Weather Processor Data: Fri, 20 Mar 2026 07:01:16 +0000 ----------------------------------------------------------- FOUS11 KWBC 200701 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 301 AM EDT Fri Mar 20 2026 Valid 12Z Fri Mar 20 2026 - 12Z Mon Mar 23 2026 ...Upper Great Lakes to the Northeast... Days 1-3... The first in a series of clipper systems will produce periods of snow across northern New York and northern New England today. Low- level WAA ahead of the clipper will support periods of snow, even down to the valley floors in northern New England. However, snowfall rates and elevation will play critical roles in snowfall accumulations. Most notably, the Adirondacks, Green, and White Mountains are most favored for >1"/hr snowfall rates. WPC probabilities depict localized moderate probabilities (40-60%) for snowfall totals >4" with the peaks of these mountain ranges (including Mt. Washington) sporting low chances (10-30%) for snowfall accumulations as high as 6". Otherwise, most elevations below 1,000ft are likely to see anywhere from a coating to as much as 3". The WSSI does depict some Minor Impact potential, particularly in the Adirondacks and bordering the St. Lawrence River in NY's North Country. Snow will taper off across northern New England by Friday night. As this clipper exits to the east Saturday morning, the next clipper system is already making its way towards the Upper Great Lakes. There remains a decent amount of model spread in the amplitude and progression of this clipper, largely because it is essentially an unorganized cluster of sheared 500mb vort maxima tracking over the northern Great Lakes and Northeast. There will be sufficient upper-level ascent thanks to the left-exit region of a 500mb jet streak will accompany the clipper. There is also agreement on model guidance on healthy 850-700mb WAA via WSWrly flow that collides with sufficiently cold boundary layer temperatures over northern NY and the rest of northern New England. However, guidance is not yet in agreement on where the strongest 850-700mb FGEN takes shape, and as a result, disagree on the placement of the QPF axis to the north of the storm track. WPC Day 3 cluster analysis shows the departing trough over Nova Scotia and the depth of the primary 500mb shortwave trough over the Upper Midwest are the most sensitive factors in determining what this clipper ultimately produces, and because of the notably shorter wavelengths, confidence in where the heaviest snowfall will occur is not clear out to Day 3. So what we do know-- It is late March and elevation matters a ton. However you slice it across deterministic guidance or probabilistic guidance, the Adirondacks, Green, Whites, and Berkshires are most favored for accumulating snowfall. Even as far west as the MI U.P. and MN Arrowhead, snowfall totals approaching 4" are possible. WPC probabilities show low-to-moderate chances (30-50%) for snowfall totals >4" in the Hurons of the MI U.P. between Saturday night and through Sunday. Farther east, the >2,000ft elevations in the Adirondacks, Greens, and Whites sport moderate chances (40-60%) for snowfall totals >8" on Sunday. Below 1,000ft, probabilities for snowfall amounts >4" are low (10-30%) with most accumulations less than 4" expected at this time. WPC's WSSI-P depicts moderate chances (40-60%) for Minor Impacts in the MN Arrowhead to much of northern MI due to a combination of snow and ice (WPC probabilities show low-to-moderate chances, or 30-50%, for ice accumulations of at least one-hundreth of an inch) late Saturday into early Sunday. Minor probabilities are highest in northern New England where moderate probabilities (40-60%) are present throughout the northern Appalachians. In fact, some localized 40-50% probabilities for Moderate Impacts are shown across south-central and Downeast Maine. The chances for significant icing across the CONUS is less than 10 percent. Mullinax $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.28-Linux * Origin: Capitol City Online (1:2320/107) ----------------------------------------------------------- [Voltar]