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   FOUS11 KWBC 100716   
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   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   216 AM EST Tue Feb 10 2026   
      
   Valid 12Z Tue Feb 10 2026 - 12Z Fri Feb 13 2026   
      
      
   ...Sierra Nevada to the Central Rockies...   
   Days 1-3...   
      
   Mid-level low over the Pacific will gradually pivot eastward   
   towards northern CA through Wednesday, lingering across the state   
   as it slowly fills. Immediately downstream of this feature, a   
   subtropical jet streak will intensify, especially late this evening   
   into Wednesday morning, reaching towards 150 kts as it pivots over   
   central CA. This upper jet will provide favorable LFQ diffluence   
   overlapping the most significant height falls for pronounced   
   synoptic ascent, while additionally transporting Pacific moisture   
   onshore CA before spreading into the Great Basin and Central   
   Rockies. The evolution of this synoptic pattern suggests that SW   
   flow downstream of the primary trough axis will support prolonged   
   moisture advection, which is reflected by IVT probabilities from   
   both the GEFS and ECENS exceeding 90% for 250 kg/m/s for around 24   
   today into Wednesday. This moisture will be wrung out by the   
   significant deep layer ascent (aided by upslope flow especially   
   across the Sierra) to produce heavy snowfall above generally   
   6000-7000 ft, with the most intense snowfall rates (2+"/hr   
   according to the WPC prototype snowband tool) occurring across the   
   Sierra tonight into Wednesday. WPC probabilities across the Sierra   
   are high (>70%, 2-day totals) for more than 12 inches in the high   
   SIerra, but widespread 8+ inches is likely (>70%) for the breadth   
   of the Sierra and into parts of the northern California terrain.   
      
   As the system continues eastward and the upper jet strengthens   
   over the Great Basin to central Rockies, moisture will continue to   
   funnel from the sub-tropics into the Four Corners region on   
   southwesterly flow. Snow levels will waver around 6000-7000ft with   
   modest amounts expected in an area that has seen very little snow   
   this season. WPC probabilities for at least 8 inches of snow are   
   >50% above 7000ft or so in UT and 8000ft in WY, highest over the   
   Uintas and Wind Rivers/Tetons. Snow will linger longest over the   
   CO Rockies through Thursday as the moisture plume stalls there as a   
   result of a second shortwave trailing the lead system, maintaining   
   SW flow through the end of this period. WPC probabilities for at   
   least 8 inches are high for 8+ inches across much of the highest   
   terrain of the Colorado Rockies, with a local maximum above 12   
   inches expected across the Park Range.   
      
      
   ...Eastern Great Lakes and Northeast...   
   Days 1-2...   
      
   A clipper-type low will dig southeast from Ontario through New   
   England today, exiting into the Gulf of Maine late tonight. This   
   clipper will be driven primarily by a closed, but weakening, mid-   
   level low tracking atop it, with elongated vorticity to its south   
   producing additional ascent. As this upper low shifts off New   
   England, it will interact with an occlusion well off the coast,   
   helping to rapidly deepen a surface low over the Atlantic. This   
   synoptic evolution will result in 3 areas of moderate to heavy   
   snowfall:   
      
   1) Pronounced warm-air-advection (WAA) developing south of the   
   clipper will surge northeast atop a warm front across the Mid-   
   Atlantic and into the Northeast. This will create an expanding   
   shield of precipitation, and although some light mixed   
   rain/snow/freezing rain is expected over the northern Mid-Atlantic,   
   much of this precipitation should fall as snow across New England   
   and Upstate New York. The snow that occurs will likely be heavy at   
   times within a WAA band, likely exceeding 1"/hr (60-90% chance),   
   with the short temporal duration limiting the total snowfall.   
   Still, impactful snow is likely this evening and tonight spreading   
   from west to east.   
      
   2) Post-clipper cold-air-advection (CAA) will become impressive in   
   the wake of the low. This will create increasing lake effect snow   
   (LES) despite significant ice cover now over the Great Lakes, as   
   well as intensifying upslope snow into the terrain of the   
   Adirondacks and Greens. Very dry air beneath the subsidence   
   inversion will impinge into the DGZ from above during this time, so   
   that will act to limit snowfall intensity within the upslope   
   regime, but additional accumulations are likely. LES will also be   
   somewhat modest, and focused east of Lake Ontario into the Tug Hill   
   and then southeast towards the Finger Lakes region, as well as far   
   SW NY east of Lake Erie.   
      
   WPC probabilities for 2+ inches of snow are high (>70%) for much   
   of northern Upstate NY, as well as central/northern New England.   
   However, the more substantial snowfall is likely in the higher   
   elevations where WPC probabilities suggest a high risk (>70%) for   
   at least 4 inches in the Adirondacks, Greens, and Whites, with   
   locally as much as 8 inches possible. For the LES areas, WPC   
   probabilities are moderate (50-70%) for least 4 inches. For the   
   freezing rain, a swath of moderate probabilities (>50%) exists for   
   0.01+" of ice from the Finger Lakes through the Poconos and into   
   southern New England and Long Island. Although amounts should be   
   less than 0.1"   
      
   3) Finally, as the surface low deepens rapidly offshore and near   
   Nova Scotia Wednesday, the guidance continues to suggest a   
   lingering inverted trough will pivot near the coast of Maine. Where   
   this occurs, additional ascent will be locally impressive, leading   
   to the potential for several inches of additional snowfall. These   
   inverted troughs can sometimes lead to sneaky-heavy snowfall   
   accumulations, so while WPC probabilities are moderate for 6+   
   inches (50-70%), locally higher totals are possible as reflected by   
   significant spread in the WSE plumes along the coast of Maine.   
      
   Weiss   
      
      
   $$   
      
   = = =   
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