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   FOUS11 KWBC 071950   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   250 PM EST Wed Jan 7 2026   
      
   Valid 00Z Thu Jan 08 2026 - 00Z Sun Jan 11 2026   
      
      
   ...Pacific Northwest, Great Basin, Northern/Central Rockies...   
   Days 1-2...   
      
   An offshore, well-defined, mid-level shortwave, in tandem with a   
   ~100 kt upper level jet, will dig inland into the Pacific Northwest   
   this evening. As the northern stream portion of this amplifying   
   trough advances steadily eastward across the Intermountain West   
   into the Rockies, a southern stream wave is forecast to dig south   
   through the Great Basin into the Southwest tomorrow.   
      
   Heavy snow currently developing along the Cascades will continue   
   to spread south through this evening and persist along the range   
   into tomorrow. Pockets of moderate to heavy snow are also expected   
   to develop further east from the Blue Mountains into the northern   
   Rockies tonight. Rates should generally start to wane across the   
   entire region by late tomorrow as a building upstream ridge begins   
   to move inland. Areas of light to moderate snow will likely   
   continue into early Friday before drying out completely across most   
   areas by late in the day.   
      
   The heaviest amounts are expected to fall along the northern   
   Cascades, where snow levels are forecast to start the period below   
   2000 ft before dropping below 1000 ft tomorrow. WPC probabilities   
   indicate that accumulations greater than 8 inches are likely for   
   many parts of the Washington and northern Oregon Cascades above   
   2000 ft, including the major passes in northern Washington.   
      
   Further south, the digging southern wave will bring crashing snow   
   levels along with brief but potentially intense snow showers across   
   the Great Basin tonight. WPC PWPF indicates some of the northern   
   and central Nevada mountains may see amounts over 8 inches.   
      
      
   ...Four Corners into the High Plains...   
   Days 1-2...   
      
   A lead negatively-tilted shortwave will lift out of the southern   
   Four Corners tonight into Thursday, briefly interacting somewhat   
   with the wave digging southward from the Pacific Northwest. This   
   interaction will allow snow to first blossom across the high   
   valleys and mountains of the central and southern Rockies. As the   
   lead wave exits, the elongated vorticity lobe spinning southeast   
   from the Pacific Northwest will amplify into a deep longwave trough   
   as it approaches the Four Corners Thursday night. The resultant   
   jet streak downstream of this trough axis will deepen and pivot   
   northeast, reaching as high as 140 kts across the Southern Plains,   
   leaving favorable LFQ diffluence into the High Plains and Four   
   Corners. Where this jet streak overlaps with the most robust height   
   falls, lee cyclogenesis will likely result, likely in the   
   northeast plains of New Mexico as reflected by the latest guidance.   
      
   This low will move slowly Friday morning before elongating into   
   faster flow to the northeast by the end of the forecast period.   
   Before this occurs, a cold front will dig southward through the   
   High Plains, with the resulting wind field becoming more E/NE and   
   upsloping into the terrain of CO and NM. This will provide   
   additional ascent to the region, which will already be influenced   
   by favorable synoptic lift, suggesting a period of moderate to   
   heavy precipitation Thursday night through Friday afternoon. Most   
   of this will fall as snow, especially as the cold front sags south   
   and cools the column through favorable CAA. However, there is still   
   uncertainty into how much snow will fall, especially north of the   
   Palmer Divide, where a significant low-level moisture gradient is   
   expected to set up. The ECMWF and its ensemble members have been   
   much drier and farther north than the other camps in previous   
   cycles, but the latest guidance trends seem to be coming around on   
   that idea. Farther south, locations across southern CO and northern   
   NM have higher confidence in impactful snowfall, including the   
   higher elevations of the Palmer Divide and along the I-25 urban   
   corridor. In a normal winter, this event would be fairly run-of-   
   the-mill, but given how warm and dry it's been so far, this could   
   still end up being an impactful event for much of the region.   
      
   Moderate snow then quickly pulls northeast into KS/OK/TX by Friday   
   morning beneath the upper jet streak before ending by Friday   
   evening.   
      
   The latest WPC probabilities are high on Day 1 for at least 6   
   inches of snow across the UT/CO Rockies and into the high   
   elevations of the southern Rockies, including the White Mountains   
   of AZ. Late Day 1 into Day 2 as the surface low consolidates and   
   upslope flow ramps up, WPC probabilities show a moderate to high   
   risk (50-80% chance), for at least 6 inches of snow in the Front   
   Range, Palmer Divide, Raton Mesa, and Sangre de Cristos. Low to   
   moderate probabilities for >4 inches then extend into the High   
   Plains of southeast CO, southwest KS, far western OK, and far   
   northwest portions of the TX Panhandle.   
      
      
   ...Upper Midwest into the Great Lakes...   
   Day 3...   
      
   The deep positively tilted wave responsible for the snow across   
   the Four Corners (particularly southeast CO and northeast NM) will   
   eject northeastward into the central Plains late Friday into   
   Saturday. Meanwhile, another potent wave dropping southward out of   
   Canada is expected to rapidly close off over the northern Plains   
   and Upper Midwest. These two features are progged to phase together   
   later Saturday into Saturday night, forming a large, closed, mid-   
   level low over the region. This mid-level evolution, combined with   
   impressive jet dynamics from a powerful 250mb 150kt+ jet streak,   
   will support the rapid development and deepening of a surface   
   cyclone across the eastern Great Lakes. As the low develops, a   
   stream of rich Gulf moisture (with anomalies in excess of 250% of   
   normal) will be drawn northward and wrapped into the low pressure   
   system, likely forming a TROWAL and deformation axis across the   
   Upper Midwest and Great Lakes. The resulting isentropic ascent and   
   strengthening frontogenesis underneath this axis could support a   
   band (or bands) of heavy snowfall, with the potential for   
   significant accumulations. This is especially the case late Day 3   
   on Saturday and especially heading into the Day 4 period on Sunday.   
      
   The latest WPC probabilities show low to medium chances (20-50%)   
   for 24-hr snowfall >4" across eastern Wisconsin into northern   
   Michigan on Day 3, increasing to medium to high (50-80%) just   
   beyond the forecast period on Day 4. In fact, Day 4 probabilities   
   increase to over 50% for snowfall >6" across northern Michigan,   
   highlighting the potential for a more significant event. Given   
   these already notable probabilities, trends and future model   
   cycles will need to be monitored closely as we get closer.   
      
      
   Pereira/Miller/Weiss   
      
      
   $$   
      
   = = =   
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