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   FOUS11 KWBC 032058   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   358 PM EST Sat Jan 3 2026   
      
   Valid 00Z Sun Jan 04 2026 - 00Z Wed Jan 07 2026   
      
      
   ...Northern Plains/Upper Midwest/Great Lakes/Interior Northeast...   
   Days 1-3...   
      
   Single band lake effect snow from Lake Ontario is forecast to sag   
   south as it eases in intensity into the evening the latest clipper   
   (this one perhaps the weakest this week) works its way east from   
   Michigan.   
      
   The next clipper of Pacific origin and crosses the northern Plains   
   early Sunday with widespread wintry precip breaking out around   
   midday near the MN/Dakotas border. Elevated moisture (PWs above   
   0.5" and the 90th climatological percentile), ascent driven by   
   height falls/PVA, intensifying left-exit jet level diffluence, and   
   strengthening WAA will accompany this feature. Rates quickly become   
   heavy over northern MN Sunday afternoon with a wintry mix on the   
   southern edge of the precip, but mostly snow, heavy at times with   
   >1"/hr rates (per the 12Z HREF) within banded structures. The   
   system will remain progressive, with a preference for QPF from the   
   wetter global models vs the CAMs which have a narrower precip   
   shield as often has on synoptically forced winter storms. The risk   
   for 6" through Sunday night has risen over northern MI with Day 1.5   
   PWPF now around 35% around both sides of the Straits of Mackinac.   
   Day 1.5 probs for >4" are over 30% from the Bayfield Peninsula of   
   WI across the U.P. and Upper L.P. along with far northern WI and   
   northern Door Co.   
      
   The strong warm nose could result in a corridor of impactful icing   
   over central MN (including the Twin Cities metro) and   
   western/central WI. WPC ice probabilities for >0.1" remain less   
   than 10%, but some icy roadways and hazardous travel are possible   
   Sunday afternoon and evening.   
      
   This wave tracks into New York Monday before weakening as it   
   continues to push into a ridge. Day 2 PWPF for >4" is limited to   
   around 30% for the Tug Hill Plateau where some lake enhancement can   
   be expected on westerly low level flow.   
      
   The next wave is southern stream, coming from CA and crossing   
   Nebraska/Iowa Monday night. The northern precip shield should bring   
   mainly light to moderate wintry mix over central MN and northern   
   WI into Tuesday. While 12Z guidance generally agrees on a narrow   
   swath of mainly freezing rain, there is still meridional   
   differences of central vs northern WI. Even the 12Z EC-AIFS shifted   
   north with its QPF axis (northern WI) from the 06Z run (which   
   favored north-central WI). So stay tuned on Tuesday icing threats   
   for the Upper Midwest.   
      
      
      
   ...Western U.S. Mountain Ranges...   
   Days 1-3...   
      
   A persistent longwave trough positioned off the Pacific Coast will   
   continued to shed impulses onshore at least through Monday night,   
   with each subsequent impulse spreading energy across most of the   
   Intermountain West.   
      
   The southern stream trough off CA with the northern stream end   
   shifting over the Northwest will maintain 850-500mb heights at or   
   below the 10th climatological percentile into Monday before finally   
   relaxing as the southern stream low likely closes off west of CA.   
   Pacific moisture flows inland on WAA ahead of the main trough axis,   
   but lowering height falls will allow lower snow levels to continue   
   shifting across the West.   
      
   Sierra Nevada...Days 1/2...   
      
   The current trough pushing into OR/northern CA this afternoon   
   shifts south across CA through Sunday with the heaviest precip on   
   the Sierra Nevada. Snow levels drop to around 6000ft tonight on   
   along the length of the Sierra Nevada and even drop to around   
   6500ft in the SoCal ranges Sunday.   
      
   The next wave is the northern stream that shifts into the OR/WA   
   coast Sunday and works its way down through central CA into Monday   
   night before focusing offshore. Snow levels on the Sierra Nevada   
   are lower with the next wave, generally around 5000ft, but drop to   
   around 4500ft Monday evening though snow rates will be less than   
   from the current wave.   
      
   Day 1 PWPF for >24" is 50-80% above 7000ft across the length of the   
   Sierra Nevada. Then for Day 2 the PWPF for additional >12" over   
   the length of the Sierra Nevada is 50-80% above about 6500ft.   
      
   With prolonged heavy snow for the Sierra and northern CA   
   mountains, totaling 4-6+ feet in some areas, and snow levels   
   below pass levels, travel will remain extremely challenging through   
   Monday. Localized extreme impacts are possible due to the   
   combination of heavy snow and low SLR.   
      
   Cascades...Days 1-3...   
   Repeating waves into the Pacific Northwest through Sunday evening   
   maintain moderate to heavy snow rates on the WA/OR Cascades with   
   snow levels remaining around 4000/5000ft tonight. As the northern   
   stream shortwave trough pushes through later Sunday, the snow   
   levels drop to 3000/4000ft before rates ease Sunday night. Day 1   
   PWPF for >8" is 50-80% in the higher Cascades with 40-70% for >6"   
   on Day 2.   
   There's a lull for the Cascades then through Monday night before   
   the next northern stream trough approaches Washington with snow   
   levels starting on the WA Cascades around 1200ft Tuesday morning,   
   rising to around 2500ft by Tuesday evening. Day 3 probs for >6" are   
   50-90% throughout the WA Cascades and Olympics above about 2500ft.   
      
      
   Northern to Central Rockies...   
   Days 1-3...   
      
   The current lull over the northern Rockies ends by this evening as   
   moisture streaming from CA flows across ID and western MT/WY   
   through tonight before drifting south to UT/southern WY Sunday   
   night. Snow levels begin around 6000ft at onset and drop to around   
   5000ft Sunday (3000-4000ft for northern ID/MT). Day 1 snow probs   
   for >8" are 50-80% in the central ID and western WY ranges as well   
   as around Glacier NP and west through northern ID. The focus shifts   
   south a bit for Day 2 where probs for >8" are 50-80% for the   
   Wasatch Front and Uinta as well as the Wind River again in WY while   
   central ID values are around 50%.   
      
   Day 3 probabilities are lower across the Rockies as rates decrease   
   under weakening flow. Probs for >6" are 50-80% in the Tetons and   
   40-60% in the Park Range of CO, the Wind Rivers, central ID up   
   through the Bitterroots.   
      
      
   Jackson   
      
      
   $$   
      
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