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   FOUS11 KWBC 162023   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   323 PM EST Mon Feb 16 2026   
      
   Valid 00Z Tue Feb 17 2026 - 00Z Fri Feb 20 2026   
      
      
   ...Pacific & Interior Northwest...   
   Days 1-3...   
      
   An active period of winter weather expected this week across the   
   Pacific and Interior Northwest as repeated shortwaves dive through a   
   longwave trough entrenched across the region.   
      
   The period begins with increasing southerly mid-level flow downstream   
   of the lead shortwave which will be digging along the British Columbia   
   coast. This shortwave will continue to expand southward, with the trough   
   axis finally moving onshore WA/OR Tuesday night. This impulse will continue   
   to track eastward into the Great Basin and Northern Rockies on Wednesday,   
   with a secondary shortwave moving onshore immediately in its wake. This   
   mid-level evolution will push 500mb heights down below the 0.5 climatological   
   percentile tonight through Wednesday morning, leading to snow levels   
   for which the NBM suggests will fall below 1000 ft as far as northern   
   CA, with the 10th percentile (which may be a better proxy due to steep   
   lapse rates beneath the cold core trough aloft) dropping to the surface   
   across most of the area. While the heaviest precipitation is expected   
   within surges of WAA D1 and D3, this could result in the first light   
   snowfall accumulations down to the valley floors and lowlands of WA   
   and OR.   
      
   For D1, the heaviest precipitation is expected across OR and into   
   ID, as well as the southern WA Cascades. Here, the IVT will maximize   
   within the broad WAA plume and within broad mid-level divergence/height   
   falls downstream of the lead shortwave trough. Additionally, S/SW flow   
   will impinge favorably into the Cascades for upslope enhancement, with   
   snow levels falling well below pass levels, including potentially even   
   to I-5 through the Willamette Valley. The heaviest snow is expected above   
   2,000 ft, where WPC probabilities are high (>70%) D1 and low (30%) D2   
   for 4+ inches each day, leading to locally more than 12 inches of snowfall   
   through 00Z/Thursday. This will create hazardous travel, especially   
   across Santiam, Willamette, and Siskiyou Passes. Light snow accumulations   
   are expected even onto the Coastal terrain of WA/OR where there exists   
   a 30-50% chance of at least 2 inches.   
      
   A brief break in precipitation is expected much of D2 before the second   
   shortwave approaches with renewed ascent and moisture spreading into   
   the area. A period of renewed snow is likely, especially across the   
   WA/OR Cascades and surrounding lowlands as snow levels again fall below   
   500 ft. WPC probabilities for at least 1 inch of snow reach 30% even   
   into the Portland, OR metro area and surrounding Seattle, WA, with   
   an additional 6+ inches of snowfall likely (70% chance) across the   
   southern WA and most of the OR Cascades.   
      
      
   ...California...   
   Days 1-3...   
      
   ...Multiple days of heavy and disruptive snowfall to affect the   
   California mountain ranges this week...   
      
   A series of potent Pacific storm systems are working together to   
   direct copious amounts of moisture at the mountain ranges of the   
   "Golden State". While heavy snow has been unfolding in the   
   Siskiyou, Shasta, Trinity, and Salmon mountains of northern CA   
   since Sunday, very heavy snowfall has been ongoing today along the   
   Sierra Nevada with snow levels currently between 5,000 and   
   6,000ft. Tonight, the snow levels will drop precipitously to then   
   falling to as low as 2,500ft by Tuesday morning in the northern   
   Sierra, and 4,000 ft for the southern Sierra Nevada. Snowfall rates   
   between 1-2"/hr will be common with some instances of >3"/hr   
   snowfall rates in the central and southern Sierra Nevada. Heavy   
   snow will continue through tonight in the Transverse Ranges above   
   6,000ft. This first disturbance is the result of a strong shortwave   
   trough that will be pivoting east into California through this   
   evening. By Tuesday morning that upper level energy will be well   
   into the Intermountain west, through upsloping and a surface trough   
   will keep higher elevation snow going through tonight, albeit with   
   decreasing intensity.   
      
   On Tuesday, another round of heavy snow is expected across just   
   about all of the CA mountain ranges as a second, arguably stronger   
   upper level low dives south along the West Coast, closely following   
   the first. This will spike onshore flow and additional moisture   
   supply on the southern and eastern flanks of the upper low. Renewed   
   heavy snow will start out across the northern California ranges   
   Tuesday morning, then spread south down the Sierra Nevada from   
   Tuesday afternoon through Tuesday night. Once again, 1-2 inch/hour   
   rates will be common with 3-4 inch/hour rates locally not out of   
   the question. Snow levels will continue to fall to around 1,000 ft   
   in far northern California (including the northern coastal range)   
   Tuesday night, around 2,500ft in the Sierra Nevada, and between   
   4,000 and 5,000 ft into the Transverse Ranges. Snow will continue   
   to fall across California's mountain ranges trough Wednesday as yet   
   another 500mb shortwave trough west of WA continues to sustain   
   what feels like an endless supply of Pacific moisture into the   
   Golden State. However, during the day Wednesday snowfall rates   
   could diminish in most of the mountains down to light snow or even   
   flurries at times. With the longwave trough overhead, snow levels   
   could creep down as low as 1,000ft in central CA and may support   
   minor accumulations down to 1,000ft.   
      
   On Thursday a pair of shortwaves, both moving SSE, but one   
   impacting the Northern California ranges, and the other following   
   the previous disturbances hugging the coast until it turns inland   
   over Southern California, will keep moderate snow ongoing along   
   most of California's ranges. Rates will not be quite as heavy on   
   Thursday as on previous days. Snow levels will fall in the   
   Transverse Ranges to as low as 3,500 feet Thursday morning, while   
   staying between 1,500 and 2,500 feet from the Sierra Nevada north.   
      
   California's mountain ranges welcome the snow, although it will   
   come down fast and furious through mid-week. Through the end of   
   this discussion's timeframe (00Z Fri), snowfall will be measured   
   in feet above 4,000ft along the Sierra Nevada. WPC probabilities   
   show high chances (>90%) for >30" of snow along Donner Pass through   
   00Z Friday and more snow still to come. The WSSI shows a large   
   swath of Extreme Impacts (Substantial disruptions to daily life;   
   extremely dangerous travel or impossible driving conditions,   
   extensive closures) for elevations generally above 5,000ft,   
   although some Major impacts as low as 4,000ft are possible. Major   
   to locally Extreme impacts are showing up in the peaks of the San   
   Gabriel and San Bernadino mountains, with mostly Moderate-to-Major   
   Impacts (increasingly more disruptive to travel jumping from   
   Moderate to Major). There are also likely to be some Major impacts   
   in the Coastal Range of northwest CA above 2,000ft. Note that there   
   are Minor to locally Moderate Impacts expected along I-5 around   
   Mount Shasta, signifying potential travel delays for I-5 in the   
   more elevated terrain of northern CA.   
      
      
   ...Intermountain West...   
   Days 1-3...   
      
   Pacific moisture ahead of the longwave upper trough off the West   
   Coast will spill over the Cascades and Sierra Nevada and reach many   
   ranges across the Intermountain West this week that badly need the   
   boost in snowpack. With a lack of a frigid airmass ahead of this   
   healthy moisture source, the bulk of the heavy snow will be largely   
   confined to many of the taller mountain peaks. The heaviest   
   snowfall on Monday will reside in the Blue, Sawtooth, Wind River,   
   Uinta, and as far south as Mt. Charleston and the Mogollon Rim. WPC   
   72-hour probabilities are high (>70%) for snowfall totals >12" in   
   these mountain ranges through Thursday afternoon.   
      
   On Tuesday, the highly anomalous upper-low off the Pacific NW coast   
   will help to usher the initial upper low over southern CA east into   
   the Intermountain West, causing widespread height falls and a   
   larger plume of Pacific moisture to pass over the Rockies. The   
   potent closed low then heads inland over the interior NW and   
   northern Rockies on Wednesday while opening up into a trough,   
   prompting snow levels to crash and most valleys are likely to see at   
   least a coating of snow. Still, the lack of a frigid airmass at the   
   surface will keep the bulk of the heavy snow in the mountains with   
   ranges such as the Wasatch, Bear River, Tetons, Uinta, Wind River,   
   Mogollon Rim, and CO Rockies seeing anywhere from 1-2 feet of snow.   
   Expect Minor to Moderate Impacts, per the WSSI, with travel over   
   passes from the Lewis Range and Bitterroots to as far south as the   
   Mogollon Rim likely to contend with hazardous travel conditions.   
      
   By Thursday, much of the Intermountain West will be in a lull   
   between storm systems, as the next in the series of shortwaves   
   moves across California. Some snow will spill over into much of   
   Nevada, while areas further east see the snow stop completely   
   during the day. Snow with the shortwave over California moves   
   across the Four Corners into Thursday night and Friday.   
      
      
   ...Northern Plains & Upper Great Lakes...   
   Days 2-3...   
      
   A shortwave emerging form the Great Basin will track rapidly   
   northeast Tuesday, reaching the Dakotas Tuesday evening while amplifying.   
   As this trough becomes negatively tilted and expands across the Northern   
   Plains/Upper Midwest, it will interact with the LFQ of a strengthening   
   subtropical jet streak arcing from the Desert Southwest to the Great   
   Lakes, to support surface cyclogenesis Tuesday evening. This low   
   is then expected to move very slowly through Wednesday before   
   gradually filling over the Western Great Lakes Thursday night.   
      
   As this low tracks slowly eastward, it will interact with impressive   
   IVT surging above the 99th climatological percentile into Minnesota,   
   with the accompanying moisture and theta-e ridge axis then wrapping   
   cyclonically around the system and lifting into a pronounced TROWAL.   
   The associated synoptic lift, aided by increasing WAA, will expand   
   precipitation   
   across the northern tier of the CONUS from far eastern MT through the   
   western Great Lakes, with periods of heavy snow likely as strongly sloped   
   FGEN driving omega into the TROWAL supports heavy precipitation   
   rates. The most impressive ascent appears to intersect the DGZ, so   
   despite this being subjectively elevated (nearing 500mb) it will   
   support heavy snow rates and dynamic cooling into a column that is   
   initially too warm to support snow. However, once precipitation   
   changes to snow, it will become heavy, supported by the WAA/fgen   
   beneath the TROWAL and accompanying CSI evident in cross- sections,   
   to support rates that will likely exceed 1"/hr at times (60-90%   
   chance). These intense rates will be accompanied by strong and   
   gusty winds, resulting in widespread moderate impacts (30-60%   
   chance) from ND through the Arrowhead of MN. Here, there is a high   
   probability (>70% chance) of more than 4 inches of snowfall   
   accumulating, with locally 8-10 inches possible. Some even higher   
   totals, exceeding 12 inches, may occur (30-50% chance) along the   
   Arrowhead of MN where upslope flow with lake- enhanced moisture   
   will combine to bring greater snowfall and resulting impacts.   
      
   Additionally, with the pronounced WAA rotating around the surface low,   
   an area of freezing rain is also expected, especially from near Duluth,   
   MN eastward across northern WI and into northern MI where the warm nose   
   will be most prevalent, but low-level easterly flow will maintain   
   sub- freezing surface temperatures. In this area, WPC probabilities   
   are moderate (50-70%) for at least 0.1" of ice, with locally more   
   than 0.25" possible, most likely across the northern L.P. of MI.   
      
      
   ...Northeast...   
   Days 2-3...   
      
   A strong surface low moving slowly across the Dakotas/Minnesota   
   Wednesday will remain entrenched within an elongated mid-level   
   trough extending into the Mid-Atlantic states. Vorticity lobes   
   downstream of this wave will spread northeast from the Mid-Atlantic   
   states into the Northeast, before getting sheared rapidly to the east   
   as mid- level flow becomes strongly confluent south of secondary shortwave   
   energy crossing Maine and Nova Scotia. The resultant mid-level PVA   
   and divergence will overlap with a narrow ribbon of impressive low-   
   level WAA to produce a stripe of heavy precipitation from Upstate NY   
   through southern/central New England.   
      
   This precipitation will expand eastward from the Great Lakes Wednesday   
   morning, exiting off the New England coast by Thursday morning. While   
   the guidance continues to feature some latitudinal variability within   
   what will likely be a narrow corridor of precipitation, the evolution   
   of the upper jet streak (initially downstream a poleward arcing, but   
   becoming more zonal and stretch south of the precipitation) will force   
   a quasi-laterally translating band of precipitation, but with slow weakening   
   of intensity through Thursday morning. This is reflected by just modest   
   fgen in the 925- 850mb layer, and although some fgen may increase late   
   as a surface wave develops offshore leading to more pronounced low-   
   level convergence over New England, this will occur as the column dries   
   from the top down, limiting moist ascent, so most of the precipitation   
   should remain of modest intensity, with locally higher rates possible,   
   especially Wednesday, during the period of most impressive WAA.   
      
   Thermally, the antecedent column is marginal to support wintry precipitation,   
   and it appears any significant snowfall accumulations will be confined   
   to higher elevations above 1,000 ft, or where the most intense dynamic   
   cooling can overwhelm the above- freezing low- levels. This is most   
   likely from Upstate NY into western VT where conditional instability   
   into a DGZ of modest depth is possible (30% chance from the SREF). This   
   will support briefly heavier snowfall rates, which could linger as the   
   band of precipitation tracks along its long axis. This is   
   reflected by WPC probabilities that reach as high as 10-30% for 4+   
   inches of snow, especially in the Adirondacks and Greens, with   
   moderate probabilities for 2+ inches covering much of central New   
   England and the northern half of Upstate NY. It is important to   
   note that the WSE mean snowfall for much of this area lies well   
   below the maximum values, so some locally higher amounts are   
   probable where any banding persists. South of this axis of moderate   
   to heavy snow, a corridor of icing exceeding 0.1" is possible   
   (10-30% chance) from the southern shore of Lake Ontario through the   
   capital region of NY near Albany.   
      
      
   Weiss/Wegman   
      
      
   $$   
      
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