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   FOUS11 KWBC 162220   
   QPFHSD   
      
   Probabilistic Heavy Snow and Icing Discussion   
   NWS Weather Prediction Center College Park MD   
   520 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 south down   
   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 1,000 feet as far   
   south as northern CA. 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. This includes potentially down 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 from 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. This setup will 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. The accompanying moisture and theta-e ridge axis   
   will then wrap cyclonically around the system and lift 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.   
   Periods of heavy snow are 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 500 mb), 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, supporting 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 subsequent 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. Low-level easterly flow   
   will maintain sub-freezing surface temperatures in these same   
   areas, setting the stage for a freezing rain/icing event. WPC   
   probabilities are moderate (50-70%) for at least 1/10 inch of ice,   
   with locally more than a quarter inch 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 the   
   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. The guidance continues to feature some latitudinal   
   variability within what will likely be a narrow corridor of   
   precipitation. The evolution of the upper jet stream (initially   
   downstream a poleward arcing, but becoming more zonal and   
   stretching 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 925-850 mb 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. This will limit moist   
   ascent, so most of the precipitation should remain of modest   
   intensity, with locally higher rates possible. This is most likely   
   on Wednesday, during the period of most impressive WAA.   
      
   Thermally, the antecedent column is marginal to support wintry   
   precipitation, and it appears any significant snowfall accumulation   
   will be contained both to higher elevations above 1,000 ft, and to   
   where the most intense dynamic cooling can overwhelm the above-   
   freezing low levels. The most significant accumulations are 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.   
      
      
   Weiss/Wegman   
      
      
      
      
      
   $$   
      
   = = =   
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