811 FOUS11 KWBC 030740 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 340 AM EDT Thu Apr 3 2025 Valid 12Z Thu Apr 03 2025 - 12Z Sun Apr 06 2025 ...Northeast... Days 1 & 3... An icy wintry mix will continue from the White Mountains and through much of interior Maine this morning as ongoing WAA and intense 850mb FGEN sustains an icy setup over northern New England. The lingering sub-freezing boundary layer will gradually erode as the warm front advances northward with only northern Maine holding on to any notable wintry mix through midday. WPC probabilities depict low chances (10-30%) for additional ice accumulations >0.1" in the White Mountains and western Maine through this morning. Following a break in the action Thursday night through Saturday morning, the next round of wintry mix arrives Saturday afternoon as moisture from the Mississippi Valley streams northward into New England. Similar to the Day 1 setup, low-mid level WAA and 850mb FGEN are the primary mechanisms of lift that will promote precipitation. The antecedent air-mass is not nearly as cold as the Wed-Thurs air-mass. However, the modestly cold air-mass will be tough to erode in the higher terrain, thus making the White Mountains and western Maine the most likely areas to see a mix of snow and freezing rain through Saturday night. WPC probabilities show moderate- to- high chances (50-70%) for >0.1" of ice, with low chances (10-30%) for ice accumulations >0.25". ...Intermountain West & Southern High Plains... Days 1-3... The weather pattern over the western third of the Lower 48 is primarily driven by a pair of upper level disturbances; one tracking across Montana today and early Friday, and the other is a closed upper low over the Southwest. Starting in Montana, a cold front at the leading edge of the 500mb shortwave trough will act as a trigger for snow showers, some of which could have snow squall- like impacts with bursts of snow and gusty winds Thursday afternoon. With high pressure building in from Alberta, easterly upslope flow into the Lewis Range and Absaroka through Thursday evening. Snow associated with this upper trough is also expected as far south as the Big Horns and even as far east as western North Dakota Thursday night. By Friday morning, the cold front makes its way south through the Central Plains and Central Rockies with NErly upslope flow aiding in minor snow accumulations along the Front Range of the WY/CO Rockies through Friday morning. Farther south, the closed upper low will make its way toward New Mexico with 200-500-700mb heights along the AZ/NM and Mexico borders below the 10th climatological percentile. As the 700mb low reaches western New Mexico Friday afternoon, winds over southeast CO and northeast NM will turn easterly at the same time the aforementioned cold front to the north plunges south. Southern CO and northern NM will also be co-located beneath the divergent left- exit region of a 500mb jet streak located over northern Mexico. The heaviest snowfall looks to ensue Friday afternoon and into Friday night across the Front Range, Palmer Divide, San Juans, and Sangre De Cristo (including Raton Pass). By Saturday morning, snow is forecast for most of the Southern Rockies and even parts of the southern High Plains as the cold front continues to dive south and the deformation zone on the northern and western periphery of the 700mb low moves in overhead. Note that with the time of year, it will have to snow exceptionally hard (>1"/hr) for snow to accumulate outside of the mountain ranges given the higher sun angle and warmer soil temperatures. Still, periods of moderate snow combined with 30-40 kt 850mb winds will cause poor visibilities through Saturday afternoon before the snow finally tapers off Saturday evenings. WPC probabilities depict moderate-to-high chances (50-70%) for snowfall >8" along the >9,000ft peaks of the Sangre De Cristo and San Juans between Friday afternoon and Saturday afternoon. Along the I-25 corridor, the most concerning area for heavy snowfall is along Raton Pass where up to 12" of snow in the forecast. WSSI depicts Moderate impact potential in the Sangre De Cristo, Raton Mesa, and San Juans. Note that there are some Moderate Impacts in the plains of eastern NM and the TX Panhandle with Blowing Snow the primary impact in these areas. Mullinax $$