Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 348 PM EST Tue Jan 30 2024 Valid 00Z Wed Jan 31 2024 - 00Z Sat Feb 03 2024 ...California, Great Basin, Four Corners... Days 1-3... Atmospheric River (AR) shifts into far northern CA into southern OR early Wednesday as it curls around deep low pressure occluding/stalling west of Washington. Associated cold front pushes inland Wednesday night as a digging/reinforcing trough rounds the low into the central CA coast at the head of a powerful WNWly Pacific jet. The AR (with PW anomalies +2 to +3 sigma) will progress south down the CA coast through Thursday ahead of this secondary wave. Snow levels are inherently high in the core of the AR with values initially around 9000ft late tonight near the OR/CA border, though height falls associated with the approaching wave drop them to around 7000ft as precip reaches the Sierra Nevada Wednesday night, reaching 6000ft under the trough axis Thursday. Snow will become increasingly impactful to many passes over the Sierra Nevada Wednesday afternoon into Thursday, expanding eastward across the Great Basin Thursday and into the Four Corners Thursday evening and the southern Rockies Friday. Heavy snowfall and intense snowfall rates of 2-4"/hr are likely in the highest elevations of the Shasta/Siskiyou/Trinity ranges Wednesday then down the length of the Sierra Nevada Wednesday night into Thursday, where multiple feet of snow is likely above 8000ft or so. As the moisture and lift press inland late Thursday, a broad area locally heavy mountain snow (snow levels generally 5000-7000ft) spreads over central ID, the Basin and Range of NV, all UT ranges, northern AZ along the Mogollon Rim, and the San Juans in southwestern CO where Day 3 snow probs for over 6" are at least moderate. 40 to 60 percent probs for over 12" are noted for the San Juans on Day 3 (00Z Fri- 00Z Sat). ...Northern Maine... Days 2/3... A clipper currently over northern Alberta skirts east in zonal flow to central Quebec by Wednesday night before crossing northern Maine late Thursday. Southerly flow rides over a front sagging into Maine ahead of the low with moderate snow generally limited to far northern Maine where Day 2.5 (12Z Thur-12Z Fri) snow probs 40-70% for over 4". The probability of significant icing greater than 0.10" is less than 10% for days 1-3. Jackson