Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 457 PM EDT Mon Mar 15 2021 Valid 00Z Tue Mar 16 2021 - 00Z Fri Mar 19 2021 ...Southwest across the Southern Rockies onto the Southern High Plains... Days 1-2... A compact upper low shifting southeast from Northern CA this afternoon will shift east to AZ late tonight and across NM into the TX Panhandle through Tuesday night. Mountain snows will persist into this evening for the far southern Sierra Nevada to the Tehachapi along with Southern CA ranges with snow levels around 3000ft and locally heavy amounts possible across the higher terrain. Locally heavy snow in higher terrain also occurs farther east tonight across southern NV/Utah mountains, as well as across the higher terrain of northern AZ before tracking across the San Juan Mtns of CO Tuesday and the Sangre de Christos of southern CO/northern NM Tuesday night. Day 1 snow probabilities are moderate for 6 or more inches in southern UT and the San Juans of CO. As the system moves across New Mexico and into the Texas Panhandle late Tuesday into early Wednesday, a period of strong northeasterly flow along the northwest side of the low, along with favorable forcing aloft, should support a period of heavy snow along and east of the Sangre de Cristo Mountains (including the Raton Pass and Raton Mesa) in southeastern Colorado. Day 1.5 snow probabilities are high for 6 or more inches for the eastern slopes in southern CO into northeastern NM. The lee side surface low develops Tuesday night into Wednesday as it moves east from the TX Panhandle across OK with TROWAL development and potential for snow to accumulate despite initially warm conditions over the southern High Plains near the CO/NM border into KS and OK/northern TX Panhandles where Day 2 probabilities for 4 or more inches decrease to the east/lower elevations. ...Central Appalachians... Day 1... A shortwave trough spinning off the occluding low over the central CONUS will shift east across the Midwest tonight and off the Mid-Atlantic coast later Tuesday. A wintry mix with ice accretion is likely as precipitation spreads across the central Appalachians this evening and continues into Tuesday morning. Day 1 ice probabilities are 40 to 60 percent for 0.10-inch or more along with 20 percent probabilities for a quarter inch or more for the crest of the central Appalachians including the Allegheny Mountains of WV down to the Blue Ridge Plateau of southwest VA. ...Northern California and Pacific Northwest... Day 3... The next system is a potent low that drifts toward the Pacific Northwest coast Wednesday night with the associated cold front reaching the coast from northern CA up through WA on Thursday. Ample Pacific moisture is drawn from the sub-tropics ahead of this low with PWs progged to top 0.75" which makes for snow levels 4500ft to 5000ft on Thursday. Day 3 snow probabilities are 50 to 70 percent for 6 or more inches for the higher Klamath Mtns and CA Cascades with low probabilities for the Olympics (where the snow level will be closer to 3500ft). Jackson