Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 303 PM EST Mon Jan 22 2024 Valid 00Z Tue Jan 23 2024 - 00Z Fri Jan 26 2024 ...Southern Plains to the Great Lakes and Northeast... Days 1-2... A mid-to-upper level trough near the MOKSORAK this afternoon/evening will continue to lift northeastward tonight into the Corn Belt and eastern Great Lakes tomorrow. Cold air mass is slowly eroding over southern areas as high pressure to the east allows southerly flow aloft to reach the surface, changing freezing rain to rain from south to north. However, Canadian high pressure over Ontario will slip eastward, trying to slow the WAA into the Midwest/Great Lakes tonight into Tuesday. As the system continues northeastward, strength of the WAA atop the cold surface will promote a rather wide zone of freezing rain on the north side of the expanding precipitation shield. WPC probabilities of at least 0.10" icing are moderate (40-70%) from central/northern IL eastward across northern/central IN into Lower MI and northern OH. With precipitation extending eastward to the Appalachians Tue evening into early Wed, icing will also spread eastward along I-80 across northern PA toward the DE Water Gap/Catskills. Within this broad area, there is a non-zero chance of at least 0.25" icing over the Midwest, depending on the precise thermal setup. As the models continue to struggle with the depth/strength of the warm layer/WAA on the northern side of the precipitation shield, an area of snow is likely in the colder air mass where the WAA will not be strong enough to bring in >0C air (generally along or north of the track of the mid-level vort). An axis of light to embedded moderate snow is forecast from eastern IA eastward into Lower MI D1 then into northern PA and much of NYS, where WPC probabilities for at least 4 inches of snow are generally low (<20%) as amounts may only be in the 1-3" range. ...Great Basin/Southwest... Days 1-2... Digging mid-level trough over SoCal this evening will continue eastward in AZ and briefly close off as a weakening upper jet noses into northern Mexico, placing the Southwest in the left exit region under broad divergence before shifting into the Plains late Tue into Wed. Snow levels will be around 7000ft but fall a bit as the colder air moves in aloft. Axis of moisture ahead of the surface front will steadily move through AZ tonight, favoring the southern NV Ranges and higher mountains peaks as well as across the Mogollon Rim into the White Mountains for appreciable snow. There, WPC probabilities for at least 6 inches of snow are highest, generally 30-50%. ...Pacific Northwest and northern Great Basin... Days 1-3... Active northern stream in quasi-zonal flow will maintain a more or less steady stream of moisture into the Pac NW, northern Rockies, and northern Great Basin for the next few days. Snow levels will waver around 4000-5000ft which will affect some passes across the Cascades and Rockies especially into Wednesday. WPC probabilities of at least 8 inches for the next few days are highest above 6000ft. Fracasso