Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 346 PM EST Wed Jan 22 2020 Valid 00Z Thu Jan 23 2020 - 00Z Sun Jan 26 2020 ...Pacific Northwest... Days 1-3... Snow levels continue to rise tonight in a plume of elevated Pacific moisture on a southwest flow, reaching 7000ft over WA/OR by Thursday morning. Snow levels drop below 5000ft behind a cold front Thursday night, but precip rates drop as expected behind the front. The next tropically sourced plume of Pacific moisture pushes onshore centered around the OR/CA border with a warm front Friday night and snow levels will rise above 6000ft for much of OR by Saturday with much of northern CA rising above 8000ft snow levels. The risk for 6 or more inches of snowfall will be limited to the highest mountains of WA/OR all three days and the high northern Rockies of ID/MT for Day 1. Snow melt and heavy rain are the greater threats in the Pacific Northwest, so please see the excessive rainfall discussions (QPFERD) for further information. ...Great Plains/Ozarks/Midwest/Great Lakes... Days 1-3... A reinforcing shortwave shifting to the base of the trough from western SD/NE this evening will merge with the plume of precip streaming from the west Gulf to the upper Mississippi Valley and from a closed low late Thursday over eastern KS. This low will then drift east across the Midwest through Saturday, making for a prolonged snow event over portions of the central/northern tier. This includes northern MO where snow is not likely to taper off until Friday afternoon. Risks for 4 or more inches of snow are scattered and low: around 10 percent over northeast NE late tonight ahead of the approaching shortwave, around 5 percent over west-central IL on Day 2 as the low develops, and around Lake Michigan on Day 3 as the low drifts east. An icing threat continues over AR/MO where surface cold air continues to get overrunning precip through Thursday. Day 1 probs for a quarter inch or more of ice are 20 to 30 percent over south-central MO in the Ozarks. ...Mid-Atlantic/Upstate New York... Day 3... The aforementioned low is forecast to push northeast over OH to Lake Erie on Saturday. A new low develops off the occlusion over the central-Mid-Atlantic coast Saturday with enhanced moisture spreading from PA to NY through the day. Thermal profiles suggest a wintry mix inland from the coast. There are 20 to 30 percent probs for 4 or more inches in the northern Allegheny mountains along the PA/NY border on Day 3 with a 10 percent prob for a tenth inch of ice or more along the northeast PA border into upstate NY. Jackson