Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 415 PM EST Tue Jan 18 2022 Valid 00Z Wed Jan 19 2022 - 00Z Sat Jan 22 2022 ...Great Lakes to the Northeast... Days 1-2... A clipper system currently centered over northern Minnesota will continue to track quickly to the east -- moving north of the northern Great Lakes overnight, before continuing across southern Ontario to Quebec on Wednesday. Warm advection precipitation ahead of the system will shift from the northern Great Lakes region this evening, before spreading across northern New York and northern New England on Wednesday. Model consensus suggests mostly light accumulations for the impacted regions. Northwesterly flow behind the system is expected to support developing lake effect snow snows across the U.P. of Michigan beginning this evening, with locally heavy amounts possible along the favored snow belts, especially along the Keweenaw Peninsula. By late Wednesday, winds veering to the northwest across southern Lake Michigan will support the development of heavy lake effect bands impacting portions of southwestern Lower Michigan and Northwest Indiana. ...Ohio Valley to the Northeast... Day 2... The trailing cold front associated with the previously noted clipper system is expected to push into the northern Mid Atlantic and Ohio Valley on Wednesday. A southern stream shortwave, currently over the Southwest, is forecast to lift northeast from the southern Plains through the Ohio Valley Wednesday evening-overnight. This is expected to support developing precipitation north of the front, with deepening cold air supporting rain changing to a wintry mix or all snow from the Ozarks through the Ohio Valley and into the central Appalachians and northern Mid Atlantic Wednesday night into Thursday, and then across portions of southern New York and New England during the day on Thursday. Overall, the majority of the guidance is only showing light accumulations. WPC probabilities suggest accumulations of 1-2 inches at most for most locations, with some potential for locally heavier amounts mainly centered across the Ohio Valley into the central Appalachians late Wednesday into early Thursday. ...Pacific Northwest and Northern Rockies... Days 1-3... Frontal boundary trailing the previously described clipper system will remain banked along northern Rockies, supporting additional light snows across the region through the evening. Then on Thursday, a shortwave trough shifting southeast from the Gulf Alaska through western Canada and the Pacific Northwest is forecast to bring snows back into the northern Cascades by early Thursday, before shifting southeast through the northern Rockies later in the day into early Friday. WPC probabilities do show some indication for localized amounts of 6 inches or more across the higher terrain, but overall models show a fast-moving system, with limited potential for widespread heavy amounts. ...Gulf Coast to the Southern Mid Atlantic... Day 3... Previously noted cold front will continue to drop farther southeast, settling into the northwestern Gulf of Mexico on Thursday. By late Thursday, a positively-tilted upper trough amplifying over the southern Plains and northern Mexico will support precipitation developing in the shallow arctic air north of the front. By Thursday evening, a wintry mix, including freezing rain is possible across portions of South-Central Texas before spreading farther south into South Texas and east along the Texas Coast. This wintry mix is expected to continue to spread farther east Friday morning, impacting portions of southern Louisiana, Mississippi, and Alabama. Latest WPC probabilities show 30 percent or greater probabilities for accumulating ice as far south as southern Louisiana on Friday. On Friday, an amplifying northern stream wave moving across the Ohio Valley, along with increasing low-to-mid level frontogenesis, is expected to support precipitation developing well to the northwest of the surface boundary. A strong arctic high centered over the Northeast, ridging south through the Mid Atlantic, may set the stage for another wintry mix, including accumulating ice, across portions of the Carolinas and Virginia on Friday. WPC probabilities indicate that accumulating ice is likely from central South Carolina through the eastern Carolinas, with a significant threat for accumulations of 0.10 inch or more centered over southeastern North Carolina. Still a great deal of uncertainty going forward, with significant model spread regarding the strength and track of a low developing along the front, and off of the Southeast to Mid Atlantic Coast late in the period. Pereira