Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 334 PM EST Thu Jan 24 2019 Valid 00Z Fri Jan 25 2019 - 00Z Mon Jan 28 2019 ...Great Lakes... Days 1-3... An active period of lake enhanced and lake effect snow owing to cyclonic flow from a large low-mid level low shifting south from the Hudson Bay will continue across the Great Lakes with episodes of lake effect snow expected to continue through the weekend. Much below normal temperatures should lead to gradually increasing ice coverage on the lakes over the coming days, but for now ice coverage is low enough to warrant full lake effect potential through the next three day forecast period. A weak shortwave trough rounding the Hudson Bay low and on the eastern side of the arctic cold front moving east from MI this afternoon. Northwesterly flow behind the front and steep low level lapse rates are resulting in lake effect snow off Lake Superior this afternoon and will expand to the rest of the Great Lakes into Friday. Continued westerly to northwesterly flow (particularly Saturday night when additional surface low pressure develops north of the Lakes) is expected through Sunday with lake effect snow persisting in typical snow belts. ...Northeast... Days 1 and 3... Northwesterly flow behind the low exiting ME this evening will allow wrap around snow over interior northern ME. Day 1 WPC probabilities are low to moderate for two inches over northern ME. Surface low pressure ahead of the low shifting south from the Hudson Bay will swing through Ontario and Quebec Saturday night through Sunday. Moist southerly flow east of the low will result in mainly light precipitation across the interior northeast. Abundant cold air across the region from will make for all snow with moderate Day 3 WPC probabilities for two inches across the interior northeast from western PA to ME. ...Northern Plains... Day 3... A reinforcing shortwave trough will dig south across the Canadian Prairies Sunday and reach the border with MT by Sunday evening. Surface low pressure ahead of the trough and along a strong baroclinic zone will reach the Dakotas by Sunday evening. Strong frontogenesis should result in a heavy band of snow. Moderate Day 4 WPC probabilities for four inches are across central ND. ...Central and Northern Rockies... Day 1... A weak shortwave trough will shift southeast from the Canadian Prairies tonight on a strong northwesterly jet streak. Mid-level forcing will promote enough vertical ascent for snow from MT to CO, with low-moderate WPC probabilities for 2 inches along the MT/WY and Dakota borders. Higher terrain from MT to CO will also see snow with moderate to high probabilities for four inches. The probability for significant icing is less than 10 percent nationwide days 1-3. Jackson/Taylor