Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 447 PM EDT Sat Mar 25 2023 Valid 00Z Sun Mar 26 2023 - 00Z Wed Mar 29 2023 ...Pacific Northwest, Northern & Central Rockies, Central Plains to Midwest... Days 1-2... Lobes of vorticity in the broad troughing over the West eject east over the Plains to the Midwest through Monday. A lingering stationary boundary over the northern Rockies onto the central High Plains will continue to provide low-level focus for modest to heavier snowfall from central Idaho, south-central Montana and northern Wyoming ranges where there are moderate Day 1 snow probabilities for 8"+ on the higher terrain and western slopes (like near Red Lodge, MT). There are moderate Day 2 snow probabilities for 4"+ over the eastern Absarokas and Bighorns. A vort lobe that lingered over northeast CO today will eject east in the strengthening WSWly jet centered over the southern Plains tonight. Snow continues along the stationary front over western Neb where thee are moderate Day 1 snow probabilities for 4"+. Farther east and north of a weak surface low there will be sufficient cold air intrusion and convergence for moderate snow across southern Neb into central IA where Day 1 snow probs are moderate for 2"+ with a risk for localized 4" into Sunday morning. The feature will need to be tracked as it shifts east over the Midwest to the eastern Great Lakes, but the peak diurnal in late March should limit snowfall accum along the WI/IL border and over southwest MI. There is a risk for some snow accum near Detroit and again over Buffalo NY Monday night from this feature. Finally for Day 1, continued onshore flow under the trough brings moderate probabilities for 4"+ to the WA/OR coastal ranges and Cascades with snow levels around 1500ft. A weakening upper low center currently drifting into Idaho reinvigorates a bit Sunday night over Wyoming with lee-side troughing allowing more snow over the central High Plains with moderate Day 2 probabilities of 6"+ over northeastern CO with low probs for 4"+ extending just over the borders into WY/Neb/KS. The consensus is for this feature to weaken as it shifts east from the High Plains and not have a long track east like the feature tonight. ...Michigan... Day 1... Wrap around snow continues over Michigan this evening as low pressure lifts over Lake Huron and into central Ontario. Day 1 snow probs are low for over 2" additional after 00Z. ...New England... Day 1... Coastal low pressure develops tonight over the Gulf of Maine along the surface front from the Great Lakes low that is lifting over the Northeast. A warm nose continues to spread north ahead of this front and cause a wintry mix over interior New England tonight with the column cold enough for all snow in Maine. Probabilities for an additional tenth inch of ice are up to 10% in VT/NH. Energy continues to translate from the low departing the Great Lakes to the coastal low through Sunday with snow continuing for northern Maine where Day 1 snow probabilities are high for 6"+. The focus for snow pushing into Atlantic Canada Sunday afternoon. ...Oregon/California... Day 3... A potent upper low over the Gulf of Alaska today will shift south well offshore before intensifying as it pivots east toward the coast near the OR/CA border Monday afternoon and then shift south just off the northern CA coast Tuesday. A plume of Pacific moisture shifts inland late Monday with increasing precip rates and snow levels generally around 2000ft. Day 3 snow probabilities are high for a foot or more over the Klamath/Shasta Siskiyou and northern Sierra Nevada. This low will be a weather maker for CA at least through Thursday as it shifts south. Jackson