Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 419 AM EST Sun Jan 29 2023 Valid 12Z Sun Jan 29 2023 - 12Z Wed Feb 01 2023 ...Southwest to the South-Central Rockies... Days 1-2... An amplifying western end to the upper trough across the Northwest will close tonight over northern CA before stalling off Southern CA late Monday through Tuesday. Meanwhile the rest of the trough will remain positively-tilted as it pivots over the Intermountain West. An overlap over forcing and moisture will result in periods of moderate to heavy snow, generally along and ahead of the associated southward advancing cold front. Overall transient and narrow features and modest moisture should limit snowfall overall. Today, the heaviest snow is likely across the northern Sierra Nevada, northern Wasatch, and through the northern CO Rockies where WPC probabilities for more than 6 inches are 50-70%, and locally 12 inches is possible for the Park Range in CO. The coastal low development off CA tonight limits precip for the southern Sierra, but will allow mountain snow in SoCal with snow levels around 3500ft. Heavy snow briefly impacts southeastern NV/southwestern UT ranges tonight/Monday and northern Arizona Monday/Monday night with only a slow progression south through western CO through this time. Pacific moisture gets shunted much farther south around the stalled low by Tuesday, cutting off precip for the Desert SW by late Tuesday. ...Northern Great Lakes, and Far Northern New York/New England... Days 1-2... A shortwave trough moving across the Midwest this morning will track up the St Lawrence to northern Maine this afternoon/evening. Continued banded snow north of the low center will occur through today with Day 1 probabilities for 4+" moderately high along the NY/New England border with Canada as well as much of far northern Maine. Cyclonic flow over Lake Superior bring moderate 4" probabilities to the eastern and western coastal portions of the U.P. A secondary elongated shortwave will move shift east over the northern Great Lakes Tuesday with steep lapse rates in Wly flow across the Great Lakes, albeit with modest inversion heights. Periods of heavy LES are expected in the favored W snow belts with Day 2 snow probabilities for 4"+ limited to the Keweenaw Peninsula and near Whitefish Pt on the U.P. though some LES will come off Lake Michigan as well as single band potential off Lake Ontario near Syracuse. ...Central Texas through the Mid-South... Days 2-3... Low pressure stalling off southern CA Monday/Tuesday will direct Pacific moisture across Mexico and Texas/the southeast US which will overrun Arctic which is currently plunging down the Plains (the cold front has pushed through the TX Panhandle at time of writing). Generally light precip is expected through Monday, but the arrival of the Pacific moisture late Monday night/Tuesday should lead to swaths of moderate intensity precipitation. Rather warm subtropical air is expected to spread north through the low levels, but cold/dry air will have continued reinforcement from high pressure centered over the central Plains through Tuesday. Model uncertainty in precip placement and cold air strength is high, though the CMC and NAM generally do well with surface cold air and they are rather bullish on ice accretion Tuesday/Tuesday night over central and north Texas over to the Mid-South - AR/western TN. This will need to be monitored closely. As of now Day 3 ice accum probabilities for a quarter inch are 10 to 40% over north-central TX with 20 to 40% probabilities for a tenth inch over southeast OK and much of AR into western TN/northwest MS. Jackson