Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 428 AM EST Tue Jan 31 2023 Valid 12Z Tue Jan 31 2023 - 12Z Fri Feb 03 2023 ...Significant and Long-Duration Ice Storm For Portions of Texas and Oklahoma through the Mid-South through Wednesday night... ...West-Central Texas through the Mid-South... Days 1-3... A stalled upper low will linger over the northern Baja through tonight before shifting east across northern Mexico and west Texas through Thursday morning. This will invigorate tropical Pacific moisture advection over Mexico today which will along with increasing jet dynamics (the threat area will be in the right entrance region of the jet) and frontogenesis will promote an increase in precip coverage and intensity over Texas (where shallow saturation/freezing drizzle has occurred overnight) and east-northeast through the Mid-South. The Arctic-sourced airmass dominating the Plains and Mississippi Valley is centered at 1034mb over Kansas will maintain the north surface wind and continued dry/cold air over west-central Texas to the Mid-South through Wednesday night - until the upper trough approaches and disruptions the overrunning low to mid level flow. Increasing moisture and lift ahead of the stalled low over northern Mexico will support the westward expansion of heavier precipitation across Texas through Wednesday. This includes portions of the Rolling Plains, Concho Valley, and Hill Country. The depth and magnitude of the low level cold air will determine ptype between freezing rain and sleet with sleet more likely farther north and west as well as in elevated convective activity. Model preference on freezing rain coverage and ptype for sleet is with the Canadian Regional, NAM Nest, ECMWF with some inclusion of the ARW and HRRR. Day 1 ice accretion 0.25"+ is moderately high over central TX and across North TX to the eastern TX/OK border where QPF is greater an shallower cold air should allow more freezing rain than sleet. Lower probabilities for 0.25"+ extend over southern/central AR (not around warmer Texarkana) with moderate or higher probabilities for 0.1"+ extending from west Texas through central TN. With the western shift in the heavier precip Wednesday, the Day 2 ice probabilities for 0.25"+ are over West-central through North TX with lower probabilities over south-central AR. Despite a bit of a shift, there is plenty of overlap among Days 1-2, raising the prospects of storm total ice accretion of half inch to possibly three-quarters of an inch. As of now the highest risk area may be around the Dallas-Fort Worth Metroplex. Other major metro areas expected to be impacted include Austin, Little Rock, and Memphis. Periods of freezing rain are expected to continue into Thursday though a break down of the warm nose is expected and only light precip perhaps near the upper trough axis is expected, with notable precip expected to shift farther east. Forecast confidence remains limited in part by continued model spread with respect to the southern extent and persistence of the cold air, particularly with the extent during the greatest cold Wednesday morning. However, most areas currently below freezing will remain so through at least Wednesday night. ...Great Lakes... Day 1-3... Cold westerly flow will persist across the Great Lakes through Wednesday night from air rounding the deep cold gyre centered over northern Hudson Bay. Typical westerly snow belts of the Keweenaw Peninsula and near Whitefish point on the U.P. and the Tug Hill Plateau east of Lake Ontario have moderate Day 1.52 probabilities for 6"+. A reinforcing trough that dislodges the deep low center crosses the Great Lakes Thursday with flow shifting NWly and lake enhanced snow off each lake which could result in locally heavy snow bands. Lake ice cover is under 9% per GLERL and this particularly cold air will be have the saturated layer in the DGZ through Wednesday, but then the DGZ goes below the surface Thursday under the coldest air of the season. Jackson ...Key Messages for Jan 30-Feb 1 Southern Plains to Mid-South Ice Storm... --Several rounds of freezing rain, mixing with sleet at times are expected through Wednesday night. --Freezing rain accumulations around half inch are likely over much of West, Central and North Texas, with locally heavier amounts possible. Over a quarter inch of ice is forecast over southern Oklahoma, south-central Arkansas and east through the greater Memphis area. --Accumulating ice on roadways, especially bridges and overpasses, will cause dangerous travel conditions. --Power outages and tree damage are expected.