Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 435 AM EDT Mon Apr 1 2024 Valid 12Z Mon Apr 01 2024 - 12Z Thu Apr 04 2024 ...Southwest/Central and Southern Rockies... Day 1... Light to moderate snow is expected to continue early in the period along the Mogollon Rim, and the southeastern Arizona and southwestern New Mexico mountains as a deep, positively-tilted upper trough advances across the region. Precipitation will begin to blossom further to the northeast, as a well-defined shortwave moving through the base of the broader-scale trough ejects out into the southern High Plains later today. Moisture focusing along a front sagging south in the wake of the departing low will fuel localized heavy snow accumulations from the Colorado Front Range to the Raton Mesa and Sangre de Cristos Mountains. WPC PWPF shows moderate (40 percent) or higher probabilities for accumulations of 8-inches or more in this areas. Models continue to indicate a mostly rain event for the lower elevations further east. ...Central Plains... Day 1... Ongoing precipitation across Kansas and Nebraska is expected to continue through the early part of the period as leading shortwave energy lifts out of the western U.S. trough. Light to moderate precipitation is expected to focus on the northwest side of an associated low-to-mid level low lifting from western Kansas into eastern Nebraska this morning. Models are not suggesting a widespread heavy snowfall event, with marginal temperatures and low SLRs contributing to a limited threat. However, there is some signal for banding to develop near the Nebraska-South Dakota border, which along with colder air sliding in from the north, may support some localized heavier totals. WPC PWPF shows slight (10 percent) or higher probabilities for accumulations of 4 inches or more centered mainly along and north of the central Nebraska-South Dakota border. ... Great Lakes into the Northeast... Days 2-3... ...The potential for a late season significant winter storm is increasing... Models continue to indicate that a late-season winter storm will likely develop mid week, producing widespread gusty winds and heavy snow portions of the Great Lakes and the interior Northeast. The previously noted shortwave emanating from the Southwest is forecast to lift northeast through the central Plains and mid Mississippi Valley, into the Great Lakes where it will begin to phase with an equally well-defined northern stream shortwave diving southeast out of central Canada. This will support a rapidly developing surface low that will track northeast from the mid Mississippi Valley on Tuesday morning into Michigan by the evening, where it will lift north and then retrograde as a deep upper low forms overhead. Models continue to show a track favorable for heavy snow developing across northern Lower Michigan, supported initially by low-to-mid level frontogenesis and favorable upper jet forcing centered across the region late Tuesday evening. Snow will begin to taper off as the low drops back to the southeast, but not before several inches of heavy snow fall across portions of the region. WPC PWPF shows moderate probabilities for accumulations of 4 inches or more centered over interior northern Lower Michigan along with a slight chance for amounts exceeding 8 inches. As the upper low begins to move east across the Great Lakes, additional southern stream energy lifting out of the south will support the development of a triple-point low that will become the primary surface feature as it tracks from the Mid Atlantic to Long Island-southern New England late Wednesday into early Thursday. Overall, model timing has slowed a little with the overnight runs, but the overall consensus continues to show widespread moderate to heavy precipitation becoming likely across the Northeast by late Wednesday continuing into early Thursday. Rain or mixed precipitation at the onset will likely transition to all snow across much of eastern Upstate New York and central to northern New England, with several inches of heavy, wet snow appearing likely across the higher terrain. By early Thursday, WPC PWPF shows high probabilities (70 percent) for accumulations of 8 inches or more covering much or the Adirondacks, Green, and White mountains. Moderate probabilities extend as far south as the Catskills and east into central Maine. *** Key Messages for Early April Nor'easter *** ---Long duration winter storm becoming likely Confidence is increasing that a large storm system will produce gusty winds and late-season heavy snows across portions of the Great Lakes and the Northeast mid to late week. ---Widespread heavy snow. Heavy snow may develop across portions of the Great Lakes early Wednesday through early Thursday. Secondary low pressure development along the coast is likely to bring heavy snow and mixed freezing rain/sleet to the Northeast late Wednesday through Friday. ---Significant impacts from heavy snow and wind The combination of heavy snow rates and gusty winds will likely result in hazardous travel due to low visibility and snow-covered roads. Additionally, the heavy and wet snow could impact infrastructure. ---Forecast changes anticipated Uncertainty remains with the timing and location of the storm track, which will affect where the most significant impacts will occur. Keep up to date with the latest forecasts as this storm evolves.