Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 303 AM EST Sat Jan 27 2024 Valid 12Z Sat Jan 27 2024 - 12Z Tue Jan 30 2024 ...Pacific Northwest... Days 1-2... Southwest flow will maintain a moisture plume into WA/OR with lighter QPF into ID and northwestern MT. However, snow levels will be well above pass level (7000-8000ft), confining any accumulation to the highest mountain peaks. Within and east of the Cascades, lingering cold air at the surface will be loathe to retreat, resulting in some areas of freezing rain this morning. ...Northeast... Days 2-3... Mid-level trough over the Lower MS Valley this morning will close off and continue northeastward through the OH Valley into early Sunday. Upper jet structure will transition toward a southern cyclonically curved portion across the Southeast/southern Mid-Atlantic with a downstream northern jet max arced anticyclonically across eastern Maine into the Canadian Maritimes, leaving the northern Mid-Atlantic and Northeast in between with broad divergence atop incoming height falls. At the surface, low pressure over the Mid-South this morning will move toward eastern Ohio and start to weaken as the dynamics transfer to the triple point low over SE VA. That low will then become the dominant center in typical Miller-B fashion and continue to deepen as it moves steadily northeastward close to the benchmark overnight Sunday into early Monday. This will keep the Northeast on the colder NW side of the system, but any surface high pressure over the region currently will weaken and move eastward, allowing milder air to push up along the coast. Inland, a marginal thermal environment currently exists (even into southern Canada), which will favor an elevation-dependent snow for areas of NY into central New England. Once the system moves enough east, wraparound flow will drag down colder air as the precipitation starts to wind down, bringing at least some snow toward the New England coast/Cape Cod south of BOS before ending. The system will benefit from strong dynamics and embedded mid-level FGEN to drive modest to perhaps locally heavier snowfall rates, but this will balanced by time of day (heaviest QPF Sunday afternoon over NY) and relatively low SLRs to start given the only marginal thermal structure (DGZ fairly high). Farther east into VT/NH and northern MA, heavier snowfall after dark on Sunday could allow for heftier accumulations. Ensemble guidance has shifted the QPF a bit farther north, favoring a heavier axis of snowfall from western NY eastward, between I-90 and I-86/Rt 17, especially over the Catskills. As the system deepens off the SNE coast, higher totals are also likely over southern VT/northern MA/southern NH at the nose of the 850-700 moisture influx and aided by elevation. Valley locations will likely see less accumulation especially at precip onset, but colder air (and higher SLRs) will rush into the area overnight Sunday into Monday as snowfall ends across the area. WPC probabilities for at least 4 inches of snowfall are highest (generally above 60%) over western NY (western Finger Lakes region), the Catskills, Berkshires, southern Greens/Whites/Monadnocks and Worcester Hills (as well as into the Merrimack Valley). Probabilities for at least 8 inches of snow are about 20-40% over the Catskills into central New England. Fracasso