Subj : Major Winter Storm Discus To : All From : Dumas Walker Date : Wed Apr 03 2024 08:30 am FOUS11 KWBC 030855 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 455 AM EDT Wed Apr 3 2024 Valid 12Z Wed Apr 03 2024 - 12Z Sat Apr 06 2024 ....Great Lakes/Northeast... Days 1-3... ....Major late season winter storm this week... As expected, phasing northern and southern streams are supporting the development of a deep closed over the western Great Lakes region this morning. Its associated surface low is now centered near southern Lake Michigan where it is forecast to linger for the next several hours before drifting to the southeast later today. Snow will continue to spread across much of Wisconsin, as well as portions of southeastern Minnesota, eastern Iowa, and northern Illinois. Additional accumulations for much of this area are expected to be an inch or two, with pockets of locally heavier amounts. Much heavier amounts are likely to the north across portions of Upper Michigan where persistent easterly to northeasterly winds off of Lake Superior will contribute to several more hours of heavy, wet, lake-enhanced snow. The heaviest amounts are forecast to center over Marquette and Baraga counties, where WPC PWPF show high probabilities (70 percent or greater) for additional accumulations of a foot or more today. Moderate (40 percent or greater) to high probabilities for additional accumulations of 6 inches or more extend further west into far northeastern Wisconsin. Snow is expected to continue over Upper Michigan and northern Wisconsin through the overnight, but diminish by early Thursday as the low moves east of the region. Meanwhile, warm advection precipitation will continue to spread into the Northeast this morning, with it expected to begin as or quickly mix with sleet across a good portion of eastern Upstate New York and central New England during the afternoon. As the upper low begins to interact with additional southern stream energy lifting out of the South, a triple-point low will begin to develop and deepen over the Mid-Atlantic this afternoon. Models show this feature continuing to deepen as it moves northeast toward Long Island and southern New England overnight. As the low approaches, strong vertical ascent afforded in part by left-exit region upper jet forcing will support increasing precipitation rates, with snow likely to become the predominant p-type across much of northern New York into interior central and northern New England. By this evening and continuing into the overnight, HREF guidance shows snowfall rates of 1-2 inches spreading from Upstate New York into New England. By daybreak, the heaviest snows are expected to center over New Hampshire and western Maine. As the coastal low tracks into and then lingers near the Gulf Maine, snow will spread east across Maine on Thursday, while continuing to impact the remainder of northern New England and parts of northern New York through Friday. WPC PWPF shows storm total amounts likely exceeding a foot over portions of the Adirondack, Green, and White mountains, as well as much of Maine. Some parts of the region may see over two feet, with the PWPF indicating moderate or higher probabilities for reaching these amounts over the White Mountains into western Maine. ....Central and southern Appalachians.... Days 1-3... Shortwave energy embedded within deep cyclonic flow will support showers across the region beginning Thursday, with thermal profiles supporting snow across the higher elevations. The heaviest accumulations are expected to fall along the Allegheny Mountains in West Virgina, where several inches are possible by the end of the period. WPC PWPF shows probabilities for accumulations of 4 inches or more climbing above 70 percent across this region during the Day 2 period (ending 12Z Friday). ....Western U.S.... Days 1-3... An amplified upper trough associated with a low dropping south from the Gulf of Alaska will begin to dig into the northwestern U.S. today Wednesday. Backing flow ahead of the advancing trough will support deepening moisture and the increasing potential for snow along a low-to-mid level front extending northeastward from the southern Cascades. While widespread heavy accumulations are not expected, locally heavy amounts are possible from the southern Cascades to the Blue Mountains late today into early Thursday. By early Thursday, models show a deep upper low centered along the Northwest coast that will then dig further south into northern California and Nevada by early Friday. This will bring heavy snows into the Sierra Nevada and parts of central and northern Nevada. Meanwhile, energy lifting east of the low and a lingering frontal boundary will support additional heavy amounts across northeastern Oregon. From Friday into Saturday, the upper low is forecast to lift northeast across Nevada into southern Idaho, bringing additional snows to portions of northern Nevada, eastern Oregon, and southern to central Idaho. While the mountains will likely see the heaviest amounts, this will be an anomalously deep system that will bring snow levels well down into many of the valleys. Meanwhile, snow with locally heavy totals will also extend south into the southern California mountains and along the Mogollon Rim, and east into portions of the central Rockies. Regarding three day totals, WPC PWPF shows high probabilities for accumulations of 8 inches covering much of the Sierra Nevada, the Oregon Cascades, and the Blue Mountains. Locally high probabilities these amounts also cover the central and Nevada mountains into southeastern Oregon and southwestern Idaho, as well as the central Idaho ranges. Pereira ***Key Messages for Early April Nor'easter*** ---Western Great Lakes snow through today Snow will continue throughout the region today, with additional heavy snow likely across portions of Upper Michigan and northern Wisconsin. Before ending on Thursday, snowfall accumulations over 2 feet are likely in parts of Upper Michigan. ---Northeast snow and wind through Friday Heavy, wet snow and some sleet will spread into the Northeast Wednesday today and continue through Friday. Snowfall accumulations of 1-2 feet are likely across portions of northern New York and New England. ---Significant impacts from heavy snow and wind Heavy snowfall rates and gusty winds will result in dangerous travel conditions, with whiteout conditions and snow-covered roads. The combination of wet snow, a high snow load, and strong wind gusts could also cause tree damage and power outages. ---Moderate coastal flooding in the Northeast Prolonged onshore flow late today and continuing through Thursday will result in moderate coastal flooding for portions of the Northeast coast. Impacts include widespread roadway flooding, coastal and bayside flooding, impassable roads, and some damage to vulnerable structures. $$ --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175) .