Subj : Major US Winter Storm To : All From : Dumas Walker Date : Sat Mar 23 2024 09:03 am FOUS11 KWBC 230810 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 410 AM EDT Sat Mar 23 2024 Valid 12Z Sat Mar 23 2024 - 12Z Tue Mar 26 2024 ....Northeast... Day 1... This morning, heavy snow is underway from northern New York to much of interior New England. Strong 850-700mb FGEN aloft coinciding beneath the right-entrance region of a strengthening 250mb jet streak over southern Quebec is aiding in the formation of distinct heavy snow bands setting up from the Tug Hill and Adirondacks to the Green and White Mountains. As the day unfolds, another jet streak along the Mid-Atlantic coast will intensify and place its diffluent left-exit region over New England through Saturday evening. This "kissing jets" setup forces vertical ascent at mid- upper levels of the atmosphere to become exceptionally strong, while simultaneously, a 40-50 knot southerly 850mb jet is directing copious amounts of moisture poleward towards New England. Add in a sufficiently cold air-mass from the Tug Hill on north and east through central and northern Maine, and the stage is more than set for prolific snowfall rates producing a heavy, wet snowfall over northern New England. It is worth noting surface temperatures are likely to remain <32F from the southern tier of New York and even as far south as the Poconos to result in some minor ice accumulations. Latest guidance has the surface-925mb layer remaining colder longer and thus allowing for a longer period of freezing rain. The areas with moderate-to-high chances (50-70%) for ice accumulations greater than a tenth of an inch are the Berkshires, the Green, the Monadnock and Merrimack Valley of southern New Hampshire, and south-central Maine. Ice accumulations will be most likely confined to trees, bushes, and power lines, while sidewalks and side roads may also see some slushy accumulation during the day. The bigger impact lies in the snowfall, however, as the WPC Snowband Probability Tracker (SPT) shows snowfall rates of 2-3"/hr are anticipated Saturday afternoon and into Saturday night across northern New England. The WSSI shows Major Impacts (largely due to Snow Amount and some cases of Snow Load) from the Adirondacks and the Green and White Mountains through the heart of Maine. Areas under Major impacts can expect considerable disruptions to daily life that include dangerous, to even impossible, travel conditions, widespread closures and disruptions, and given the dearth of heavy, wet snow expected, the potential for tree damage and power outages. WPC PWPF shows high chances (>70%) for snowfall totals >12" across Vermont's Northeast Kingdom, northern New Hampshire, and northern Maine. Snow will conclude shortly after midnight as high pressure builds in from the west on Sunday. ....The West... Days 1-3... An upper low barreling into the Pacific Northwest will accompany a second upper level disturbance tracking into southern California to direct a slug of Pacific moisture into California and as far north as the Cascades. The combination of upper level diffluence along with strong topographically-enhanced snowfall rates will result in periods of heavy snow along the Sierra Nevada and in the Northern California mountain ranges (Siskiyou/Salmon/Trinity) at elevations >5,000ft. Periods of heavy snow will also occur in parts of the Cascades (>5,000ft) and in the Great Basin (elevations >7,000ft). By Saturday night, snow will advance east towards the Wasatch, the Mogollon Rim, the western Colorado Rockies, and northern New Mexico Rockies. Heavy snowfall along the Mogollon Rim will generally occur at elevations >7,000ft, while the Wasatch, Uinta, Colorado and northern New Mexico Rockies will witness heavy snow at elevations >8,000ft. The Sierra Nevada and Northern California ranges sport locally moderate-to-high chances (50-70%) per WPC PWPF for snowfall totals >12". There will likely be some portions of these mountains ranges that surpass two feet of snow as lingering upslope flow continues into Sunday. Snow will also linger through Sunday in the Four Corners region at elevations >7,000ft before gradually dissipating by Monday morning. ....Northern Rockies & High Plains, Central Rockies, Upper Midwest... Days 1-3... **Major Winter Storm Set to Impact Northern/Central Rockies to Upper Midwest Beginning This Weekend** The upper low in the Pacific Northwest will spawn a new surface low in central Wyoming later this afternoon, while a strong dome of high pressure over south-central Canada and lower pressure in the Intermountain West maintains persistent easterly low-level upsloping flow into the northern High Plains and northern Rockies. This will keep periods of light snow falling in parts of eastern Montana and the western Dakotas, but snow accumulations will be more likely to occur on grassy surfaces, sidewalks, and side roads during the day. By Saturday night, low pressure will rapidly deepen over eastern Colorado. In response to the rapid pressure falls in the central High Plains, the 850mb LLJ will exceed 50kts over eastern Kansas and eastern Oklahoma. These southerly 850mb wind speeds are above the 99th climatological percentile and ushering in copious amounts of Gulf of Mexico moisture poleward into the Northern Plains and Upper Midwest through Sunday. By Sunday morning, heavy snow will be blanketing much of Montana with the main shield of snow gradually overtaking the Dakotas. The aforementioned 850mb moisture will wrap around the northern and northwestern flank of an elongated 700mb low located in central Nebraska. Strong 850-700mb FGEN over the Upper Mississippi Valley will result in heavy snow over southern Minnesota and northern Wisconsin that could produce 1-2"/hr snowfall rates Sunday afternoon and into Sunday evening. As the day unfolds the Central Plains will lie beneath the divergent left-exit region of a 250mb jet streak centered over northern Mexico, while to the north, the right- entrance region of a 250mb jet streak in southern Ontario further maximizes the intense vertical ascent atop the atmosphere. This will allow for the surface low on Sunday to deepen to exceptionally deep levels (sub 980 by Sunday evening). NAEFS at 00Z Monday shows much of southeast Colorado, the OK/TX Panhandles, and western Kansas sporting MSLP values that fall outside the observed 1979-2009 CFSR database. Monday morning will see the strong 850mb warm air advection in the Upper Mississippi Valley ultimately lead to a changeover from snow to an icy wintry mix at first, then to all rain in southern Minnesota, northern Wisconsin, and the U.P. of Michigan. This will cut down on snowfall totals but the icy wintry mix in some areas could still cause hazardous travel Monday morning. Meanwhile, in central South Dakota, southeast North Dakota, and northern Minnesota, snow will remain the primary p-type with strong wind gusts >40mph causing blizzard conditions through Monday afternoon. Snow will liner along the Red River of the North and northwest Minnesota Monday night but rain will be the primary p-type in northern Wisconsin and the Michigan U.P.. The latest WSSI shows Major Impacts in eastern South Dakota, southeast North Dakota, central Minnesota, and northwest Wisconsin. These areas sport moderate-to-high chances (50-70%) for snowfall totals >12" for the event, while areas near the northwest South Dakota and western Minnesota border have moderate chances (40-60%) for >18" of snowfall. WPC PWPF also shows high chances (>70%) for >8" of snowfall in central South Dakota, along the Minnesota Arrowhead, and in northern Wisconsin. Farther south, as a strong cold front pushes through and upslope flow ensues, periods of moderate-to-heavy snow have moderate-to-high chances (50-70%) for producing >4" along the Colorado Front Range, the Palmer Divide, and on south along the Sangre De Cristo. Light snow accumulations are also possible in the High Plains of eastern Colorado and but wind gusts topping 50 mph could lead to significant blowing snow impacts. For more details on impacts, please review our latest Key Messages below. Mullinax ***Key Messages for Northern Plains Winter Storm*** --A significant March winter storm begins today An extensive and high impact storm system will produce widespread heavy snow and gusty winds over the Northern Plains into the Upper Midwest beginning today and lasting into early next week. --Widespread heavy snow expected Heavy snow will spread across much of central and eastern Montana by Saturday night, then expand into the Northern Plains and Upper Midwest on Sunday and continue into Monday. There is a high chance (>70%) of at least eight inches of snow extending from portions of the Dakotas and north-central Nebraska northeastward through Minnesota into northern Wisconsin. --Hazardous impacts due to snow, snow load, and wind Heavy snow and gusty winds will produce areas of blowing and drifting snow and possible blizzard conditions Sunday into Monday. Hazardous travel, along with some disruptions and closures are expected late Saturday into early next week. Strong winds and heavy, wet snow on trees and power lines may result in tree damage and power outages. --Strong wind gusts in the Central and Southern Plains Blustery wind gusts in excess of 50 mph on Sunday may result in power outages, blowing dust that causes reduced visibility, and damage to property. $$ --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175) .