Subj : HVYSNOW: Probabilistic Heavy Snow And Icing Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Feb 16 2025 08:46:50 FOUS11 KWBC 160846 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 346 AM EST Sun Feb 16 2025 Valid 12Z Sun Feb 16 2025 - 12Z Wed Feb 19 2025 ....Great Lakes/Northeast...=20 Days 1-3... A powerful multi-hazard winter storm will continue to push=20 into/through the Northeast today as the sharpening shortwave=20 beneath the 160kt jet exits the Midwest. Cold air over the=20 Northeast will eventually be scoured out nearly up to the Canadian=20 border as low pressure lifts from near PIT this morning to central=20 NYS this afternoon. By then, a new area of low pressure over Cape=20 Cod will start to become the dominant low and lift into the Gulf of Maine as the old parent low weakens into western New England. The=20 new low will then move into Atlantic Canada tonight. The evolution=20 will favor all snow near the Canadian border and into interior=20 Maine where it will stay coldest thanks to the transfer of energy=20 to the coast, a transient mixed area of sleet/freezing rain to the=20 south, and rain surging northward after starting as snow this=20 morning farther south. Icing will hang on longer in the colder=20 terrain areas like the Adirondacks, Catskills, Berkshires/Greens,=20 and Worcester Hills/Monadnocks but also across coastal Maine on the north side of the new area of low pressure. The low pressure=20 center will continue to deepen as it pulls away tonight into the=20 low 970s mb and the synoptic snow will end Monday morning.=20 WPC probabilities for at least 6 inches of snow today are highest=20 north of I-90 in NY, north of the MA/VT/NH border, and=20 north/northwest of I-95 through Maine. Totals near the Canadian=20 border and over northern Maine may eclipse a foot (probs 30-70%+).=20 Between the coast and I-90 or so, ice will be the main problem=20 before some areas change over, briefly, to a cold rain (esp the=20 valleys via strong southerly flow). WPC probabilities for at least=20 0.25" icing are highest (40-70%) in the Berkshires/southern Greens=20 and into the Worcester Hills/Monadnocks. On the backside of the system, colder air will rush in across the=20 Great Lakes and into the central Appalachians, supporting lake=20 effect snow and upslope snow, respectively. Over eastern WV into=20 the MD Panhandle and the Laurel Highlands, upslope will provide for modest snow totals with WPC probabilities of at least 4 inches=20 >70%. Though that area will see snow ending on Monday, the lake=20 effect machine will keep cranking for the next few days as an upper low swings through the region out of Canada. The flow will back=20 from NW to WNW and favor the typical lake belts, but especially=20 over the eastern U.P. of Michigan and southeast of Lake Ontario.=20 There, WPC probabilities for at least 8 inches of snow over the=20 next few days are high (>70%) and are moderate (40-70%) for 18=20 inches of snow in localized areas that remain under banding.=20 ....Pacific Northwest/Rockies/Northern High Plains... Days 1-3... An active Pacific jet will guide a lead system into the Northwest=20 today, followed by onshore flow into Monday, then another system by Tuesday into Wednesday. Snow levels will be a bit below pass level and waver there for the next couple of days. East of the Divide a=20 very cold air mass will be in place thanks to high pressure over=20 Canada that pushes southward through the Plains, setting up upslope flow into western MT. For the first system, Sun-Mon (though into=20 Tue over WY), the highest snow totals will be over the Cascades=20 eastward into the central Idaho ranges, western MT/WY and into=20 northern CO/southern WY. Several feet of snow are likely in the=20 higher terrain with only a brief break between systems. IVT values=20 exceeding the 90th percentile will move through the region today,=20 but then drop after tonight as the jet flattens out a bit.=20 Nevertheless, the nearly continuous terrain-enhanced snow will=20 accumulate well over 1-2 ft with WPC probs > 70% in the mountains.=20 Snow will be fairly heavy over western-central MT on the upslope=20 side as well, where WPC probs for at least 8 inches of snow are=20 >50% around Billings up to Great Falls.=20 The next system will enter the PacNW D3 (Tues afternoon) with some light snow for the Cascades. This will push eastward into D4. ....Central Plains/Mid-MS Valley/Mid-South...=20 Days 1-3... Eastward extension of the Western US moisture will reach the=20 central Plains later this evening as WNW flow rushes through the=20 region. 700mb WAA will help drive light to modest snow across the=20 Black Hills southeastward into Nebraska overnight with fairly high=20 SLRs >15:1. Light snow will extend farther into northern MO by=20 early Monday before tapering off thereafter as the pattern shifts a bit. WPC probabilities for at least 4 inches of snow D1-1.5 are=20 30-80% in this NW to SE stripe but diminish to <30% over northern=20 MO.=20 Overnight Mon into Tue, height falls will dig through the Four=20 Corners with a multi-stream jet east of 100W. A strong Arctic front will push southward and increase low-level convergence, helping to drive an expansion of snow through KS and into northern OK and=20 eastward, growing heavier as the shortwave aloft reaches the Plains Tues evening. Heavy snow is expected to develop over eastern KS=20 into western MO beneath a quickening upper jet east of the=20 Mississippi, bleeding southward into northern/northeastern OK and=20 northern AR overnight. By the end of the period, the shortwave will continue into the Mid-South with light to moderate snow into TN.=20 On the southern side of the precip shield, colder air at the=20 surface will undercut the milder >0C thermals aloft over central AR where freezing rain is likely to form (with some sleet to the=20 north).=20 WPC probabilities for at least 4 inches of snow are >50% from=20 northwestern KS eastward to southern IL/western KY/northwestern TN, including northern OK/AR. Within this broad region, an axis of=20 heavier snow is likely to develop with rates >1"/hr and snow totals >8". WPC probabilities for at least 8" are >50% over southeastern=20 KS and southern MO. Farther south, ice probs for at least 0.10" are >30% around the Ouachita Mountains.=20 Fracasso ....Winter Storm Key Messages are in effect. Please see current=20 Key Messages below... https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!4AZw-ucawhkep6Z6Gn1ZandzoOVlwTL2kJqJJdio1FJHQ= 7BS2cc3thylAk2S-6orJQfQ1EdnbZkzg86Q7WqlfzYEiOs$=20 https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!4AZw-ucawhkep6Z6Gn1ZandzoOVlwTL2kJqJJdio1FJHQ= 7BS2cc3thylAk2S-6orJQfQ1EdnbZkzg86Q7Wqlj-uEOzY$=20 $$ =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .