Subj : HVYSNOW: Probabilistic Heavy Snow And Icing Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Feb 19 2025 07:02:00 FOUS11 KWBC 190701 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 201 AM EST Wed Feb 19 2025 Valid 12Z Wed Feb 19 2025 - 12Z Sat Feb 22 2025 ....Southern Mid-Atlantic States...=20 Day 1... A significant winter storm will continue to spread eastward into=20 the southern Mid-Atlantic with potentially major impacts including=20 heavy snow and significant ice. See the latest Key Messages linked=20 at the end of the discussion.=20 Surface low along the Central Gulf coast will cross North Florida=20 early this afternoon and parallel the Southeast Coast tonight. The=20 northern stream shortwave responsible for the heavy snow in the=20 Plains will continue eastward into the southern Mid-Atlantic,=20 helping to spread generally light snow to the southern=20 Appalachians, aided by some orographic enhancement. WPC=20 probabilities for at least 4 inches are generally <30%. As the Gulf low transitions to a western Atlantic/coastal low,=20 precipitation will progress to the VA/NC coast with snow to the=20 north (solidly cold column over VA) and freezing rain and sleet to=20 the south where warmer air aloft will overrun the cold surface=20 temperatures near and just below freezing over eastern NC and into=20 portions of eastern SC as well. Snowfall to the north will likely=20 maximize later this afternoon and evening as the surface low starts to deepen over the Gulf Stream, with locally heavier rates >1"/hr=20 over southeastern VA, leading to moderate/heavy amounts. WPC=20 probabilities for at least 6 inches of snow are >50% there. There=20 is a much larger footprint of >2" probabilities of at least 40%,=20 extending from southwestern VA eastward, as far north as=20 Fredericksburg, VA to Rehoboth Beach, DE, and as far south as the=20 Raleigh-Durham metro.=20 Into NC, several hours of freezing rain are likely starting this=20 afternoon and continuing into the evening. Accretion will depend on rainfall rates (which limit accretion), wind, and time of day, but most of the guidance still indicates the potential for a couple=20 tenths of an inch of ice, roughly along and east of I-95 in eastern NC. WPC probabilities for at least 0.10" ice are >40% with some=20 areas likely seeing >0.25" ice. Precipitation will wind down=20 overnight and end by Thursday morning. ....Great Lakes/Northeast...=20 Days 1-2... Lake effect snow will diminish this morning as height falls over=20 the Corn Belt move into the region, favoring widespread light snow=20 over the Great Lakes and Midwest tonight into Thursday. WPC=20 probabilities for at least 4 inches of snow are low (<40%) except=20 for some lingering lake bands and/or lake enhanced snows. ....Pacific Northwest through the Central Rockies... Days 1-3... A potent but progressive Pacific system will start to move into=20 the Northwest this morning, spanning the latitudes from NorCal up=20 to the Canadian border. IVT will be modestly high (~90th=20 percentile) into NorCal/southern OR/northern NV toward Idaho,=20 supporting light to moderate snows for the terrain with snow levels near 3000ft to the north and 5000ft to the south that will rise a=20 bit as the core of the moisture plume pushes through. The system=20 will move steadily along which will end QPF from west to east=20 starting as early as tonight over the Cascades and on Thursday over the Great Basin. Moisture will wane with decreasing synoptic=20 support into Thursday, with snow confined mainly to the Unitas and=20 higher CO Rockies by then. For the 2-day period, WPC probabilities=20 for at least 8 inches of snow are highest (>70%) over the higher=20 terrain above 6000ft closer to the coast, 7000-8000ft over the=20 Great Basin, and 9000ft over CO/WY. A new system will to enter the=20 Northwest by D3 with lighter snow into the northern Cascades. ....Southeastern Mass... Day 2... The exiting system from the Southeast/southern Mid-Atlantic will=20 track northeastward and may clip southeastern MA/Cape Cod on=20 Thursday on its way into Atlantic Canada. The question revolves=20 around the speed of the incoming northern stream upper low and how=20 much it can capture the exiting system and pump up the downstream=20 ridge. 00Z guidance still shows at least some snow into the region, but vary on how much. The best chances for snowfall over 4 inches=20 remains over Nantucket (~70%) as well as both Martha's Vineyard and Cape Cod (40-60%), with low probs (10-20%) from Block Island to=20 New Bedford to Plymouth. 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_2.png__;!!DZ3fjg!9sVcZe4TlHpniV6jCGyvBRat6RhwKKhfV5vDeJcEpZbHI= 3DIxoXOdFgeWi1xsDCLbhLvxvOujjMZE38LNF3kw8MjcUs$=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) .