Subj : HVYSNOW: Probabilistic Heavy Snow And Icing Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Dec 05 2024 06:30:11 FOUS11 KWBC 050629 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 129 AM EST Thu Dec 5 2024 Valid 12Z Thu Dec 05 2024 - 12Z Sun Dec 08 2024 ....Eastern Great Lakes and Northeast...=20 Days 1-3...=20 Strong low pressure moving through Quebec this morning will=20 continue eastward, with WAA-driven snow over northern New England.=20 500mb heights/wind are near the CFSR reanalysis min/max=20 (respectively) with this potent system. The associated cold front,=20 responsible for numerous snow squalls yesterday afternoon and=20 overnight, will help feed moisture into northern/interior Maine=20 where sub-freezing temperatures will support all snow this morning. Low pressure will quickly translate into Atlantic Canada early=20 this afternoon, with the FROPA turning winds around to the=20 northwest and helping to enhance orographic lift across much of the Northeast into the central Appalachians. Strong pressure gradient=20 will also maintain windy conditions with blowing/drifting snow over the interior and near-blizzard/blizzard conditions in the higher=20 elevations (esp WV). Lake-effect snow, already in progress over MI, will redevelop/strengthen over the eastern Great Lakes by this=20 afternoon on NW flow with some double (Lake) dip increase in=20 moisture. CAM guidance continues to depict some rather robust=20 single bands off some of the lakes with a far reach inland of at=20 least lighter snow. Winds will eventually back and lighten by=20 tomorrow with less coverage/intensity overall but still some more=20 potent bands possible. A trailing shortwave out of Canada will=20 swing through the Lakes late Friday, again enhancing some lake-=20 effect snows across MI into NY and NW PA.=20 WPC probabilities for at least 12 inches of additional snow after=20 12Z Thu are highest (>50%) east of Lake Erie (NW PA into SW NY) and southeast of Lake Ontario (between ART and SYR). Moderate snow=20 (>8") is likely over the higher terrain of the Adirondacks into the Green and White Mountains due to upslope flow. In addition, the=20 eastern U.P. of Michigan and the western side of Lower Michigan=20 show moderate (40-70%) and low (10-40%) probabilities,=20 respectively, of at least another 8 inches of snow through=20 Saturday.=20 Lastly, with the progression of the cold front this morning, the=20 threat of snow squalls remains for parts of the northern Mid-=20 Atlantic into New England. This may produce a quick drop in=20 visibility coincident with gusty winds and slippery travel.=20 ....Pacific Northwest/Northern Rockies...=20 Day 3... Upper low in the northeastern Pacific will stream eastward along=20 50N into British Columbia, bringing in a surge of moisture to the=20 Cascades then into the northern Rockies on Saturday. Snow levels=20 will be on the higher side, about 8000ft at precip onset, but will=20 lower to around 5000-6000ft Saturday afternoon as the front moves=20 in, and falling farther to around 3500ft as the precipitation=20 lightens into Sunday morning. Snow will likely affect the higher=20 passes, where the probability of at least 6 inches is >50% above=20 4000ft or so. East of the Cascades, some icing and/or a wintry mix=20 of sleet/freezing rain will be possible as colder surface=20 temperatures are overrun by mild air aloft. Into the northern=20 Rockies, moisture will get wrung out over the higher terrain with=20 several inches likely (>50% chance of 6 inches) on the higher=20 mountain ridges.=20 The probability of significant ice >0.25" across the CONUS is less than 10 percent.=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!_SE21lAdIfWr2_E8riMb_I83_oj2-e2RtStvv7M3CA5zx= aP-iR8mkCa83hFy0rm25LoL5Zg-zgN9lFM2TYGyrW9ETZs$=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) .