Subj : HVYSNOW: Probabilistic Heavy Snow And Icing Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jan 21 2025 20:04:37 FOUS11 KWBC 212004 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 304 PM EST Tue Jan 21 2025 Valid 00Z Wed Jan 22 2025 - 00Z Sat Jan 25 2025 ....Great Lakes... Days 1-3... Upper troughing centered near the Davis Strait will send=20 shortwaves around its base across the Great Lakes for the next=20 couple of days, maintaining the lake-effect snow with some breaks=20 in between events and accentuated with a broader area of light=20 snow. Ongoing heavy snow east of Lake Ontario into the Tug Hill=20 will slowly weaken overnight as the trough axis passes through,=20 while the multi-band event over the Upper Great Lakes continues in=20 advance of a surface feature. That area of low pressure will=20 traverse Lake Superior and head eastward through southern Canada,=20 spreading light snow over the region tomorrow into Thursday before=20 weakening. 850mb temperatures are cold (-20C and lower) resulting=20 in more than enough lake-850 delta-T with fluffy snow given the=20 cold air mass.=20 The heaviest snow will be on D1 east of Lake Ontario and also over northwestern Lower MI and the eastern U.P. on SSW winds. WPC=20 probabilities for at least 8 inches of snow over the next 72 hours=20 are highest in these locations (>40%) with a broader area of >4"=20 probs >50% over the northwestern U.P. and downwind of Lake Erie=20 just south of Buffalo.=20 =20 ....Northern Rockies/High Plains... Days 1-3... Upper ridge axis over CA/OR will favor northerly flow across the=20 Northern Rockies onto the western High Plains with a few waves of=20 snowfall over the next three days. Though moisture is rather=20 limited, favorably-enhanced terrain will help wring out several=20 additional inches of the Little Belt and Big Snowy mountains into=20 the Bighorns and Black Hills. Lighter snow is expected for much of=20 the rest of the region days 1-2. The next system on D3 will focus=20 over western MT as the 120-kt jet moves through. WPC probabilities=20 for at least 8 inches of snow for the period are highest over the=20 aforementioned mountains.=20 ....Texas, Gulf Coast, and Southeast... Day 1... ....Significant and historic winter storm pushing through the=20 Southeast/southern Mid-Atlantic tonight... The winter storm responsible for significant and record-breaking=20 snowfall over parts of the northwest Gulf Coast will continue=20 eastward and northeastward tonight. Cold air mass supports snow all the way into the FL Panhandle with a mix of sleet/freezing rain=20 just to the south over the eastern portions of the I-10 corridor=20 and along the I-95 corridor from near Charleston southward to south of Jacksonville. For the period after 00Z tonight, snow will=20 spread quickly into eastern NC (and even up into southeast MA/Cape=20 Cod/Islands) with the Southeast in the RRQ of a 200kt jet exiting=20 the East Coast into Atlantic Canada and a strong baroclinic zone=20 just offshore as the Arctic air has been entrenched to the coast.=20 Question remains how much mixing there will be on the=20 southern/southeastern side (southeast GA/coastal SC/northern FL)=20 and how quickly there may be ptype transition. So far for this=20 storm, things have been colder rather than warmer so have nudged in this direction for the first few periods of this forecast=20 (starting 00Z tonight). With the long positively-tilted trough axis approaching the East Coast 00-06Z tonight, broad SW flow will=20 continue to funnel moisture up and over the cold dome with enhanced FGEN out of southeast GA northeastward to the NC Outer Banks.=20 There, WPC probabilities for at least 4 inches of snow are >30%=20 and even >50% over eastern NC.=20 Colder air will continue to push through the FL Panhandle this=20 evening with a mix changing to snow into the Tallahassee area where WPC probabilities for at least an inch of snow are >50% (extending northeastward across southeastern GA and increasing to >70%. To=20 the south/southeast, a mix of sleet/freezing rain will likely=20 result in a zone of icing over northeastern GA into=20 southeastern/coastal GA/SC (roughly TLH-CHS-JAX-GNV) where enough=20 WAA above the surface may prevent a changeover to all snow until=20 perhaps the end of the event. WPC probabilities of at least a=20 hundredth of an inch of ice are >30% over northern FL into=20 southeastern GA and up to Charleston, SC. Within this region, WPC=20 probabilities for at least 0.10" icing are highest (>30%) between=20 TLH and JAX northward to around Brunswick, GA.=20 Travel will be severely impacted tonight in much of the region.=20 See our Key Messages for more information that cover this system as well as the extreme cold over much of the eastern half of the=20 Lower 48. 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!8gpedAsCx7E8ZQR3vNfRrdKioWHQff0zoOjV8mlqPiLEm= lS7Posz1lg-uVKMbfRo5OLzpah_cukxPk9WGyMdseV7gx8$=20 https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!8gpedAsCx7E8ZQR3vNfRrdKioWHQff0zoOjV8mlqPiLEm= lS7Posz1lg-uVKMbfRo5OLzpah_cukxPk9WGyMdqebfQMk$=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) .