GaWx

If it comes in early, it could start as early as ~2 hours before this map, which is for the hour 3-4PM. So, say as early as ~1PM. Models have been speeding up the start and precip often starts a couple of hours earlier than models suggest:

Coldest Euro weekly for SE US for any week I’ve ever seen. This is for today through Sunday (1/20-26): coldest is 18-19F BN in darkest shade on Gulf coast meaning they’re having normals for St. Louis near 32! Further N around ATL-RDU, they’ll be near Chicago normals! The upcoming storm will be, oddly enough, when the stratospheric polar vortex strength is near record highs, near twice the normal strength in terms of zonal winds at 60N!

This is beautiful textbook split flow (from 18Z GFS), the pattern that has given the SE some of its biggest winter storms: N stream has WNW H5 flow to our north in the OH valley bringing the Siberian cold while moist WSW H5 flow is over us and to our south bringing plentiful moisture over the low level cold:

3” would be near Albany alltime record!

A 1/29/2014 last minute repeat?

Like the 12Z it has mainly sleet and ZR here and in much of SE GA. Also, 12Z and now 18Z even more is bringing start of virga earlier.

Regarding 12Z runs as of 3PM, NAM and CMC were a couple of degrees too cold at KATL but Icon, GFS, and Euro were within 1F fwiw.

Just after JAX, CHS did the same: URGENT - WINTER WEATHER MESSAGE NATIONAL WEATHER SERVICE CHARLESTON SC 234 PM EST MON JAN 20 2025 WINTER STORM WARNING IN EFFECT FROM 5 PM TUESDAY TO NOON EST WEDNESDAY... * WHAT...HEAVY SNOW EXPECTED. TOTAL SNOW AND SLEET ACCUMULATIONS UP TO TWO INCHES. * WHERE...IN GEORGIA, BULLOCH, CANDLER, EFFINGHAM, EVANS, JENKINS, SCREVEN, AND TATTNALL COUNTIES. IN SOUTH CAROLINA, ALLENDALE, BEAUFORT, CHARLESTON, COASTAL COLLETON, COASTAL JASPER, DORCHESTER, HAMPTON, INLAND BERKELEY, INLAND COLLETON, INLAND JASPER, AND TIDAL BERKELEY COUNTIES. * WHEN...FROM 5 PM TUESDAY TO NOON EST WEDNESDAY. ————————— * WHAT...HEAVY MIXED PRECIPITATION EXPECTED. TOTAL SNOW AND SLEET ACCUMULATIONS UP TO ONE INCH AND ICE ACCUMULATIONS UP TO ONE QUARTER OF AN INCH. * WHERE...COASTAL BRYAN, COASTAL CHATHAM, COASTAL LIBERTY, COASTAL MCINTOSH, INLAND BRYAN, INLAND CHATHAM, INLAND LIBERTY, INLAND MCINTOSH, AND LONG COUNTIES. * WHEN...FROM 5 PM TUESDAY TO NOON EST WEDNESDAY.

Would y’all and others mind posting this kind of thing in banter? Otherwise it will just add clutter to this storm thread. TIA

12Z Euro: Kuchera snow: Sleet: ZR: qpf: 12Z qpf 6Z as comparison showing slight NW trend at 12Z, mainly in NC

12Z Euro: fairly similar to 6Z; so the only major 12Z model without a notable NW/wetter trend though it did trend slightly NW vs 6Z in NC

The Euro has been trending drier for awhile as it had been near the wettest and was correcting toward the others. Will that drying continue with the 12Z or will it now stop or maybe even reverse the drying considering the 12Z model consensus? We’ll know fairly soon.

12Z UKMET starting off better too with a NW/snowier trend since 18Z run yesterday.

12Z GEFS 10:1, though not dramatically so, is consistent with the 12Z model consensus of a snowier/NW trend for many areas vs 6Z. 6Z: 12Z:

Large NW trend on just about everything at 12Z! I’m surprised it isn’t more active in here.

Agreed! But you can’t deny the NW trends/wetter.

12Z CMC joins NAM, Icon, and GFS with NW trend and wetter! This seems similar to the late Jan of 2014 sudden late NW trend that lead to ATL and other areas into well inland SC/NC getting huge impact. I‘m not saying big impact to ATL and those other well inland areas yet. But keep watching!

Yeah, these TT snow maps are way overdone on the SE side due to counting all wintry as snow. But you can see the snowier/NW trend. The qpf also shows the significant wetter/NW trend! So, at 12Z, NAM, Icon, and GFS further NW. This is similar to the last day or two strong NW trend for late Jan 2014! 6Z GFS 12Z GFS

The 12Z Icon also got a bit wetter and is similar to the 12Z NAM. It wasn’t nearly as dramatic a change as the NAM’s but the 6Z Icon had already been much further NW and wetter than 6Z NAM. 6Z Icon 12Z Icon Look at how much further NW and wetter the 12Z Icon is vs the 18Z Icon on Saturday:

Warning: This is probably a great example of getting “NAM’ed”. What the heck? 6Z (3 km) had this qpf: 12Z: How could it increase so much in just one run? Not far from me it increased from 0.08” to 1.12”! The NW end of the precip went from a line from FL/AL/GA intersection to Albany to just N of SAV to CHS to 40 miles offshore from the SC/NC border on the 6Z to way up to a just N of Columbus/Macon to Augusta to just N of CAE to Fayetteville line on the 12Z! That’s a 100-125 mile NW shift! Any opinions?

The Euro suite, which had been one of the wettest and is why I said I was fading it, continues its gradual drying trend while the Icon, which had been one of the driest, has been trending wetter. So, now the Icon and Euro are pretty close. The extremely low dewpoints are going to mean lots of virga to start. Will the virga overperform and minimize how much reaches the ground? Quite possible and it may be the main reason for big differences in qpf and changes from run to run.

What happened to the 0Z UKMET? Were the weenies too much for it?

0Z ICON continues the general trend of this model moistening up in NW FL as well as in the GA/SC coastal areas: 0Z Icon qpf 0Z Icon 10:1 snow Icon snow from 24 hours ago:

18Z Euro: still going for at least a once in a generation storm in much of deep SE/Gulf coast! Looks to be a pretty quick mover. I’m fading these amounts as of now in deference to some of the drier other models. Kuchera snow: Sleet: ZR: qpf:

18Z Icon: 10:1 (Kuchera not available) so these amounts need to be reduced some especially SE side; regardless, overall trend for these areas has been a notable increase and further north for N end vs what yesterday and especially Fri runs showed: the Wed/Thu runs were actually pretty snowy before Fri became much drier; now bouncing back a good bit! qpf: overall wetter trend recently due to slightly stronger low Compare to qpf as of run 24 hours ago: