GaWx

12Z 1/3/24 EPS 7 days before 1/10 storm (ignore VA/KY and further north snow as that was from an earlier storm): 12Z 1/14/24 EPS 7 days before projected 1/21 storm:

I’ve saved a lot of EPS mean snow maps with lots of snow and this one easily takes the cake for the heaviest overall from E half of NC to the Gulf coast, especially this far out! This is massive for being 7 days out, especially in those areas. Some of the members start as snow as early as late afternoon on Mon (1/20).

1/7/1988. 4.2” officially of mainly sleet at KATL and maybe a little less in Dunwoody. Stayed on the ground for a long time! Opposite (sort of) occurred 2/1979. Was expected to be mainly snow and ended up almost all sleet (4.2” also at KATL!!) after no more than first hour or so of snow.

Thanks. Here’s my personal experience. I was in Dunwoody for the 2/2014 storm. It started as rain that quickly changed to ZR. Fortunately, the ZR lasted only a few hours and was fairly light. It changed to a long period of sleet (~1”, my 3rd highest there) followed by snow to end it. But the southside (airport to Tony) eastward to Augusta wasn’t so lucky as they had majority ZR and major problems. The Eisenhower Tree at Augusta National fell because of it. We’re you then in ATL area?

Thanks. Regardless, the Euro was too cold further out or 7-10 days before last week’s storm. Remember those runs with single digits at ATL, for example? Also, storm tracks for that storm out 7+ days were much further SE than what verified. But we’re now getting right to day 7/crucial forecast time. It did much better for last week’s storm at 96-140, consistent with what you said. But we’re not there yet. By late tomorrow we will be getting to 140. This as you’ve implied is a much different setup with a much colder Siberian high that is progged to be 20 mb stronger to our north/NW vs the weak and weakening high for last week’s storm.

No. It and the models as a whole are cold biased, which is why the storms often track NW and temps are often not as cold as one gets closer. But there are always exceptions. Nobody knows if this will be an exception, but it is a much different setup vs last week’s storm.

12Z Euro as you said now has a winter storm back (1st since 12Z run on 1/12): Snow: Sleet: ZR:

GFS runs with significant SE coastal wintry precip within 1/21-2: Jan 11 6Z and 12Z Jan 12 6Z and 18Z Jan 13 0Z, 6Z, 12Z, 18Z Jan 14 0Z, 6Z, 12Z So, 11 of last 14 and 8 in a row! The 12Z CMC has ZR later, on 1/23-4, with it still falling some areas especially just inland at the end (fortunately only light along coast SAV northeastward):

Here’s 12Z GFS sleet for all to look at and especially for @dsaur

See above as I added it centered on AL/GA/SC.

12Z GFS fwiw (taking with a huge grain) as a result of 24 hours straight of ZR has close to the worst icestorm on record in the SAV area with 1.45” (Hunter) and 1.63” (airport further inland) at reporting stations and a general 1.25-1.65” over much of the area away from the islands. The 6Z GFS also had a lot of ZR with 1.30” at airport and 0.66” at Hunter. Statesboro had a whopping 1.89”! Needless to say, I might be taking a 2nd Jan trip to snowy Atlanta (in this case for two reasons) if something like this were to somehow materialize:

12Z Icon is much drier than most other models for 1/21 (similar to 0Z run) but it is likely delayed but not denied as the run stops too early to see. It has light snow moving ENE over extreme S LA from a W GOM development while the SE is very cold due to a 1040 mb Siberian high right there: Note the split flow with the very cold WNW flow into the Midwest while at the same time there’s moistening WSW H5 flow over the SE going over the lower level very cold dome:

1) EPS 0Z 1/3/24 EPS (7 days before 1/10 storm): amounts were dropping then: Compare that to 0Z 1/14/24 EPS (7 days before potential 1/21/24 threat): much higher most of GA, SC, NC especially E NC to FL panhandle and with substantial increase since 12Z: 2) GEFS 0Z 1/3/24 GEFS (7 days before 1/10 storm): amounts were dropping then: Compare that to 0Z 1/14/24 GEFS (7 days before potential 1/21/24 threat): much higher ALL of GA, SC, NC, and FL panhandle and with substantial increase since 12Z:

Big increases on 0Z ensemble snow means throughout SE on GEFS, EPS, and GEPS for 1/21-2 vs 12Z: EPS: 12Z 0Z CMC ens: 12Z 0Z

Tony, It’s because those half county areas are on the border between one category and the adjacent one. They’re barely in the higher category. For example, that one county N of Columbus with the higher category is likely only barely above 1” vs their neighbors barely under 1”.

GEFS: 0Z vs 12Z 12Z 0Z big increase in S VA, NC, SC, GA, and Gulf coast!

GFS runs with significant SE coastal wintry precip within 1/21-2: Jan 11 6Z and 12Z Jan 12 6Z and 18Z Jan 13 0Z, 6Z, 12Z, 18Z Jan 14 0Z So, 9 of last 12 and 6 in a row! Normally when the models tease this area the NW trend takes the wintry precip away as it gets closer. That has yet to happen at all in this case. The coastal wintry GFS runs for 1/21-2 started at just over 10 days out. We’re now down to 7.5 days out and there’s no NW trend yet. The prior threat trended NW enough to end the coastal threat by 6 days out. If this doesn’t trend NW by during the Wednesday runs, this would be looking like a totally different situation. It already looks suspiciously different and I wonder if it is due to the Siberian high/extreme cold making this a different situation. 12/1989 and 1/2018 also had extreme cold to the north feeding those coastal storms. Edit: 2 of the last 6 Euro 0Z/12Z runs have had it then, both on 1/12: 0Z and the insane 12Z. The two on 1/13 were dry. The 0Z 1/14, just out, is also dry. No CMC runs through 0Z 1/14 have had it yet. So, since 1/13, GFS has been on an island. @Awesomesauce81 @gtg947h

I’m not really familiar with WxModels to be able to compare them.

0Z GFS has 12/1989 or 1/2018: chances of this actually occurring with these amounts on or near the coast…history says small; but note that these types of runs haven’t yet gone away

0Z GFS

0Z GFS

If so I have no access to them.

0Z Icon is significantly colder run vs runs from 12/24 hours ago. Coldest of season by far 1/20-1 and bone dry/no nearby surface low. Has lows on 1/21 of 10/9 at ATL/RDU! The plumbers would be busy! Minn/SPaul highs below 0F 1/19-20! Chicago barely gets above 0F on 1/20! Most of TN highs on 1/20 only in teens! Unlike those stupid cold Euro runs for last week, this frigid run actually seems possible due to Siberian high.

Here are the op model surface low positions as of 1/1-3 runs for 1/9-10 that I saved. They all verified poorly since the actual track was much further NW than the models showed: 12Z 1/1 Euro 0Z 1/2 GFS 12Z 1/2 GFS 12Z 1/2 Icon 12Z 1/2 CMC 12Z 1/3 Icon 18Z 1/3 Euro-AI Some models shifted NW on 1/3. Then on 1/4 (6 days before the storm), just about all modeled well down into the Gulf tracks that gave SE coast significant wintry precip were abandoned as the NW trend continued, including in the ensemble means. So, that means the NW trend was strongest 6-7 days prior to the 1/10 storm. So, looking ahead to 1/21 and projecting similar timing, I’ll be looking to see if the far SE tracks giving significant coastal wintry are largely abandoned 6-7 days prior to 1/21 or on 1/14-5. So, by Wednesday we’ll see what happens. Could this time be different? Of course it could. What is different with this one? - More runs develop the low not til offshore the SE coast as opposed to mainly developing in the Gulf for the 1/10 storm. - A much colder Siberian high. For example, Chicago’s coldest preceding and during the 1/10 storm was only down to 14F. Progs for 1/20 are for 15-20F colder - Related to this, the surface high coming down is progged to maintain much stronger intensity just before and on 1/21. Most model runs at this forecast point had at best a rapidly weakening 1020s high to the N or NE of the 1/10 storm, which verified pretty closely. The Euro had even weaker with an Alberta clipper low to the north on many AI runs. Remember that? In stark contrast, the progged high to the north of the upcoming threat is mainly 1038-1045 or 15-20 mb stronger! - So, we’ll have to see how this evolves.

Here are some comparisons between 1/10-1 as of 1/2 and possible 1/21-2 (11 days later) as of today (1/13): 1. 12Z EPS: 1/2 run for 1/10-11 1/13 run for 1/21-2: eerily similar in GA/SC and a bit more in NC 2. 12Z GEFS: 1/2 run for 1/10-11: 1/13 run for 1/21-2: significantly more N GA, N SC, and NC with ~same S GA and S SC