GaWx

Looking at the last 5 Euro runs, one can see the Gulf to SW Atlantic low has been trending weaker while the center of the Arctic high has been trending eastward. Despite the amounts having come down some, the 0Z is still as modeled a big/historic hit for near and on the coast and the 0Z EPS is supportive see below). But if the low keeps trending weaker, this could easily end up minor even there. After all, getting an historic hit has to be exceedingly difficult by its definition. I thought KCHS forecasting 2-4” (extremely rare) three days in advance was quite bold and risky. The Euro is the only major 0Z global op that is giving the area that much per Kuchera. Uk, GFS, and Icon have only light precip at best. 0Z CMC is only other one close as it’s got 1-3” Kuchera, but it has overall been trending drier. 0Z EPS 10:1 (I’d reduce it 1/3 on SE side):

0Z Euro: Kuchera

Today’s Euro Weekly run in the SE for Jan 20-26 is the coldest yet and would easily mean by far the coldest week of the winter to date with 15-18F BN in most of VA/NC/SC/GA/AL/NW FL! That equates to a mean of 25-33F! That means that the bulk of the active posters are forecasted to be in/near the Jan normals for Chicago for N areas like RDU/GSO and St. Louis for more S areas like CHS:

From NWS CHS: surrealistic! MONDAY NIGHT INTO TUESDAY, THE HIGHLY AMPLIFIED UPPER TROUGH TRENDS TOWARD A POSITIVE TILT WHILE SEVERAL SOUTHERN STREAM SHORTWAVES DEVELOP. LATE MONDAY NIGHT, A WEAK COASTAL TROUGH IS FORECAST TO DEVELOP JUST OFF THE GA COAST. ALTHOUGH THE BRUNT OF THE MOISTURE AND FORCING ARE EXPECTED TO REMAIN OFFSHORE, WEAK MOIST ISENTROPIC ASCENT COULD PRODUCE SOME LIGHT PRECIP ALONG THE GA COAST LATE MONDAY NIGHT. OUR HOURLY TEMPERATURE VALUES DURING THIS TIME WOULD BE RIGHT AROUND FREEZING, SO IF ANY PRECIPITATION DOES DEVELOP, IT COULD FALL AS LIGHT FREEZING RAIN. DURING THE DAY TUESDAY, A STRONG DIGGING SHORTWAVE WILL TRAVERSE THE SOUTH CENTRAL UNITED STATES. EXTENSIVE CLOUD COVER AND COLD AIR ADVECTION WILL YIELD A CHILLY DAY WITH HIGHS ONLY IN THE MID/UPPER 30S IN SOUTHERN SC AND LOW/MID 40S IN SOUTHEAST GA. MOISTURE WILL SLOWLY OVERSPREAD THE AREA FROM THE SOUTHWEST LATE TUESDAY, AND EVENTUALLY SOME FORCING FOR ASCENT WILL TRANSPIRE. HOWEVER, MOST GUIDANCE HAS TRENDED A BIT DRIER ON TUESDAY WITH LITTLE TO NO PRECIPITATION THROUGH SUNSET. WE HAVE NOT FULLY JUMPED ON THIS POSSIBILITY GIVEN THAT MODELS ARE NOTORIOUS FOR STARTING PRECIPITATION TOO LATE IN THESE SCENARIOS, SO WE MAINTAINED CHANCE POP TUESDAY AFTERNOON. AS FAR AS PRECIPITATION TYPE, MODEL SOUNDINGS SUPPORT SNOW ACROSS THE INLAND HALF OF OUR AREA, THEN THINGS GET TRICKY AS ONE MOVES CLOSER TO THE COAST. A DECENT WARM LAYER IN THE LOWEST COUPLE THOUSAND FEET, COMBINED WITH FAIRLY DRY AIR WITHIN THE DENDRITIC GROWTH ZONE, INDICATES THE POTENTIAL FOR RAIN OR SNOW IN THE REST OF THE FORECAST AREA. ALONG THE GA COAST THE ATMOSPHERE LOOKS TOO WARM TO SUPPORT ANYTHING OTHER THAN RAIN. THIS IS ALL CONTINGENT ON ANY PRECIPITATION EVEN OCCURRING, WHICH STILL LOOKS IFFY FOR TUESDAY AFTERNOON. AT THIS POINT, GIVEN THE LOW CONFIDENCE IN ANY QPF, WE DO NOT SHOW ANY SNOW OR ICE ACCUMULATIONS FOR TUESDAY AFTERNOON. LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/ THE FORECAST IS QUITE INTERESTING IN THE LONG TERM PERIOD, ALBEIT EXTREMELY CHALLENGING. THE PRIMARY UPPER SHORTWAVE WILL PASS THROUGH THE SOUTHEAST TUESDAY NIGHT AND WEDNESDAY. MEANWHILE THE ARCTIC HIGH PRESSURE WILL REMAIN ANCHORED OVER THE CENTRAL APPALACHIANS, MAINTAINING A COLD NORTHERLY FLOW IN LOW/MID LEVELS. DEEP SYNOPTIC FORCING ASSOCIATED WITH THE SHORTWAVE WILL SPUR WIDESPREAD PRECIPITATION TUESDAY NIGHT INTO WEDNESDAY MORNING. MODELS ARE ACTUALLY IN REASONABLY GOOD AGREEMENT ON THE TOTAL LIQUID PRECIPITATION RANGING FROM 0.25-0.50" FAR INLAND AND 0.5-0.75" ELSEWHERE. HOWEVER, DETERMINING THE SNOWAMT AND ICEACCUM IS MUCH MORE CHALLENGING BECAUSE IT DEPENDS ON P-TYPES. MODEL SOUNDINGS INDICATE A LACK OF ICE NUCLEI ACTIVATION AT THE ONSET OF THE MAIN FORCING TUESDAY EVENING. HOWEVER, THERE SHOULD BE AMPLE COLD, DRY AIR IN THE LOW-LEVELS SUCH THAT TEMPS WILL QUICKLY COOL TO FREEZING AT THE SURFACE. THIS COULD YIELD FREEZING RAIN FOR MANY AREAS FOR A FEW HOURS AT THE BEGINNING OF THE EVENT. THEN, GUIDANCE SHOWS THE ENTIRE PROFILE QUICKLY MOISTENING AND BECOMING MORE OF A SNOW PROFILE FROM LATE TUESDAY MORNING [SIC] THROUGH WEDNESDAY MORNING. EVEN AFTER THIS OCCURS, THERE IS STILL PARTICULARLY HIGH UNCERTAINTY ABOUT HOW THINGS WILL PLAY OUT ACROSS COASTAL GA. AS FAR AS ACCUMULATIONS, IT IS OF COURSE ON EVERYONE'S MIND. BEING THAT IT'S MORE THAN 3 DAYS OUT AT THIS POINT, IT'S STILL A LITTLE EARLY TO CONFIDENTLY FORECAST ACCUMULATIONS. AT THIS JUNCTURE WE'RE BALLPARKING ONE OR TWO TENTHS OF AN INCH OF FREEZING RAIN ACCRETION AND 2-4" OF SNOW. IT STILL APPEARS THE GREATEST ICE ACCRETIONS WOULD PROBABLY BE IN COASTAL SOUTHEAST GA WHERE THE PRECIPITATION STAYS AS FREEZING RAIN LONGER THAN ELSEWHERE. ONE THING THAT IS A NEAR CERTAINTY IS THAT THESE ACCUMULATION FORECASTS WILL CHANGE BETWEEN NOW AND TUESDAY NIGHT. THE INITIAL PRECIPITATION SHOULD TAPER OFF WEDNESDAY MORNING. TEMPS WEDNESDAY AND WEDNESDAY NIGHT WILL BE QUITE COLD, ESPECIALLY IF WE HAVE SNOWPACK. WE COULD SEE SOME SUNSHINE BY LATE WEDNESDAY AFTERNOON, BUT PROBABLY NOT ENOUGH TO FULLY MELT ANY ACCUMULATED PRECIPITATION. HIGHS MIGHT RISE A FEW DEGREES ABOVE FREEZING. WEDNESDAY NIGHT LOWS WILL BE IN THE MIDDLE TEENS. WITH A FEW KNOTS OF WIND ON TOP OF THAT, WIND CHILLS MAY DIP BELOW 10F LATE AT NIGHT, POTENTIALLY REQUIRING AN EXTREME COLD WARNING. THE FORECAST FOR WEDNESDAY NIGHT THROUGH SATURDAY IS NOW A LOT TRICKIER THAN WE PREVIOUSLY THOUGHT. MODELS ARE STARTING TO SHOW ADDITIONAL SHORTWAVES MOVING THROUGH THE SOUTHEAST DURING THIS TIME, WITH A POSSIBLE COASTAL TROUGH DEVELOPING THURSDAY OR THURSDAY NIGHT. QUITE A FEW MODELS ARE NOW SHOWING A FEW TENTHS OF AN INCH OF QPF THURSDAY THROUGH FRIDAY. WITH ARCTIC HIGH PRESSURE STILL IN PLACE, SOUNDINGS SHOW THAT SOME OF THIS COULD FALL AS FREEZING RAIN. WE ADDED ZR TO THE FORECAST DURING THIS TIME FRAME, THOUGH THERE REMAINS A LOT OF UNCERTAINTY ABOUT WHEN THIS WOULD OCCUR. IF WE DO GET A PROLONGED PERIOD OF FREEZING RAIN ON TOP OF ACCUMULATING SNOWFALL, THIS WOULD RESULT IN SIGNIFICANT IMPACTS THROUGH MUCH OF THE WEEK.

I looked up Cordele, which looks like it is ~20 miles to the west of Rochelle, because they have good snow records back 90 years. Here are the only measurable snows there: 2/1973: 3.5” 2/2010: 1.5” 1/1935: 0.8” 12/1943: 0.5” 1/2018: 0.3” So, EPS is saying 90%+ chance for at least 3rd highest snow on record! And there’s ~40% chance to break the record if you can believe that!

Regardless of what this storm does or doesn’t do, the EPS is about as perfect as can be for us for 3.5 days out. Hope we get 1”+! This suggests 70-90% chance for our corridor!! Also, note 90%+ for ILM, MB, Charleston, Albany, Dothan, Pensacola, Mobile, Biloxi, and N.O.!!

12Z EPS members snow (excludes sleet/ZR): it is 10:1 rather than Kuchera. So, I’d take ~1/4 off for deep SE but still this is about the best ever for deep SE/Gulf coast. May not be next opportunity like this for many years to come! It may be finally our time to shine. Not a flake or pellet in 7 years. And maybe history about to be made?! We’ll see as this is still ~3.5 days out so not getting hopes up too high. Also, there’s the very real danger of a bad icestorm even into N FL! @metallica470 @Awesomesauce81 @gtg947h

12Z EPS 10:1 looks amazingly good for many and even historic for deep SE! Ens maps like this in deep SE/Gulf coast almost unheard of: Qpf:

And most of GA/SC among others

12Z Euro similar to 6Z: Sleet ZR

What about Feb 12 or 13 of 1899?

12Z GEFS vs 6Z/0Z: further SE/weaker GOM low, drier

Snow line further S on 12Z CMC: better run for deep SE

Areas in SE GA/S SC that were ZR on 0Z CMC have sleet on 12Z CMC due to further SE track

12Z CMC SE of 0Z 0Z CMC

CMC will be further SE than 0Z

Early maps suggest 12Z GFS will also come in a bit S of prior runs.

I don’t know about NW trend of model consensus stopping as 12Z Icon came in slightly N of its prior. But it may be more that the 12Z CMC trends south because CMC has been N of the others and is correcting itself. Also, Icon has been S of most others and was due to trend N.

Compare 12Z RGEM 84 with 0Z CMC 96: big diff! 12Z RGEM 84 0Z CMC 96 had the low/precip much further N and related to that the low was 4 mb stronger/more amped

The 12Z 84 RGEM is ~150 miles further S with the Gulf low vs the 0Z CMC 96 and precip shield is significantly further south along with it. Thus, I’m expecting the 12Z CMC to come in significantly south of the 0Z CMC with the precip/snow line/540 line, etc.

This means the 12Z CMC should come in a little south of its 0Z with slightly lower thicknesses and a little further S snow line. Also, 12Z RGEM well south of NAM.

Yep. Stronger low. Precip further n

Euro early maps show low/precip will likely be further N than 18z

Also has offshore wave 2 Thu. Complex situation!

0Z Uk further N with qpf vs 12Z