894
FXUS62 KGSP 091432
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
932 AM EST THU JAN 9 2025
SYNOPSIS
AN AREA OF LOW PRESSURE WILL FORM NEAR THE TEXAS COAST EARLY TODAY
AND TRACK ACROSS THE GULF COAST AND REACH THE CAROLINAS FRIDAY INTO
EARLY SATURDAY. MOISTURE SPREADS OVER OUR REGION IN THE COLD AIR
WITH WINTRY WEATHER FORECAST WHICH ENDS ON SATURDAY AS THE LOW MOVES
OFF TO THE EAST. DRY AND COLD WEATHER RETURNS EARLY NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 931 AM THURSDAY: THE COLD WEATHER ADVISORY ACROSS THE NORTHERN
MOUNTAINS REMAINS WELL PLACED THIS MORNING AND NO CHANGES WERE
NEEDED THERE. OTHERWISE, ANOTHER COLD AND DRY DAY REMAINS IN STORE
WITH ARCTIC HIGH PRESSURE CENTERED OVER THE REGION. THE ONGOING
FORECAST IS ON TRACK AND NO CHANGES WERE NEEDED.
OTHERWISE, UPPER RIDGING QUICKLY RIPPLES ACROSS THE EASTERN CONUS
TODAY AHEAD OF DEEP DIGGING TROUGH IN THE WEST. SUNNY SKIES
EXPECTED, AS DRY AIR FINALLY OVERTAKES THE LAST OF THE NW FLOW
STRATOCU THIS MORNING. THE AXIS OF DRY AND COLD SFC HIGH PRES WILL
REACH THE FORECAST AREA BY EARLY EVENING, ALLOWING WINDS TO
GRADUALLY WEAKEN. BUT ENOUGH OF A BREEZE WILL MAKE IT FEEL CHILLY
ONCE AGAIN ACROSS MOST OF THE AREA. HIGHS EXPECTED TO BE SIMILAR TO
YESTERDAY IN THE MOUNTAINS AND A CATEGORY OR TWO COOLER ACROSS THE
PIEDMONT. OVERALL, 10 TO 20 DEG BELOW NORMAL.
TONIGHT, SOUTHERN STREAM UPPER LOW/TROUGH WILL BEGIN TO EJECT
INTO THE SOUTHERN PLAINS, HELPING DEVELOP A MATURE CYCLONE OVER
THE NORTHWEST GULF. MOISTURE WILL SPREAD NORTH AND EAST ACROSS
THE LOWER MS VALLEY AND INTO THE TN VALLEY. HIGH CLOUDS SHOULD
QUICKLY THICKEN AND LOWER INTO A SOLID MID CLOUD DECK ATOP THE
FORECAST AREA OVERNIGHT. TEMPS WILL STILL MANAGE TO FALL INTO THE
TEENS ACROSS THE MOUNTAINS, AND MAINLY LOW TO MID 20S ACROSS THE
PIEDMONT. WINDS SHOULD BE LIGHT, SO WIND CHILLS SHOULDN'T BE AS
MUCH OF A CONCERN. DRY SUB-CLOUD LAYER WILL KEEP ANY MEASURABLE
PRECIP FROM REACHING THE GROUND THRU DAYBREAK FRIDAY. WITH THAT
SAID, ISOLATED NON-ACCUMULATING SLEET OR FLURRIES CANNOT BE RULED
OUT IN THE FAR WESTERN ZONES BEFORE 7 AM.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
KEY MESSAGES:
1) A WINTER STORM WATCH REMAINS IN EFFECT FOR OUR ENTIRE AREA FROM 7
AM FRI THROUGH 7 AM SAT. NO CHANGES/UPGRADES WILL BE MADE TO THE
WATCH AT THIS TIME.
2) MODEL GUIDANCE HAS TRENDED A BIT TOWARD MORE WARM AIR ALOFT AND
THEREFORE MORE MIXED PRECIP ACROSS THE CENTRAL/NORTHERN PART OF THE
AREA, AND MORE FREEZING RAIN ACROSS THE SOUTH.
AS OF 245 AM THURSDAY: 00Z GUIDANCE IS LARGELY STICKING TO ITS
RESPECTIVE CAMPS, WITH THE SLIGHTLY DRIER/COLDER/FARTHER SOUTH
ECMWF, THE QUITE WET AND WARM NAM (WARM AS IN "WARM NOSE"/MORE MIXED
PRECIP AND FREEZING RAIN), AND THE GFS/CANADIAN WHICH REPRESENT MORE
OF A COMPROMISE. HOWEVER, THE LATTER TWO GUIDANCE SOURCES SEEM TO BE
TRENDING SLIGHTLY TOWARD THE NAM CAMP, WHILE A CONSENSUS OF THE LAST
SIX HOURS OF THE CONVECTION-ALLOWING MODELS ALSO TEND TO PUSH A WARM
NOSE RATHER FAR NORTH INTO THE CWA BY 00Z SATURDAY. AS SUCH, WE'VE
TRENDED THE FORECAST TOWARD MORE IN THE WAY OF SLEET DEVELOPING AS
FAR NORTH AS THE I-40 CORRIDOR IN THE NC PIEDMONT (AND SOUTHERN TIER
OR TWO OF MOUNTAIN ZONES), AS WELL AS A QUICKER TRANSITION TO
FREEZING RAIN FOR AREAS ALONG AND SOUTH OF THE I-85 CORRIDOR FRI
AFTERNOON/EVENING. THIS ADDS BOTH COMPLEXITY AND MORE UNCERTAINTY TO
THE FORECAST, AS THERE ARE NOW CONCERNS ABOUT SLEET CUTTING INTO
SNOWFALL TOTALS ACROSS THE MOUNTAINS OF SOUTHWEST NC AND NORTHEAST
GA. THESE ARE THE AREAS WHERE WE HERETOFORE HAVE BEEN MOST CONFIDENT
THAT A) ALL PRECIP WILL FALL AS WINTRY PRECIP AND B) LIQUID
EQUIVALENT PRECIP IS EXPECTED TO BE ADEQUATE FOR WINTER STORM
WARNING CRITERIA TO BE MET (IF THE PRECIP WERE TO ALL FALL AS SNOW),
BUT MORE SLEET WOULD PLACE A RATHER LARGE FLY IN THAT OINTMENT.
MEANWHILE, CONFIDENCE IN FORECAST ACCUMS REMAINS MODERATE AT MOST
ACROSS THE REMAINDER OF THE AREA DUE TO EITHER CONCERNS ABOUT
ADEQUATE LIQUID EQUIVALENT PRECIP (MOST OF OUR NC ZONES OUTSIDE THE
SOUTHWEST MOUNTAINS), CONCERNS ABOUT MIXED PRECIP BEING THE PRIMARY
PRECIP TYPE (MUCH OF UPSTATE SC) AND/OR THE POTENTIAL THAT A FEW
AREAS MAY SEE A TRANSITION TO PLAIN OLD RAIN BEFORE ANY WARNING
CRITERIA IS REACHED (BECOMING AN INCREASING POSSIBILITY ACROSS
PORTIONS OF THE LAKELANDS AND VICINITY). IN FACT, OUR CURRENT
OFFICIAL FORECAST DOES NOT FEATURE WARNING CRITERIA SNOW OR ICE
OUTSIDE OF THE AFOREMENTIONED SOUTHWEST NC/NORTHEAST GA AREA (WHERE
WE ARE STILL FORECASTING GENERAL 3-6" TOTALS). HOWEVER, WITH THE
INCREASE IN FREEZING RAIN...AND A SWATH OF 0.1"-0.25" ICE ALONG AND
SOUTH OF THE I-85 CORRIDOR, WE DO HAVE SOME LOCATIONS JUST SOUTH OF
I-85 IN THE UPSTATE AND GEORGIA THAT ARE CLOSE TO THE 1/4 INCH
THRESHOLD. ALL THIS IS TO SAY THAT...IN COLLABORATION WITH
NEIGHBORING OFFICES, NO UPGRADES OR CHANGES TO THE WINTER STORM
WATCH WILL OCCUR ON THIS SHIFT. HAVING SAID THAT, THE POTENTIAL
STILL EXISTS FOR SIGNIFICANT WINTER WEATHER IMPACTS, ESPECIALLY
ACROSS THE SOUTHWEST HALF OF OUR AREA...PERHAPS THE GREATEST CONCERN
AT THIS POINT IS THE POTENTIAL FOR A BONAFIDE ICE STORM TO
MATERIALIZE FOR A PART OF THE AREA IF GUIDANCE TRENDS FURTHER TOWARD
A STRONGER/MORE ADVECTIVE/WETTER SOLUTION.
PRECIP WILL TAPER OFF AND SKIES CLEAR QUICKLY AFTER MIDNIGHT EARLY
SATURDAY, WITH A RESUMPTION OF DRY AND UNSEASONABLY COLD WEATHER
EXPECTED FOR THE DURATION OF THE SHORT TERM, WITH TEMPERATURES
EXPECTED TO BE MORE THAN 10 DEGREES BELOW CLIMO SATURDAY AND SAT
NIGHT. IN FACT, SAT NIGHT COULD PROVE TO BE ONE OF THE COLDEST
NIGHTS OF THE SEASON OVER ANY LINGERING AREAS OF SNOWPACK.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
AS OF 310 AM THURSDAY: UPPER RIDGING BRIEFLY BUILDS OVER THE EAST
EARLY IN THE EXTENDED, ONLY TO BE DISPLACED BY TUESDAY AS A SERIES
OF SHORT WAVE TROUGHS PASSING OVER THE NORTHEAST QUADRANT OF THE
COUNTRY CARVE OUT ANOTHER BROAD LONG WAVE TROUGH CENTERED NEAR THE
EAST COAST FROM TUESDAY THROUGH THE END OF THE PERIOD. THEREFORE,
AFTER A BRIEF MODERATION IN TEMPERATURES ON MONDAY (STILL SEVERAL
DEGREES BELOW NORMAL), THE COLD WEATHER IS EXPECTED TO RETURN FOR
THE LATTER HALF OF THE EXTENDED, WITH TEMPERATURES OF 10 OR MORE
DEGREES BELOW CLIMO FORECAST FROM MON NIGHT THROUGH WEDNESDAY. BY
THE MIDDLE OF NEXT WEEK, GLOBAL MODELS INDICATE A BLOCKING PATTERN
WILL BECOME ESTABLISHED ACROSS THE CONUS...SO THE COLD WEATHER MAY
NOT BE GOING ANYWHERE FOR A WHILE.
AVIATION /15Z THURSDAY THROUGH MONDAY/
AT KCLT AND ELSEWHERE: VFR AT ALL TERMINALS THROUGH THE PERIOD. ONE
LAST QUIET DAY BEFORE THE STORM. SKY SHOULD REMAIN CLEAR UNTIL
TONIGHT, WHEN HIGH CLOUDS START TO STREAM IN FROM THE WEST AND
THICKEN TOWARD 12Z FRI. PRECIP IS EXPECTED TO DEVELOP AFTER 12Z,
APPROACHING KCLT TOWARD 18Z FRI, SO WILL PROBABLY BE THE LAST
ROUTINE TAF ISSUANCE WITHOUT ANY WINTRY PRECIP BEFORE FRI-SAT'S
STORM SYSTEM. WINDS WILL CONTINUE TO BE GUSTY AT KAVL THRU MOST
OF THE DAY, WHILE LOW-END GUSTS WILL BE POSSIBLE AT KCLT AND KHKY
LATER THIS MORNING INTO THIS AFTN. WINDS WILL BE LIGHT/VARIABLE
OR CALM TONIGHT.
OUTLOOK: A LOW PRESSURE SYSTEM WILL ARRIVE FROM THE WEST ON FRIDAY
WITH WINTRY PRECIPITATION SPREADING FROM WEST TO EAST DURING
THE DAY. EXPECT SOME COMBINATION OF SNOW, SLEET, AND/OR FREEZING
RAIN TO AFFECT ALL TERMINALS FROM FRIDAY AFTERNOON THROUGH EARLY
SATURDAY MORNING. THE STORM SHOULD MOVE OUT BY MIDDAY SATURDAY AT
THE LATEST. DRY WEATHER RETURNS BY EARLY SUNDAY AND CONTINUES INTO
EARLY NEXT WEEK.
GSP WATCHES/WARNINGS/ADVISORIES
GA...WINTER STORM WATCH FROM FRIDAY MORNING THROUGH SATURDAY
MORNING FOR GAZ010-017-018-026-028-029.
NC...WINTER STORM WATCH FROM FRIDAY MORNING THROUGH SATURDAY
MORNING FOR NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510.
COLD WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ033-049-050.
SC...WINTER STORM WATCH FROM FRIDAY MORNING THROUGH SATURDAY
MORNING FOR SCZ008>014-019-101>109.
SYNOPSIS...JDL
NEAR TERM...ARK/TW
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...ARK
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