297
FXUS62 KCAE 201744
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
1244 PM EST MON JAN 20 2025
SYNOPSIS
WELL BELOW NORMAL TEMPERATURES ARE EXPECTED THROUGH THE WEEK AS
AN ANOMALOUSLY DEEP TROUGH AND SURFACE HIGH PUSHES AN ARCTIC
AIR MASS INTO THE CENTRAL AND EASTERN US. A CHANCE OF SNOW REMAINS
IN THE SOUTHEASTERN MIDLANDS ON TUESDAY NIGHT INTO WEDNESDAY
MORNING. COLD WEATHER IS EXPECTED TO CONTINUE THROUGH FRIDAY, WITH
ONE OR MORE COLD WEATHER ADVISORIES POSSIBLE. TEMPERATURES ARE
FORECAST TO BEGIN WARMING TO NEAR NORMAL AGAIN OVER THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGE(S):
- THE COLDEST AIRMASS SO FAR THIS SEASON IS MOVING INTO THE
AREA.
- A COLD WEATHER ADVISORY HAS BEEN ISSUED FOR TONIGHT WITH WIND
CHILL TEMPERATURES 10 TO 15 DEGREES OVERNIGHT INTO TUESDAY
MORNING.
BROAD AMPLIFIED UPPER TROUGH OVER THE CONUS. THE TROUGH WILL
TAKE ON A POSITIVE TILT AS IT AMPLIFIES FROM THE GREAT LAKES
REGION TO THE MIDWEST LATER TONIGHT. ADDITIONAL SHORT WAVE
ENERGY IS MOVING OVER THE RIDGE OFF THE WEST COAST TOWARD THE
DESERT SOUTHWEST AND WILL LEAD TO FURTHER AMPLIFICATION OF THE
LONG WAVE TROUGH. AT THE SURFACE, THE VERY STRONG PRESSURE RIDGE
(NEAR 1050MB) OVER WESTERN CANADA INTO THE ROCKY MOUNTAINS WILL
FOLLOW THE TROUGH INTO THE MIDWEST AND EXTEND EAST NORTH OF THE
CAROLINAS BY LATE EAST AND SETTLE NORTH OF THE CAROLINAS BY
LATE TONIGHT. THIS ARCTIC AIR MASS IS QUITE COLD AND THIS IS THE
COLDEST AIR MASS OF THE SEASON FOR THE AREA. COLD ADVECTION
THROUGH THE DAY, WITH FULL INSOLATION TEMPS WILL STRUGGLE
THROUGH THE 30S TO NEAR 40 DEGREES LATE THIS AFTERNOON. THE
PRESSURE GRADIENT IS WEAKENING AS THE RIDGE BUILDS IN AND THE
DEEP LOW OFF THE NEW ENGLAND COAST MOVES FURTHER OUT TO SEA.
TEMPERATURES WILL LIKELY DROP QUICKLY THIS EVENING WITH CLEAR
SKIES AND A VERY DRY AIR MASS, DEWPOINTS BELOW 10 DEGREES IN
SOME AREAS. BUT LATER TONIGHT, MODELS SUGGEST INCREASING MID AND
HIGH LEVEL CLOUDS TOWARD MORNING. THIS MAY LIMIT NOCTURNAL
COOLING SOMEWHAT ESPECIALLY IN THE CSRA AND SOUTHEAST MIDLANDS
AS WEAK WARM ADVECTION DEVELOPS THERE AND TEMPS STAY IN THE LOW
20S. TO THE NORTH, CLOUDS SHOULD BE THINNER AND HIGHER
CONFIDENCE FOR LOW TEMPS TO FALL INTO THE TEENS. EVEN SO, WITH
SOME WIND OVERNIGHT, WIND CHILL TEMPS WILL LIKELY BE BELOW 20
DEGREES IN MANY AREAS AROUND DAYBREAK. THIS IS SUPPORTED BY NBM,
HREF AND LREF GUIDANCE. THEREFORE, A COLD WEATHER ADVISORY IS IN
EFFECT FOR ALL AREAS TONIGHT INTO TUESDAY MORNING.
SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/
KEY MESSAGE(S):
- THE FORECAST CONTINUES TO TREND DRIER WITH RESPECT TO SNOWFALL
POTENTIAL ON TUESDAY NIGHT
- VERY COLD TEMPERATURES ARE EXPECTED TO CONTINUE
WELL, THE SAGA CONTINUES WITH THIS FORECAST. OVER THE PAST 24 HOURS,
GUIDANCE HAS CONTINUED TO TREND TOWARDS THE DRIER SOLUTIONS AMONGST
THE SUITE OF GUIDANCE AS A WHOLE WITH RESPECT TO THE POTENTIAL SNOW
ON TUESDAY NIGHT. SHORTWAVE RESPONSIBLE FOR THE THREAT CAN BE EASILY
SEEN IN SATELLITE IMAGERY, PUSHING SOUTHWARD ACROSS THE WESTERN
CONUS AND CURRENTLY SITUATED ATOP THE SIERRA NEVADA MOUNTAINS
ON THE CA/NV BORDER. GUIDANCE IS IN GOOD AGREEMENT AND
GENERALLY HAS THIS FEATURE CORRECTLY PLACED AT THE MOMENT.
MODELS HAVE CONTINUED TO TREND TOWARDS THIS DIGGING FURTHER
SOUTH ALONG THE WESTERN PERIPHERY OF THE CONUS SCALE LONG WAVE
TROUGH, DIGGING ALL THE WAY INTO NORTHERN MEXICO BEFORE EJECTING
EASTWARD. AS A RESULT, THE SURFACE HIGH HAS TRENDED SLIGHTLY
EASTWARD AND LED TO A GREATER SUPPRESSION OF THE OVERALL
"COASTAL LOW" (IF YOU CAN EVEN CALL IT THAT AT THIS POINT) TRACK
FOR OUR SYSTEM IN QUESTION.
THE BULK OF TUESDAY LOOKS ON TRACK, WITH CLOUDS INCREASING FROM WEST
TO EAST ACROSS THE FORECAST AREA THROUGH THE DAY. THESE WILL
GENERALLY BE MID AND HIGH LEVEL CLOUDS AS UPPER LEVEL LIFT
SLOWLY INCREASES. THIS SHOULD PUT A CAP ON HIGH TEMPERATURES IN
THE UPPER 30S FOR MOST PLACES WITH SOME IN THE NORTHERN
FORECAST AREA POTENTIALLY REMAINING IN THE MID 30S. THIS GETS
US INTO THE EVENT IN QUESTION AND CONFIDENCE CONTINUES TO
INCREASE THAT THIS WILL BE MOSTLY A NON- EVENT FOR OUR FORECAST
AREA. GUIDANCE - AMONGST ENSEMBLE, DETERMINISTIC, AND HI-RES
MEMBERS - CONTINUES TO INDICATE A DRIER AND DRIER SOLUTION TO
THE FORECAST. ONE REASON IS THAT THE OVERALL UPPER LEVEL PATTERN
IS LOOKING LESS AMPLIFIED THAN IT WAS AMONGST GUIDANCE 2-3 DAYS
AGO. GUIDANCE SLOWLY SHIFTED THE PRIMARY SHORTWAVE TROUGH
ACROSS THE WESTERN CONUS SOUTHWESTWARD BY EARLY TUESDAY, WHILE
SPEEDING UP THE LEADING NORTHERN STREAM SHORTWAVE ACROSS THE
GREAT LAKES. THE INTERACTION BETWEEN THESE TWO FEATURES IS MUCH
SLOWER AND LESS DIRECT NOW, WHICH LEADS TO THE FORCING BEING
WEAKER AND SHIFTED SOUTHWARD. ANOTHER REASON IS THAT GUIDANCE IS
HANDLING THE STRENGTH OF THE SURFACE HIGH AND ARCTIC AIRMASS
BETTER THAN IT WAS. THE BAROCLINIC ZONE IN THE GULF OF MEXICO
AND OFF THE CAROLINAS COASTLINE THAT WOULD BE THE IMPETUS FOR
CYCLOGENESIS AHEAD OF THE APPROACHING TROUGH WAS CONSISTENTLY
MODELED TOO FAR NORTH UNTIL ABOUT 36 HOURS AGO. THIS OWES TO
JUST HOW STRONG THIS HIGH IS AND HOW FAR SOUTH THIS COLD AIR
EXTENDS; THIS IS TRULY AN ANOMALOUS AIRMASS. SO THE COMBINATION
OF THOSE TWO THINGS AND MODELS PICKING UP ON THEM IS REALLY WHAT
HAS DRIVEN THE TREND TOWARDS DRIER AND DRIER SOLUTIONS LOCALLY.
THIS AIRMASS IS FORECAST TO BE EXTREMELY DRY LOCALLY. LOW LEVEL
DEWPOINT DEPRESSIONS ON TUESDAY AFTERNOON ARE FORECAST TO BE ON
THE ORDER OF 20F-30F! THE ECMWF IS THE MOST "AGGRESSIVE" WITH
PRECIPITATION LOCALLY ON TUESDAY EVENING BUT THAT SEEMS TO
LARGELY BE A MIRAGE. THE MAJORITY OF MODEL SOUNDINGS REVEAL
MOIST MID & UPPER LEVELS ATOP A VERY DRY LOW- LEVEL AIRMASS.
AND WHILE MANY OF THESE MODELS SUGGEST THERE MAY ACTUALLY BE
NEGATIVE OMEGA IN THE DGZ, GUIDANCE (INCLUDING THE ECMWF)
UNIFORMLY IS SHOWING STRONG SUBSIDENCE VIA POSITIVE OMEGA IN THE
LAYER IMMEDIATELY BENEATH THE DGZ. THIS IS LIKELY DUE TO
850-700 HPA COLD/DRY AIR ADVECTION, AND THIS IS GOING TO MAKE
THE LOW-LEVEL DRY AIR DIFFICULT TO OVERCOME. SO WHILE MANY HI-
RES MODELS HAVE GOOD LOOKING COMPOSITE REFLECTIVITY FORECASTS
OVER THE AREA ON TUESDAY EVENING/NIGHT THAT MAKE IT LOOK LIKE IT
WOULD BE SNOWING, THAT IS NOT REFLECTIVE OF THE KIND OF
ACCUMULATED PRECIP THAT WE'D BE SEEING. SENSIBLE WEATHER
IMPACTS ARE LIKELY TO BE FAIRLY MINIMAL AT THIS POINT, CONFINED
TO THE SOUTHEASTERN TIER OF COUNTIES IN OUR FORECAST AREA. THERE
IS STILL DECENT OVERLAP OF GUIDANCE SUGGESTING SOME SNOW COULD
ACCUMULATE HERE, BUT EVEN NBM PROBABILITIES OF 1" OR MORE HAVE
DECREASED SIGNIFICANTLY FROM WHERE THEY WERE AT THIS TIME
YESTERDAY ACROSS THIS TIER OF COUNTIES. AS SUCH, NOT PLANNING
ANY WINTER WEATHER PRODUCTS WITH THIS FORECAST PACKAGE. EVEN IF
THE SOUTHEASTERN MIDLANDS MOISTEN UP A BIT FASTER THAN GUIDANCE
SUGGESTS IT WILL BE TOUGH TO GET MUCH MORE THAN AN INCH WITH
THE WAY THINGS HAVE TRENDED. THIS SYSTEM IS FORECAST TO MOVE
THROUGH IN A FEW HOURS, AND PROBABILITIES OF >0.1" OF TOTAL QPF
ARE ONLY IN THE 40-50% RANGE (DOWN FROM 60-70% 24H AGO). IT
SHOULD STILL BE COLD ON TUESDAY NIGHT WITH LOWS GETTING INTO THE
20S.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
KEY MESSAGE(S):
- COLD WEATHER EXPECTED TO CONTINUE THROUGH FRIDAY
- SLOW WARM UP LIKELY BEGINNING THIS WEEKEND AND CONTINUING INTO
EARLY NEXT WEEK
VERY COLD CONDITIONS LOOK TO CONTINUE ON WEDNESDAY, THURSDAY, AND
FRIDAY. ARCTIC HIGH SHOULD CONTINUE TO TRAVERSE EASTWARD DURING THIS
PERIOD, WITH A SURFACE RIDGE AXIS SETTLED ACROSS THE FORECAST AREA
BY SATURDAY MORNING. THE RESULTING COLD LOOKS ANOMALOUSLY COLD, BUT
LIKELY WON'T BE HISTORICALLY COLD. THERE IS STILL A STRONG SIGNAL
AMONGST GUIDANCE FOR HIGHS TO REMAIN IN THE UPPER 30S OR LOW 40S ON
WEDNESDAY AND THURSDAY WITH LOWS GETTING INTO THE TEENS OR LOW 20S
BOTH NIGHTS AS WELL. CLOUDS DO LOOK TO COMPLICATE THINGS ON
THURSDAY, THOUGH, ESPECIALLY WITH RESPECT TO HOW COLD WE CAN GET ON
WEDNESDAY NIGHT. GUIDANCE IS IN VERY GOOD AGREEMENT ON A SHORTWAVE
PUSHING SOUTHEASTWARD ON WEDNESDAY AND THURSDAY & FORCING A BROAD
COASTAL LOW OFF THE NC/SC COASTS BY THURSDAY NIGHT. CLOUDS ARE
EXPECTED TO INCREASE IN COVERAGE ON WEDNESDAY NIGHT AHEAD OF
THIS, WHICH SHOULD HELP TEMPS TO STABILIZE OR EVENT RISE
SLIGHTLY AFTER 1A OR 2A EARLY THURSDAY. BUT BEFORE THIS, TEMPS
WILL LIKELY FALL INTO THE MID OR UPPER TEENS GIVEN HOW DRY WE
WILL BE & IDEAL RADIATIONAL COOLING CONDITIONS UNDERNEATH THE
HIGH ON WEDNESDAY NIGHT. CLOUDS WILL PROBABLY HANG AROUND
THROUGH SOME PART OF THURSDAY NIGHT, HELPING KEEP LOWS ONLY IN
THE LOW TO MID 20S. THERE IS A CHANCE FOR PRECIP ON THURSDAY AS
THE COASTAL LOW GETS GOING; HOWEVER, THIS CHANCE LOOKS
RELATIVELY LOW. GUIDANCE APPEARS TO BE BOOSTED BY THE CANADIAN
MEMBERS WHICH ARE FAR MORE AGGRESSIVE THAT THE GFS OR ECMWF
(WHICH HAVE DONE MUCH BETTER WITH THIS INITIAL SYSTEM) SO OPTED
TO GO WITH ONLY SLIGHT CHANCE POPS ON THURSDAY. IF WE DO GET
PRECIPITATION, IT WILL LIKELY BE SOME KIND OF VERY LIGHT WINTRY
MIX BUT IT IS HARD TO SPECULATE ON WHAT EXACTLY THAT LOOKS LIKE
AT THIS TIMEFRAME.
BEYOND THURSDAY, TEMPS SHOULD SLOWLY BEGIN TO MODERATE. FRIDAY AND
FRIDAY NIGHT LOOK TO BE THE LAST REALLY COLD DAYS THIS PERIOD. THE
SURFACE HIGH IS FORECAST TO SETTLE ACROSS THE AREA AND TEMPS SHOULD
FALL INTO THE LOW 20S. THIS MAY BE SLIGHTLY TOO WARM, AS WELL, GIVEN
FRIDAY NIGHT LOOKS TO BE OUR ONLY NIGHT FEATURING TRUE RADIATIONAL
COOLING CONDITIONS DURING THIS PERIOD. ONCE THE SHORTWAVE TROUGH
EXISTS STAGE RIGHT WITH THE COASTAL LOW, HEIGHTS LOOK TO RISE
THROUGH EARLY NEXT WEEK & LEAD TO TEMPS CLOSER TO NORMAL.
AVIATION /18Z MONDAY THROUGH FRIDAY/
HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE FORECAST PERIOD.
HIGH PRESSURE WILL KEEP SKIES CLEAR TODAY WITH A DRY AIRMASS IN
PLACE. MID AND HIGH LEVEL CLOUDS WILL BEGIN TO INCREASE LATE TONIGHT
AS SOUTH TO SOUTH-WESTERLY FLOW ALOFT INCREASES AHEAD OF AN
AMPLIFIED UPPER TROUGH. NORTHWEST WINDS 5 TO 10 KNOTS SHIFTING TO
LIGHT NORTHEAST TONIGHT WITH THE SURFACE RIDGE SETTING UP TO THE
NORTH OF THE AREA. NORTHEAST WINDS THEN CONTINUE INTO TUESDAY AS
CLOUD COVER INCREASES AND CLOUD BASES DROP. FOR THIS TAF PERIOD,
EXPECT VFR CONDITIONS TO PERSIST.
EXTENDED AVIATION OUTLOOK
RESTRICTIONS POSSIBLE LATE TUESDAY
INTO TUESDAY NIGHT AS MOISTURE INCREASES AND LOW PRESSURE MOVES
NEAR THE COAST WITH SOME POSSIBLE WINTRY PRECIPITATION TUESDAY
NIGHT INTO WEDNESDAY MORNING.
CAE WATCHES/WARNINGS/ADVISORIES
SC...COLD WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM EST
TUESDAY FOR SCZ016-018-020>022-025>031-035-037-038-041-
115-116-135>137.
GA...COLD WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM EST
TUESDAY FOR GAZ040-063>065-077.
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