232
FXUS62 KCAE 151841
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
141 PM EST SUN DEC 15 2024
SYNOPSIS
WEAK COLD AIR DAMMING WILL LINGER INTO MONDAY MORNING, WITH
BELOW AVERAGE TEMPS EXPECTED. WELL ABOVE NORMAL TEMPS ARE
EXPECTED MONDAY THROUGH WEDNESDAY, WITH RAIN CHANCES INCREASING
BY MID- WEEK AS WELL. COLDER AIR RETURNS BY NEXT WEEKEND WITH A
DEEP TROUGH DIGGING INTO THE EASTERN US.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGE(S):
- WEAK COLD AIR DAMMING CONTINUES ACROSS CENTRAL, EASTERN SC AND
EASTERN GA.
WEAK WEDGE CONDITIONS REMAIN IN PLACE AS SURFACE RIDGING
CONTINUES DOWN THE LEE SIDE OF THE APPALACHIANS WITH A DEEP HIGH
PRESSURE CENTER OVER NEW ENGLAND. AN APPROACHING SHORTWAVE
TROUGH ACROSS THE OHIO VALLEY IS DRIVING WIDESPREAD MOISTURE
ADVECTION AND SOUTHERLY COMPONENT FLOW BELOW 500MB. SO WHILE
THIS IS A PRETTY CLASSIC WEDGE SETUP, THE MOISTURE COMPONENT IS
FAIRLY LIMITED WITH PWAT'S ONLY RISING TO AROUND 1.0".
CONSEQUENTLY, ISENTROPIC LIFT AND OVERRUNNING FROM 925MB
THROUGH 700MB IS ONLY PRODUCING PERSISTENT LOW-MID LEVEL STRATO-
CU ACROSS THE AREA. SHOWERS AND DRIZZLE ARE CONFINED TO THE
UPSTATE WHERE MOISTURE ADVECTION, OROGRAPHIC LIFT, AND SYNOPTIC
SCALE LIFT ARE STRONGER. HI-RES GUIDANCE REMAINS IN GOOD
AGREEMENT, ONLY SNEAKING A FEW ISOLATED SHOWERS INTO THE EXTREME
WESTERN MIDLANDS THROUGH MONDAY MORNING AND THE HI-RES MEMBERS
SHOW THE DIFFUSE GRADIENT THAT EXTENDS ACROSS THE CENTRAL AND
EASTERN MIDLANDS. HIGH TEMPS WILL REMAIN IN THE MID-UPPER 40'S
IN THE WESTERN MIDLANDS BUT THEN LIKELY HIT OR EXCEED 60 IN THE
EASTERN MIDLANDS. SOME CLEARING AND BREAKDOWN OF THE CLOUD COVER
IS LIKELY ACROSS PARTS OF THE EASTERN MIDLANDS, POSSIBLY INTO
THE CENTRAL MIDLANDS THIS AFTERNOON BUT WIDESPREAD LOWER STRATUS
WILL LIKELY REDEVELOP LATER THIS EVENING AND OVERNIGHT.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
KEY MESSAGE(S):
- IMPROVING CONDITIONS FOR MONDAY
- WELL ABOVE NORMAL TEMPS EXPECTED MONDAY AND TUESDAY
IN THE WAKE OF THE SHORTWAVE TROUGH ON SUNDAY, SHORTWAVE RIDGING IS
EXPECTED TO PUSH INTO THE REGION ON MONDAY, DEVELOPING TO ZONAL FLOW
BY TUESDAY. SURFACE HIGH PRESSURE SHOULD REMAIN IN PLACE TO START
MONDAY BUT GUIDANCE SUGGESTS THAT THE SURFACE HIGH WILL BEGIN
TO FILL AND WEAKEN THROUGHOUT THE DAY. THIS SHOULD LEAD TO A
GRADUAL WIND SHIFT FROM NORTHEASTERLY TO EASTERLY TO
SOUTHEASTERLY THROUGH THE DAY. SO THE EARLY CAD CONDITIONS THAT
MAY REDEVELOP TONIGHT SHOULD GENERALLY BEGIN TO LESSEN
THROUGHOUT THE DAY ON MONDAY. THE NORTHERN FA MAY CONTINUE TO
SEE CLOUD COVER AND COOLER TEMPS BUT IN GENERAL EXPECTING
CLOUDS TO BECOME LESSER THROUGH THE DAY. WITH THE RISING HEIGHTS
AND SHORTWAVE RIDING, TEMPS ARE FORECAST TO BE REALLY NICE AND
UP INTO THE MID TO UPPER 60S FOR MANY. OVERNIGHT ON MONDAY, HIGH
CLOUDS SHOULD PUSH BACK INTO THE REGION AHEAD OF ANOTHER
APPROACHING TROUGH. LOOK FOR LOWS IN THE MID TO UPPER 40S.
TUESDAY LOOKS TREMENDOUS. MID TO HIGH LEVEL CLOUDS ARE EXPECTED
AS THE SHORTWAVE TROUGH MOVES TO OUR NORTH WHILE A WEAKENING
FRONT APPROACHES THE AREA. NOT EXPECTING PRECIP WITH THIS GIVEN
THE FORCING BEING WELL TO OUR NORTH. HIGH SHOULD APPROACH
15F-20F ABOVE NORMAL IN THE LOW TO MID 70S ACROSS THE AREA,
ESPECIALLY WITH SOME WEAK COMPRESSIONAL HEATING AHEAD OF THAT
WEAKENING FRONT. OVERNIGHT, LOOK FOR TEMPS TO CONTINUE THAT
WARMTH WITH LOWS FORECAST TO BE IN THE LOW OR MID 50S.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
KEY MESSAGE(S):
- LITTLE CHANGE IN THE FORECAST THINKING FOR THE LONG TERM
PERIOD.
- WARM WEATHER WED/THUR
- RAIN CHANCES ON WED/THUR, WITH COOLER TEMPS ARRIVING FRI/SAT
THE DETAILS OF THE LONGER TERM ARE BEGINNING TO COME INTO BETTER
VIEW AS GUIDANCE GETS A BETTER HANDLE ON THE SYNOPTIC PATTERN DURING
THIS TIME FRAME. STILL EXPECTING TROUGHING ACROSS THE EASTERN US FOR
MUCH OF THIS PERIOD, WITH MUCH COOLER TEMPS BY THE END OF THE PERIOD
INTO NEXT WEEKEND. WEDNESDAY STILL LOOKS QUITE WARM, THOUGH, AS A
LOW PRESSURE SYSTEM AND COLD FRONT ARE FORECAST TO GET ORGANIZED TO
OUR WEST. RIDGING IS FORECAST TO PRECEDE THIS, AND WITH SOUTHERLY
FLOW AHEAD OF THE FRONT, TEMPS ARE LIKELY TO JUMP INTO THE 70S
AGAIN DESPITE INCREASING CLOUDS AND RAIN CHANCES THROUGH THE
DAY. ENSEMBLES AND OPERATIONAL MODELS HAVE GRADUALLY LOWERED
RAIN CHANCES IN GENERAL DURING THIS PERIOD. THEY'VE TRENDED
QUICKLY OVER THE PAST 4-5 RUNS TO A LESS AMPLIFIED, MORE COMPACT
AND FASTER NORTHERN STREAM SHORTWAVE PUSHING TO OUR NORTH. A
COLD FRONT SHOULD ACCOMPANY THIS ON WEDNESDAY NIGHT, BUT
PRECIPITATION CHANCES ARE STILL SORT OF UP IN THE AIR. LREF
MEMBERS HAVE ALL BACKED OFF ON RAINFALL PROBABILITIES IN THE
WED/THUR TIMEFRAME BUT THEY ALL STILL HAVE DECENT PROBABILITIES
OF RAINFALL. HOWEVER, IF THE MODELS CONTINUE TO TREND TOWARDS
THE SHORTWAVE REMAINING NORTH OF THE AREA, WE ARE LIKELY TO SEE
LESSER RAINFALL CHANCES. TRANSIENT HIGH PRESSURE IS FORECAST TO
PASS THROUGH ON THUR/FRI WITH A COOL DOWN EXPECTED. THEN,
ENSEMBLES AND OPERATIONAL MODELS ARE IN GOOD AGREEMENT THAT
ANOTHER, DEEPER TROUGH SHOULD SHIFT INTO THE REGION AND USHER IN
A COLD AIRMASS FOR NEXT WEEKEND. ECMWF EFI IS ALREADY SIGNALING
TO ANOMALOUS COLD IN THE DAYS 7-9 PERIOD (THE END OF THIS
PERIOD AND JUST BEYOND IT). SO BEYOND FRIDAY, LOOK FOR THE
REALLY COOL TEMPS TO POTENTIALLY RETURN.
AVIATION /19Z SUNDAY THROUGH FRIDAY/
VFR CONDITIONS EXPECTED SUNDAY AFTERNOON. CIG RESTRICTIONS
LIKELY AGAIN SUNDAY NIGHT INTO MONDAY MORNING.
WEAK COLD AIR DAMMING CONDITIONS CONTINUE ACROSS THE REGION, BUT
ALL SITES ARE NOW SITTING WITH VFR CIGS BETWEEN 4K AND 8K FEET.
THIS IS EXPECTED TO HOLD IN PLACE THE REST OF SUNDAY AFTERNOON
BEFORE LOWERING CIGS ARE LIKELY LATER SUNDAY EVENING INTO MONDAY
MORNING. CURRENTLY, IT LOOKS LIKE CIGS SHOULD GENERALLY FALL TO
MVFR AFTER ~0800Z FOR ALL SITES WITH SOME PERIODIC DROPS TO IFR
CLOSER TO SUNRISE; CONFIDENCE IS TOO LOW IN TIMING HOWEVER FOR
TAF MENTION YET FOR IFR, SO RAN WITH MVFR MENTION THROUGH 15Z
MONDAY. THE SETUP AND SOME GUIDANCE DOES SUGGEST SOME LIFR CIGS
ARE POSSIBLE BETWEEN 1100-1300Z, BUT AGAIN CONFIDENCE IS TOO
LOW CURRENTLY BUT THE POSSIBILITY SHOULD BE MONITORED AS THE
FORECAST CONFIDENCE IMPROVES. WINDS THROUGHOUT SUNDAY AFTERNOON
WILL REMAIN OUT THE NORTHEAST, AROUND 5-10 KNOTS, BEFORE GOING
CALM OVERNIGHT.
EXTENDED AVIATION OUTLOOK...INCREASING POTENTIAL FOR SHOWERS AND
ASSOCIATED RESTRICTIONS WEDNESDAY INTO THURSDAY.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
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