501
FXUS62 KCAE 201816
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
116 PM EST FRI DEC 20 2024
SYNOPSIS
A STRONG COLD FRONT CLEARS SKIES OUT TODAY AND TONIGHT. BREEZY
CONDITIONS ARE EXPECTED THIS AFTERNOON THROUGH THIS EVENING.
THIS WILL BE FOLLOWED BY SEVERAL DAYS OF COLD WEATHER WITH
SUBFREEZING TEMPERATURES AT NIGHT. A WARMING TREND IS EXPECTED
TOWARDS CHRISTMAS ALONG WITH THE NEXT CHANCE OF RAIN.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGE(S):
- A FEW SCATTERED SHOWERS EXPECTED LATE THIS AFTERNOON AND EARLY
EVENING ACROSS THE NORTH MIDLANDS AND PEE DEE.
- COLDER AIR WILL BE SPREADING INTO THE AREA TONIGHT.
A FAST MOVING CLIPPER TYPE SYSTEM MOVING ACROSS THE OHIO VALLEY
THIS AFTERNOON WITH A TRAILING ARCTIC COLD FRONT NOW MOVING
EAST ACROSS TENNESSEE AT 17Z. WINDS HAVE ALREADY SHIFTED TO
WEST/NORTHWEST BEHIND A WEAKER FRONT EARLIER THIS MORNING. DRY
AIR ADVECTION IS DEVELOPING AND EXPECT DEW POINTS TO DROP AROUND
10 DEGREES OVER THE NEXT COUPLE OF HOURS.
GUSTY WINDS OVER 30 MPH ARE LIKELY ACROSS THE AREA AS THIS
PRIMARY FRONT MOVES THROUGH AND IMMEDIATELY PROCEEDING IT AS
850-700MB WINDS RAMP UP OVER 40 KNOTS; A LAKE WIND ADVISORY IS
IN EFFECT FROM 4PM THROUGH 11PM. THIS FORECAST IS ON THE HIGHER
END OF GUIDANCE (~90TH PERCENTILE FROM THE HREF-NBM).
CLIMATOLOGICALLY, THIS SHARP OF TROUGH AND SURFACE FRONT TENDS
TOWARDS THE EXTREMES OF GUIDANCE WITH STRONG, UNIDIRECTIONAL,
NORTHWESTERLY FLOW THROUGHOUT THE DRY ADIABATIC MIXED BOUNDARY
LAYER BELOW 700MB.
A ROBUST SHORT WAVE TROUGH IS DIVING SOUTHEAST THROUGH
KENTUCKY/TENNESSEE. AS THE LONG WAVE TROUGH AMPLIFIES IN THE
EASTERN CONUS THIS AFTERNOON AND TONIGHT, THE STRONG "SHARP"
SHORT WAVE TROUGH WILL MOVE THROUGH SC WITH THE STRONGEST
LIFT/PVA ACROSS THE NORTH MIDLANDS AND PEE DEE. THE POLAR JET
ALOFT IS STRONG AROUND 130 KTS MOVING SOUTHEAST THROUGH THE
AREA. UPPER LEVEL DIVERGENCE EVEN INTO CENTRAL SC APPEARS QUITE
STRONG. RESIDUAL LOW-LEVEL MOISTURE IS IN PLACE STILL ACROSS THE
NORTH CENTRAL PORTION OF SC. RELATIVELY STEEP 0-3KM LAPSE RATES
AROUND 8C/KM WITH MU CAPE 50 TO POSSIBLY 200 J/KG NOTED BETWEEN
0C AND -10C. SOUNDINGS LOOK COLD ALOFT WITH MOISTURE INTO THE
ICE PRODUCING LAYER AROUND -15C. COMBINE THAT WITH AN EXTREMELY
WELL MIXED LAYER BELOW THE ICE-SNOW PRODUCING CLOUD BASE AND WET
BULB ZERO TEMPS IN THE 30'S, AND ITS A PRETTY GOOD SETUP. SO
DESPITE SURFACE TEMPS IN THE UPPER 40'S, WE COULD SEE SOME BRIEF
GRAUPEL, PRIMARILY IN THE PEE DEE. THE LATEST CAMS SUGGEST
SCATTERED LOW-TOPPED CONVECTION MOVING THROUGH THE NORTHERN
MIDLANDS AND PEE DEE LATE THIS AFTERNOON THROUGH THE EARLY
EVENING AND THIS IS CONSISTENT WITH GLOBAL DETERMINISTIC
GUIDANCE AND GOOD RUN-RUN CONSISTENCY.
COLD AIR ADVECTION OVERNIGHT WITH MAINLY CLEAR SKY, THE WINDS
WILL GRADUALLY DIMINISH AFTER MIDNIGHT. EXPECT LOW TEMPS IN THE
LOW TO MID 30S.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
KEY MESSAGE(S):
- NOTICEABLY COOLER AND DRIER THIS WEEKEND WITH SUBFREEZING
OVERNIGHT TEMPERATURES.
- A COLD WEATHER ADVISORY MAY BE NEEDED FOR SUNDAY NIGHT INTO MONDAY
MORNING.
THE REGION WILL BE UNDER THE INFLUENCE OF LONGWAVE RIDGING THIS
WEEKEND AS A FEW MOISTURE-STARVED SHORTWAVES MOVE MAINLY NORTH OF
THE FORECAST AREA. SURFACE HIGH PRESSURE WILL EXTEND FROM THE
CANADIAN BORDER SOUTH TO THE GOMEX AND ADVECT EASTWARD WHILE
DEEPENING OVER NEW ENGLAND BY SUNDAY. THIS WILL BRING MUCH COOLER
AND DRIER CONDITIONS TO THE AREA, WITH HIGH TEMPERATURES SATURDAY 5-
8 DEGREES BELOW NORMAL (LOW 50S) AND 8-12 DEGREES BELOW NORMAL BY
SUNDAY (LOW TO MID 40S). PWATS WILL BE AROUND 0.3" WITH DEWPOINTS IN
THE 20S, OR PERHAPS THE TEENS SUNDAY INTO SUNDAY NIGHT.
FAVORABLE RADIATIONAL COOLING CONDITIONS ARE EXPECTED SATURDAY NIGHT
UNDER CLEAR SKIES AND A WEAKENING PRESSURE GRADIENT. THIS SHOULD JET
OVERNIGHT LOWS INTO THE LOW TO MID 20S. HOWEVER, EVEN COLDER
TEMPERATURES ARE EXPECTED SUNDAY NIGHT WITH THE SURFACE HIGH PASSING
MORE TO OUR NORTHEAST, ALLOWING CAA TO DROP VALUES INTO THE UPPER
TEENS TO LOW 20S. COMBINED WITH SOME WEAK BOUNDARY LAYER WINDS,
THERE REMAINS THE POSSIBILITY FOR WIND CHILL VALUES TO DIP INTO THE
MID-TEENS. COLD WEATHER ADVISORY CRITERIA FOR US RANGES FROM 10
DEGREES ALONG THE SC/NC BORDER TO 15 DEGREES ACROSS THE REMAINDER OF
THE MIDLANDS AND CSRA. CURRENT LREF PROBABILITIES OF APPARENT TEMPS
<16 DEGREES F RANGE FROM ABOUT 45 PERCENT ACROSS THE PEE DEE TO
ABOUT 25% IN THE COLUMBIA AREA SOUTHWEST TO AUGUSTA. SO, WHILE THESE
PROBABILITIES ARE STILL LOW, THEY BEAR WATCHING OVER THE NEXT 24
HOURS TO DETERMINE IF A HEADLINE WILL BE NEEDED.
LONG TERM /MONDAY THROUGH FRIDAY/
KEY MESSAGE(S):
- A VERY GRADUAL WARMING TREND STARTS MONDAY, THOUGH TEMPERATURES
WILL BE BELOW NORMAL THROUGH MIDWEEK.
- THE NEXT STORM SYSTEM ARRIVES AROUND CHRISTMAS DAY.
MONDAY STARTS OFF DOWNRIGHT COLD, BUT WEAK UPPER RIDGING WILL
START TO PHASE ACROSS THE REGION. TEMPERATURES RISE A FEW
DEGREES FROM SUNDAY, KICKING OFF A SLOW WARMING TREND THROUGH
MID- WEEK. ADDITIONAL TEMPERATURE AND MOISTURE ADVECTION OCCURS
TUESDAY AND WEDNESDAY AS THE THE SURFACE HIGH PULLS AWAY AND
UPPER LEVEL SOUTHWEST FLOW STRENGTHENS AHEAD OF A DISTURBANCE
MOVING ACROSS THE DEEP SOUTH. CONFIDENCE IS INCREASING THAT THIS
SYSTEM WILL BRING THE NEXT THREAT FOR WIDESPREAD RAIN ACROSS
THE REGION FOR PERHAPS WEDNESDAY AND THURSDAY, THOUGH THE
DETAILS HAVE YET TO BE WORKED OUT. STILL, PWAT VALUES WILL RISE
CLOSE TO 1" AND TEMPERATURES WILL RISE INTO THE 50S ON TUESDAY
TO THE LOW 60S BY WEDNESDAY AND THURSDAY. LOWS WILL FOLLOW SUIT,
STARTING OUT IN THE 20S MONDAY NIGHT, RISING INTO THE 30S
TUESDAY NIGHT AND THE 40S BY WEDNESDAY AND THURSDAY NIGHTS.
AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
VFR CONDITIONS THROUGH THE PERIOD.
SATELLITE IS SHOWING SCATTERED CUMULUS MAINLY NORTHEAST OF THE
CAE/CUB AT 17Z OTHERWISE CLEAR SKY. THE PRESSURE GRADIENT IS
TIGHTENING ACROSS THE AREA AND A COLD FRONT WILL PUSH THROUGH
AROUND 22Z WITH INCREASING WEST-NORTHWEST WINDS 15 TO 20 KNOTS
WITH GUSTS TO AT LEAST 25 KNOTS INTO THE EARLY EVENING. THE
WINDS WILL DIMINISH OVERNIGHT. AS THE FRONT MOVES INTO THE AREA,
EXPECT SCATTERED TO BROKEN STRATO-CUMULUS ESPECIALLY NEAR THE
CAE AND CUB TERMINALS. ANY CEILINGS SHOULD BE VFR. WITH A STRONG
UPPER LEVEL TROUGH MOVING THROUGH THE AREA, A FEW SHOWERS ARE
POSSIBLE, BUT CURRENT THINKING HAS THESE SHOWERS NORTH OF THE
TERMINALS, FOCUSED NEAR THE NC/SC BORDER BETWEEN 21Z-01Z.
EXTENDED AVIATION OUTLOOK...NO SIGNIFICANT IMPACTS TO AVIATION.
CAE WATCHES/WARNINGS/ADVISORIES
SC...LAKE WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 11 PM EST THIS
EVENING FOR SCZ016-018-020>022-025>031-035-037-038-041-
115-116-135>137.
GA...LAKE WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 11 PM EST THIS
EVENING FOR GAZ040-063>065-077.
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