618
FXUS62 KCAE 201918
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
218 PM EST FRI DEC 20 2024
SYNOPSIS
A STRONG COLD FRONT BRINGS BREEZY CONDITIONS THIS AFTERNOON,
ALONG WITH A FEW SHOWERS ACROSS THE NORTHERN FORECAST AREA. 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 COLDER AND DRIER THIS WEEKEND WITH SUBFREEZING
OVERNIGHT TEMPERATURES.
A COLD, DRY AIR MASS WILL DOMINATE OUR WEATHER THIS WEEKEND AS
SURFACE HIGH PRESSURE IN THE GREAT LAKES REGION MOVES EAST INTO
NEW ENGLAND. DAYTIME TEMPERATURES WILL BE 5-10 DEGREES COLDER
THAN TODAY ON SATURDAY AND EVEN LOWER ON SUNDAY. WHILE CAA AND
CLEAR SKIES WILL BE PRESENT AT NIGHT, CONDITIONS WILL NOT BE
PERFECT FOR RADIATIONAL COOLING DUE TO THE POSITION OF THE
SURFACE HIGH, KEEPING WINDS FROM GOING COMPLETELY CALM. WHILE
LATEST GUIDANCE HAS TRENDED SLIGHTLY WARMER WITH OVERNIGHT
TEMPERATURES, CONFIDENCE REMAINS HIGH THAT LOWS WILL BE WELL
BELOW FREEZING, ESPECIALLY SUNDAY NIGHT. WILL CONTINUE TO
MONITOR FOR A POSSIBLE COLD WEATHER ADVISORY SUNDAY NIGHT, EVEN
THOUGH CONFIDENCE IN ITS ISSUANCE HAS DECREASED.
LONG TERM /MONDAY THROUGH THURSDAY/
KEY MESSAGE(S):
- GRADUAL WARMING TREND THROUGH THE PERIOD.
- THE NEXT STORM SYSTEM ARRIVES AROUND CHRISTMAS DAY.
THE EXTENDED BEGINS WITH SLIGHTLY WARMER TEMPERATURES ON MONDAY
AS HIGH PRESSURE MOVES OFFSHORE. THIS BEGINS A GRADUAL WARMING
TREND THAT WILL CONTINUE THROUGH CHRISTMAS WEEK. HOWEVER, HIGH
TEMPERATURES WILL REMAIN BELOW NORMAL MONDAY AND TUESDAY THEN
NEAR NORMAL WEDNESDAY AND THURSDAY. MOISTURE INCREASES DURING
THE MID-WEEK PERIOD AS THE NEXT STORM SYSTEM APPROACHES, WITH
RAIN POSSIBLE AROUND CHRISTMAS DAY. WHILE TIMING DIFFERENCES IN
THE GUIDANCE REMAIN, THE MOST LIKELY TIME FOR MEASURABLE
RAINFALL LOOKS TO BE WEDNESDAY NIGHT.
AVIATION /19Z 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 UNTIL 11 PM EST THIS EVENING FOR SCZ016-018-
020>022-025>031-035-037-038-041-115-116-135>137.
GA...LAKE WIND ADVISORY UNTIL 11 PM EST THIS EVENING FOR GAZ040-
063>065-077.
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