277
FXUS62 KCHS 220124
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
824 PM EST SUN DEC 21 2025
SYNOPSIS
A COLD FRONT WILL PASS THROUGH THE REGION THIS EVENING. HIGH
PRESSURE WILL THEN PREVAIL THROUGH THE REMAINDER OF THE HOLIDAY
WEEK.
NEAR TERM /UNTIL 6 AM MONDAY MORNING/
22/01Z SURFACE OBSERVATIONS SHOW A BACKDOOR COLD FRONT IS
MAKING STEADY SOUTHWARD PROGRESS AND SHOULD CLEAR THE ALTAMAHA
RIVER PRIOR TO MIDNIGHT. A WIND SHIFT TO THE NORTH ALONG WITH A
LOWERING OF DEWPOINTS WILL OCCUR WITH FROPA. HIGH PRESSURE WILL
STEADILY BUILD SOUTH WITH A COOLER AND CONSIDERABLY DRIER
AIRMASS SETTLING IN. POST-FRONTAL COLD AIR ADVECTION (CAA) IS
MODERATE WITH 850 HPA TEMPERATURES FORECAST TO FROM +10-12C TO
+5-8C BY DAYBREAK. ONGOING CAA AND A TIGHTENING PRESSURE
GRADIENT ASSOCIATED WITH THE HIGH ITSELF WILL KEEP WINDS
ELEVATED THROUGH THE NIGHT. NEAR TERM STATISTICAL GUIDANCE
CONTINUES TO TREND WARMER OVERNIGHT WHICH MATCHES SOME OF THE
DIRECT MODEL OUTPUT TRENDS AS WELL. LOWS WERE NUDGED UP SLIGHTLY
AGAIN, RANGING FROM THE LOWER 40S INLAND TO THE UPPER 40S/LOWER
50S AT THE BEACHES WITH SOME UPPER 30S ACROSS NORTHERN PARTS OF
DORCHESTER AND BERKELEY COUNTIES AWAY FROM THE SANTEE-COOPER
LAKES.
LAKE WINDS: RAP SOUNDINGS SHOW AS MUCH AS 30 KT OF WIND
DEVELOPING IN THE MIXED LAYER OVERNIGHT WITH THE BULK OF THE
HIGHER WINDS CONFINED TO THE 1000-950 HPA LAYER. AS CAA STRENGTHENS,
EXPECT WINDS TO REACH 15-20 KT IF NOT A SOLID 20 KT WITH GUSTS
AS HIGH AS 25-30 KT. A LAKE WIND ADVISORY HAS BEEN ISSUED
THROUGH MID-MORNING MONDAY TO ACCOUNT FOR THESE WINDS AND WIND
GUSTS. WAVES AS HIGH AS 1-2 FT CAN BE EXPECTED. THE AREA OF
HIGHEST WINDS AND WAVES SHOULD OCCUR OVER THE CENTRAL AND
SOUTHWEST PORTIONS OF THE LAKE AND SHOULD LARGELY MISS THE
PNOS1 LAKE WIND OBSERVATION SITE GIVEN THE FLOW SETUP.
THEREFORE, OBSERVATIONS OUT OF PNOS1 MAY NOT NECESSARILY
REPRESENT THE WORST CONDITIONS ON THE LAKE OVERNIGHT.
SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/
MONDAY: SURFACE HIGH PRESSURE WILL BE CENTERED OVER THE
PIEDMONT OF NORTH CAROLINA WITH HIGH CLOUDS STREAMING OVERHEAD.
LOW LEVEL WINDS WILL BE GUSTY AT TIMES IN THE MORNING HOURS WITH
THE NOCTURNAL LOW LEVEL JET EXPECTED TO PEAK AROUND 30 MPH WITH
SOME SURFACE WIND GUSTS OF 20 TO 25 MPH POSSIBLE. AS THE DAY
PROGRESSES, WINDS WILL BECOME LESS GUSTY AS THE LOW LEVEL JET
SIGNIFICANTLY WEAKENS.
IN THE MID LEVELS OF THE ATMOSPHERE A POTENT SHORTWAVE WILL BE
QUICKLY EXITING NEW ENGLAND WITH SURFACE HIGH PRESSURE FOLLOWING
SUITE. THIS MEANS BY LATE MONDAY, THE SURFACE HIGH WILL ALREADY
BE OFF OF THE COAST OF NORTH CAROLINA WITH A COASTAL TROUGH
MOVING INLAND OVER GEORGIA AND SOUTH CAROLINA. NO PRECIPITATION
IS FORECAST WITH THE COASTAL TROUGH AS AN UPTICK IN DEWPOINTS
(AND RELATIVE HUMIDITY) ARE THE ONLY SENSIBLE WEATHER CHANGES
FORECAST. HIGH CLOUDS WILL BE STREAMING OVERHEAD THROUGH THE
DAY, BUT MOSTLY SUNNY SKIES ARE STILL EXPECTED WITH HIGHS IN THE
LOWER 60S. MONDAY NIGHT EXPECT LOWS IN THE LOWER 40S WITH SOME
GUIDANCE HINTING AT THE POTENTIAL FOR FOG OR STRATUS DEVELOPMENT
AS HIGHER DEWPOINTS SURGE WEST.
TUESDAY THROUGH THURSDAY: ANOTHER MID-LEVEL WAVE WILL DIVE
SOUTHEAST ACROSS ONTARIO AND QUEBEC LATE TUESDAY WHICH WILL
SPELL THE END OF THE SURFACE HIGH PRESSURE AND THE AGEOSTROPHIC
CONVERGENCE COMES TO AN END. EXPECT WARMING TEMPERATURES TUESDAY
AS THE AIR MASS QUICKLY STARTS TO MODIFY. TO PUT IT INTO
PERSPECTIVE, 1000/850MB THICKNESSES MONDAY ARE FORECAST TO BE
AROUND 1340M, AND BY TUESDAY AFTERNOON ARE EXPECTED TO BE 1365 -
1370M. THIS MEANS TEMPERATURES WILL RAPIDLY RISE INTO THE 50S
BY MID TUESDAY MORNING WITH HIGHS AROUND 70 DEGREES FORECAST.
TEMPERATURES WILL FURTHER WARM INTO THE LOWER TO MID 70S FOR
WEDNESDAY AND THURSDAY. THE LATEST RUN OF THE NBM SHOWS A HIGH
DEGREE OF CONFIDENCE WITH THESE TEMPERATURES AS THE INTERQUARTILE
RANGE (IQR) FOR HIGHS WEDNESDAY-FRIDAY IS ONLY 2-4 DEGREES. NO
PRECIPITATION IS FORECAST.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
THE FORECAST FOR FRIDAY REMAINS HIGH CONFIDENCE WITH ABOVE
NORMAL TEMPERATURES CONTINUING. FORECAST CONFIDENCE STARTS TO
DECREASE SATURDAY THANKS TO A POTENT MID-LEVEL LOW JUST EAST OF
THE HUDSON BAY. THIS LOW COULD POTENTIALLY PUSH A STRONG COLD
FRONT THROUGH THE AREA SATURDAY WITH TEMPERATURES RETURNING TO
MORE SEASONABLE VALUES.
HOWEVER, MODEL GUIDANCE VARIES WITH THE STRENGTH AND POSITION
OF THIS LOW. SOME ENSEMBLE MEMBERS SHOW A STRONGER MID-LEVEL LOW
AND SLOWER MOVEMENT OF THE WAVE NORTHEAST, WHILE OTHER MEMBERS
SHOW A MUCH WEAKER WAVE AND QUICKER MOVEMENT TO THE NORTHEAST.
THE DEEPER WAVE WOULD FAVOR NEAR NORMAL TO SLIGHTLY BELOW NORMAL
TEMPERATURES SATURDAY INTO SUNDAY, WHILE THE LESS AMPLIFIED
WAVE AND FASTER MOVEMENT WOULD FAVOR SEASONABLE TEMPERATURES
AGAIN MODERATING TO ABOVE NORMAL. TAKING A LOOK AT THE LATEST
WPC CLUSTER ANALYSIS REVEALS AROUND 65% OF MODEL SOLUTIONS
FAVORING THE FASTER/ LESS AMPLIFIED PATTERN WITH 20% SHOWING A
HIGHLY AMPLIFIED SOLUTION AND AROUND 15% ADVERTISING A BLEND
BETWEEN THESE SOLUTIONS. EITHER WAY, NO PRECIPITATION IS
FORECAST.
AVIATION /01Z MONDAY THROUGH FRIDAY/
22/00Z TAF DISCUSSION:
KCHS/KJZI/KSAV: VFR THROUGH 23/00Z.
EXTENDED AVIATION OUTLOOK:
MONDAY AND TUESDAY: MOSTLY VFR CONDITIONS. TWO PERIODS OF MVFR
CIGS OR LOWER ARE POSSIBLE WITH THE FIRST BEING MONDAY MORNING
BEHIND THE COLD FRONT. THE SECOND CHANCE WILL BE TUESDAY MORNING
AS MOISTURE RICH AIR RETURNS TO THE REGION. THESE RESTRICTIONS
WILL BE POSSIBLE DUE TO FOG OR STRATUS DEVELOPMENT.
WEDNESDAY AND THURSDAY: VFR CONDITIONS.
MARINE
THE SMALL CRAFT ADVISORY HAS BEEN EXPANDED TO INCLUDE CHARLESTON
HARBOR WITH THE EXPECTATION OF WINDS 15-20 KT WITH FREQUENT
GUSTS TO 25 KT.
THROUGH TONIGHT: SMALL CRAFT ADVISORIES REMAIN IN PLACE FOR ALL
AREAS. WINDS AND SEAS WILL BUILD TONIGHT AS A COLD FRONT DROPS
THROUGH THE WATERS. NORTHEAST WINDS WILL REACH AS HIGH AS 20-25
KT WITH GUSTS TO 30 KT AND SEAS BUILDING TO 4-7 FT.
MONDAY AND TUESDAY: BREEZY NORTHEAST WINDS BEHIND A COLD FRONT
ARE EXPECTED MONDAY MORNING WITH GUSTS 25 TO 30 KT. SEAS 4 TO 7
FT. THE NORTHEAST WINDS WILL THEN START TO RELAX LATE MONDAY
MORNING WITH SEAS SLOWLY STARTING TO COME DOWN MONDAY AFTERNOON.
ALL NEARSHORE WATER SMALL CRAFT ADVISORIES WILL BE DONE BY LATE
MONDAY EVENING WITH THE OFFSHORE GEORGIA WATERS REMAINING
THROUGH TUESDAY AFTERNOON DUE TO THE POTENTIAL FOR 6 FT SEAS.
WEDNESDAY AND THURSDAY: HIGH CONFIDENCE IN NO MARINE HEADLINES.
WIND GUSTS 15 KT OR LESS WITH SEAS 2 TO 3 FT.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...LAKE WIND ADVISORY UNTIL 9 AM EST MONDAY FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY UNTIL 9 AM EST MONDAY FOR AMZ330.
SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST MONDAY NIGHT FOR
AMZ350.
SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO MIDNIGHT EST
MONDAY NIGHT FOR AMZ352-354.
SMALL CRAFT ADVISORY UNTIL 6 PM EST TUESDAY FOR AMZ374.
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
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