221
FXUS62 KCHS 311120
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
720 AM EDT MON MAR 31 2025
SYNOPSIS
SHOWERS AND THUNDERSTORM WILL OCCUR THIS AFTERNOON AND EVENING
AHEAD OF AN APPROACHING COLD FRONT. THE FRONT LINGERS NEARBY
MID-WEEK, BEFORE STRONGER HIGH PRESSURE PREVAILS LATE THIS
WEEK.
NEAR TERM /THROUGH TONIGHT/
EARLY THIS MORNING: BEHIND A DEPARTING SUBTLE COASTAL TROUGH
AND SHORT WAVE ALOFT, WIDESPREAD LOW STRATUS AND PATCHY FOG WILL
OCCUR. THIS IS THE RESULT OF THE WET GROUNDS AND CONSIDERABLE
MOISTURE TRAPPED BENEATH THE INVERSION. LOW LEVEL WINDS ARE A
BIT TOO STRONG FOR ANY SIGNIFICANT FOG CONCERNS, AND AS SUCH WE
HAVE NO WORSE THAN THE QUALIFIER OF "PATCHY" FOG.
FOR TODAY INTO THIS EVENING: IT'S A GOOD NEWS, BAD NEWS
SITUATION. THE GOOD NEWS IS THAT WIDESPREAD SHOWERS AND
T-STORMS WILL OCCUR LATER THIS AFTERNOON AND THIS EVENING,
HAVING A HUGE IMPACT ON THE ONGOING BRUSH AND WILDFIRES. THE
BAD NEWS IS THAT THE CONVECTION WILL BE ASSOCIATED WITH A SQUALL
LINE, WITH STRONG AND SEVERE T-STORMS THAT SWEEPS THROUGH THE
ENTIRE FORECAST COMMUNITIES.
THE SCENARIO ALOFT FEATURES A LOW AMPLITUDE SHORT WAVE TROUGH
THAT MOVES QUICKLY WITHIN THE WEST-SOUTHWEST FLOW, PASSING FROM
ALABAMA AND MISSISSIPPI THIS MORNING INTO GEORGIA THIS
AFTERNOON, REACHING SOUTHERN SOUTH CAROLINA LATE. AT THE
SURFACE, A STRONG COLD FRONT EXTENDING FROM LOW PRESSURE IN
QUEBEC WILL CROSS THE CENTRAL AND SOUTHERN APPALACHIANS BY LATE
IN THE DAY. THE LOCAL VICINITY WILL REMAIN WITHIN A WARM AND
MOIST AIR MASS AHEAD OF THIS FRONT, AND WITH CONTINUED WARM
ADVECTION THROUGH THE DAY, AND A WARM-ISH START TO THE DAY,
HIGHS LOOK TO PEAK AT 80-84F DEGREES AWAY FROM THE BEACHES.
THOSE SHORELINE COMMUNITIES WILL BE HELD DOWN MUCH COOLER WITH
THE EFFECTS OF THE RESULTANT SEA BREEZE. DUE TO THE MORNING FOG
AND CONSIDERABLE WIDESPREAD LOW STRATUS, THERE IS LITTLE TO NO
POTENTIAL FOR ANY SHOWERS AFTER DAYBREAK THROUGH MIDDAY.
HOWEVER, THE LOWER CLOUDS LIFT AND ERODE SOMEWHAT DURING THE
EARLY AFTERNOON, WHICH IS WHEN INSTABILITY STARTS TO CLIMB.
MUCAPE REACHES AS MUCH AS 1500-2500 J/KG, WITH MODEST 0-6 KM
SHEAR, AND PWAT CLIMBING BACK UP NEAR 1.50 INCHES. THIS PRE-
STORM ENVIRONMENT WILL SET THE STAGE FOR THE APPROACH OF A
SQUALL LINE.
THERE COULD BE A FEW SHOWERS OR EVEN AN ISOLATED T-STORM OUT
AHEAD OF THE SQUALL LINE DURING THE EARLY AFTERNOON, AS
SUGGESTED BY OCCASIONAL RUNS OF THE HI-RES MODELS. BUT THE MAIN
ACTIVITY WILL BE WITH THE SQUALL LINE LOOKS TO ARRIVE FROM THE
WEST DURING THE MID AFTERNOON, PASSING QUICKLY OFF THE COAST
DURING THE MIDDLE EVEN HOURS. USING A BLEND OF THE HREF, HRRR,
AND RAP, THE MOST LIKELY TIMING OF THE SQUALL LINE (SUBJECT TO
CHANGE) IS AROUND 3-5 PM FROM ALLENDALE TO TATTNALL COUNTY, NEAR
THE I-95 CORRIDOR AROUND 5-7 PM, AND ACROSS THE CHARLESTON TRI-
COUNTY AROUND 6-8 PM. SOME GUIDANCE IS SLOWER, SOME IS QUICKER
ON THIS TRANSPIRING, BUT MOST TIMES A SQUALL LINE COMES IN
EARLIER THAN ANTICIPATED. THIS IS SOMETHING WE'LL HAVE TO KEEP
WATCH FOR.
AFTER COLLABORATION/COORDINATION WITH SPC AND WFO'S ILM AND JAX,
WE OPTED TO SHRINK THE COVERAGE OF THE ENHANCED RISK TO A
SLIGHT RISK OVER THE COASTAL PLAIN OF BOTH SOUTH CAROLINA AND
GEORGIA. EVEN SO, A CONVECTIVE WATCH WILL BE ISSUED AT SOME
POINT DURING THE AFTERNOON FOR ALL AREAS. THE OVERALL
ENVIRONMENT WILL BE MOST CONDUCIVE FOR DAMAGING WIND GUSTS OF 60
MPH OR GREATER GIVEN DCAPE VALUES AROUND 1000 J/KG, AND
STRONGER WINDS MOVING IN WITH THE 850 MB AND 700 MB JET OF AT
LEAST 40 KT. THIS IS SUPPORTED BY THE CSU MLP, NADOCAST, AND THE
CIPS ANALOG GUIDANCE, WHICH HAS SEVERE WIND PROBABILITIES OF AT
LEAST 30%. THE TORNADO RISK IS A BIT MORE UNCERTAIN, AS THE
SHEAR ISN'T THAT IMPRESSIVE, AND STP IS AT BEST 1-2 UNITS. BUT
THERE IS LITTLE DIFFERENCE IN THE HEIGHT OF THE LFC AND LCL, AND
THERE IS AT LEAST A 10% PROBABILITY OF 2-5 KM UPDRAFT HELICITY
IN EXCESS OF 75 M2/S2. SO THERE IS AT LEAST A LOW END CHANCE FOR
ISOLATED TORNADOES. THE RISK OF HAIL LOOKS THE LOWEST GIVEN
THAT WBZ AND THE FREEZING LEVEL ARE QUITE HIGH.
GIVEN THE PROGRESSIVE NATURE OF THE SQUALL LINE, RAINFALL
AMOUNTS WILL BE ON THE ORDER OF 1/3 TO 2/3 INCHES, BUT WITH
LOCALLY HIGHER AMOUNTS APPROACHING 1 INCH. FORTUNATELY THE HIGH
TIDE OCCURS AFTER THE SQUALL LINE PASSES OFFSHORE.
FOR THE REST OF TONIGHT, SINCE THE TRAILING COLD FRONT DOESN'T
MOVE IN UNTIL OVERNIGHT, SO WE STILL CARRY A MENTION OF A FEW
MORE SHOWERS. PATCHY FOG WILL LIKELY FORM DUE TO SOME CLEARING
OF THE SKIES, LIGHT WINDS, AND THE WET GROUNDS. LOWS WILL
GENERALLY BE ONLY DOWN INTO THE UPPER 50S AND LOWER 60S.
SHORT TERM /TUESDAY THROUGH THURSDAY/
TUESDAY: PATCHY FOG BURNS OFF AFTER SUNRISE, THOUGH IT MAY LINGER A
TOUCH LONGER FOR THOSE ALONG THE COAST. A SURFACE HIGH PRESSURE
BUILDS IN FROM THE NORTH THROUGHOUT THE DAY, WITH UPPER LEVEL
RIDGING TAKING PLACE ALOFT. THIS WILL RESULT IN HIGHS ONLY A COUPLE
DEGREES COOLER DESPITE THE RECENT FROPA, WITH AFTERNOON HIGHS IN THE
UPPER 70S TO LOWER 80S.
WEDNESDAY: UPPER LEVEL RIDGING STARTS TO STRENGTHEN THROUGHOUT THE
DAY, WHICH IN COMBINATION WITH WARM AIR ADVECTION (WAA) IN THE MID-
LEVELS WILL RESULT IN AFTERNOON HIGHS IN THE LOWER TO UPPER 80S
ACROSS THE REGION, CLOSER TO THE MID/UPPER 70S ALONG THE COAST. THE
WAA AND MOISTURE IN THE MID-LEVELS WILL RESULT IN PARTLY TO MOSTLY
CLOUDY SKIES THROUGHOUT THE DAY. CAN'T RULE OUT A FEW SCATTERED
SHOWERS AS WELL, THOUGH RAINFALL AMOUNTS WILL REMAIN ON THE LOW SIDE
(< 0.05").
THURSDAY: AS UPPER LEVEL RIDGING CONTINUES ON THURSDAY, WITH
SITUATIONAL AWARENESS TABLES SHOWING RECORD HIGH 500 HPA
GEOPOTENTIAL HEIGHTS OCCURRING IN RELATION TO 30-YEAR NORMALS,
WARM/HOT TEMPERATURES ARE EXPECTED. THE NBM CONTINUES TO WARM-UP
TOWARDS THE 50TH PERCENTILE, AND WITH THE AFOREMENTIONED
SIGNALS IN THE ENSEMBLES, DID MIX IN SOME TEMPERATURES NEAR THE
75TH PERCENTILE OF GUIDANCE, RESULTING IN AFTERNOON HIGHS IN THE
LOWER TO UPPER 80S FOR INLAND AREAS, AND MID 70S TO LOWER 80S
ALONG THE COAST. CAN'T RULE OUT SOME 90 DEGREE TEMPERATURES, AS
NBM PROBABILITIES SHOW 40-60% CHANCES ACROSS INLAND SC COUNTIES,
REACHING UP INTO THE 60-80% RANGE FOR INLAND GA COUNTIES. THE
GOOD NEWS IS THE AFTERNOON SEA-BREEZE WILL BE COMING ASHORE IN
THE MID/LATE AFTERNOON HOURS, WHICH WILL HELP COOL THE REGION
BACK DOWN AGAIN.
LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/
THE LONG TERM CONTINUES TO REMAIN LARGELY WARM AND DRY AS A STRONG
UPPER LEVEL RIDGE SETS UP JUST OFF TO OUR SOUTH. ACCORDING TO THE
SITUATIONAL AWARENESS DISPLAYS, 1000 HPA TEMPERATURE ARE ALL IN THE
90+ PERCENTILE COMPARED TO 30-YEAR NORMALS, WITH 850 HPA
TEMPERATURES AT THE MAX OF 30-YEAR NORMALS AT TIMES...FROM BOTH THE
NAEFS AND ECMWF. THE EURO EFI IS ALSO COMING IN WARM, WITH A COUPLE
SHIFT OF TAILS BEING NOTED AS WELL. SO, EXPECT WELL ABOVE NORMAL
TEMPERATURES THURSDAY THROUGH SATURDAY, WITH DAILY CHANCES FOR
REACHING 90+ DEGREES HIGHEST (70-90% CHANCES) FOR AREAS WELL WEST OF
THE I-95 CORRIDOR, WHILE ALSO INCLUDING THE NORTHERN HALF OF
BERKELEY AND DORCHESTER COUNTIES IN SC. RECORD HIGH DAILY MAXIMUMS
MAY OCCUR, THOUGH THE CURRENT FORECAST FALLS ABOUT 1-2 DEGREES SHY
FRIDAY-SUNDAY AT THE CLIMATE SITES. RECORD HIGH DAILY MINIMUMS ALSO
MAY OCCUR, WITH THE CURRENT FORECAST WITHIN 2-3 DEGREES THURSDAY-
SATURDAY, AND IS GOING TO BE LARGELY DEPENDENT ON THE STRENGTH OF
THE AFTERNOON SEA-BREEZE.
A STRONG UPPER LEVEL WAVE MOVING OUT OF THE ONTARIO PROVIDENCE
SUNDAY INTO MONDAY, ACCOMPANIED BY A SURFACE HIGH PRESSURE MOVING
INTO THE CENTRAL PLAINS, WILL SEND A COLD FRONT TOWARDS THE REGION
SOMETIME SUNDAY/MONDAY. SCATTERED SHOWERS ARE EXPECTED PRIOR TO THE
FRONTAL PASSAGE, WITH CURRENT FORECASTED HIGHS ON MONDAY IN THE
LOWER/MID 70S.
AVIATION /12Z MONDAY THROUGH FRIDAY/
KCHS/KJZI/KSAV: GIVEN THE BUILD DOWN OF LOW STRATUS, IFR OR
LIFR CONDITIONS WILL OCCUR THIS MORNING. CEILINGS WILL BE DOWN
AT LEAST IN THE AIRFIELD MINIMUM RANGE UNTIL ABOUT 14-15Z. AS
MIXING HEIGHTS CLIMB, A RETURN TO MVFR CEILINGS WILL THEN OCCUR,
BEFORE VFR RETURNS BY 17-18Z. A SQUALL LINE WITH ITS ASSOCIATED
CONVECTION WILL THEN SWEEP THROUGH FROM ABOUT 21Z TO 01Z,
RESULTING IN AT LEAST MVFR CONDITIONS AND BRIEFLY STRONG AND
GUSTY WINDS PEAKING AT LEAST AROUND 30 KT. VFR RETURNS
THEREAFTER, WITH SOME CHANCE FOR A FEW MORE SHOWERS LATER ON AS
THE COLD FRONT MOVES THROUGH. BEHIND THE FRONT THERE WILL ONCE
AGAIN BE THE DEVELOPMENT OF LOW STRATUS BUILDING DOWN, WITH SOME
CLEARING ATOP THE PRE-EXISTING WET GROUNDS. FLIGHT RESTRICTIONS
WILL ONCE AGAIN OCCUR LATE TONIGHT.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTIONS CONTINUE TO REMAIN
POSSIBLE TUESDAY MORNING DUE TO BOTH SEA AND LAND FOG, WITH MVFR/IFR
VSBYS POSSIBLE. AFTER THAT, ASIDE FROM POSSIBLE LOW CEILINGS
WITH ANY ISOLATED SHOWER ACTIVITY ON WEDNESDAY, GENERALLY QUIET
AVIATION CONDITIONS ARE EXPECTED.
MARINE
TODAY AND TONIGHT: GIVEN THE WARM AND HUMID AIR MASS ATOP THE
COOLER OCEAN WATERS, AND LOW STRATUS, PATCHY FOG WILL IMPACT THE
MARINE AREA INTO THIS AFTERNOON. THIS INCLUDES CHARLESTON
HARBOR AND THE PORT OF SAVANNAH DURING THIS MORNING. CONDENSATION
PRESSURE DEFICITS THOUGH AREN'T LOW ENOUGH TO CAUSE A DENSE FOG
ADVISORY, BUT WE CONTINUE TO MONITOR. OTHERWISE, THE SYNOPTIC
PATTERN SHOWS HIGH PRESSURE CENTERED EAST OF BERMUDA, WHILE A
STRONG COLD FRONT MOVES INTO THE SOUTHEAST THIS EVENING, AND
MOVES INTO OR NEAR THE LOCAL WATERS DURING TONIGHT. MAINLY S OR
SW WINDS OF 15 KT OR LESS WILL OCCUR DURING THIS TIME, WITH SOME
GUSTS OF 20 KT IN CHARLESTON HARBOR THIS AFTERNOON DUE TO SEA
BREEZE INFLUENCES AND THE NEARBY SURROUNDING WARMER LAND MASS.
SEAS WILL AVERAGE 3-5 FEET THROUGHOUT, WITH THE MOST COMMON
OCCURRENCES OF THE 5 FOOT SEAS CLOSE TO 20 NM OFFSHORE AND OVER
THE OUTER GEORGIA WATERS. THERE MIGHT BE SOME LATE NIGHT FOG
ONCE AGAIN AS WINDS TURN W OR WSW DURING THAT TIME, ALLOWING
LAND BASED FOG TO PUSH IN.
THE BIGGEST CONCERN FOR MARINERS WILL BE STRONG AND SEVERE
T-STORMS THAT OCCUR WITH THE SQUALL LINE, AS IT IMPACTS THE
LOCAL WATERS AROUND 6-10 PM. DAMAGING WIND GUSTS IN EXCESS OF
40 OR EVEN 50 KT CAN OCCUR, ALONG WITH FREQUENT LIGHTNING
STRIKES AND BRIEF VERY HEAVY RAINS THAT REDUCE VISIBILITIES
UNDER 1 NM AT TIMES. SPECIAL MARINE WARNINGS WILL BE REQUIRED
DURING THIS TIME.
TUESDAY: PATCHY FOG WILL LIKELY LINGER/DEVELOP BEHIND THE EXITING
SHOWERS, WITH PERIODS OF WEAK AND VARIABLE WINDS ALLOWING FOR
CONVERGENCE OF HIGHER SURFACE MOISTURE.
WEDNESDAY-FRIDAY: SURFACE HIGH PRESSURE BUILDS IN FROM THE NORTH,
WITH GENERALLY QUIET MARINE CONDITIONS FORECASTED THROUGH THE END OF
THE WEEK, WITH WINDS AROUND 10 KNOTS AND SEAS AVERAGING 3 TO 4
FT.
CLIMATE
RECORD HIGH TEMPERATURES:
APRIL 4:
KSAV: 91/1963
APRIL 5:
KCHS: 89/1978
KSAV: 90/1988
APRIL 6:
KCHS: 90/1967
KSAV: 90/1967
RECORD HIGH MINIMUM TEMPERATURES:
MARCH 31:
KCXM: 68/1938
APRIL 2:
KCHS: 65/2012
APRIL 3:
KCHS: 67/2012
KCXM: 68/2012
KSAV: 68/2012
APRIL 4:
KCHS: 70/1974
KCXM: 69/1974
KSAV: 69/1974
APRIL 5:
KCHS: 65/2017
KCXM: 67/2023
KSAV: 66/1957
APRIL 6:
KSAV: 68/2023
EQUIPMENT
THE KCLX RADAR REMAINS OFFLINE FOR DOME MAINTENANCE THROUGH
APRIL 1, 2025. RADAR DATA WILL NOT BE AVAILABLE DURING THIS
TIME. USERS ARE URGED TO USE ADJACENT WSR-88D SITES WHICH ALSO
COVER MUCH OF SOUTHEAST SOUTH CAROLINA, SOUTHEAST GEORGIA AND
THE ADJACENT COASTAL WATERS. THESE INCLUDE:
KCAE - COLUMBIA, SC
KLTX - WILMINGTON, NC
KJAX - JACKSONVILLE, FL
KJGX - ROBBINS AFB, GA
KVAX - MOODY AFB, GA (MAY ALSO BE UNAVAILABLE DUE TO
MAINTENANCE)
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
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