549
FXUS62 KCHS 210000
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
800 PM EDT TUE MAY 20 2025
SYNOPSIS
A COLD FRONT WILL PUSH OFFSHORE WEDNESDAY AFTERNOON INTO
WEDNESDAY EVENING, FOLLOWED BY HIGH PRESSURE THROUGH THE
WEEKEND.
NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/
QUIET CONDITIONS AS THE BOUNDARY LAYER STABILIZES AND WE RETURN
TO A SOUTHWESTERLY FLOW AT THE SURFACE. WINDS WILL BE PICKING
UP AS THE SURFACE PRESSURE GRADIENT INCREASES AHEAD OF AN
APPROACHING COLD FRONT. LOW TEMPERATURES WILL BE IN THE 70S.
SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/
WEDNESDAY: A BROKEN LINE OF SHOWERS/TSTMS AHEAD OF AN APPROACHING
COLD FRONT WILL BE IN A WEAKENING PHASE AS IT APPROACHES THE FAR
INTERIOR AREAS PRIOR TO DAYBREAK. SOME REMNANT SHOWER/TSTM ACTIVITY
COULD PUSH INTO INTERIOR SOUTHEAST GEORGIA JUST AFTER DAYBREAK, BUT
CONFIDENCE IN ANYTHING MEANINGFUL HAPPENING IS LOW. GUIDANCE STILL
SHOWS LITTLE IN THE WAY OF SIGNIFICANT FORCING AHEAD OF THE FRONT
WITH MODEL CROSS SECTIONS SHOWING THE CORRIDOR OF STRONGEST UVVS
DISPLACED TO THE NORTH WHERE A PASSING SHORTWAVE/VORTICITY LOBE WILL
TRAVERSE NORTH CAROLINA. SOME LOW-LEVEL FORCING IS NOTED, LIKELY
ALONG/NEAR THE FRONTAL SURFACE ITSELF, BUT THE BEST 850 HPA THETA-E
POOLING WILL OCCUR SOUTH OF I-16 DURING PEAK HEATING AND THIS IS
WHERE THE BEST OVERLAP OF INSTABILITY AND THETA-E WILL OCCUR. GIVEN
THE WESTERLY LOW-LEVEL FLOW AHEAD OF THE FRONT WITHIN AN ENVIRONMENT
WITHOUT ANY STRONG FORCING MECHANISMS, IT IS UNCLEAR EXACTLY HOW
MUCH COVERAGE OF SHOWERS/TSTMS WILL OCCUR DURING THE AFTERNOON HOURS
AND ITS VERY POSSIBLE CONVECTION WILL REMAIN LARGELY ABSENT THROUGH
FROPA. A BLEND OF THE LATEST HREF AND 13Z NBM WAS FAVORED TO
CONSTRUCT POPS, WHICH YIELDS RAIN CHANCES OF 10-30%, HIGHEST ACROSS
THE GEORGIA COASTAL COUNTIES. THE FRONT SHOULD CLEAR THE COAST
DURING THE EVENING HOURS WHICH WILL END ANY CHANCE FOR MEASURABLE
RAIN. MODIFIED SOUNDINGS DO SHOW MODEST TO LOCALLY STRONG MIXED-
BASED INSTABILITY WITHIN A BELT OF AROUND 30 KT OF 0-6KM BULK SHEAR.
THIS COULD SUPPORT AN ISOLATED SEVERE TSTM WITH DAMAGING WINDS AND
LARGE HAIL, BUT AN ORGANIZED SEVERE WEATHER EVENT SEEMS HIGHLY
UNLIKELY AT THIS TIME. HIGHS WILL WARM INTO THE LOWER-MID 90S, A BIT
COOLER AT THE BEACHES WHERE A PINNED SEA BREEZE WILL BE LATE TO FORM.
THURSDAY AND FRIDAY: A MODEST CYCLONIC FLOW ALOFT WILL PREVAIL
THROUGH THE PERIOD AS HIGH PRESSURE TRIES TO BE BUILD INTO THE
REGION. A WEAK, SECONDARY COLD FRONT WILL PUSH OFFSHORE THURSDAY
EVENING WHICH WILL HELP TO REINFORCE THE RELATIVELY COOLER AND DRIER
AIRMASS THAT WILL FILTER IN ON THURSDAY. THE FRONT WILL PASS THROUGH
DRY WITH NO MEANINGFUL MOISTURE RETURN OCCURRING PRIOR TO IS
PASSAGE. HIGHS WILL WARM INTO THE UPPER 80S/LOWER 90S THURSDAY WITH
80S FOR FRIDAY (MAYBE EVEN A FEW UPPER 70S ACROSS THE FAR INTERIOR
ADJACENT TO THE CSRA). LOWS FRIDAY MORNING WILL DROP INTO THE LOWER
60S WELL INLAND TO AROUND 70 AT THE BEACHES AND DOWNTOWN
CHARLESTON.
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
MOSTLY QUIET CONDITIONS WILL PREVAIL FOR MUCH OF THE EXTENDED
PERIOD. RAIN CHANCES WILL INCREASE SLIGHTLY SUNDAY INTO MONDAY AS A
WEAK WARM FRONT LIFTS NORTH THROUGH THE AREA AHEAD OF A DEVELOPING
STORM SYSTEM TO THE WEST. TEMPERATURES WILL START OUT NEAR TO
SLIGHTLY BELOW NORMAL OVER THE UPCOMING WEEKEND, THEN BEGIN TO
RECOVER BACK TO LEVELS SLIGHTLY ABOVE NORMAL.
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
00Z TAFS: MAINLY VFR. A COLD FRONT MAY BRING SOME SHOWERS AND
THUNDERSTORM ON THURSDAY. BUT PROBABILITIES WILL BE TOO LOW TO
WARRANT MENTION IN THE TAFS. ADDITIONALLY, GUSTY WINDS ARE
EXPECTED LATE IN THE TAF TIME PERIOD.
EXTENDED AVIATION OUTLOOK: THERE ARE NO CONCERNS WITH A >50%
CONFIDENCE LEVEL.
MARINE
TONIGHT: S WINDS WILL VEER TO THE SW OVERNIGHT. SEAS WILL
AVERAGE 2-3 FT.
WEDNESDAY: SOUTHWEST WINDS WILL INCREASE AHEAD OF AN APPROACHING
COLD FRONT. WINDS COULD GET AS HIGH AS 15-20 KT OVER THE SOUTH
SANTEE-EDISTO BEACH NEARSHORE LEG AND CHARLESTON HARBOR DURING THE
AFTERNOON HOURS. GUSTS COULD GET CLOSE TO 25 KT, BUT ITS DURATION IS
SOMEWHAT UNCERTAIN. FOR THIS REASON, A SMALL CRAFT ADVISORY HAS NOT
BEEN ISSUED. THE NEED FOR AN ADVISORY WILL BE REEVALUATED OVERNIGHT.
WINDS WILL SHIFT OFFSHORE DURING THE EVENING HOURS AS A COLD FRONT
SHIFTS OFFSHORE. SEAS WILL BUILD 2-3 FT, EXCEPT 4-5 FT OVER THE
SOUTH SANTEE-EDISTO BEACH NEARSHORE LEG.
THURSDAY THROUGH SUNDAY: THERE ARE NO MAJOR CONCERNS. OFFSHORE WINDS
WILL TURN BACK MORE SOUTHWESTERLY THURSDAY BEFORE RETURNING OFFSHORE
THURSDAY NIGHT AS A REINFORCING COLD FRONT SHIFTS OFFSHORE. OFFSHORE
WINDS WILL PERSIST THROUGH FRIDAY BEFORE TURNING NORTHERLY SATURDAY
AHEAD OF A DEVELOPING WARM FRONT. WINDS WILL THEN VEER SOUTHERLY
SUNDAY AS THE WARM FRONT LIFTS NORTH.
CLIMATE
RECORD HIGH MINIMUM TEMPERATURES:
MAY 20:
KCHS: 72/2022
KCXM: 76/2022
KSAV: 73/1896
MAY 21:
KCHS: 74/2022
KCXM: 78/1998
KSAV: 74/2017
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
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