020
FXUS62 KCHS 202324
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
724 PM EDT THU AUG 20 2026
WHAT HAS CHANGED
ALL KEY MESSAGES AND SECTIONS WERE UPDATED.
KEY MESSAGES
- 1) HEAT REMAINS A CONCERN INTO FRIDAY.
- 2) INCREASED RISK FOR SHOWERS AND THUNDERSTORMS INTO THE
WEEKEND.
DISCUSSION
KEY MESSAGE 1: HEAT REMAINS A CONCERN INTO FRIDAY.
FRIDAY: MID-LEVEL TROUGHING WILL DOMINATE THE EAST COAST WHILE
A WEAK SURFACE FRONT APPROACHES THE LOCAL FORECAST AREA.
TEMPERATURES ARE STILL FORECAST TO BE ABOVE NORMAL (MID 90S),
BUT HEAT INDEX VALUES LOOK TO FALL SHORT OF HEAT ADVISORY
CRITERIA ACROSS MOST OF THE REGION. THE ONLY LOCATIONS THAT
COULD SEE HEAT INDEX VALUES OF 108 OR GREATER WOULD BE ALONG THE
COASTAL COUNTIES, ESPECIALLY IN SC. HOWEVER, GIVEN THE
INCREASED COVERAGE OF PRECIPITATION THERE IS LITTLE CONFIDENCE
IN HITTING THE HEAT ADVISORY CRITERIA. THEREFORE, ONE HAS NOT
BEEN ISSUED AT THIS JUNCTURE.
THIS WEEKEND INTO EARLY NEXT WEEK: TEMPERATURES WILL COOL
SLIGHTLY, WITH HIGHS IN THE LOW 90S (STILL ABOVE NORMAL FOR THIS
TIME OF YEAR). THE EXTENDED FORECAST LOOKS TO BE HEAT-HEADLINE
FREE WITH HEAT INDEX VALUES TOPPING OUT IN THE 100-103 RANGE
EACH AFTERNOON.
KEY MESSAGE 2: INCREASED RISK FOR SHOWERS AND THUNDERSTORMS
INTO THE WEEKEND.
FRIDAY: A MORE APPRECIABLE CHANGE IN THE PATTERN IS EXPECTED ON
FRIDAY AS THIS MID-LVL RIDGE FINALLY BREAKS DOWN AND BROAD
TROUGHING BEGINS TO BUILD ACROSS THE EASTERN HALF OF THE CONUS.
SEVERAL EMBEDDED SHORTWAVES ARE FORECAST TO ROUND THE BASE OF
THIS TROUGH WHILE A SLOW-MOVING SURFACE FRONT APPROACHES THE
REGION FROM THE WEST AND NORTHWEST. THIS WILL PROVIDE GREATER
CONVECTION COVERAGE THAN THE PREVIOUS DAY (THURSDAY).
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP
MID- DAY/EARLY AFTERNOON, BEFORE BECOMING NUMEROUS AND
WIDESPREAD IN THE AFTERNOON/EVENING HOURS. EXPECT MOISTURE TO
INCREASE SUBSTANTIALLY AHEAD OF THIS APPROACHING FRONT, WITH
PWAT VALUES FORECAST TO RISE ABOVE 2 INCHES (NEAR THE 90TH
PERCENTILE FOR LATE AUGUST AT KCHS). DESPITE SOMEWHAT GREATER
CLOUD COVER AND TEMPERATURES SEVERAL DEGREES LOWER THAN THE
PREVIOUS COUPLE DAYS, SUFFICIENT HEATING SHOULD STILL YIELD
MODERATE TO LOCALLY STRONG INSTABILITY. THE COMBINATION OF
INSTABILITY, ABUNDANT MOISTURE, AND APPRECIABLE DCAPE VALUES
WILL SUPPORT ANOTHER RISK FOR STRONG TO SEVERE STORMS. THUS, THE
SPC HAS HIGHLIGHTED THE MAJORITY OF THE REGION IN A MARGINAL
RISK (LEVEL 1/5) FOR SEVERE THUNDERSTORMS ON FRIDAY. AGAIN,
DAMAGING WIND GUSTS WILL BE THE GREATEST THREAT (WITHIN THE
STRONGER STORMS), ALONG WITH LOCALIZED FLOODING POSSIBLE.
SATURDAY: ANOTHER SCATTERED TO NUMEROUS SHOWER AND THUNDERSTORM
DAY AS THE FRONT STALLS NEAR THE REGION. THE EXACT CORRIDOR OF
GREATEST COVERAGE IS LESS CERTAIN AND WILL DEPEND HEAVILY ON THE
FRONTAL POSITION. STRONG WIND GUSTS REMAIN POSSIBLE AGAIN, BUT
TRAINING STORMS AND LOCALIZED FLASH FLOODING COULD BECOME AN
INCREASING CONCERN GIVEN PWATS NEAR 2 INCHES AND STORMS
POTENTIALLY TRACKING PARALLEL TO THE BOUNDARY.
AVIATION /00Z FRIDAY THROUGH TUESDAY/
21/00Z TAFS:
KCHS/KJZI/KSAV: VFR FOR MUCH OF THE PERIOD. RISK FOR
SHOWERS/TSTMS WILL INCREASE LATE IN THE AFTERNOON. PROB30S WERE
INTRODUCED AFTER 21Z TO ACCOUNT FOR THIS AT ALL TERMINALS.
EXTENDED AVIATION OUTLOOK: A FRONT IN OUR VICINITY WILL BRING
SHOWERS AND THUNDERSTORMS FRIDAY INTO THE WEEKEND, LEADING TO
OCCASIONAL FLIGHT RESTRICTIONS.
MARINE
TONIGHT: NO SIGNIFICANT MARINE CONCERNS ARE EXPECTED ACROSS THE
LOCAL WATERS THROUGH TONIGHT, WITH WINDS AND SEAS REMAINING
BELOW SMALL CRAFT ADVISORY CRITERIA. A TYPICAL SUMMERTIME
PATTERN WILL DOMINATE WITH GENERALLY SOUTH-SOUTHWESTERLY FLOW
AROUND 10 KT AND SEAS 2-3 FT.
FRIDAY THROUGH TUESDAY: OUTSIDE OF SHOWERS AND THUNDERSTORMS,
OVERALL MARINE CONDITIONS WILL REMAIN FAIRLY TYPICAL FOR LATE
SUMMER, WITH SOUTH-SOUTHWESTERLY WINDS GENERALLY 5-15 KT WITH
SEAS RANGING FROM 2-4 FT THROUGH EARLY NEXT WEEK. THE MAIN
CONCERN FOR MARINERS WILL BE THE INCREASING THUNDERSTORM THREAT
THROUGH THE WEEKEND AS A FRONT APPROACHES AND THEN STALLS
NEARBY.
CLIMATE
RECORD HIGH MINIMUM TEMPERATURES:
AUGUST 21:
KCHS: 79/2010
KCXM: 82/2023
KSAV: 80/1902
AUGUST 22:
KCHS: 79/2023
AUGUST 24:
KCHS: 76/2010
KCXM: 80/1975
AUGUST 25:
KCHS: 77/1982
AUGUST 26:
KCHS: 78/1998
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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