921
FXUS62 KCHS 171138
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
738 AM EDT MON AUG 17 2026
WHAT HAS CHANGED
THE AVIATION SECTION HAS BEEN UPDATED.
KEY MESSAGES
- 1) HEAT WILL REMAIN A CONCERN THROUGH THE MIDDLE OF THE WEEK.
- 2) SOME STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE EACH
AFTERNOON THIS WEEK.
DISCUSSION
KEY MESSAGE 1: HEAT WILL REMAIN A CONCERN THROUGH THE MIDDLE OF
THE WEEK.
TODAY: A WARM PATTERN WILL REMAIN IN PLACE WITH LARGE-SCALE
RIDGING ACROSS THE DEEP SOUTH AND SOUTHEAST UNITED STATES. MUCH
LIKE THE PREVIOUS COUPLE DAYS, STRONG HEATING IS EXPECTED DURING
MORNING AND AFTERNOON HOURS. TEMPS COULD BE A FEW DEGREES
WARMER THAN THE PREVIOUS DAY, PEAKING IN THE MID-UPPER 90S WITH
SOME SPOTS REACHING 100 DEGREES GIVEN A WEST-NORTHWEST DOWNSLOPE
FLOW PATTERN AND RATHER SPARSE CONVECTION THAT IS MAINLY
CONFINED TO AN AFTERNOON SEA BREEZE. DESPITE SOME MIXING OUT OF
LOW-LVL MOISTURE ACROSS THE LOCAL AREA LATE MORNING AND
AFTERNOON, SFC DEWPTS IN THE MID-UPPER 70S (HIGHEST ACROSS THE
COASTAL CORRIDOR) SUPPORT HEAT INDEX VALUES UP TO THE 105- 111
RANGE INLAND TO 112-117 RANGE NEAR THE COAST. A HEAT ADVISORY
REMAINS IN EFFECT FOR INLAND AREAS TODAY WHILE AN EXTREME HEAT
WARNING ALSO REMAINS IN EFFECT FROM 11 AM TO 8 PM.
TUESDAY: HOT/HUMID CONDITIONS WILL REMAIN ACROSS THE SOUTHEAST
UNITED STATES WITH LARGE-SCALE RIDGING CENTERED ACROSS THE DEEP
SOUTH AND NORTHERN GULF REGIONS. RECORD WARMTH IS POSSIBLE,
ESPECIALLY AS THE HEAT WAVE PEAKS WITH ANOTHER DAY OF FAVORABLE
DOWNSLOPE FLOW ACROSS THE LOCAL AREA. MANY AREAS COULD SEE TEMPS
PEAK AROUND 100 DEGREES ALONG THE I-95 CORRIDOR AS AFTERNOON
CONVECTION IS LIMITED. THE SETUP FAVORS SOME MIXING OUT OF SFC
DEWPTS ACROSS INLAND AREAS, BUT MOISTURE POOLING ALONG/NEAR AN
AFTERNOON SEA BREEZE SUPPORTS SFC DEWPTS IN THE MID-UPPER 70S.
THE COMBINATION OF HOT AND HUMID CONDITIONS FAVORS EXTREME HEAT
WARNING CRITERIA, MAINLY ALONG AND EAST OF I-95, AND HEAT
ADVISORY LEVEL CONDITIONS INLAND. AN EXTREME HEAT WATCH HAS BEEN
ISSUED FOR SC/GA COASTAL COUNTIES AS A RESULT, AND ALSO
INCLUDES DORCHESTER COUNTY, FROM 11 AM TO 8 PM ON TUESDAY.
WEDNESDAY INTO FRIDAY: THERE ARE SIGNS OF THE EXPANSIVE RIDGE
STARTING TO WEAKEN WHILE SCATTERED CONVECTION RETURNS DURING
PEAK HEATING HOURS MID TO LATE WEEK. WE COULD SEE HEAT ADVISORY
CONDITIONS PRIOR TO SHOWERS/THUNDERSTORMS DEVELOPING WEDNESDAY
AND THURSDAY, ESPECIALLY ALONG THE COASTAL CORRIDOR. FRIDAY
REMAINS WARM, BUT GUIDANCE SUPPORTS GREATER CONVECTIVE COVERAGE
AND SOME RELIEF FROM THE HEAT DURING PEAK HEATING HOURS, AS
SHORTWAVE ENERGY ASSOCIATED WITH A LARGE-SCALE TROUGH APPROACHES
THE MID-ATLANTIC AND SOUTHEAST STATES THIS WEEKEND.
KEY MESSAGE 2: SOME STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE
EACH AFTERNOON THIS WEEK.
THE HEAT AND HUMIDITY MENTIONED IN KEY MESSAGE 1 WILL PROVIDE
INSTABILITY ACROSS OUR AREA EACH AFTERNOON THIS WEEK. WHILE EACH
MODEL HAS DIFFERENCES REGARDING HOW MUCH WILL BE IN PLACE AND
WHERE THE HIGHEST VALUES WILL BE, THE GENERAL CONSENSUS SEEMS TO
BE SBCAPE VALUES IN THE 2,000-3,000 J/KG RANGE WITH LOCALLY
HIGHER PEAKS. DCAPE VALUES SHOULD EASILY EXCEED 1,000 J/KG.
THERE ARE NOTABLE DIFFERENCES BETWEEN THE VARIOUS CAMS AND THE
DETERMINISTIC MODELS, WITH MANY POINTING TO IT BEING DRY EACH
AFTERNOON OR MINIMAL CONVECTION. HOWEVER, THE AMOUNT OF
INSTABILITY IN PLACE IS HARD TO IGNORE. LIKEWISE, IT WON'T TAKE
MUCH FOR ISOLATED TO SCATTERED CONVECTION TO FORM ALONG THE SEA
BREEZE EACH AFTERNOON AND THEN SHIFT INLAND. THEREFORE, WE
RAISED POPS EACH AFTERNOON, GENERALLY GOING WITH SLIGHT CHANCE
TO CHANCE. THE OUTFLOW AND BOUNDARY INTERACTIONS SHOULD PLAY A
MAJOR ROLE IN ADDITIONAL STORM FORMATION AND PERSISTENCE. STRONG
TO SEVERE THUNDERSTORMS ARE POSSIBLE EACH AFTERNOON WITH THE
MAIN THREAT BEING DAMAGING WINDS. HEAVY RAINFALL IS ALSO A
CONCERN DUE TO THE VERY WEAK STEERING WINDS AND ELEVATED PWATS.
BACKBUILDING AND/OR TRAINING OF STORMS COULD DROP ENOUGH
RAINFALL TO GENERATE VERY LOCALIZED FLOODING. ANY CONVECTION
SHOULD DISSIPATE EACH EVENING WITH THE SETTING SUN.
AVIATION /12Z MONDAY THROUGH FRIDAY/
12Z TAFS: VFR. THERE COULD BE SOME ISOLATED TO MAYBE SCATTERED
SHOWERS AND THUNDERSTORMS ALONG THE SEA BREEZE THIS AFTERNOON
AND EARLY EVENING. HOWEVER, THE PROBABILITIES OF DIRECT IMPACTS
TO THE TAF SITES ARE TOO LOW TO MENTION WITH THIS SET OF TAFS.
EXTENDED AVIATION OUTLOOK: VFR CONDITIONS EXPECTED AT ALL
TERMINALS TUESDAY THROUGH THURSDAY, ALTHOUGH LIMITED IMPACTS ARE
POSSIBLE WITH ISOLATED SHOWERS AND THUNDERSTORMS DURING
AFTERNOON HOURS. CHANCES FOR AFTERNOON SHOWER/THUNDERSTORMS
INCREASE THIS WEEKEND, WHICH COULD RESULT IN TEMPO FLIGHT
RESTRICTIONS AT ALL TERMINALS.
MARINE
TODAY AND TONIGHT: THE COMBINATION OF HIGH PRESSURE OVER THE
NORTHERN GULF AND SURFACE TROUGHING OVER THE SOUTHEAST U.S. WILL
YIELD A TYPICAL SUMMERTIME WIND PATTERN OVER OUR COASTAL
WATERS. EXPECT WINDS TO GRADUALLY BACK INTO THIS AFTERNOON. THE
STRONGEST WINDS WILL BE LATER THIS AFTERNOON, ESPECIALLY ALONG
THE LAND/SEA INTERFACE ASSOCIATED WITH THE SEA BREEZE. WINDS
SHOULD STAY ELEVATED THIS EVENING AND OVERNIGHT, GRADUALLY
VEERING TO THE WEST BY DAYBREAK TUESDAY. SEAS WILL AVERAGE 2-3
FT WITHIN 20 NM AND 3-4 FT IN THE 20-60 NM LEG.
EXTENDED MARINE: THERE WILL BE AREAS OF HIGH PRESSURE IN THE WESTERN
ATLANTIC AND THE NORTHERN GULF, WHILE SURFACE TROUGHING PERSISTS
OVER THE SOUTHEAST UNITED STATES. THE INTERACTION BETWEEN THESE
SYNOPTIC FEATURES WILL SUPPORT A TYPICAL SUMMERTIME WIND PATTERN
WITH WINDS/SEAS THAT REMAIN BELOW SMALL CRAFT ADVISORY LEVELS. IN
GENERAL, SOUTHWEST WINDS SHOULD BACK TO A MORE SOUTH DIRECTION EACH
DAY, PEAKING IN SPEED ALONG THE COAST DUE TO A SEA BREEZE, THEN
RETURN TO SOUTHWEST DURING THE OVERNIGHT PERIOD. SEAS WILL MAINLY BE
IN THE 2-3 FT RANGE.
CLIMATE
RECORD HIGH TEMPERATURES:
AUGUST 17:
KCHS: 102/1954
KCXM: 100/1954
KSAV: 102/1954
AUGUST 18:
KCHS: 101/1995
KCXM: 97/1995
KSAV: 100/1995
AUGUST 19:
KCHS: 98/1983
KCXM: 98/1895
KSAV: 99/1900
AUGUST 20:
KCHS: 97/2005
KSAV: 102/1900
AUGUST 21:
KCHS: 100/1983
KSAV: 101/1902
RECORD HIGH MINIMUM TEMPERATURES:
AUGUST 17:
KCHS: 80/2017
KSAV: 78/2017
AUGUST 18:
KCHS: 80/2017
KCXM: 82/2017
KSAV: 78/2010
AUGUST 19:
KCHS: 79/2010
KCXM: 83/2021
KSAV: 79/1878
AUGUST 20:
KCHS: 78/2017
KCXM: 82/2017
AUGUST 21:
KCHS: 79/2010
KCXM: 82/2023
KSAV: 80/1902
AUGUST 22:
KCHS: 79/2023
KCXM: 82/2014
KSAV: 79/1902
AUGUST 23:
KCXM: 81/2019
KSAV: 78/2016
CHS WATCHES/WARNINGS/ADVISORIES
GA...HEAT ADVISORY FROM 11 AM THIS MORNING TO 8 PM EDT THIS EVENING
FOR GAZ087-088-099>101-114-115-137-216-218-238.
EXTREME HEAT WATCH FROM TUESDAY MORNING THROUGH TUESDAY
EVENING FOR GAZ216>219-238>241.
EXTREME HEAT WARNING FROM 11 AM THIS MORNING TO 8 PM EDT THIS
EVENING FOR GAZ217-219-239>241.
SC...HEAT ADVISORY FROM 11 AM THIS MORNING TO 8 PM EDT THIS EVENING
FOR SCZ040-042>044-147.
EXTREME HEAT WATCH FROM TUESDAY MORNING THROUGH TUESDAY
EVENING FOR SCZ044-045-147>152.
EXTREME HEAT WARNING FROM 11 AM THIS MORNING TO 8 PM EDT THIS
EVENING FOR SCZ045-148>152.
MARINE...NONE.
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