573
FXUS62 KCHS 142348
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
748 PM EDT FRI AUG 14 2020
SYNOPSIS
A TROUGH OF LOW PRESSURE WILL PERSIST INLAND, WHILE HIGH
PRESSURE REMAINS OVER THE ATLANTIC THROUGH SATURDAY. A WEAK
COLD FRONT WILL THEN PASS THROUGH THE AREA SUNDAY INTO SUNDAY
NIGHT. A TROUGH WILL REDEVELOP OVER THE REGION DURING THE
MIDDLE OF NEXT WEEK.
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/
A CLUSTER OF SEVERE THUNDERSTORMS DEVELOPED ACROSS FAR SOUTHERN
SC EARLIER THIS EVENING DUE TO THE COLLISION OF TWO OUTFLOW
BOUNDARIES AND THE SEA BREEZE. THIS ACTIVITY THEN MOVED NORTH
NORTHEAST AND HAS BEEN ON A STEADY WEAKENING TREND. ELSEWHERE,
LITTLE TO NO PRECIPITATION IS OCCURRING AND UPSTREAM ACTIVITY IS
WANING AS THE BOUNDARY LAYER STABILIZES FOLLOWING PEAK
DIABATIC HEATING. ONCE THE MAIN CONVECTIVE CLUSTER PUSHES OUT OF
THE FORECAST AREA INTO THE EASTERN SC MIDLANDS BY 830 PM, ONLY
ISOLATED SHOWERS AND PERHAPS A T-STORM WILL BE POSSIBLE FOR THE
REST OF THE NIGHT.
SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/
THE UPPER TROUGH THAT HAS LINGERED JUST WEST OF THE AREA FOR
SEVERAL DAYS WILL BEGIN TO PUSH EAST ON SATURDAY, MOVING
OFFSHORE BY SUNDAY NIGHT. THIS WILL PUSH A WEAK COLD FRONT
THROUGH THE AREA SUNDAY AND SUNDAY NIGHT. PLENTY OF MOISTURE
WILL REMAIN IN PLACE THROUGH THE WEEKEND WHICH, COMBINED WITH A
SERIES OF EMBEDDED SHORTWAVES, WILL PRODUCE NUMEROUS SHOWERS
AND THUNDERSTORMS. PWATS WILL DROP PRECIPITOUSLY BY MONDAY
BEHIND THE FRONT WITH VALUES BELOW 1.5" IN MOST LOCATIONS. A
WEAK LEE TROUGH WILL EXIST ON MONDAY AND A SEA BREEZE WILL
DEVELOP IN THE AFTERNOON, SO SCATTERED SHOWERS AND TSTMS ARE
STILL EXPECTED ALBEIT WITH LOWER COVERAGE THAN OVER THE WEEKEND.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
A RETURN TO MORE UNSETTLED WEATHER IS EXPECTED DURING THE LONG TERM
PERIOD. THE FORECAST AREA WILL BECOME POSITIONED BETWEEN A MID LEVEL
TROUGH TO THE WEST AND RIDGING TO THE EAST. THIS SET-UP WILL BRING
DEEP MOISTURE AND A SERIES OF SHORTWAVES BACK INTO THE AREA.
MEANWHILE, ANOTHER SURFACE TROUGH WILL TAKE SHAPE OVER THE REGION BY
THE MIDDLE OF THE WEEK. HIGHER THAN NORMAL RAIN CHANCES ARE
EXPECTED, ESPECIALLY WEDNESDAY AND THURSDAY. TEMPERATURES WILL BE
NEAR CLIMATOLOGY.
AVIATION /00Z SATURDAY THROUGH WEDNESDAY/
ONGOING CONVECTION SHOULD MISS KCHS TO THE NORTH THIS EVENING.
OVERNIGHT, THOUGH WE CANNOT RULE OUT A BRIEF SHOWER, POTENTIAL
IS TOO LOW TO INCLUDE MENTION OF CONVECTION AT EITHER TERMINAL.
ON SATURDAY, ANOTHER ROUND OF CONVECTION IS EXPECTED, THOUGH IT
COULD BE QUITE LATE IN THE DAY TO REACH KCHS SO WE HELD OFF ON
ANY MENTION THERE. GIVEN THE EARLIER CONVECTIVE INITIATION
ACROSS SOUTHEAST GA DURING THE LAST SEVERAL DAYS, WE ADDED A
VICINITY THUNDERSTORM AT KSAV AFTER 18Z.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTIONS POSSIBLE IN
SHOWERS AND THUNDERSTORMS EACH DAY, MAINLY IN THE AFTERNOON AND
EVENING.
MARINE
TONIGHT: ELEVATED SOUTH/SOUTHWEST WINDS OVERNIGHT DUE TO AN
ENHANCED PRESSURE GRADIENT BETWEEN OFFSHORE HIGH PRESSURE AND
INLAND LOW PRESSURE. WINDS COULD GUST NEAR 20 KT AT TIMES WITH
SEAS AS UP TO 4 FEET EVEN OUTSIDE ANY STORMS.
SATURDAY THROUGH WEDNESDAY: THE SOUTHWEST GRADIENT WILL BE
SLIGHTLY ENHANCED THROUGH THE WEEKEND AS A COLD FRONT APPROACHES
FROM THE WEST AND ATLANTIC HIGH PRESSURE PERSISTS OFFSHORE. A
RELATIVELY WEAK PRESSURE PATTERN WILL THEN EXIST EARLY NEXT WEEK
BEHIND THE FRONT. THE PRIMARY MARINE CONCERN WILL CONTINUE TO
BE THE SCATTERED SHOWERS AND THUNDERSTORMS.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...JRL
SHORT TERM...JRL
LONG TERM...ETM
AVIATION...JRL
MARINE...JRL/RJB
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