Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 240519
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
119 AM EDT THU JUL 24 2014

.SYNOPSIS...
HIGH PRESSURE WILL PREVAIL IN THE ATLANTIC LATE THIS WEEK...WHILE
AN INLAND TROUGH OF LOW PRESSURE DRAWS CLOSER TO THE COAST THROUGH
FRIDAY. THIS TROUGH WILL DISSIPATE DURING THE WEEKEND..BEFORE A
COLD FRONT APPROACHES FROM THE NORTHWEST EARLY NEXT WEEK AND STALLS
NEAR THE REGION INTO THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
GENERALLY DRY THE REMAINDER OF THE NIGHT WITH A MILD SOUTH TO
SOUTHWEST FLOW IN PLACE. COULD SEE A LITTLE FOG...MAINLY IN PLACES
THAT SAW RAIN WEDNESDAY...BUT IT SHOULD NOT BE AS MUCH AS
WEDNESDAY MORNING. LOWS SHOULD MOSTLY BE IN THE MID 70S EXCEPT
CLOSER TO 80 AT THE COAST.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY/...
THURSDAY...THE FORECAST AREA WILL BECOME SITUATED BETWEEN ATLANTIC
RIDGING AND AN UPPER TROUGH STEADILY DESCENDING FROM THE NORTHWEST.
THE STRONGEST BAND OF SHORTWAVE ENERGY REMAINS JUST OUTSIDE OF THE
REGION FOR THE MAJORITY OF THE DAYTIME HOURS...WITH FORECAST MODEL
SOUNDINGS INDICATING SOLID WEST FLOW IN THE LOW/MID LEVELS AND A
CAPPING INVERSION THAT PERSISTS INTO THE AFTERNOON TIME FRAME.
THESE FACTORS COULD DELAY INITIAL CONVECTIVE DEVELOPMENT UNTIL
LATER IN THE AFTERNOON...ESPECIALLY CONSIDERING THE SEABREEZE WILL
BE PINNED TO THE COAST. MODEL SOLUTIONS SUGGEST THAT THE BULK OF
THUNDERSTORM ACTIVITY COULD ACTUALLY BE THE RESULT OF UPSTREAM
CONVECTION PROGRESSING INTO THE AREA JUST AHEAD OF THE MAIN
SHORTWAVE ENERGY AND AN AMPLIFYING INLAND SURFACE TROUGH SLIPPING
TOWARD THE COAST. HAVE THUS INDICATED THUNDERSTORM CHANCES
INCREASING FROM WEST TO EAST FROM MID/LATE AFTERNOON THROUGH THE
EARLY/MID EVENING HOURS FOLLOWING THE MOVEMENT OF THE SYNOPTIC
SCALE FEATURES. WILL NEED TO MONITOR FOR THE POTENTIAL OF ISOLATED
STRONG TO SEVERE THUNDERSTORMS LATER IN THE AFTERNOON...AS MODELS
CONTINUE TO SHOW SLIGHTLY ENHANCED MID LEVEL WIND FIELDS THAT
COULD SUPPORT DAMAGING WIND GUSTS WHERE UPDRAFT STRENGTH IS
ENHANCED BY BOUNDARY INTERACTIONS. STORM PREDICTION CENTER HAS
PLACED THE FORECAST AREA IN A 5 PERCENT RISK ZONE TO ACCOUNT FOR
THIS SMALL POTENTIAL. WARM WEST FLOW AND THE PINNED SEABREEZE WILL
SUPPORT HIGH TEMPERATURES IN THE MID 90S AWAY FROM THE LOCALLY
COOLER COASTLINE. RAIN POTENTIAL WILL GENERALLY DIMINISH
OVERNIGHT...HOWEVER A SLIGHT CHANCE FOR SHOWER/THUNDERSTORMS COULD
LINGER OVER THE COASTLINE AND CHARLESTON TRI COUNTY AREA.

FRIDAY...THE AXIS OF THE TROUGH AT BOTH THE SURFACE AND ALOFT WILL
SLIP DIRECTLY OVER THE FORECAST AREA...PROVIDING THE ENERGY AND
CONVERGENCE TO SUPPORT SCATTERED SHOWER/THUNDERSTORM COVERAGE.
LIGHTER WESTERLY MID LEVEL FLOW SUGGESTS THE SEABREEZE WILL MAKE
BETTER PROGRESS INLAND...AND BEST RAIN POTENTIAL WILL OCCUR
GENERALLY ALONG AND INLAND OF THE SEABREEZE. PRECIPITABLE WATER
VALUES WILL RISE BACK TO NEAR 2 INCHES WITH ELONGATED SHORTWAVE
ENERGY DIRECTLY ACROSS THE SOUTHEAST STATES. CONSIDERING THICKER
CLOUD COVER LIMITING INSOLATION...EXPECT HIGH TEMPERATURES TO
REMAIN IN THE LOWER 90S. THE SEVERE THUNDERSTORM POTENTIAL LOOKS
GENERALLY LOWER THAN THURSDAY MAINLY DUE TO WEAKER WIND FIELDS.

SATURDAY...THE SURFACE TROUGH WILL BE DISSIPATING BY THE
WEEKEND...WHILE AN UPPER LEVEL RIDGE PUSHES NORTH FROM THE
BAHAMAS AND DE-AMPLIFIES THE EAST COAST TROUGH ALOFT. BOTH 12Z GFS
AND 12Z ECMWF SUGGEST THAT CONVECTIVE POTENTIAL WILL BE HIGHEST
LATE MORNING INTO EARLY AFTERNOON...WITH COVERAGE POSSIBLY
BECOMING MORE ISOLATED AND FOCUSED ON THE SEABREEZE LATER IN THE
DAY. TEMPERATURES WILL RISE BACK INTO THE LOW TO MID 90S UNDER
SLOWLY INCREASING HEIGHTS ALOFT AND MORE SCATTERED CLOUD COVER.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
A FLAT LONG WAVE PATTERN OVER THE EASTERN STATES SUNDAY WILL BECOME
MORE AMPLIFIED EARLY NEXT WEEK AS THE WESTERN RIDGE POKES NORTHWARD
AND A DIGGING TROUGH DROPS THROUGH THE GREAT LAKES AND OHIO VALLEY.
THIS SENDS A FAIRLY STRONG COLD FRONT TOWARD SOUTHERN SC AND SE GA
LATE MONDAY INTO TUESDAY. NOT YET SURE HOW MUCH PUSH THERE IS BEHIND
THE FRONT...SO IT LOOKS TO HANG UP SOMEWHERE OVER OR NEARBY INTO THE
MIDDLE OF NEXT WEEK. OTHER THAN THE SEA BREEZE THERE IS NO TRIGGER
FOR CONVECTION...SO ONLY SLIGHT CHANCE POPS. BUT COVERAGE WILL BE ON
THE INCREASE LATER MONDAY INTO TUESDAY INTO THE CHANCE RANGE DUE TO
FORCING FROM THE COLD FRONT. WE/LL THEN SHOW SLIGHT CHANCE TO CHANCE
POPS WEDNESDAY SINCE THERE IS SOME SEMBLANCE OF THE FRONT STILL
NEARBY. TEMPS WILL BE ABOVE SEASONAL NORMS SUNDAY AND MONDAY...THEN
DOWN BELOW LATE JULY NORMS TUESDAY AND WEDNESDAY WITH INCREASED RAIN
CHANCES AND A GREATER COVERAGE OF CLOUDINESS.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS LIKELY. A SURFACE TROUGH AND THE SEA BREEZE
SHOULD BE ENOUGH TO FIRE SCATTERED CONVECTION THURSDAY
AFTERNOON...PERSISTING INTO THE EVENING...ESPECIALLY AT KCHS. WE
MAINTAINED VCTS FOR NOW.

EXTENDED AVIATION OUTLOOK...ALTHOUGH VFR CONDITIONS WILL PREVAIL
THROUGH THE EXTENDED RANGE...PERIODIC FLIGHT RESTRICTIONS ARE
POSSIBLE IN SCATTERED AND MAINLY DIURNALLY DRIVEN CONVECTION LATE
THURSDAY THROUGH SUNDAY.

&&

.MARINE...
A TROUGH DROPPING INTO THE CAROLINAS FROM THE NORTH WILL ENHANCE
THE PRESSURE GRADIENT...PRODUCING SW WINDS AROUND 15 KT OFFSHORE
OVERNIGHT. SEAS WILL BRIEFLY BUILD TO AROUND 4 FT OVER OUTER
PORTIONS WITH 2 TO 3 FT SEAS MORE LIKELY CLOSE IN.

THE MARINE ZONES WILL BECOME LOCATED BETWEEN ATLANTIC RIDGING TO
THE SOUTHEAST AND A TROUGH OF LOW PRESSURE INLAND. THERE WILL BE
SOME FLUCTUATIONS DUE TO THE SEA BREEZE CIRCULATIONS AND A
MODERATELY ENHANCED GRADIENT WITH THE NEARBY TROUGH. HOWEVER...
OVERALL SOUTH/SOUTHWEST FLOW WILL BE 15 KT OR LESS...EXCEPT FOR
OCCASIONAL GUSTS TO 20 KT ACROSS THE CHARLESTON COUNTY WATERS AND
THE OFFSHORE GEORGIA ZONES. SEAS WILL BE HELD IN THE 2 TO 4 FT
RANGE DUE TO THE LIMITED OFFSHORE FETCH.

SUNDAY THROUGH MONDAY...THE GRADIENT LOOKS TO TIGHTEN IN RESPONSE
TO LOW PRESSURE DEVELOPING IN THE GREAT LAKES AND TRACKING INTO
THE NORTHEAST...WHILE THE BERMUDA-AZORES HIGH PRESSURE HOLDS IN
PLACE. CONSIDERING THE DIFFICULTY IN REACHING SMALL CRAFT ADVISORY
CONDITIONS THIS TIME OF YEAR...EXPECT CONDITIONS TO REMAIN BELOW
THRESHOLDS. HOWEVER...WINDS COULD CERTAINLY PEAK AT 15 OR 20 KT
AND SEAS UP TO 3 OR 4 FT.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.

&&

$$

NEAR TERM...RJB
SHORT TERM...WMS
LONG TERM...
AVIATION...RJB
MARINE...JRL/WMS






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