Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 220813
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
413 AM EDT FRI AUG 22 2014

.SYNOPSIS...
THE REGION WILL REMAIN BETWEEN ATLANTIC HIGH PRESSURE AND AN
INLAND TROUGH OF LOW PRESSURE TODAY. A BACKDOOR COLD FRONT WILL
PUSH SOUTH THROUGH THE AREA SATURDAY NIGHT INTO SUNDAY FOLLOWED BY
COOLER AND DRIER HIGH PRESSURE THROUGH THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
TODAY...THE REGION WILL REMAIN UNDER THE INFLUENCE OF A STRONG
RIDGE CENTERED OVER THE LOWER MISSISSIPPI VALLEY. AT THE
SURFACE...ATLANTIC HIGH PRESSURE WILL PREVAIL WHILE A TROUGH OF
LOW PRESSURE LINGERS INLAND.

STRONG SUBSIDENCE AND A DOWNSLOPE FLOW ALOFT WILL RESULT IN YET
ANOTHER HOT DAY ACROSS THE AREA...WITH TEMPERATURES LIKELY RISING
TO HIGHS IN THE UPPER 90S TO NEAR 100. EVEN ALONG THE IMMEDIATE
COAST HIGHS SHOULD BE IN THE MID 90S...SIMILAR TO THURSDAY...AS
THE SEA BREEZE REMAINS PINNED TO THE COAST FOR MUCH OF THE
DAY. THE BIGGEST UNCERTAINTY IS HOW MUCH DEW POINTS MIX OUT IN THE
AFTERNOON. GENERALLY...DEW POINTS TEND TO FALL LOWER WELL INLAND
WITHIN DEEPER MIXING WHILE HOLDING STEADY OR EVEN SOMETIMES
RISING ALONG THE COASTAL CORRIDOR AS MOISTURE POOLS NEAR THE SEA
BREEZE. SINCE HIGHS TODAY ARE SIMILAR IF NOT A DEGREE OR TWO
WARMER THAN THURSDAY WHERE WE NOTICED SEVERAL AWOS AND NUMEROUS
MESONET SITES WITH HEAT INDICES AROUND 110 OR HIGHER...WE HAVE
DECIDED TO ISSUE ANOTHER HEAT ADVISORY FROM NOON TO 6 PM TODAY
FOR THE ENTIRE FORECAST AREA.

IT WILL BE VERY DIFFICULT FOR CONVECTION TO DEVELOP TODAY GIVEN
STRONG SUBSIDENCE AND LACK OF DEEP MOISTURE. HOWEVER...AN ISOLATED
SHOWER OR THUNDERSTORM IS CERTAINLY POSSIBLE...ESPECIALLY WITHIN A
BAND OF ENHANCED LOW LEVEL CONVERGENCE NEAR THE SEA BREEZE.

TONIGHT...THE EASTERN PERIPHERY OF THE STRONG UPPER RIDGE WILL
BEGIN TO ERODE AS A TROUGH DIGS DOWN THE MID-ATLANTIC COAST. THIS
WILL ALLOW A BACK DOOR COLD FRONT TO APPROACH FROM THE NORTH LATE.
DEEPENING MOISTURE AND A WEAK SHORT WAVE DISTURBANCE SHIFTING
ACROSS THE AREA COULD SUPPORT ISOLATED CONVECTION OVERNIGHT
AHEAD OF THE FRONT ACCORDING TO SOME MODELS...BUT PREFER TO KEEP
A DRY FORECAST AT THIS TIME AND ONLY INDICATE AN INCREASE IN CLOUD
COVER UNTIL CONFIDENCE INCREASES. TEMPERATURES WILL REMAIN
MILD...WITH LOWS GENERALLY IN THE MID TO UPPER 70S.


&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
SATURDAY...A WEAK COLD FRONT WILL BE APPROACHING THE AREA FROM THE
NORTH EARLY SATURDAY BUT SHOULD GET HUNG UP INLAND DURING THE DAY
DUE TO DIURNAL HEATING. MOSTLY OFFSHORE FLOW AND WEAK CONVERGENCE
SHOULD LIMIT THE SHOWER AND THUNDERSTORM POTENTIAL SO WE KEPT
CHANCES NO HIGHER THAN 20 PERCENT. IT LOOKS TO BE ANOTHER SCORCHER
WITH HIGHS IN THE UPPER 90S INLAND...POSSIBLY 100 DEGREES IN A FEW
INLAND SPOTS. ALTHOUGH DEWPOINTS IN THE MID 70S IN THE MORNING
SHOULD LOWER A BIT IN THE AFTERNOON...ESPECIALLY INLAND...HEAT
INDICES COULD STILL PEAK NEAR ADVISORY LEVELS /110 DEGREES/. THE
FRONT SHOULD MAKE A BIT MORE SOUTHWARD PROGRESS SATURDAY NIGHT...AT
LEAST IN TERMS OF A WIND SHIFT. THERE COULD BE A FEW SHOWERS DUE TO
THE FRONTAL PASSAGE WITH LOWS MAINLY IN THE MID/UPPER 70S.

SUNDAY...COOLER AIR WILL FILTER INTO THE AREA FROM THE NORTH
SUNDAY BUT MOISTURE WILL BE HANGING ON AND THUS THERE WILL BE A
CHANCE OF SOME SHOWERS AND STORMS. HEAT INDICES COULD STILL BE NEAR
105 DEGREES ACROSS SOUTHEAST GEORGIA. DRIER AIR WILL FINALLY PUSH IN
SUNDAY NIGHT MAKING FOR A BIT MORE COMFORTABLE NIGHT WITH LOWS
RANGINGIN FROM THE UPPER 60S/AROUND 70 INLAND TO MID TO UPPER 70S
ALONG THE COAST...WARMEST IN GA. THE DEWPOINT BOUNDARY AND
INCREASING COASTAL CONVERGENCE COULD PRODUCE A FEW SHOWERS.

MONDAY...A COOLER AND DRIER AIR MASS WILL BE IN PLACE WITH MUCH MORE
COMFORTABLE CONDITIONS EXPECTED. HIGHS NEAR NORMAL...RANGING FROM
THE MID 80S NORTH AND EAST PORTION OF OUR FORECAST AREA TO NEAR 90
SOUTH AND WEST PORTION /INTERIOR SOUTHEAST GEORGIA/. THERE WILL
LIKELY BE SUFFICIENT LOW-LEVEL MOISTURE/CONVERGENCE GIVEN THE
MODERATE NORTH/NORTHEAST WINDS TO PRODUCE A FEW SHOWERS...ESPECIALLY
ACROSS THE GA COAST.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
HIGH PRESSURE LOOKS TO REMAIN IN CONTROL INLAND THROUGH MID WEEK.
LOW PRESSURE...POSSIBLY A WEAK TROPICAL CYCLONE...SHOULD REMAIN WELL
OFFSHORE. THE MAIN INFLUENCE ON OUR WEATHER WILL BE SLIGHTLY HIGHER
WINDS...ESPECIALLY ALONG THE COAST. THERE COULD BE A FEW SHOWERS
FROM TIME TO TIME...AGAIN MOSTLY NEAR THE COAST. ANOTHER COLD FRONT
LOOKS TO APPROACH LATE IN THE WEEK ALTHOUGH THERE IS SOME
UNCERTAINTY REGARDING MOISTURE LEVELS AND THUS RAIN CHANCES.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 06Z SATURDAY.

EXTENDED AVIATION OUTLOOK...GENERALLY VFR OUTSIDE ISO SHOWERS/TSTMS
SATURDAY. INCREASING MOISTURE BEHIND A BACKDOOR COLD FRONT EARLY
SUNDAY COULD YIELD SOME SOME MVFR CIGS/VSBYS. GENERALLY VFR THROUGH
WED ALTHOUGH IT WILL BE BREEZY SUN-TUE.

&&

.MARINE...
TODAY AND TONIGHT...THE WATERS WILL REMAIN POSITIONED BETWEEN
ATLANTIC HIGH PRESSURE AND A TROUGH OF LOW PRESSURE INLAND. THIS
WILL MAINTAIN A SOUTH-SOUTHWEST FLOW WITH SPEEDS GENERALLY 15 KT
OR LESS...HIGHEST AT NIGHT WITH WEAK NOCTURNAL SURGING. SEAS WILL
RANGE 1-3 FT...HIGHEST ACROSS THE OUTER GEORGIA WATERS.

SATURDAY THROUGH WEDNESDAY...NO SIGNIFICANT CONCERNS UNTIL LATER
SUNDAY WHEN NORTHEAST WINDS INCREASE BEHIND A COLD FRONT. THIS WILL
ALSO CAUSE SEAS TO BUILD PROBABLY EXCEEDING ADVISORY LEVELS BEYOND
20 NM SUNDAY NIGHT AND THEN POSSIBLY IN THE NEARSHORE WATERS MONDAY.
CONDITIONS LOOK TO IMPROVE BELOW ADVISORY LEVELS WITHIN 20 NM TUE
NIGHT AND WED IN THE 20-60 NM GA ZONE. THE BRISK NORTHEAST WINDS
WILL ALSO CAUSE AN INCREASE IN TIDE LEVELS ABOVE THE NORMAL
ASTRONOMICAL TIDE...POSSIBLY REACHING CLOSE TO ADVISORY LEVELS
DURING THE EVENING HIGH TIDE CYCLES THROUGH EARLY WEEK.

MEANWHILE...LOW PRESSURE NEAR THE BAHAMAS SUNDAY/MONDAY...POSSIBLY A
WEAK TROPICAL CYCLONE...SHOULD REMAIN WELL EAST OF THE AREA.
HOWEVER...MARINERS ARE URGED TO PAY CLOSE ATTENTION TO THE LATEST
FORECASTS.

&&

.CLIMATE...
RECORD MAX TEMPS...

FRI 8/22...
KCHS 100 SET IN 1983
KCXM 98 SET IN 1983
KSAV 100 SET IN 1983

LAST TIME 100 DEGREES OR HIGHER...
KCHS JUNE 21 2011
KCXM JUNE 20 2011
KSAV JULY 26 2012

&&

.EQUIPMENT...
THE CHARLESTON SC WSR-88D /KCLX/ IS BACK IN SERVICE...BUT IS NOT
YET AT 100 PERCENT EFFICIENCY. CALIBRATION IS STILL BEING DONE
AND WILL CONTINUE INTO FRIDAY...AND THERE MAY BE INTERMITTENT
OUTAGES AND/OR PROBLEMS DURING THIS TIME. THUS USE WITH CAUTION.
IF NECESSARY...FOR DOPPLER RADAR COVERAGE OF SOUTHEAST GEORGIA AND
SOUTH COASTAL SOUTH CAROLINA UTILIZE SURROUNDING RADARS INCLUDING
KJAX...KJGX... KVAX...KCAE AND KLTX.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...HEAT ADVISORY FROM NOON TODAY TO 6 PM EDT THIS EVENING FOR
     GAZ087-088-099>101-114>119-137>141.
SC...HEAT ADVISORY FROM NOON TODAY TO 6 PM EDT THIS EVENING FOR
     SCZ040-042>045-047>052.
MARINE...NONE.

&&

$$

NEAR TERM...JAQ
SHORT TERM...RJB
LONG TERM...RJB
AVIATION...JAQ/RJB
MARINE...JAQ/RJB
CLIMATE...
EQUIPMENT...





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