158
FXUS62 KCHS 041956
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
356 PM EDT SAT JUL 4 2009
SYNOPSIS
A WEAK FRONT WILL APPROACH FROM THE NORTHWEST LATE SUNDAY...THEN
STALL ACROSS THE AREA ON MONDAY. THE FRONT WILL SLOWLY DROP SOUTH OF
THE AREA ON TUESDAY AS HIGH PRESSURE BUILDS IN FROM THE NORTH AND
PREVAILS THROUGH WEDNESDAY. AN AREA OF LOW PRESSURE MAY AFFECT THE
AREA LATE IN THE WORK WEEK...FOLLOWED BY A RETURN OF HIGH PRESSURE
FOR THE START OF THE UPCOMING WEEKEND.
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
THE SEABREEZE DEVELOPED A BIT EARLIER TODAY AND ENOUGH LOW-LEVEL
MOISTURE ACROSS SOUTHEAST GA HAS ALLOWED ISOLATED SHOWERS TO
DEVELOP IN COASTAL AREAS. THIS ACTIVITY WILL DIE OFF QUICKLY BY
SUNSET. CUMULUS SHOULD MOSTLY DISSIPATE OVERNIGHT BUT WITH THE
APPROACH OF A MID-LEVEL SHORTWAVE LATE...MID-CLOUDS COULD BE
INCREASING CLOSER TO DAYBREAK SUNDAY.
SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/
BROAD WESTERLY FLOW WILL MAINTAIN WARM WEATHER WHILE CONSIDERABLE
DRY AIR REMAINS IN THE LOW-LEVELS UNTIL LATE IN THE DAY SUNDAY.
LOW-LEVEL MOISTURE SHOULD BE ON THE INCREASE LATE IN THE DAY AS
THE SW FLOW INCREASES AHEAD OF A SHORTWAVE TROUGH. THE GUIDANCE
IS A BIT SLOWER WITH THE PROGRESSION OF ANOTHER COLD FRONT THROUGH
THE SC UPSTATE INTO THE MIDLANDS SUN AFTERNOON/EVENING. PRIOR TO
SUNSET SUNDAY THE MAIN DRIVER FOR SCATTERED SHOWERS AND STORMS
WILL BE THE SEABREEZE. A 75 KT 300 MB JET SHIFTING OFF THE MID-
ATLANTIC COAST SUNDAY NIGHT WILL PLACE THE SOUTHEAST STATES IN
THE RIGHT-ENTRANCE REGION. A SERIES OF POTENT SHORTWAVES DROPPING
FROM THE TN VALLEY INTO CENTRAL SC SHOULD DROP THE FRONT INTO THE
REGION. THERE LOOKS TO BE PRETTY GOOD COVERAGE OF CONVECTION
SUNDAY NIGHT...MAINLY DRIVEN BY CONVECTIVE CLUSTERS MOVING IN FROM
UPSTREAM AS WELL AS BOUNDARY CONVERGENCE. WE CONTINUE TO SHOW POPS
RAMPING FROM HIGH-END CHANCE TO LIKELY THROUGH THE OVERNIGHT
HOURS.
LONG TERM /MONDAY THROUGH SATURDAY/
AN UNSETTLED WEATHER PATTERN WILL BE IN PLACE AT THE START OF THE
LONG TERM PERIOD...ALONG WITH THE THREAT FOR SEVERE WEATHER. A COLD
FRONT WILL DROP INTO THE AREA ON MONDAY AS A SERIES OF DISTURBANCES
ROTATE AROUND THE BASE OF AN UPPER LEVEL TROUGH OVER THE EASTERN
UNITED STATES. WITH THE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET
POSITIONED OVER THE REGION...CHANCES FOR PRECIPITATION APPEAR
LIKELY...ESPECIALLY GIVEN A STRONG THETA-E RIDGE AXIS IN PLACE OVER
THE AREA AND PRECIPITABLE WATER VALUES OF NEARLY 2.50 INCHES. THERE
ALSO APPEARS TO BE A THREAT FOR SEVERE WEATHER...WITH A POTENTIAL
FOR A MESOSCALE CONVECTIVE SYSTEM /MCS/ TO DROP INTO THE AREA AHEAD
OF THE FRONT ITSELF. THE AMOUNT OF AVAILABLE INSTABILITY WILL BE
HIGHLY DEPENDENT ON THE EXTENT OF THE CLOUD COVER AHEAD OF THE
FRONT...BUT WITH A 35-40 KT JET IN PLACE AT 925 MB...DAMAGING WINDS
COULD BECOME A CONCERN WITH ANY SEVERE THUNDERSTORM DEVELOPMENT.
THE FRONT SHOULD DROP INTO SOUTHEAST GEORGIA...PARTIALLY AIDED BY
OUTFLOW BOUNDARIES FROM EARLIER CONVECTION...AS THE FINAL
DISTURBANCE PASSES OFFSHORE. WILL NEED TO MAINTAIN A CHANCE OF
CONVECTION THROUGH MONDAY EVENING...BUT COVERAGE SHOULD DIMINISH
DURING THE OVERNIGHT HOURS.
THE FRONT SHOULD STALL NEAR OR JUST SOUTH OF THE AREA TUESDAY INTO
WEDNESDAY AS WEAK HIGH PRESSURE BUILDS IN FROM THE NORTH. GENERALLY
EXPECT SCATTERED CONVECTION EACH DAY...WITH ISOLATED CONVECTION AT
NIGHT...WITH THE GREATEST COVERAGE OF STORMS ACROSS SOUTHEAST
GEORGIA CLOSER TO THE FRONT.
TO VARYING DEGREES...MOST OF THE MEDIUM RANGE GUIDANCE IS SHOWING A
WAVE OF LOW PRESSURE FORMING ALONG THE FRONT AND LIFTING TOWARDS THE
AREA THURSDAY INTO FRIDAY. AS A RESULT...THE FORECAST WILL REFLECT A
CHANCE OF SHOWERS AND THUNDERSTORMS FOR THE END OF THE WORK WEEK. AS
THE LOW PULLS NORTHEAST AWAY FROM THE AREA ON SATURDAY...A DRIER
WESTERLY FLOW IS EXPECTED TO DEVELOP.
HIGH TEMPERATURES WILL BE BELOW NORMAL ON MONDAY GIVEN THE EXPECTED
PRECIPITATION...BUT MODERATE TO NEAR NORMAL VALUES INTO THE MIDDLE
OF THE WEEK. DEPENDING ON IF LOW PRESSURE IMPACTS THE AREA TOWARD
THE END OF THE WEEK...TEMPERATURES COULD BE NEAR TO SLIGHTLY BELOW
NORMAL. THE WESTERLY FLOW SHOULD BRING A RETURN OF ABOVE NORMAL
TEMPERATURES FOR THE START OF THE WEEKEND.
AVIATION /19Z SATURDAY THROUGH THURSDAY/
VFR CONDITIONS TO PREVAIL AT BOTH TERMINALS THROUGH 18Z SUN. A FEW
SHOWERS AND THUNDERSTORMS COULD BE APPROACHING THE TERMINALS LATE
IN THE AFTERNOON ASSOCIATED WITH AN UPPER LEVEL DISTURBANCE.
EXTENDED AVIATION OUTLOOK...MVFR OR LOWER CONDITIONS APPEAR LIKELY
AT TIMES IN SHOWERS AND THUNDERSTORMS SUNDAY NIGHT INTO MONDAY.
VFR CONDITIONS ARE THEN GENERALLY EXPECTED TO PREVAIL OUTSIDE OF
SCATTERED CONVECTION INTO THURSDAY.
MARINE
QUIET MARINE CONDITIONS ANTICIPATED TONIGHT INTO SUNDAY BEFORE
LOW-LEVEL JETTING FROM THE SW INCREASES WINDS AND SEAS DURING THE
AFTERNOON AND EVENING. 925 MB WINDS INCREASE TO 25-30 KT SUN
EVENING AND OVERNIGHT...THUS SURFACE WINDS COULD APPROACH 20 KT
OVER THE WATERS DURING THIS PERIOD.
MONDAY THROUGH THURSDAY...ATLANTIC HIGH PRESSURE WILL PREVAIL
THROUGH MONDAY AS A COLD FRONT APPROACHES THE WATERS FROM THE
NORTHWEST. THE FRONT WILL SLOWLY DROP ACROSS THE WATERS TUESDAY...
AS WEAK HIGH PRESSURE BUILDS IN FROM THE NORTH AND PREVAILS INTO
WEDNESDAY. AN AREA OF LOW PRESSURE COULD IMPACT THE WATERS ON
THURSDAY.
A STRONG LOW LEVEL JET COULD RESULT IN SMALL CRAFT ADVISORY
CONDITIONS FOR A PORTION OF THE COASTAL WATERS LATE MONDAY INTO
MONDAY NIGHT...WITH CONDITIONS EXPECTED TO REMAIN BELOW SMALL CRAFT
ADVISORY CRITERIA FOR THE REST OF THE FORECAST PERIOD.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
JRL/JAQ
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page