Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 242009
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
409 PM EDT THU JUL 24 2014

.SYNOPSIS...
AN ATLANTIC RIDGE OF HIGH PRESSURE WILL REMAIN SOUTH OF THE AREA
INTO EARLY NEXT WEEK...WITH A WEAK TROUGH OF LOW PRESSURE
PREVAILING INLAND. A COLD FRONT COULD APPROACH LATE MONDAY AND
BECOME STATIONARY SOUTH AND SOUTHEAST OF THE AREA DURING THE
MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
LATEST RADAR TRENDS SHOW SCATTERED CONVECTION ACROSS NORTHERN
GEORGIA AND THE SOUTH CAROLINA MIDLANDS/UPSTATE BY LATE
AFTERNOON...FAIRLY COINCIDENT WITH SHORTWAVE ENERGY DOWNSTREAM OF
AN UPPER TROUGH AXIS. THE FORECAST AREA HAS REMAINED DRY AT THIS
POINT...LIKELY A RESULT OF SOLID WEST FLOW PINNING THE SEABREEZE
AND POSSIBLY A LINGERING CAP IN THE MID LEVELS. HIGH RESOLUTION
MODELS SUGGEST THAT THE BEST CHANCE FOR PRECIPITATION COULD
ACTUALLY OCCUR MORE TOWARD THE EVENING HOURS...AS APPROACHING
ELONGATED SHORTWAVE ENERGY ENHANCES AN INLAND SURFACE TROUGH
SHIFTING TOWARD THE COASTLINE. PREFER TO REMAIN RATHER
CONSERVATIVE WITH RAIN CHANCES...INCREASING POPS INTO THE 30
PERCENT RANGE MAINLY AFTER 21Z OR 22Z. THE SOUTH CAROLINA ZONES
APPEAR FAVORED FOR SCATTERED SHOWERS/THUNDERSTORMS THIS EVENING
AND EVEN INTO THE EARLY NIGHTTIME PERIOD...AS UPSTREAM CONVECTION
SHIFTS INTO THE REGION CLOSER TO THE SURFACE TROUGH AND STRONGER
SHORTWAVE ENERGY. ACTIVITY SHOULD DIMINISH AS THE NIGHT
PROGRESSES...HOWEVER A FEW SHOWERS COULD LINGER INTO THE EARLY
MORNING HOURS DUE TO THE SYNOPTIC SCALE FORCING IN THE REGION. LOW
TEMPERATURES WILL RANGE FROM THE UPPER 70S COAST TO THE LOW/MID
70S INLAND.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A WEAK FRONT/SURFACE TROUGH WILL BE STALLED NEAR TO JUST
NORTHWEST OF THE AREA THROUGH SATURDAY...THEN LIFT NORTHWARD AND
DISSIPATE BY SUNDAY. A BROAD UPPER TROUGH WILL BE OVER THE REGION
FRIDAY AND INTO SATURDAY. BY SUNDAY...THE UPPER TROUGH IS EXPECTED
TO FLATTEN AND MOVE EAST WAS A DEEP LAYER RIDGE TRIES TO BUILD
FROM THE WEST.

DEEP LAYER MOISTURE WILL BE PLENTY SUFFICIENT THROUGH AT LEAST
SATURDAY...WITH PWS 1.8 TO 2.0 INCHES. HOWEVER ONLY REALLY FORCING
FOR CONVECTION WILL BE LOWER LEVEL BOUNDARIES/SEA BREEZE. THINK THE
BEST COVERAGE WILL BE FRIDAY...FROM I-95 EASTWARD TOWARD THE
COAST...AS MAIN STEERING FLOW WILL BE WEST-SOUTHWEST. HAVE KEPT MID
RANGE CHANCE POPS FOR FRIDAY AFTERNOON AND EARLY EVENING. FOR
SATURDAY...SLIGHTLY LOWER MOISTURE VALUES AND EVEN LESS OF AN UPPER
TROUGH...SHOULD TRANSLATE TO SLIGHTLY LOWER POPS...WITH A FOCUS
AGAIN JUST INLAND TO BACK TOWARD THE COAST. BY SUNDAY...DEEP LAYER
MOISTURE WILL GO DOWN A BIT AS MEAN RH VALUES FALL BELOW 50%...AND
ALONG WITH A BUILDING DEEP LAYER RIDGE...EXPECT ONLY ISOLATED MAINLY
AFTERNOON CONVECTION.

TEMPERATURES NEAR NORMAL FRIDAY...THEN MODERATING TO ABOVE NORMAL
SATURDAY AND ESPECIALLY SUNDAY. GUIDANCE CONTINUES TO SHOW MID 90S
FOR HIGHS BOTH SATURDAY AND SUNDAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A DEEP LAYERED GYRE OVER OR NEAR SOUTHERN HUDSON BAY IN CANADA WILL
CIRCULATE OCCASIONAL SHORT WAVES THROUGH THE GREAT LAKES AND OHIO
VALLEY...WHICH IN TURN WILL CARVE OUT A BROAD AND FAIRLY WELL
AMPLIFIED TROUGH ACROSS THE EASTERN HALF OF THE COUNTRY DURING THE
EARLY AND MIDDLE PARTS OF NEXT WEEK. THIS IS DEFINITELY NOT A
SUMMER-LIKE PATTERN...AND IT WILL SEND AN UNUSUAL LATE JULY COLD
FRONT INTO THE AREA FROM THE NW LATER MONDAY AND EARLY TUESDAY.
SURPRISINGLY IT LOOKS LIKE THERE IS ENOUGH NW PUSH BEHIND THE
FRONT TO SEND IT THROUGH THE AREA...BEFORE IT STALLS OUT NOT FAR
TO THE SE AND SOUTH FOR THE MIDDLE OF THE WEEK. RAIN CHANCES WILL
CLIMB MONDAY AND TUESDAY IN CONJUNCTION WITH THE FRONT...MAINLY IN
THE 20-40 PERCENT RANGE. PROVIDED THE FRONT CLEARS THE AREA RAIN
CHANCES ARE NO MORE THAN 20 PERCENT WEDNESDAY...THEN 20-30 PERCENT
NEXT THURSDAY AS THE FRONT STARTS TO TREK BACK NORTH.
COMPRESSIONAL HEATING OUT AHEAD OF THE FRONT ALLOWS FOR ABOVE
NORMAL TEMPS MONDAY...WITH ONLY VERY MINIMAL COOL ADVECTION TO
DROP READINGS SLIGHTLY BELOW NORMAL TUESDAY THROUGH THURSDAY.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
BREEZY SOUTHWEST WINDS EXPECTED AT BOTH TERMINALS THIS
AFTERNOON...AS DECENT MIXING TAPS INTO MODERATE BOUNDARY LAYER
FLOW. EXPECT CONVECTIVE DEVELOPMENT TO BE DELAYED OR
LIMITED...AS THE BULK OF THE ACTIVITY COULD BE MAINLY ASSOCIATED
WITH UPSTREAM CONVECTION MOVING INTO THE REGION FROM THE
WEST/NORTHWEST INTO THE EVENING HOURS. THERE IS STILL BETTER
CONFIDENCE IN THUNDERSTORM IMPACTS AT KCHS THAN KSAV...AND WILL
MAINTAIN A TEMPO GROUP FOR TSRA BETWEEN 20Z AND 22Z TO NARROW DOWN
A POSSIBLE WINDOW. HAVE OTHERWISE JUST MENTIONED VCTS AT BOTH TAF
SITES UNTIL CONVECTIVE TRENDS BECOME MORE APPARENT. ALTHOUGH
ISOLATED CONVECTION COULD PERSIST INTO THE NIGHTTIME PERIOD AS A
TROUGH AT THE SURFACE AND ALOFT APPROACHES...CONFIDENCE IN TIMING
IS TOO LOW TO MENTION TSRA OR VCTS BEYOND 00Z OR 01Z. IF RAINFALL
DOES IMPACT THE TERMINALS THIS AFTERNOON...PATCHY FOG AND/OR
STRATUS IS POSSIBLE DURING THE EARLY MORNING HOURS.

EXTENDED AVIATION OUTLOOK...MAINLY VFR. BRIEF FLIGHT RESTRICTIONS
POSSIBLE IN SCATTERED AFTERNOON AND EARLY EVENING
SHOWERS...ESPECIALLY FRIDAY AND SATURDAY. A COLD FRONT COULD MOVE
INTO THE AREA BY TUESDAY...BUT CONFIDENCE ON THE TIMING AND
STRENGTH OF THIS FRONT IS LOW...GIVEN THAT FRONTS TEND TO STRUGGLE
TO MOVE INTO OUR REGION THIS TIME OF YEAR.

&&

.MARINE...
TONIGHT...A TROUGH OF LOW PRESSURE INLAND WILL PROGRESS TOWARD
THE COAST THIS EVENING AND OVERNIGHT. BREEZY SOUTH TO SOUTHWEST
WINDS FOR THE REMAINDER OF THE DAYTIME HOURS WILL DIMINISH AND
BECOME MORE SOLIDLY SOUTHWEST LATE. HAVE MAINTAINED WINDS NO MORE
THAN 15 TO 20 KT...JUST BELOW ADVISORY LEVELS...MAINLY ALONG THE
CHARLESTON COUNTY COAST AND OFFSHORE WATERS. SEAS SHOULD PEAK
NEAR 4 FT...HIGHEST EAST.

NO HIGHLIGHTS EXPECTED THROUGH MUCH OF THE WEEKEND AS THE AREA
REMAINS BETWEEN ATLANTIC HIGH PRESSURE TO THE EAST AND A WEAK TROUGH
OF LOW PRESSURE WELL INLAND. THIS WILL PRODUCE SOUTHWEST WINDS OF
GENERALLY 15 KT OR LESS AND SEAS 2-4 FEET. BY SUNDAY NIGHT AND
MONDAY...THE PRESSURE GRADIENT BEGINS TO TIGHTEN/INCREASE AS SURFACE
PRESSURES LOWER OVER THE MID ATLANTIC AND SOUTHEAST STATES...AND
HIGHER PRESSURE HOLDS ON OVER THE ATLANTIC. CURRENT FORECAST
INCREASES WINDS INTO THE 15-20 KT RANGE WITH SEAS APPROACHING 5 FT
OFFSHORE THROUGH MONDAY NIGHT. A COLD FRONT COULD MOVE INTO THE
WATERS TUESDAY...VEERING WINDS TO LIGHT NORTHERLY.

&&

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

&&

$$

NEAR TERM...WMS
SHORT TERM...RFM
LONG TERM...
AVIATION...WMS/RFM
MARINE...WMS/RFM






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