Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 020152
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
952 PM EDT WED OCT 1 2014

.SYNOPSIS...
HIGH PRESSURE WILL PERSIST ACROSS THE AREA TONIGHT INTO THURSDAY.
A STRONG COLD FRONT WILL THEN MOVE THROUGH THE REGION FRIDAY
NIGHT...WITH HIGH PRESSURE BUILDING BACK OVER THE SOUTHEAST STATES
THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
FLAT RIDGING ALOFT AND WEAK SURFACE HIGH PRESSURE WILL GENERATE
CONSIDERABLE LARGE SCALE SUBSIDENCE TONIGHT AND ALLOW FOR A RAPID
DECOUPLING OF THE TROPOSPHERE. OTHER THAN PATCHY STRATOCUMULUS
AND/OR ALTOCUMULUS NEAR THE ALTAMAHA RIVER IN CONJUNCTION WITH
WEAK ISENTROPIC LIFT AND A FEW THIN CIRRUS MOVING IN FROM THE
WEST THROUGH THE NIGHT...SKIES WILL BE MOSTLY CLEAR. THIS SETS THE
STAGE FOR ANOTHER NIGHT WITH NEAR IDEAL RADIATIONAL COOLING. WHEN
COMPARING TEMPS TO 24 HOURS AGO UNDER SIMILAR CONDITIONS WE/RE
RUNNING ABOUT THE SAME OR A TAD COOLER IN SOME LOCATIONS. WITH
LITTLE IF ANY CHANGE IN THE SYNOPTIC SITUATION WE LOOK FOR LOWS
TO DROP INTO THE UPPER 50S AND LOWER 60S FOR MOST COMMUNITIES
INLAND FROM US-17...WITH MID AND UPPER 60S NEAR/ALONG THE COAST
WHERE THERE IS A BIT OF AN ONSHORE BREEZE.

WE WERE A LITTLE TOO AGGRESSIVE ON FOG LAST NIGHT...AND THE SOILS
ARE CONTINUING TO DRY OUT. PLUS OUR GROUND TEMPS ARE STILL QUITE
WARM...IN THE LOWER 70S. SO WE/RE NOT CERTAIN ON THE EXTENT OF
FOG FORMATION...MAYBE EVEN A LITTLE GUN SHY AFTER NOT SEEING TOO
MUCH FOG LAST NIGHT. BUT SEVERAL FACTORS STILL POINT TO AT LEAST
PATCHY FOG DEVELOPING. WE/LL PASS OUR CROSS-OVER TEMPS AFTER
MIDNIGHT...FOG STABILITY INDICES ARE MAINLY IN THE TEENS AND MRI
VALUES CLEARLY SHOW THE DECOUPLED BOUNDARY LAYER. GIVEN THAT WE
ALREADY HAVE SOME LIGHT FOG DEVELOPING WHEN WE DIDN/T LAST NIGHT
AT THE SAME TIME...WE HAVE ADDED AREAS OF FOG AFTER 4 AM ALONG THE
MORE CLIMATOLOGICALLY FAVORED WEST AND NW TIER. I/M HESITANT TO
ADD DENSE FOG TO THE HAZARDOUS WEATHER OUTLOOK...LEAVING THIS
CONCERN TO THE OVERNIGHT CREW OF METEOROLOGISTS AS THEY WATCH
TRENDS.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
THURSDAY...SURFACE HIGH PRESSURE AND A RIDGE ALOFT WILL LINGER
ALONG THE EAST COAST. EXPECT SUFFICIENT SUBSIDENCE AND MID-LEVEL
CAPPING WITHIN A RATHER DRY AIR MASS TO EFFECTIVELY SUPPRESS RAIN
CHANCES ONCE AGAIN. HAVE THUS MAINTAINED A DRY FORECAST...INDICATING
SLIGHTLY MORE CLOUD COVERAGE SOUTH OF THE SAVANNAH WITHIN RETURN
FLOW ON THE PERIPHERY OF THE SURFACE HIGH. TEMPERATURES WILL RISE
WELL ABOVE SEASONAL NORMALS...PEAKING IN THE UPPER 80S AWAY FROM
THE LOCALLY COOLER COASTLINE. NIGHTTIME LOW TEMPERATURES WILL
TREND SLIGHTLY WARMER...FALLING INTO THE LOW TO MID 60S INLAND.

FRIDAY...RIDGING AT THE SURFACE AND ALOFT WILL STEADILY SLIP OFF
THE EAST COAST EARLY IN THE DAY...AS A DIGGING UPPER TROUGH MOVES
FROM THE CENTRAL UNITED STATES INTO THE OHIO AND TENNESSEE
VALLEYS. NUMERICAL MODEL SOLUTIONS CONTINUE TO SUGGEST AN EVENING
OR EVEN NIGHTTIME FRONTAL PASSAGE...DELAYING THE ONSET OF BEST
RAIN COVERAGE UNTIL AFTER SUNSET. HAVE INDICATED
SHOWER/THUNDERSTORM CHANCES INCREASING FROM SOUTHWEST TO NORTHEAST
AHEAD AND ALONG THE FRONT...PEAKING IN THE 50 TO 60 PERCENT RANGE
BETWEEN 00Z AND 06Z FRIDAY NIGHT. CONSIDERING THE EXPECTED
INCREASE IN CLOUD COVERAGE WELL AHEAD OF THE FRONT...AS WELL AS
ISOLATED PRE-FRONTAL PRECIPITATION ASSOCIATED WITH RETURN FLOW
AND/OR A SUBTLE LIFTING WARM FRONT...INSTABILITY IN MODEL
SOLUTIONS APPEARS RATHER MARGINAL FRIDAY AFTERNOON AND EVENING.
BULK SHEAR VALUES STILL REACH 30 TO 40 KT DURING THE EVENING...YET
CONSIDERING THE MARGINAL INSTABILITY AND LESS-FAVORABLE FRONTAL
TIMING...SEVERE WEATHER POTENTIAL CONTINUES TO LOOK GENERALLY LOW.
WILL CONTINUE TO MONITOR TRENDS...YET PREFER NOT TO MENTION ANY
SEVERE STORM CONCERNS IN THE HAZARDOUS WEATHER OUTLOOK. HIGH
TEMPERATURES WILL STILL BE A DEGREE OR TWO ABOVE SEASONAL NORMALS
DUE TO SOME PRE-FRONTAL COMPRESSION EFFECTS AND WARM SOUTHERLY
FLOW...YET BE COOLER THAN THE PREVIOUS DAY UNDER THE THICKENING
CLOUD COVER.

SATURDAY...THE STRONG COLD FRONT WILL MAKE RAPID PROGRESS THROUGH
THE FORECAST AREA FRIDAY NIGHT...SWIFTLY MOVING OFF THE COAST AND
FARTHER INTO THE ATLANTIC INTO SATURDAY MORNING. EXPECT
THUNDERSTORM CHANCES TO ALSO QUICKLY DECREASE FROM WEST TO EAST AS
A NOTABLY DRIER AND COOLER AIR MASS MOVES INTO THE REGION IN THE
WAKE OF THE FRONT. PREFER TO ADVERTISE RAIN CHANCES BELOW 15
PERCENT BY SUNRISE SATURDAY AND FALLING TO ZERO BY THE AFTERNOON.
DESPITE CLEARING SKIES AND MORE ABUNDANT SUNSHINE...AMPLE COLD
ADVECTION BEHIND THE FRONT WILL SUPPRESS HIGH TEMPERATURES IN THE
70S SATURDAY AFTERNOON.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
HIGH PRESSURE WILL MOVE EASTWARD OVER THE AREA THROUGH EARLY NEXT
WEEK WITH TEMPS SLOWLY MODERATING. THE COOLEST TEMPS WILL COME
SUNDAY MORNING WHEN 40S ARE POSSIBLE INLAND. THE CHILLY START WILL
YIELD A COOL AFTERNOON WITH HIGHS SUNDAY POSSIBLY NOT GETTING OUT OF
THE 60S.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
OUTSIDE OF POSSIBLE MVFR CONDITIONS IN LIGHT FOG A COUPLE OF HOURS
EITHER SIDE OF DAYBREAK THURSDAY...VFR WEATHER WILL PREVAIL.

EXTENDED AVIATION OUTLOOK...LATE NIGHT/EARLY MORNING FOG AND/OR
STRATUS ARE POSSIBLE EARLY THURSDAY AND FRIDAY. FLIGHT RESTRICTIONS
WILL BE LIKELY LATE FRIDAY INTO EARLY SATURDAY...AS A COLD FRONT
WITH SHOWERS AND THUNDERSTORMS MOVES THROUGH THE REGION. VFR
CONDITIONS WILL PREVAIL OTHERWISE.

&&

.MARINE...
TONIGHT...THE SOUTHERN EXTENSION OF A LARGE AREA OF MODIFYING
CANADIAN HIGH PRESSURE WILL BE LOCATED ACROSS THE MARINE
TERRITORY...WITH A RELAXED EAST AND NE FLOW TO PREVAIL. SEAS WON/T
BE NO MORE THAN 2 OR 3 FT...HIGHEST AS ONE NAVIGATES ACROSS THE
OUTER GA WATERS.

THURSDAY THROUGH MONDAY...HIGH PRESSURE ON THURSDAY WILL DEPART
FARTHER OFFSHORE AHEAD OF AN APPROACHING COLD FRONT LATE FRIDAY.
SOUTHERLY WINDS WILL INCREASE ON FRIDAY AHEAD OF THE
FRONT...BEFORE FLOW SHIFTS WEST EARLY SATURDAY AS THE FRONT PUSHES
THROUGH THE REGION. A TIGHT PRESSURE GRADIENT AND COLD ADVECTION
WILL SUPPORT ANOTHER SURGE BEHIND THE FRONT SATURDAY...WITH
CONDITIONS POSSIBLY REACHING MARGINAL ADVISORY LEVELS...ESPECIALLY
BEYOND 20 NM. WINDS/SEAS WILL IMPROVE RATHER QUICKLY SATURDAY
NIGHT INTO SUNDAY...AS HIGH PRESSURE BUILDS IN FROM THE WEST AND
TRANQUIL CONDITIONS PERSIST INTO MONDAY.

&&

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

&&

$$

NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...





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