National Weather Service Weather Forecast Office

Area Forecast Discussion

469
FXUS62 KCHS 030226
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1026 PM EDT WED OCT 2 2013

.SYNOPSIS...
HIGH PRESSURE WILL PREVAIL UNTIL A COLD FRONT APPROACHES FROM THE
WEST EARLY NEXT WEEK. HIGH PRESSURE WILL THEN RETURN TO THE REGION
BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
HIGH PRESSURE AT THE SURFACE WILL CONTINUE TO PREVAIL OVER THE
REGION TONIGHT...WHILE A MID LEVEL RIDGE AXIS SHIFTS OFF THE
SOUTHEAST COAST. ON THE WESTERN PERIPHERY OF THE RIDGE AXIS...SOME
MAINLY HIGH LEVEL CLOUD COVER SHOULD BEGIN TO ADVECT INTO THE REGION
FROM THE SOUTHWEST BUT OVERALL EXPECT SKIES TO REMAIN MOSTLY
CLEAR. WHILE RADIATIONAL COOLING COULD BE SOMEWHAT LIMITED BY ANY
INCREASE IN CLOUD COVER...STILL EXPECT LOWS IN THE UPPER 50S TO
AROUND 60 AWAY FROM THE IMMEDIATE COAST...WITH SOME MID 50S
POSSIBLE IN WELL SHELTERED INLAND LOCATIONS.

IT SHOULD BE NOTED THAT A FEW LOCATIONS COULD EXPERIENCE PATCHY SHALLOW
GROUND FOG...MAINLY NEAR DAWN...BUT COVERAGE WILL REMAIN TOO LOW TO
MENTION IN THE FORECAST AT THIS TIME.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
THURSDAY AND THURSDAY NIGHT...THE AXIS OF THE UPPER RIDGE ALOFT WILL
MOVE OUT OVER THE ATLANTIC ALLOWING FOR THE PATTERN TO FLATTEN OUT A
BIT DURING THE DAY. DRY HIGH PRESSURE WILL REMAIN IN CONTROL AT THE
SURFACE WITH ITS CENTER POSITIONED OFF THE NC COASTLINE. MODEL TIME
HEIGHTS AND CROSS SECTIONS SHOW A CONSIDERABLE AMOUNT OF DRY AIR
THROUGH THE COLUMN...SUPPORTIVE OF PWATS AROUND AN INCH. THE DRY
FORECAST HAS BEEN MAINTAINED AS A RESULT. THANKS TO THE RIDGE AND
HIGHER HEIGHTS ALOFT...A SEASONALLY MILD DAY IS ON TAP. THICKNESSES
SUPPORT TEMPS IN THE MID 80S WHICH IS ABOUT 5 DEGREES ABOVE CLIMO.

FRIDAY THROUGH SATURDAY...THE FLATTENED UPPER RIDGE WILL REAMPLIFY
AND BECOME INCREASINGLY CENTERED OVER THE REGION THROUGH THE FIRST
PART OF THE WEEKEND. THIS RESULTS IN HIGH PRESSURE CONTINUING TO BE
THE PRIMARY SURFACE FEATURE IN CONTROL ACROSS THE FORECAST AREA. THE
DRY FORECAST CONTINUES THROUGH THIS PERIOD AS WELL THANKS TO THE
PRESENCE OF NVA ALOFT...A PROMINENT SUBSIDENCE INVERSION...AND
CONSIDERABLE DRY AIR IN THE MID/UPPER LEVELS. THERE WILL BE A BIT OF
AN INCREASE IN MOISTURE IN THE 5 KFT RANGE THANKS TO THE ONSHORE
EASTERLY FLOW...BUT THIS WILL PRIMARILY MANIFEST ITSELF AS A MODEST
INCREASE IN MAINLY DIURNAL CLOUD COVER. MODEL THICKNESSES ACTUALLY
INCREASE AS THE RIDGE AMPLIFIES EACH DAY...AND SOME HIGHS IN THE
UPPER 80S WILL BE POSSIBLE EACH AFTERNOON.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
MEDIUM RANGE MODEL SOLUTIONS CONTINUE TO SHOW SIGNIFICANT
DISCREPANCIES REGARDING THE EVOLUTION OF SYNOPTIC SCALE FEATURES
INTO EARLY NEXT WEEK. AT THIS POINT...PREFER TO CONTINUE FAVORING
THE LESS AGGRESSIVE ECMWF/WPC SCENARIOS THROUGH THE EXTENDED
PERIOD. THE AXIS OF THE UPPER RIDGE WILL SLIP OFF THE EAST COAST
ON SUNDAY...WHILE ATLANTIC SURFACE HIGH PRESSURE RETREATS AHEAD OF
A SYSTEM MOVING INTO THE MISSISSIPPI VALLEY. THIS STRONG UPPER
TROUGH WILL SUPPORT THE DEVELOPMENT AND EASTWARD MOVEMENT OF A
COLD FRONT INTO THE OHIO/TENNESSEE VALLEYS BY EARLY
MONDAY...BEFORE LIFTING WELL NORTH INTO THE GREAT LAKES REGION.
WITH THE STRONGEST ENERGY ALOFT THUS BECOMING REMOVED FROM THE
SOUTHERN EXTENT OF THE COLD FRONT...EXPECT FRONTAL PROGRESSION TO
SLOW AS THE FEATURE RUNS INTO RESIDUAL RIDGING ALONG THE EAST
COAST. FRONTAL PASSAGE COULD BECOME DELAYED AND/OR ILL-DEFINED BY
EARLY NEXT WEEK...EVEN POTENTIALLY STALLING AND/OR WASHING OUT
JUST WEST/NORTHWEST OF THE FORECAST AREA.

HAVE REINTRODUCED RAIN CHANCES ON SUNDAY...AS RETURN FLOW AROUND
THE ATLANTIC HIGH PRESSURE ALLOWS DEEPER MOISTURE TO SHIFT INTO THE
REGION WITHIN WARM ADVECTION AHEAD OF THE FRONT. WILL THEN
HIGHLIGHT MONDAY FOR THE BEST SHOWER/THUNDERSTORM POTENTIAL...WHEN
CONVERGENCE IS MAXIMIZED AHEAD AND ALONG THE FRONTAL ZONE JUST
UPSTREAM. PREFER TO MAINTAIN SLIGHT CHANCE POPS INTO TUESDAY TO
ACCOUNT FOR THE STALLED...AND POSSIBLY DISSIPATING...FRONT IN THE
VICINITY. CONSIDERING LITTLE SIGNIFICANT AIR MASS CHANGE IF THE
FRONT DOES NOT PROGRESS INTO THE FORECAST AREA...HAVE INDICATED
ONLY A SUBTLE COOLING TREND EARLY NEXT WEEK. HIGH TEMPERATURES
WILL REACH THE LOW TO MID 80S SUNDAY AFTERNOON...THEN AVERAGE IN
THE LOW 80S MONDAY THROUGH WEDNESDAY.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 00Z FRIDAY.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED TO PREVAIL.

&&

.MARINE...
TONIGHT...WINDS/SEAS WILL CONTINUE TO REMAIN WELL BELOW SMALL CRAFT
ADVISORY LEVELS AS HIGH PRESSURE DOMINATES THE COASTAL WATERS WHILE
WEAK LOW PRESSURE REMAINS POSITIONED WELL OFFSHORE IN THE WESTERN
ATLANTIC. EAST WINDS BELOW 10 KT WILL GRADUALLY BECOME MORE
NORTHEAST OVERNIGHT. SEAS WILL RANGE FROM 1-2 FT IN NEARSHORE
WATERS TO 2-3 FT IN OFFSHORE WATERS.

THURSDAY THROUGH MONDAY...TRANQUIL CONDITIONS ARE EXPECTED ACROSS
THE WATERS THROUGH SATURDAY. HIGH PRESSURE WILL BE IN CONTROL ACROSS
THE LOCAL WATERS RESULTING IN A PREDOMINANTLY EASTERLY FLOW. WIND
SPEEDS WILL LESS THAN 15 KTS AND SEAS 1-3 FT...HIGHEST OVER THE
OUTER WATERS. THERE WILL BE A SLIGHT SURGE IN EAST/SOUTHEAST FLOW BY
SUNDAY...AS THE PRESSURE GRADIENT TIGHTENS AHEAD OF AN APPROACHING
COLD FRONT. HOWEVER...CONDITIONS ARE EXPECTED TO REMAIN BELOW SMALL
CRAFT ADVISORY THRESHOLDS THROUGH THE PERIOD.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...JAQ
SHORT TERM...BSH
LONG TERM...WMS
AVIATION...JAQ/BSH
MARINE...JAQ/DPB/BSH