National Weather Service Weather Forecast Office

Area Forecast Discussion

089
FXUS62 KCHS 032054
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
354 PM EST SUN MAR 3 2013

.SYNOPSIS...
HIGH PRESSURE WILL BUILD IN FROM THE WEST TONIGHT AND REMAIN
THROUGH EARLY THIS WEEK. LOW PRESSURE AND ITS TRAILING COLD FRONT
WILL IMPACT THE AREA TUESDAY NIGHT INTO EARLY WEDNESDAY...FOLLOWED
AGAIN BY HIGH PRESSURE THROUGH LATE WEEK.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
THE DEEP UPPER TROUGH AND ASSOCIATED STRONG SHORTWAVE WILL SHIFT
OFFSHORE TONIGHT ALLOWING HIGH PRESSURE TO MOVE IN FROM THE WEST.
CLOUD COVER SHOULD DIMINISH WITH THE LOSS OF HEATING...HOWEVER
MINIMAL IT HAS BEEN...AND WITH NVA BEHIND THE DEPARTING UPPER
SHORTWAVE. THIS WILL LEAD TO CLEARING SKIES AND DIMINISHING
WINDS...MAINLY LATE ACROSS INTERIOR PORTIONS OF THE AREA AS THE
HIGH BUILDS IN FROM THE WEST. EXPECT TEMPERATURES TO DROP INTO THE
MID TO UPPER 20S INLAND AND CLOSE TO FREEZING ALONG THE COAST.
THUS...THOSE WITH SENSITIVE VEGETATION OUTDOORS SHOULD TAKE
APPROPRIATE PROTECTIVE ACTIONS.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
MONDAY...THE ABNORMALLY DEEP TROUGH THAT IMPACTED THE AREA OVER THE
WEEKEND WILL FINALLY LIFT OUT...AND BECOMES REPLACED BY A BUILDING
RIDGE FROM THE WEST AND ITS ASSOCIATED RISING HEIGHTS. THE CYCLONIC
FLOW OF RECENT DAYS THAT EXTENDS FAR TO THE SW FROM DEEP LOW
PRESSURE NEAR THE COAST OF MAINE WILL GIVE WAY TO ANTICYCLONIC
CURVATURE OF THE ISOBARS AS HIGH PRESSURE ARRIVES FROM THE WEST.
ALTHOUGH THERE IS AN INCREASE IN JET STREAM CIRRIFORM CLOUDS IN THE
LATE MORNING AND AFTERNOON...CROSS-SECTIONS AND SOUNDINGS INDICATE
THAT THEY WILL BE MORE TRANSLUCENT RATHER THAN OPAQUE. THUS WITH
DECENT INSOLATION...A 20-30 METER RISE IN LOW LEVEL THICKNESS VALUES
AND A SOLID 8-10C CLIMB IN 850 MB TEMPS AND COLD ADVECTION
WANING...WE LOOK TO REACH THE MID 50S NORTH TO AROUND 60 SOUTH.

MONDAY NIGHT...THE SURFACE RIDGE SLIDES INTO THE ATLANTIC...THE
SYNOPTIC FLOW BACKS AROUND TO THE WEST AND SW...AND THERE IS A
STEADY INCREASE IN HIGHER LEVEL CLOUDS. THESE CLOUDS WILL THICKEN
WITH TIME FROM WEST TO EAST IN ASSOCIATION WITH THE UPPER JET AND IN
ADVANCE OF A LOW PRESSURE SYSTEM THAT ORGANIZES AS IT MOVES NE FROM
THE ARKLATEX TO KENTUCKY. WE/LL EXPERIENCE SOME RADIATIONAL COOLING
IN THE EVENING...BUT TEMPS WILL HOLD STEADY OR EVEN RISE LATE.
BOTTOM LINE THOUGHT...WE WILL BE CONSIDERABLE WARMER THAN WE WILL BE
24 HOURS PRIOR.

TUESDAY...A STRONG CUT OFF LOW WILL SHIFT FROM THE NORTHERN PLAINS
TO ILLINOIS...WITH ITS ASSOCIATED SURFACE LOW TO TREK EASTWARD
THROUGH THE OHIO VALLEY TOWARD THE CENTRAL APPALACHIANS. THE FORECAST
ZONES WILL LIE IN THE WARM SECTOR REGIME...WITH A WARM FRONT FOUND
IN NC AND A TRAILING COLD FRONT ORIENTED FROM NE TO SW TO CROSS THE
SOUTHERN PORTION OF THE MOUNTAINS BY 00Z WEDNESDAY. WITH ONLY MINIMAL
HEIGHT FALLS LATE AND THE BEST CONVERGENCE AND DEEPER MOISTURE TO
REMAIN OFF TO OUR WEST AND NW...THE CHANCES FOR ANY RAIN BEFORE
NIGHTFALL ARE SMALL. THERE IS A MOISTENING OF THE COLUMN...BUT THE
LOW LEVELS REMAIN QUITE DRY WITH DEW POINT DEPRESSIONS AS MUCH AS
20-25 DEGREES IF NOT MORE. THUS WE/LL CARRY ONLY 20 POPS IN THE
AFTERNOON NW OF A LINE FROM ABOUT JAMESTOWN TO SUMMERVILLE AND
YEMASSEE IN SC...AND NW OF A LIN FROM ABOUT SHAWNEE TO CLAXTON AND
REIDSVILLE IN GA. LATER FORECASTS MAY NEED TO ADJUST THESE POPS UP
OR DOWN...DEPENDING UPON TIMING OF THE APPROACHING FRONT. DESPITE AN
INCREASE IN CLOUD COVER...STRONG WARM ADVECTION WILL BOOST TEMPS TO
THEIR HIGHEST LEVELS IN ABOUT A WEEK. AWAY FROM THE MUCH COOLER
SHORELINE COMMUNITIES...UPPER 60S AND LOWER 70S WILL BE COMMON JUST
ABOUT EVERYWHERE. A 30-40 KT LOW LEVEL JET WILL SHIFT THROUGH THE
REGION...AND THAT ALONG WITH A TIGHTENING OF THE GRADIENT WILL ALLOW
FOR BREEZY TO WINDY CONDITIONS TO DEVELOP.

TUESDAY NIGHT...THE CUTOFF ALOFT MOVES THROUGH VIRGINIA AND
NC...WHICH TRIGGERS A TRIPLE POINT SURFACE LOW FORMING JUST TO THE
EAST OF THE FEATURE ALOFT. BETTER HEIGHTS FALLS LOCALLY WILL
ACCOMPANY THE LOW...AND THIS WILL WILL DRIVE THE COLD FRONT FAIRLY
QUICKLY THROUGH THE AREA FROM NW TO SE THROUGH THE NIGHT. POPS WILL
EASILY REACH THE 60-70 PERCENTILE...BUT EVEN THESE MAY BE
CONSERVATIVE AS REFINEMENTS WILL LIKELY BE REQUIRED ONCE THE EXACT
TIMING DETAILS ARE HASHED OUT. THERE IS LITTLE IF ANY SURFACE BASED
INSTABILITY...BUT SOME ELEVATED CAPE /200-300 J/KG/...SHOWALTERS
LESS THAN ZERO AND 0-6 KM BULK SHEAR OF 50 KT OR MORE. THEREFORE WE
CAN/T RULE OUT A LITTLE ELEVATED CONVECTION. THE QUICK PROGRESSION
OF THE FRONT SHOULD LIMIT OUR QPF VALUES...MAINLY IN THE RANGE FROM
0.10 TO 0.30 INCHES. WINDS WILL FLUCTUATE THROUGH THE NIGHT...BUT
ONCE THE FRONT MOVES THROUGH AND PRESSURES STEADILY RISE AND COLD
ADVECTION ENSUES...THEY WILL REMAIN ELEVATED AND PERIODICALLY BREEZY
OR EVEN WINDY. TEMPS WILL PLUNGE IN WAKE OF THE FRONT AND NOT FAR FROM
TYPICAL MINIMAL LEVELS.

WEDNESDAY...THE CUT OFF WILL FINALLY TRAP ITS SURFACE LOW UNDERNEATH
NEAR THE MID-ATLANTIC COAST. WE/LL BE IN THE DRY SLOT BEHIND THE
COLD FRONT THAT PULLS FAR AWAY THROUGH THE ATLANTIC...AND THE
WRAP-AROUND MOISTURE ASSOCIATED WITH THE STACKED LOW. ALTHOUGH THERE
ARE HINTS THAT SOME SHOWERS COULD MAKE A RUN FOR OUR FAR NORTHERN
AND/OR NE SECTIONS LATE...WE CURRENTLY ANTICIPATE THAT THE DAY WILL
BE FREE OF ANY PRECIPITATION. TEMPS WILL CERTAINLY BE COLDER THAN ON
TUESDAY...BUT DOWNSLOPE FLOW AND A DECENT AMOUNT OF SUNSHINE WILL
NEGATE SOME OF THE COLDER AIR IMPACTING THE REGION. EVEN SO...WE/RE
LOOKING AT HIGHS AS MUCH AS 10-15 DEGREES COLDER THAN ON TUESDAY. A
TIGHT PRESSURE GRADIENT ND THE PRESENCE OF A 25-35 KT LOW LEVEL JET
WILL PRODUCE A WINDY DAY AREA WIDE. WE MIGHT EVEN FLIRT WITH A WIND
ADVISORY IN SOME LOCALES...WITH WINDS OF 20-30 MPH SUSTAINED AND 35
OR 40 MPH IN GUSTS.

LAKE WINDS...WINDS WILL APPROACH ADVISORY CRITERIA TUESDAY AFTERNOON
AS A 30-40 KT LOW LEVEL JET PASSES OVER THE REGION. HOWEVER...MIXING
WILL BE LIMITED WITHIN A WARM ADVECTION REGIME OVER THE COOLER LAKE
WATERS. A BETTER CHANCE FOR LAKE WIND ADVISORY THRESHOLDS TO BE MET
TUESDAY NIGHT THROUGH EARLY THURSDAY...AS A SIGNIFICANTLY TIGHTENED
PRESSURE GRADIENT AND BOUTS OF STRONG COLD ADVECTION ENHANCES THE
MIXING AND SUPPORTS 20 TO 25 KT AND GUSTY OVER LAKE MOULTRIE.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS THE POTENT LOW SYSTEM RAPIDLY TRACKS INTO THE ATLANTIC THROUGH
THE LATE WEEK PERIOD...SURFACE HIGH PRESSURE AND UPPER LEVEL
RIDGING WILL FOLLOW IN ITS WAKE. EXPECT DRY CONDITIONS TO THUS
PREVAIL THURSDAY THROUGH THE WEEKEND. RISING HEIGHTS ALOFT WILL
SUPPORT A GRADUAL WARMING TREND THROUGH THE PERIOD...WITH
TEMPERATURES PEAKING IN THE LOW TO MID 60S THURSDAY AND
FRIDAY...THEN POSSIBLY THE LOW 70S SATURDAY AND SUNDAY. LOW
TEMPERATURES WILL ALSO MODERATE INTO THE UPPER 30S TO LOWER 40S BY
LATE PERIOD.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
VFR. MAIN CONCERN WILL BE WIND GUSTS IN THE UPPER TEENS THROUGH
THIS AFTERNOON...MAINLY AT KSAV. SMALL CHANCE FOR LLWS AT KSAV
THIS EVENING ABOUT 03-09Z AS 1500 FT WINDS APPROACH 30 KT.

EXTENDED AVIATION OUTLOOK...THERE IS A LOW TO MODERATE CHANCE OF
REDUCED CONDITIONS AT TIMES TUESDAY NIGHT AS A COLD FRONT MOVES
THROUGH THE AREA...ACCOMPANIED BY NUMEROUS SHRA. WINDY CONDITIONS
WILL ALSO IMPACT THE TERMINALS TUESDAY AFTERNOON THROUGH THURSDAY.

&&

.MARINE...
TONIGHT...ANOTHER SURGE LOOKS LIKELY OVER THE WATERS AS THE
PRESSURE GRADIENT TIGHTENS AS HIGH PRESSURE BUILDS IN FROM THE
WEST. SHOULD SEE FREQUENT GUSTS TO 25-30 KT OVER THE WARMER
WATERS BEYOND 20 NM AND 25 KT GUSTS WITHIN 20 NM OF THE GEORGIA
COAST. THUS...WILL HAVE ADVISORIES FOR ALL THE NORTH COASTAL
GEORGIA WATERS OUT TO 60 NM THROUGH THE NIGHT. SEAS WILL NOT BUILD
MUCH DUE TO THE OFFSHORE WEST TO NORTHWEST FLOW...4 FT OR LESS
WITHIN 20 NM AND UP TO 6 FT CLOSER TO 60 NM OUT.

MONDAY...AS COLD ADVECTION SHUTS OFF AND THE PRESSURE PATTERN
FINALLY RELAXES AS HIGH PRESSURE BUILDS FROM THE WEST...WINDS AND
SEAS WILL DECREASE THROUGH THE DAY. ONGOING SCA/S WILL END BY 15Z
AND IMPROVING CONDITIONS WILL DEVELOP FOR THE BALANCE OF THE DAY.

MONDAY NIGHT...HIGH PRESSURE WILL SITUATE ITSELF ATOP THE
WATERS...RESULTING IN QUIET MARINE CONDITIONS.

TUESDAY...HIGH PRESSURE ACROSS THE MARINE AREA EARLY WILL GIVE WAY
TO AN AREA OF LOW PRESSURE AND ITS COLD FRONT THAT MOVES THROUGH THE
SE QUADRANT OF THE NATION. THE PRESSURE GRADIENT WILL ONCE AGAIN
BECOME ENHANCED AS THIS PATTERN TRANSPIRES. ALTHOUGH THE WARM
ADVECTION WILL LIMIT MIXING...OUR WINDS AND SEAS WILL NONETHELESS BE
ON A STEADY RISE. AND WE COULD BE LOOKING AT MARGINAL SMALL CRAFT
ADVISORY CONDITIONS YET AGAIN.

TUESDAY NIGHT THROUGH WEDNESDAY...STRONG LOW PRESSURE WILL MOVE EAST
THROUGH THE MID ATLANTIC STATES...WITH ITS ASSOCIATED COLD FRONT TO
SWEEP THROUGH THE COASTAL WATERS THE LATTER PART OF TUESDAY NIGHT.
LARGE ISALLOBARIC PRESSURE FALLS WILL BE FOLLOWED BY LARGE
ISALLOBARIC PRESSURE RISES. THAT ALONG WITH STRONG COLD ADVECTION
DEVELOPING IN WAKE OF THE COLD FRONT WILL LEAD TO A HIGH PROBABILITY
OF GALES OVER MOST IF NOT ALL WATERS. THESE CONDITIONS WILL THEN
PERSIST THROUGH WEDNESDAY...POSSIBLY EVEN INTO WEDNESDAY NIGHT WITH
ANOTHER SURGE OF COLD ADVECTION AND STEADY PRESSURE RISES AS THE
SURFACE LOW MOVES INTO THE WESTERN ATLANTIC. MARINERS ARE ADVISED
THAT A FEW T-STORMS COULD PRECEDE THE COLD FRONT TUESDAY
NIGHT...PERHAPS ACCOMPANIED BY WINDS IN EXCESS OF 35 KT.

THURSDAY AND FRIDAY...THE ATLANTIC LOW WILL EVENTUALLY MOVE AWAY AND
GIVE WAY TO HIGH PRESSURE. IT/LL TAKE AWHILE...BUT IMPROVING
CONDITIONS WILL ARRIVE DURING THIS TIME.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 10 AM EST
     MONDAY FOR AMZ354-374.

&&

$$

SYNOPSIS...
NEAR TERM...RJB
SHORT TERM...33
LONG TERM...
AVIATION...RJB/33
MARINE...RJB/33