AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
110 AM EST SUN FEB 5 2012

.SYNOPSIS...
THE WESTERN EXTENT OF ATLANTIC HIGH PRESSURE ACROSS THE AREA EARLY
TONIGHT WILL SHIFT EAST. A COLD FRONT WILL APPROACH FROM THE NORTH
SUNDAY...THEN MOVE THROUGH THE REGION SUNDAY NIGHT. AN AREA OF
LOW PRESSURE WILL DEVELOP OFF THE CAROLINA COAST MONDAY AND TRACK
OFFSHORE MONDAY NIGHT...FOLLOWED BY HIGH PRESSURE FOR TUESDAY AND
WEDNESDAY. UNSETTLED CONDITIONS ARE POSSIBLE FOR THE END OF THE
WEEK...AS A SERIES OF DISTURBANCES PASS NEAR THE REGION.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
THE LOCAL AREA LIES UNDER THE WESTERN PERIPHERY OF ATLANTIC HIGH
PRESSURE EARLY TONIGHT...WITH FLAT SHORT WAVE RIDGING ALOFT. A
STATIONARY FRONT IS FOUND NOT FAR TO THE NW...WITH WEAK WAVES OF
LOW PRESSURE RIDING EAST ALONG IT IN GA AND AL. FOR EARLY TONIGHT
OUR SKIES WILL FLUCTUATE BETWEEN PARTLY AND MOSTLY CLOUDY...AS
ALTOCUMULUS AND CIRRIFORM CLOUDS MOVE THROUGH FROM THE WEST.

AFTER 1 AM A SHORT WAVE WILL HEAD TOWARD SC/GA...BUT WEAKEN WITH
TIME AS IT MOVES IN LATE TONIGHT. THERE SURE ISN/T MUCH FORCING
WITH THIS FEATURE AS IT APPROACHES. BUT IT ALONG WITH A CONTINUED
INCREASE IN MOISTURE...ADDITIONAL FORCING FOR ASCENT FROM A 25-30
KT LOW LEVEL JET THAT SCRAPES THE NW TIER...AND THE FRONT
ATTEMPTING TO SAG CLOSER TO THE REGION...WE SHOULD BE ABLE TO
SQUEEZE OUT ISOLATED SHOWERS ALONG OUR NW TIER CLOSE TO DAYBREAK.
BUT NOTHING MORE THAN 20 POPS IS NEEDED.

TEMPS WILL FALL SLOWLY DURING THE OVERNIGHT HOURS WITH MORE CLOUD
COVER MOVING IN...AND THE WARM SOUTH TO SW SYNOPTIC FLOW. LOWEST
TEMPS WILL BE SOME 13-18 DEGREES ABOVE NORMAL...OR ACTUALLY NOT
FAR FROM WHAT NORMAL MAX TEMPS ARE SUPPOSED TO BE!!

CONDITIONS ARE CERTAINLY NOT IDEAL FOR FOG TONIGHT...GIVEN THAT
TOO MUCH MIXING WILL PERSIST AND THERE LOOKS TO BE TOO MUCH
CLOUDINESS. BUT SINCE IT IS ALREADY MENTIONED IN THE FORECAST AND
SOME STRATUS THAT FORMS LATE COULD LOWER ENOUGH...WE/LL KEEP
PATCHY FOG IN THE FORECAST FOR AFTER 3 AM.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY/...
SUNDAY...WEAK LOW PRESSURE ALONG A DESCENDING COLD FRONT WILL DRIFT
SOUTHEAST ON SUNDAY...DOWNSTREAM OF AN UPPER SHORTWAVE TROUGH
TRACKING INTO THE TENNESSEE VALLEY. NEARLY ZONAL FLOW ALOFT IS STILL
EXPECTED TO PREVAIL ACROSS MUCH OF THE SOUTHERN STATES AS THE FRONT
DROPS INTO THE REGION LATE IN THE DAY...CREATING A NOTICEABLE
SEPARATION BETWEEN THE BEST UPPER DYNAMICS TO THE NORTHWEST AND THE
MORE RAPIDLY PROGRESSING SURFACE SYSTEM. THERE STILL APPEARS TO BE
SOME POTENTIAL FOR SCATTERED SHOWERS ON SUNDAY...WITH DECENT DEEP
LEVEL MOISTURE EVIDENT IN MODEL RELATIVE HUMIDITY FIELDS AND TYPICAL
SURFACE CONVERGENCE ASSOCIATED WITH THE APPROACHING FRONT.
HOWEVER...THERE REMAINS SOME CONCERN OVER THE LACK OF LARGE SCALE
UPPER LEVEL SUPPORT DURING FRONTAL PROGRESSION AND EVEN SOME
NEGATIVE VORTICITY OVER THE AREA DURING THE DAYTIME HOURS. PREFER TO
KEEP RAIN CHANCES CAPPED IN THE 30 TO 35 PERCENT RANGE FOR SUNDAY
AFTERNOON AND EARLY EVENING AS A RESULT. ALTHOUGH NUMERICAL MODELS
ARE SUGGESTING WEAK INSTABILITY COULD DEVELOP MID DAY...WILL KEEP
THUNDER OUT OF THE FORECAST AT THIS POINT DUE TO THE AFOREMENTIONED
LIMITED UPPER SUPPORT.

DESPITE BROKEN TO OVERCAST SKIES EXPECTED ON SUNDAY...SOLID
SOUTHWEST/WEST WINDS WILL PREVAIL WITHIN A WARM ADVECTION
REGIME...MAINTAINING UNSEASONABLY WARM CONDITIONS ACROSS THE
FORECAST AREA ON SUNDAY. EXPECT TEMPERATURES TO RISE INTO THE MID
70S SUNDAY AFTERNOON...WITH PERHAPS A FEW AREAS REACHING THE UPPER
70S IN FAR SOUTHEAST GEORGIA.

SUNDAY NIGHT THROUGH MONDAY NIGHT...THE SHORTWAVE TROUGH WILL
CONTINUE TO SWEEP EAST/SOUTHEAST SUNDAY NIGHT...PROVIDING THE
FINAL OFFSHORE PUSH TO THE FRONTAL SYSTEM BY DAYBREAK MONDAY.
ALTHOUGH DRY AIR WILL BEGIN TO SHIFT INTO THE AREA FROM THE
SOUTHWEST...THE WAVE OF LOW PRESSURE ALONG THE DEPARTING FRONT
WILL INTENSIFY UNDER INCREASED UPPER LEVEL SUPPORT AND OVER THE
WARMER GULF STREAM WATERS. THE MAIN QUESTION FOR SUNDAY NIGHT AND
MONDAY WILL BE THE POTENTIAL FOR SHOWERS TO LINGER ACROSS THE
NORTHERN PORTIONS OF THE FORECAST AREA...CLOSEST TO THE SURFACE
LOW OFF THE NORTH CAROLINA COASTLINE. WILL MAINTAIN JUST A SLIGHT
CHANCE FOR SHOWERS FOR LOCATIONS NORTH OF THE SAVANNAH
RIVER...WITH RAIN CHANCES DECREASING FROM SOUTHWEST TO NORTHEAST AS
THE COASTAL LOW SHIFTS FARTHER INTO THE ATLANTIC BY MONDAY EVENING.

NORTHERLY FLOW ON THE BACK SIDE OF THE LOW SYSTEM WILL SUPPORT
MUCH COOLER TEMPERATURES BEGINNING SUNDAY NIGHT. LOWS WILL FALL
INTO THE UPPER 40S INLAND TO THE LOW 50S SUNDAY NIGHT. HIGH
TEMPERATURES ON MONDAY COULD BE NEARLY 10 TO 15 DEGREES COOLER
THAN ON SUNDAY...SUPPRESSED IN THE UPPER 50S FAR NORTHERN AND
INLAND ZONES TO THE UPPER 60S NEAR THE ALTAMAHA RIVER IN SOUTHEAST
GEORGIA. THE COOLING TREND WILL CONTINUE INTO MONDAY NIGHT...WHEN
CLEARING SKIES AND DIMINISHING WINDS WILL ALLOW TEMPERATURES TO
FALL INTO THE 40S ACROSS MUCH OF THE FORECAST AREA.

TUESDAY...ZONAL FLOW WILL RESUME ACROSS THE SOUTHEAST STATES BY
TUESDAY...AS THE OFFSHORE LOW AND ASSOCIATED SHEARED SHORTWAVE
DRIFT FARTHER OUT TO SEA. SURFACE HIGH PRESSURE WILL BUILD INTO
THE REGION AND MAINTAIN DRY AND MILD CONDITIONS. TEMPERATURES WILL
REBOUND SLIGHTLY INTO THE MID TO UPPER 60S WITH NO RAIN EXPECTED.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
CONSIDERABLE UNCERTAINTY CONTINUES TO PLAGUE THE LONG TERM PERIODS
AS MODEL SOLUTIONS REMAIN IN POOR AGREEMENT AND RUN TO RUN CONTINUITY
IS NOT IDEAL. AS A RESULT...FORECAST CONFIDENCE REMAINS LOW AND
WILL CONTINUE TO TRY TO CAPITALIZE ON WINDOWS OF OPPORTUNITY WHERE
MODEL SOLUTIONS ARE MORE CLOSELY ALIGNED WHILE FOLLOWING THE
MAJORITY CONSENSUS WHERE SOLUTIONS DIVERGE MORE SIGNIFICANTLY.

MODEL ARE IN DECENT AGREEMENT SHOWING HIGH PRESSURE HOLDING IN PLACE
OVER THE REGION TUESDAY NIGHT AND WEDNESDAY...SO WILL CONTINUE TO
ADVERTISE A RAIN FREE FORECAST. SOLUTIONS THEN DIVERGE SIGNIFICANTLY
FOR THE END OF THE WEEK AND INTO THE FIRST HALF OF THE UPCOMING
WEEKEND. WILL FOLLOW MODEL CONSENSUS WHICH SUGGESTS THAT A SYSTEM
WILL LIFT NORTHEASTWARD OUT OF THE GULF OF MEXICO WEDNESDAY NIGHT
AND THURSDAY...AND OFF THE SOUTHEAST COAST THURSDAY NIGHT AND
FRIDAY. GIVEN THE UNCERTAINTY IN TIMING...WILL KEEP POPS IN THE
SLIGHT CHANCE/CHANCE RANGE WEDNESDAY NIGHT THROUGH FRIDAY...WITH THE
MOST PROBABLE CHANCES FOR RAINFALL EXPECTED TO FALL IN THE
THURSDAY/THURSDAY NIGHT TIME FRAME AT THIS POINT. HIGH PRESSURE IS
THEN EXPECTED TO BUILD BACK INTO THE REGION FRIDAY NIGHT AND
SATURDAY...SO WILL ADVERTISE RAIN FREE CONDITIONS.

TEMPERATURES ARE EXPECTED TO RUN ABOVE CLIMATOLOGY THROUGH THE LONG
TERM PERIODS.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
LAYERED CLOUDS ON THE INCREASE ACROSS THE COASTAL TAF CORRIDOR
THIS MORNING. 00Z FORECAST SOUNDINGS NOT NEARLY ROBUST ON
FOG/STRATUS DEVELOPMENT POTENTIAL LATE. WE HAVE TRENDED LATER ON
MVFR POTENTIAL AT KSAV BUT THERE IS STILL POTENTIAL FOR ADVECTION
STRATUS/IFR TOWARD DAWN AS AREAS TO THE S WITH LESS CLOUD COVER REACH
CROSS-OVER VALUES LATER TONIGHT. AT KCHS...WE CONTINUE TO SHOW
MAINLY VFR GIVEN STRONGER LOW LEVEL WIND FIELDS AND THE VEERING
LOW LEVEL FLOW TOWARD DAWN. BOTH TERMINALS COULD SEE BRIEF
CONVECTIVE RAINS THIS AFTERNOON THEN ATTENTION TURNS TOWARD THE
ARRIVAL OF A BACKDOOR COLD FRONT FROM N TO S AFTER SUNSET TONIGHT.
WE HAVE INTRODUCED MVFR CIGS AT KCHS AFTER 03Z/06.

EXTENDED AVIATION OUTLOOK...MVFR OR LOWER CONDITIONS ARE EXPECTED
SUNDAY NIGHT THROUGH MONDAY NIGHT AS A COLD FRONT AND LOW PRESSURE
SYSTEM AFFECT THE REGION. VFR CONDITIONS ARE EXPECTED TO RETURN
TUESDAY THROUGH WEDNESDAY NIGHT. ANOTHER STORM SYSTEM COULD RESULT
IN REDUCTIONS TO CEILING AND/OR VISIBILITY ON THURSDAY.

&&

.MARINE...
THE COASTAL WATERS WILL LIE UNDER THE WESTERN PORTION OF ATLANTIC
HIGH PRESSURE TONIGHT...ALLOWING FOR SOME WEAK NOCTURNAL JETTING
TO OCCUR AFTER MIDNIGHT. WINDS WILL VEER FROM SOUTH TO SW...BUT
WILL REACH NO MORE THAN 15 KT. SEAS WILL BE COMPRISED OF BOTH WIND
DRIVEN WAVES AND SWELLS...WITH SIGNIFICANT WAVE HEIGHT ACHIEVING
AS MUCH AS 4 OR 5 FEET.

SUNDAY THROUGH THURSDAY...A COLD FRONT WILL REMAIN NORTH OF THE
WATERS THROUGH THE DAYTIME HOURS SUNDAY...THEN SWEEP SOUTHWARD
THROUGH THE MARINE AREA SUNDAY NIGHT. AN ASSOCIATED AREA OF LOW
PRESSURE WILL THEN DEVELOP ALONG THE FRONT OFF THE CAROLINA
COAST MONDAY MORNING AND TRACK NORTHEAST FARTHER INTO THE
ATLANTIC MONDAY AND MONDAY NIGHT. HIGH PRESSURE WILL THEN BUILD
BACK OVER THE MARINE AREA TUESDAY THROUGH WEDNESDAY...WITH ANOTHER
AREA OF LOW PRESSURE EXPECTED TO TRACK NORTHEAST JUST OFF THE
COAST OF SOUTHERN SOUTH CAROLINA AND SOUTHEAST GEORGIA ON
THURSDAY. A BRIEF SURGE COULD OCCUR ACROSS PORTIONS OF THE MARINE
AREA BEHIND THE FRONT SUNDAY NIGHT INTO MONDAY...HOWEVER WINDS AND
SEAS ARE EXPECTED TO REMAIN BELOW ADVISORY CRITERIA THROUGH THE
PERIOD.

&&

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

&&

$$