« Back
NWS Peachtree City, Ga » Text Product » CHS Area Forecast Discussion


Printer-friendly Version
Current Version              Previous Versions:   1  2  3  4  5  6  7  8  9  

Area Forecast Discussion

298
FXUS62 KCHS 031957
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
357 PM EDT THU SEP 3 2015

.SYNOPSIS...
AN AREA OF LOW PRESSURE WILL MOVE OFF THE GEORGIA COAST
TODAY...AND A WEAK TROUGH WILL PERSIST ACROSS THE SOUTHEAST
THROUGH FRIDAY NIGHT. A COLD FRONT WILL CROSS THE REGION FROM
NORTH TO SOUTH SATURDAY...AND HIGH PRESSURE WILL BUILD INTO THE
AREA FROM THE NORTH. THE FRONT WILL BECOME STATIONARY SOUTH OF THE
REGION...AND LOW PRESSURE COULD DEVELOP OFF THE SOUTHEAST COAST.
THE REGION WILL THEN REMAIN SITUATED BETWEEN INLAND HIGH PRESSURE
AND OFFSHORE LOW PRESSURE UNTIL THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
REST OF THE AFTERNOON...A FEW WEAK SHOWERS ARE ATTEMPTING TO DEVELOP
WITHIN THE LARGE AREA OF SUBSIDENCE THAT COVERS MUCH OF THE REGION.
BY THE LATE AFTERNOON THE SUBSIDENCE WILL DIMINISH IN RESPONSE TO A
SHARP SHORTWAVE NOW PUSHING ACROSS CENTRAL GEORGIA. SO THE BETTER
CONVECTIVE DEVELOPMENT WILL BE DELAYED UNTIL THE LATE AFTERNOON
HOURS AND INTO THE EVENING. MODELS STILL DO NOT SHOW VERY IMPRESSIVE
DEVELOPMENT...NOR A VERY IMPRESSIVE NEAR STORM ENVIRONMENT. DCAPES
DO RISE TO AROUND 1000 J/KG AS DRIER MID LEVEL AIR MOVES IN...SO WE
COULD STILL SEE A COUPLE OF STRONG STORMS. OVERALL SEVERE THREAT
REMAINS LOW. COVERAGE ALSO STILL EXPECTED TO REMAIN LIMITED TO THE
SCATTERED CATEGORY.

TONIGHT...THE SHORTWAVE AND ITS ASSOCIATED VORT MAX WILL PUSH
THROUGH IN THE FIRST HALF OF THE NIGHT AND THE BEST CHANCE FOR ANY
LAND BASED CONVECTION WILL BE DURING THIS TIME. THE MODELS REMAIN
QUITE UNIMPRESSIVE WITH THEIR RESPONSE...BUT THE FORECAST HANGS ON
TO A TIER OF SLIGHT CHANCE POPS ACROSS SOUTHEAST GEORGIA THROUGH
ABOUT MIDNIGHT. THEREAFTER...CONVECTIVE CHANCES WILL BECOME
INCREASINGLY CONFINED TO THE ADJACENT COASTAL WATERS. THERE IS A LOW
END CHANCE FOR SHALLOW GROUND FOG LATE TONIGHT AS WINDS GO CALM AND
NEAR SURFACE RH/S INCREASE...BUT THE OVERALL PROBABILITY IS TOO LOW
TO INTRODUCE INTO THE FORECAST. LOWS ARE EXPECTED TO FALL MAINLY
INTO THE MID 70S AWAY FROM THE IMMEDIATE COAST.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
FRIDAY...A WEAK PRESSURE PATTERN WILL EXIST ACROSS THE LOCAL AREA IN
ADVANCE OF A BACKDOOR COLD FRONT FROM OFF THE DELMARVA TO MINNESOTA.
WHILE ALOFT WE FIND A NW FLOW SANDWICHED BETWEEN A BROAD AND DEEP
TROUGH IN THE WESTERN ATLANTIC AND AN AMPLIFIED RIDGE FROM THE LOWER
MS VALLEY TO THE UPPER MIDWEST. WITH SUFFICIENT INSOLATION AND 850
MB TEMPS THAT ARE FORECAST TO REACH 19-20C...OR AROUND 2 STANDARD
DEVIATIONS ABOVE NORMAL...WILL LEAD TO AN UNSEASONABLY WARM DAY. NOT
ANYWHERE NEAR RECORD HIGHS...BUT STILL PEAKING IN THE LOWER AND
MIDDLE 90S INLAND FROM THE INTRA-COASTAL. ASSOCIATED HEAT INDICES
WILL CLIMB TO 100-105F...BUT BELOW OUR HEAT ADVISORY CRITERIA. A
STRONG CAP AND THE LACK OF ANY SIGNIFICANT FORCING SUGGEST THAT THE
CHANCES FOR CONVECTION ISN/T MORE THAN 20-30 PERCENT...DRIVEN MAINLY
BY A WEAK AFTERNOON SEA BREEZE AND IN CLOSE PROXIMITY TO A SUBTLE
TROUGH INLAND. LOW LEVEL LAPSE RATES ARE RATHER HIGH FOR EARLY
SEPTEMBER AND THERE IS A FAIRLY DRY MID LEVEL ENVIRONMENT WHICH
COULD SPUR A COUPLE OF ISOLATED STRONG T-STORMS.

FRIDAY NIGHT...CONVECTION WILL WANE IN THE EVENING AS NOCTURNAL
INFLUENCES TAKES OVER. THEN THE UPSTREAM BACKDOOR COLD FRONT
APPROACHES FROM THE NORTH TOWARD THE SANTEE RIVER CLOSE TO DAYBREAK
SATURDAY. THIS MAY ALLOW FOR A LIMITED OVERNIGHT RISK FOR SHOWERS
AND STORMS...MAINLY NORTHERN ZONES. TEMPS WILL REMAIN ABOVE NORMAL
IN ADVANCE OF THIS FEATURE. IF CLOUD COVER THINS OUT ENOUGH...GIVEN
FAVORABLE CONDENSATION SUGGESTS AN INLAND FOG RISK. WE WILL RE-
EVALUATE IN LATER FORECAST PACKAGES.

SATURDAY THROUGH SUNDAY...A REX BLOCK PATTERN WILL DEVELOP
ALOFT...WITH AN UNUSUAL EAST/SE TO WEST/NW ALIGNED TROUGH DEVELOPING
ALOFT NEARBY SATURDAY...THEN INTO THE AREA BY SUNDAY. TO THE NORTH
WE FIND A DEEP ANTICYCLONE OVER THE NE STATES. THIS PATTERN WILL
SEND THE BACKDOOR COLD FRONT INTO AND THROUGH OUR AREA
SATURDAY...BEFORE IT STALLS NOT FAR TO THE SOUTH ON SUNDAY. A HIGH
PRESSURE WEDGE WILL DEVELOP IN WAKE OF THE COLD FRONT AS IT BUILDS
SOUTH/SW FROM THE NE AND NEW ENGLAND. SLIGHTLY COOLER AIR WILL
ARRIVE IN RESPONSE TO THIS TRANSITION...WITH MID AND UPPER 80S MORE
COMMON FOR HIGHS AND EVEN SOME UPPER 60S SNEAKING INTO THE NW TIER
FOR LOWS SATURDAY NIGHT. SHORT WAVES EMBEDDED WITHIN THE CYCLONIC
FLOW ALOFT WILL RIDE INTO AND THROUGH THE REGION PERIODICALLY
THROUGH THE WEEKEND. THAT WILL COMBINE WITH DECENT MOISTURE AND THE
FORCING FROM THE COLD FRONT AND A BACKDOOR SEA BREEZE ION SATURDAY
TO TRIGGER SCATTERED POPS. WHILE WE LOSE THE FORCING FROM THE COLD
FRONT ON SUNDAY...WE GAIN BETTER LOW LEVEL CONVERGENCE FROM OFF THE
ATLANTIC WITHIN A DEEP EASTERLY FLOW FROM OFF THE ATLANTIC. THIS
WILL LEAD TO MOSTLY LOW TOPPED AND SCATTERED CONVECTION AREAWIDE.
THERE ARE INDICATIONS OF A LITTLE BETTER SHEAR OVER SOUTHERN ZONES
SATURDAY...AND IF THAT COMES TO FRUITION AND THE FRONT IS SLOWER IN
ARRIVING THIS COULD ALLOW FOR A RISK OF A FEW STRONG OR MARGINALLY
SEVERE STORMS.

MEANWHILE IN THE SW ATLANTIC...SHORT WAVE ENERGY ASSOCIATED WITH
THE REMNANTS OF ERIKA MAY ALLOW FOR A BROAD AND WEAK REGION OF LOW
PRESSURE TO FORM THE NE OF THE BAHAMAS SATURDAY...BEFORE IT LIFTS
NORTHWARD ON SUNDAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A BLOCKING PATTERN WILL MAINTAIN SURFACE HIGH PRESSURE TO THE
NORTH...A STATIONARY FRONT WEAKENING TO A TROUGH OF LOW PRESSURE
SOUTH/SOUTHEAST OF THE AREA...A BROAD AREA OF SURFACE LOW PRESSURE
OFF THE SOUTHEAST COAST AND BROAD LOW PRESSURE ALOFT OVER THE
SOUTHEAST. LABOR DAY INTO TUESDAY...LONG FETCH ONSHORE FLOW ENHANCED
BY SURFACE FEATURES AND THE UPPER LOW/POOL OF VORTICITY ALOFT SHOULD
PROVIDE SUFFICIENT MOISTURE/INSTABILITY TO SUPPORT AT LEAST
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS DURING THE DAYTIME HOURS
ACROSS THE REGION...AND POPS ARE EXPECTED TO REFOCUS CLOSER TO THE
COAST AND ACROSS ADJACENT COASTAL WATERS DURING THE NIGHTTIME HOURS.
CAPPED MAXIMUM POPS AT 50 PERCENT THROUGH THE PERIOD...ALTHOUGH
LOCALLY WETTER PERIODS/HIGHER POPS ARE POSSIBLE ESPECIALLY NEAR THE
COAST. TEMPERATURES IN THE LOWER 80S ON THE BEACHES AND MID 80S
INLAND ARE EXPECTED LABOR DAY...THEN TEMPERATURES SHOULD MODERATE
INTO THE MID/UPPER 80S INLAND TUESDAY. BY THE MIDDLE OF NEXT WEEK
THROUGH THE END OF THIS FORECAST PERIOD...INLAND HIGH PRESSURE AND
OFFSHORE LOW PRESSURE WILL WEAKEN...THE UPPER LOW/TROUGH AXIS WILL
RETROGRADE WEST OF THE REGION AND ATLANTIC HIGH PRESSURE WILL EXPEND
INTO THE REGION FROM THE EAST. THIS SCENARIO SHOULD SUPPORT A TREND
TOWARD WARMER/ABOVE NORMAL TEMPS AND SLIGHTLY LOWER POPS.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
VFR CONDITIONS ARE EXPECTED TO PREVAIL AT KCHS AND KSAV THROUGH
18Z FRIDAY. ISOLATED TO WIDELY SCATTERED SHOWERS AND THUNDERSTORMS
WILL DEVELOP LATER THIS AFTERNOON...BUT ARE EXPECTED TO REMAIN
AWAY FROM THE TERMINALS. OTHERWISE...VERY LOW END CHANCES FOR
SHALLOW GROUND FOG LATE TONIGHT AND PROBABILITIES ARE TOO LOW TO
INCLUDE IN THE FORECAST AT THIS POINT.

EXTENDED AVIATION OUTLOOK...LOW TO MODERATE POTENTIAL FOR PERIODIC
FLIGHT RESTRICTIONS IN MAINLY DIURNAL SHRA/TSRA AND/OR LATE
NIGHT/EARLY MORNING STRATUS INTO EARLY NEXT WEEK. OTHERWISE
GENERALLY VFR CONDITIONS WILL PREVAIL.

&&

.MARINE...
TONIGHT...A VERY WEAK PRESSURE GRADIENT WILL REMAIN IN PLACE ACROSS
THE LOCAL WATERS. THE PREVAILING FLOW WILL BE SOUTHWEST TO WEST-
SOUTHWEST WITH SPEEDS GENERALLY NO MORE THAN 6-8 KT. SEAS WILL BE 1-
2 FT...HIGHEST BEYOND 20 NM.&&

FRIDAY...A LAX PRESSURE PATTERN WILL PREVAIL...ALLOWING A WEAK
AFTERNOON SEA BREEZE TO KICK IN AS WINDS CLOCK AROUND FROM WEST/NW
IN THE MORNING TO EAST/SE IN THE AFTERNOON. SEAS WON/T BE ANY HIGHER
THAN 1 OR 2 FT.

FRIDAY NIGHT AND SATURDAY...BROAD AND WEAK LOW PRESSURE BEGINS TO
FORM TO THE NORTH/NE OF THE BAHAMAS AS A BACKDOOR COLD FRONT ARRIVES
FROM THE NORTH LATE FRIDAY NIGHT...PUSHING INTO AND THROUGH THE AREA
SATURDAY. BEHIND THE FRONT AN INLAND HIGH PRESSURE WEDGE WILL
DEVELOP...AND THAT ALONG WITH A BACKDOOR TYPE SEA BREEZE WILL CAUSE
MODEST NE/EAST PINCHING TO OCCUR. NOT ENOUGH FOR ANY ADVISORY
CONDITIONS...BUT ENOUGH TO BOOST WINDS UP TO AROUND 15 KT AND
GUSTY WITH SEAS AS HIGH AS 3 OR PERHAPS 4 FEET.

SUNDAY THROUGH TUESDAY...DECENT PINCHING WILL PERSIST AT THE START
OF THE PERIOD BETWEEN BROAD LOW PRESSURE TO THE EAST/SE AND AN
INLAND WEDGE RELUCTANT TO RELAX IT/S HOLD OVER THE SE. GRADUALLY
THOUGH THE GRADIENT STARTS TO SLACKEN AS THE ATLANTIC LOW HEADS
NORTHWARD AND THE INLAND HIGH WEAKENS. WINDS AND SEAS LOOK TO STAY
BELOW ANY ADVISORY THRESHOLDS...UNLESS THE PINCHING IS STRONGER THAN
NOW ANTICIPATED FOR SUNDAY. WE/LL NEED TO MAINTAIN A CLOSE WATCH FOR
BACK SWELL ARRIVING IN RESPONSE TO THE BROAD LOW PRESSURE SYSTEM IN
THE ATLANTIC.

RIP CURRENTS...AN ELEVATED RISK FOR RIP CURRENTS COULD DEVELOP OVER
THE UPCOMING HOLIDAY WEEKEND AS A MODERATE NE TO EAST WIND DEVELOPS
AND SMALL SWELLS COULD START IMPACTING THE BEACHES BEGINNING
SATURDAY.

WATERSPOUTS...LIGHT WIND FIELDS AND SUFFICIENT ATMOSPHERIC
CONDITIONS MAY SUPPORT A RISK FOR WATERSPOUTS FRIDAY AND SATURDAY
MORNINGS ALONG ANY CONVERGENCE LINES THAT DEVELOP.

&&

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

&&

$$
SYNOPSIS...
NEAR TERM...BSH
SHORT TERM...
LONG TERM...SPR
AVIATION...BSH
MARINE...



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.