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


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

Area Forecast Discussion

685
FXUS62 KGSP 041810
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
210 PM EDT FRI SEP 4 2015

.SYNOPSIS...
A COLD FRONT IS EXPECTED TO PUSH SOUTH ACROSS THE REGION TODAY.
THIS WILL BE FOLLOWED COOL AND MOIST HIGH PRESSURE WHICH WILL
PERSIST THROUGH THROUGH THE HOLIDAY WEEKEND. A GRADUAL WARMING TREND
WILL FOLLOW TOWARD THE MIDDLE OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 130 PM...SATELLITE IMAGERY SHOWS ENHANCED CU OVER THE
RIDGETOPS AND RADAR IMAGERY SHOWS THAT DEEP CONVECTION HAS INITIATED
ACROSS PARTS OF NC AND ALONG THE BLUE RIDGE IN VA. COVERAGE SHOULD
GRADUALLY EXPAND FROM THERE. MADE SOME MINOR TWEAKS TO PRECIP
CHANCES MAINLY OVER THE UPSTATE AND NE GEORGIA TO DELAY ONSET FOR A
BIT LONGER. STILL THINK WE COULD SEE A FEW STORMS BECOME STRONG ENUF
TO PRODUCE DAMAGING WIND GUSTS NOW THAT WE HAVE REALIZED THE
EXPECTED ENVIRONMENT WITH DCAPE 1000+ J/KG. TEMPS LOOK GOOD.

REMAINDER OF PREVIOUS DISCUSSION...

COPIOUS LOW LEVEL MOISTURE REMAINS OVER THE AREA. THIS COMBINED WITH
THE EXPECTED HEATING WILL LEAD TO MODERATE INSTABILITY. EXPECT
CONVECTION WILL DEVELOP AGAIN TODAY...BUT WILL HAVE A LITTLE LATER
START TIME. CONVECTION BEGINS NEAR THE BLUE RIDGE AND SPREADS EAST
AND SOUTH THRU THE DAY AND INTO THE EARLY EVENING. BEST COVERAGE
WILL BE ACROSS NC WITH LIKELY POP FOR THE I-40 CORRIDOR. THERE WILL
BE MINIMAL SHEAR...BUT ISOLATED SVR STORMS ARE POSSIBLE GIVEN THE
INSTABILITY AND DCAPE APPROACHING 1000 J/KG. CONVECTION DIMINISHES
THRU LATE EVENING...BUT RETURNS OVERNIGHT AS THE E TO NE FLOW
STRENGTHENS. HIGHS TODAY WILL AGAIN RISE INTO THE 90S OUTSIDE OF THE
MTNS AND MID 80S FOR THE VALLEYS. LOWS WILL BE ABOVE NORMAL.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AT 230 AM EDT FRIDAY...ON SATURDAY MORNING A POSITIVELY TILTED
UPPER RIDGE WILL EXTEND FROM TX TO NEW ENGLAND...WHILE A AN UPPER
TROUGH EXTENDS FROM THE WESTERN ATLANTIC TO THE CAROLINAS AND GA. BY
SUNDAY AN UPPER LOW CLOSES OF NEAR THE SC COAST...SOUTH OF THE
PERSISTENT UPPER RIDGE. WEAK MID LEVEL ENERGY ROUNDING THE UPPER
LOW WILL MOVE INLAND FROM THE COAST TO THE SOUTHERN APPALACHIANS.

AT THE SURFACE...ON SATURDAY A RIDGE OF HIGH PRESSURE WILL BE IN
PLACE ALONG THE EASTERN SEABOARD. MODEL DATA SHOWS A LACK OF
ISENTROPIC UPGLIDE OVER THE RIDGE...AND EVEN LOW LEVEL FLOW LACKS AN
ORTHOGONAL COMPONENT INTO THE BLUE RIDGE. ELEVATED INSTABILITY WILL
BE PRESENT HOWEVER...SUPPORTING CONVECTION THAT WILL BE MAXIMIZED
DURING DAYTIME HEATING. TEMPERATURES WILL EXHIBIT A REDUCED DIURNAL
RANGE...WITH MAXIMUMS BELOW NORMAL...AND MINIMUMS NEAR NORMAL.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AT 150 PM EDT FRIDAY...STARTING MONDAY NIGHT THE 500MB PATTERN HAS
A SHALLOW RIDGE OVER THE SOUTHEAST STATES WITH A TROUGH AXIS OVER THE
WESTERN DAKOTAS AND PROGRESSING EAST IMPINGING ON THE SE RIDGE.  THE
RIDGE WILL FLATTEN OUT THROUGH MID WEEK THEN THE TROUGH DIGS OVER
THE SE WITH AXIS BECOMING ESTABLISHED JUST WEST OF THE APPALACHIANS
BY LATE FRIDAY.  RIDGE WILL BUILD AT WEEKS END OVER THE FAR WEST.

AT THE SURFACE...HIGH PRESSURE WILL BE OVER THE CAROLINAS AND MID
ATLANTIC TUESDAY THEN DRIFTS EAST AS COLD FRONT CROSSES THE MISS
VALLEY. THIS COLD FRONT REACHES THE OHIO VALLEY BY THURSDAY AND WILL
BE CROSSING OUR AREA BY FRIDAY.  SCATTERED CONVECTION WILL INCREASE
AS THE FRONT GETS CLOSER LATE IN THE WEEK.

OVERALL...THE INSTABILITY WILL BE MODEST AT BEST.  CAPE
VALUES AROUND 1000 ON THE GFS FOR PIEDMONT GA AND SC LATE
TUESDAY...WEAKER VALUES WED AND 700 TO 1000 THURSDAY AND FRIDAY.
WIND SPEEDS IN THE LOW TO MID LEVELS NOT EXCESSIVE AS H8GHER WINDS
AT THE END OF THE WEEK IN THE TROUGH.  EVEN THEN THE 700MB WIND WILL
BE AROUND 20 KTS WHICH IS FAIRLY LIGHT.

TEMPS A LITTLE ABOVE NORMAL IN MID WEEK...DIPPING TO A LITTLE BELOW
NORMAL NEXT WEEKEND WITHIN THE TROUGH.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...SEEING SOME STORMS INITIATE TO THE EAST WHERE SATELLITE
IMAGERY HAD SOME ENHANCED CU. THIS ACTIVITY SHOULD WORK ITS WAY INTO
THE CLT METRO AREA THRU MID AFTERNOON. PREVIOUS AMEND INTRODUCED A
TEMPO AT 21Z FOR TSRA AND THINK THAT TIMING STILL LOOKS OK FOR THE
MOST PART...AS WE NEED TO SPECIFY A FOUR HOUR WINDOW...BUT THIS
COULD EASILY NEED TO BE AMENDED AGAIN BEFORE THAT. AFTER A ROUND OF
STORMS MOVES THRU THE AREA...WILL KEEP ONLY CONVECTIVE DEBRIS ACROSS
THE REGION OVERNIGHT...WITH A LIGHT NE WIND. THE MODEL GUIDANCE
SUGGESTS BRINGING A LOW CLOUD DECK DOWN FROM THE NE IN THE EARLY
MORNING HOURS. A SIMILAR EVOLUTION OCCURS IN MOST SITUATIONS LIKE
THIS...WITH PLENTY OF MOISTURE...AND EASTERLY COMPONENT TO THE LOW
LEVEL FLOW...WITH HIGH PRESSURE TO THE NE. THE LAMP GUIDANCE WAS
GENERALLY ACCEPTED...BUT CEILINGS WERE KEPT TO MVFR ACROSS THE WRN
PIEDMONT OF NC. LATER TAFS WILL HAVE TO ADDRESS THE POSSIBILITY OF
IFR CEILINGS AROUND DAYBREAK...BUT FOR NOW IT IS MORE LIKELY TO STAY
MVFR. ON SATURDAY...LOW CLOUD BASE WILL GRADUALLY RISE TO VFR AS
BOUNDARY LAYER DEEPENS. ADDITIONAL SHOWERS OR STORMS SHOULD DEVELOP
WITH HEATING AROUND MIDDAY.

ELSEWHERE...SCATTERED STORMS WILL FORM FIRST ACROSS THE HIGHER
TERRAIN AND THEN SLOWLY DEVELOP DOWN ACROSS THE REST OF THE FCST
AREA THRU EARLY EVENING. CONFIDENCE ONLY HIGH ENUF AT KAVL/KHKY TO
INCLUDE A TEMPO FOR NOW. THE UPSTATE SC TAF SITES WERE LIMITED TO
VCTS/PROB30 BASED ON LACK OF COVERAGE IN CONVECTION ALLOWING MODELS.
THERE COULD BE A ROUND OF SHOWERS IN THE EARLY MORNING SATURDAY AS A
BACK DOOR SFC BOUNDARY MOVES DOWN FROM THE NE...BUT CONFIDENCE NOT
HIGH ENUF TO MENTION. EXPECT VALLEY FOG TO FORM AT KAVL IN THE PRE-
DAWN HOURS...MOST LIKELY RESTRICTING VSBY TO MVFR...UNLESS PRECIP
FALLS THERE TODAY. THINK LOW CLOUD CEILING WILL REACH KHKY SATURDAY
MORNING...BUT GET HUNG UP MOVING SW AS SUN STARTS TO WARM ATMOSPHERE
AFTER 12Z. WIND SHOULD REMAIN N TO NE THRU THE PERIOD. MORE SHOWERS
CAN BE EXPECTED WITH HEATING ON SATURDAY.

OUTLOOK...A MOIST EASTERLY FLOW WILL CONTINUE THRU SUNDAY...BRINGING
A GOOD CHANCE OF IFR/MVFR RESTRICTIONS SATURDAY NIGHT AND SUNDAY
MORNING. LIGHT PRECIP WILL REMAIN POSSIBLE. THE THREAT FOR
RESTRICTIONS WILL CONTINUE THRU SUNDAY NIGHT. DRY AIR WORKING IN
FROM THE E ON MONDAY WILL BEGIN TO DIMINISH THE THREAT FOR EARLY
NEXT WEEK.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     MED   73%     HIGH  82%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  84%     HIGH  92%
KHKY       HIGH 100%     HIGH 100%     MED   76%     MED   79%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  89%     HIGH  94%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JAT
NEAR TERM...PM/RWH
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...PM



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