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Area Forecast Discussion

519
FXUS62 KGSP 281817
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
217 PM EDT THU APR 28 2016

.SYNOPSIS...
A COLD FRONT WILL CROSS THE AREA TONIGHT...WITH HIGH PRESSURE
BUILDING IN FRIDAY INTO SATURDAY. A LOW PRESSURE SYSTEM WILL
APPROACH FROM THE WEST LATE SATURDAY THROUGH SUNDAY NIGHT. THE LOW
WILL LIFT NORTHEAST ALONG THE COAST EARLY NEXT WEEK...BUT LEAVE A
TRAILING COLD FRONT NEAR THE CAROLINA COAST.

&&

.NEAR TERM /THROUGH FRIDAY/...
THE CU FIELD IS QUITE HEALTHY ACROSS MUCH OF THE FORECAST AREA THIS
AFTERNOON...WITH THE BEST BUBBLING NOTED ALONG THE BLUE RIDGE...AND
INDEED WE HAVE FINALLY SEEN SOME ISOLATED DEEP CONVECTION (ONLY
SHOWERS AT THIS POINT) INITIATE ALONG THE BLUE RIDGE...AND ALSO
ACROSS OUR EASTERN PIEDMONT ZONES. SBCAPE IS QUITE ROBUST ACROSS THE
EASTERN HALF OF THE FORECAST AREA...WHERE VALUES AS HIGH AS 2500
J/KG ARE NOTED PER THE LATEST SPC MESOANALYSIS. NEVERTHELESS...OTHER
THAN TERRAIN EFFECTS...THERE REALLY ISN/T MUCH TO FOCUS CONVECTION
ACROSS THE AREA THIS AFTERNOON. A SYNOPTIC SURFACE
TROUGH...EXTENDING FROM A WEAK SURFACE WAVE ACROSS THE OHIO VALLEY/
CTRL APPALACHIANS IS CURRENTLY ANALYZED ACROSS THE SOUTHERN
APPALACHIANS. THIS IS EXPECTED TO PUSH OUT ACROSS THE PIEDMONT LATER
THIS AFTERNOON...WHICH COULD ALLOW FOR BETTER COVERAGE OF DEEP
CONVECTION IN THOSE AREAS. THEREFORE...WILL CONTINUE WITH POPS
RANGING FROM LOW CHANCE ACROSS THE MAJORITY OF THE FORECAST
AREA...TO 40-50 PERCENT FROM THE BLUE RIDGE EAST IN NC. BEING THE
AREA IS ON THE PERIPHERY OF THE STRONGER MID-LEVEL FLOW...DEEP LAYER
SHEAR IS NOT OUTSTANDING (30-35 KTS)...BUT CERTAINLY ADEQUATE FOR
ORGANIZED AND/OR ROTATING STORMS. A COUPLE OF SEVERE STORMS STILL
APPEAR TO BE A GOOD BET IN LIGHT OF THE ROBUST BUOYANCY.

DRIER DEWPOINTS ARE EXPECTED TO OVERSPREAD THE AREA THIS
EVENING...AS THE SURFACE TROUGH PROGRESSES EAST. THIS SHOULD BRING A
PRETTY QUICK END TO CONVECTIVE CHANCES. THE REMAINDER OF THE NEAR
TERM WILL BE INACTIVE/MOSTLY CLEAR AND QUITE WARM...WITH TEMPS
EXPECTED TO AVERAGE ABOUT 10 DEGREES ABOVE CLIMO THROUGH THE PERIOD.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
AS OF 200 PM EDT THURSDAY...THE SHORT TERM FCST PERIOD INITIALIZES
ON FRIDAY NIGHT AMIDST SHORTWAVE H5 RIDGING OVER THE SOUTHEAST WHILE
AN H5 CYCLONE ROTATES OVER THE SOUTHERN ROCKIES.  AT THE
SURFACE...HIGH PRESSURE OVER THE NORTHEAST WILL BUILD SOUTH ALONG
THE EASTERN SEABOARD ATTEMPTING TO SETUP A SHORT LIVED WEDGE...WHILE
CYCLOGENESIS DEVELOPS/STRENGTHENS OVER THE SOUTHERN PLAINS. A
WARM FRONT LOOKS TO SPREAD NORTH OVER THE DEEP SOUTH IN
ASSOCIATION WITH THE A FORE MENTIONED SFC CYCLONE INTO SATURDAY
WITH CONVECTION ACTIVATING ALONG IT OVER PORTIONS OF NORTH MS/AL
AS WELL AS WEST/MIDDLE TN. CLOSER TO HOME...THE WEDGE FRONT MAKES
A PUSH INTO THE REGION ON SATURDAY MORNING BEFORE RETREATING
NORTHEAST INTO THE MID/LATE AFTERNOON HOURS AS THE CONVECTIVELY
ACTIVE WARM FRONT SURGES.

THE UPPER TROF WILL BE ON THE MOVE SUNDAY WITH THE SFC CYCLONE
MOVING NORTHEAST.  THE COLD FRONT ASSOCIATED WITH SAID CYCLONE IS
EXPECTED TO PUSH THROUGH THE OH/TN VALLEYS ON SUNDAY POSSIBLY
YIELDING STRONG/SEVERE CONVECTION THANKS TO AN ABUNDANTLY UNSTABLE
AIRMASS BACKED UP BY AN APPROACHING H5 SHORTWAVE.  AS FOR NORTHEAST
GA AND THE WESTERN CAROLINAS...THE FRONT SHOULD REMAIN TO THE WEST
THROUGH PEAK HEATING HOWEVER SOUNDINGS CONTINUE TO FAVOR SUBSTANTIAL
INSTABILITY ABOUT THE REGION THANKS TO MID 60S DEWPOINTS AND MODEST
LOW/MID LEVEL LAPSE RATES...ALL SUPPORTING SCATTERED SHRA/TSRA.
EXPECTING ANY DEVELOPMENT TO WEAKEN WITH HEATING LOSS INTO THE
EVENING HOURS SUNDAY AS THE FRONT CONTINUES APPROACHING FROM THE
WEST...LIKELY BANKING AGAINST THE WESTERN SLOPES OF THE SOUTHERN
APPS BY MID MORNING MONDAY.

AS FOR THE FCST...POPS WILL INCREASE FROM THE WEST SATURDAY WITH
SLIGHT CHANCES FAVORED OVER THE SW MTNS BY LATE
MORNING...SPREADING/INCREASING NORTH AND EAST INTO THE AFTERNOON
HOURS WHERE MID CHANCES POPS ARE MENTIONED.  FURTHER INCREASES ARE
WARRANTED SATURDAY NIGHT INTO SUNDAY GIVEN THE WARM FROPA WITH THE
VAST MAJORITY OF THE FCST AREA UNDER LIKELY POPS BY DAYBREAK...WHILE
CATEGORICAL LEVELS ARE ANCHORED ALONG THE SOUTHERN BLUE RIDGE
ESCARPMENT.  THESE POP LEVELS WILL PERSIST THROUGH THE DAY BEFORE
GRADUALLY LOWERING INTO THE OVERNIGHT.  REGARDING ANY HAZARDOUS
WX...CANT RULE OUT A STRONG/SEVERE THUNDERSTORM ON SATURDAY ALONG
THE WARM FRONT...WITH BETTER CHANCES BEING ON SUNDAY WHEN
INSTABILITY IS FCST TO BE HIGHER AND DEEPER THROUGH THE COLUMN.
PRECIPITATION TOTALS WILL RANGE FROM 1-2 INCHES OVER THE WEEKEND
WITH LOCALLY HEAVIER AMOUNTS POSSIBLE ASSOCIATED WITH ANY DEEPER
CONVECTION.  TEMPERATURES THROUGH THE PERIOD WILL REMAIN ABOVE
NORMAL.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 100 PM THURSDAY...THE MODEL GUIDANCE CONTINUES TO DISPLAY
SIGFNT DIFFERENCES WITH THE LARGE SCALE PATTERN AND SENSIBLE WX
ACROSS THE SE CONUS BEGINNING MON. THE GFS IS STILL THE DRIER AND
MORE SUPPRESSED MODEL ALLOWING STRONG CANADIAN HIGH PRESSURE TO BUILD
IN AFTER A MOIST FROPA MON...WHILE THE ECMWF HAS A MUCH WETTER SOLN.
THE ECMWF IS PHASING AN UPPER TROF ACROSS THE MIDWEST AND SWINGS IT SE
INDUCING AN INVERTED GOM TROF...WHICH THEN MOVES NE ALONG STATIONARY
FRONT OVER THE CAROLINAS. THE GFS ENS MEANS ALSO SHOW MUCH SPREAD
WITH THE H5 PATTERN BEGINNING MON...BUT IT/S MEANS SUPPORT THE SPLIT
FLOW PATTERN OF THE OP GFS. WITH SO MUCH UNCERTAINTY...WILL MAINTAIN
LOW END POPS GIVING MORE WEIGHT TO CLIMO AND CONSMOS. INSTABILITY
SHUD REMAIN FAIRLY LOW AFTER THE FROPA AND LOWERING SFC TD/S...SO
NOT ANTICIPATING STRONG OR SEVERE ACTIVITY....MAINLY ISOL TO SCT
GENERAL TSTMS. TEMPS COULD BE AN ISSUE AS THE AMOUNT OF DEEP
MOISTURE AND AIR MASS CHANGE/MIX IS STILL UNCLEAR. SO...WILL ALSO
GIVE MOS MORE WEIGHT WITH TEMPS REMAINING A CAT OR SO ABOVE NORMAL
MON...THEN RETURNING TO NORMAL VALUES TUE THROUGH THE PERIOD.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AT KCLT/KHKY...BEGINNING TO SEE ISOLATED SHOWERS DEVELOP ACROSS WESTERN
NC EARLY THIS AFTERNOON. FOR THE NEXT COUPLE OF HOURS...THE BEST
CHANCES FOR CONVECTION WILL EXIST NEAR THE BLUE RIDGE...AND A VCTS/
TEMPO FOR TSRA WILL CONTINUE AT KHKY BEGINNING AT 19Z. A TEMPO FOR
TSRA WAS INTRODUCED AT THE 15Z UPDATE AT KCLT...AND WHILE CONFIDENCE
IS NOT GREAT THAT THIS WILL WORK OUT...CONFIDENCE WAS NOT LOW ENOUGH
TO REMOVE IT...ESPECIALLY IN LIGHT OF THE FACT THAT WE ARE ALREADY
SEEING SOME CONVECTION DEVELOP ABOUT 20 MILES SOUTH OF THE TERMINAL.
OTHERWISE...CONVECTION SHOULD DIMINISH BY AROUND SUNSET...AS DRIER
AIR PUSHES ACROSS THE AREA IN THE WAKE OF A SURFACE TROUGH. THIS IS
EXPECTED TO RESULT IN VFR CONDITIONS THROUGH THE PERIOD...ALTHOUGH
SOME FOG MAY DEVELOP TOWARD DAYBREAK NORTH AND EAST OF KCLT. SW
WINDS OF AROUND 10 KTS...WITH GUSTS AS HIGH AS 20 KTS WILL BE
POSSIBLE THIS AFTERNOON...ESP AT KCLT. WINDS WILL DIMINISH AFTER
SUNSET...TURNING TOWARD THE W AND NW BY THE END OF THE EVENING.

ELSEWHERE...THUNDER CHANCES ARE EXPECTED TO BE LESS AT THE UPSTATE
SC TERMINALS AND KAVL THIS AFTERNOON...AS THE STRONGEST INSTABILITY
IT SETTING UP ACROSS THE FOOTHILLS AND PIEDMONT OF NC.
NEVERTHELESS...THE LATEST TRENDS INDICATE SCATTERED SHOWERS SHOULD
DEVELOP OVER THE NEXT COUPLE OF HOURS...WARRANTING A VCSH MENTION.
CERTAINLY CANNOT RULE OUT A DIRECT HIT ON ANY OF THESE TERMINALS...
OR EVEN SOME OCCL THUNDER...BUT PROBABILITIES ARE TOO LOW TO INCLUDE
IN A TEMPO ATTM. OTHERWISE...TRENDS SIMILAR TO KCLT...WITH VFR
CONDITIONS EXPECTED.

OUTLOOK...VFR CONDITIONS SHOULD PERSIST THROUGH FRIDAY NIGHT.
UNSETTLED WEATHER/POSSIBLE RESTRICTIONS/CONVECTION RETURN FROM THE
WEST OVER THE WEEKEND.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.CLIMATE...
RECORDS FOR 04-29

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      89 1970     46 1999     63 1956     28 1967
   KCLT      91 1888     48 1999     65 1994     33 1973
                                        1991
                                        1914
   KGSP      91 1917     47 1999     67 1975     32 1992

&&

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

&&

$$
SYNOPSIS...SBK
NEAR TERM...JDL
SHORT TERM...CDG
LONG TERM...SBK
AVIATION...JDL
CLIMATE...GSP



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