Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 250535
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
135 AM EDT MON MAY 25 2015

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVER THE REGION TONIGHT. THE HIGH SLIDES
FARTHER EASTWARD AND TAKES ON A SUMMERTIME BERMUDA PATTERN FOR
MEMORIAL DAY AND REMAINS THERE THROUGH THE WEEK. THIS PRODUCES A
MOIST SOUTHERLY FLOW WITH INCREASED CHANCES FOR WIDESPREAD
CONVECTION EACH DAY AND EVENING.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 135 AM...SAT PIX SHOW ONLY SMALL AREAS OF STRATOCU REMAINING
UNDER THE INCREASING CIRRUS VEIL. GUIDANCE...EVEN THE USUALLY
RELIABLE NAM...HAVE BACKED OFF GREATLY ON THE AMOUNT OF DEVELOPING
STRATOCU AND ANY DEVELOPING UPSLOPE SHRA. HAVE FOLLOWED THESE TRENDS
BY REMOVING POP UNTIL AFTER DAYBREAK AND KEEPING LOW CLOUD CIGS
LIMITED TO AREAS ALONG AND WEST OF I-26. FCST LOWS ON TRACK WITH
ONLY MINOR CHANGES FOR CURRENT CONDITIONS.

1000 PM UPDATE...IR SATELLITE FAINTLY SHOWS SOME STRATOCU HAVE
DEVELOPED OVER THE I-77 CORRIDOR AND NRN MTNS. IN THE MOIST UPSLOPE
FLOW THIS IS NOT ESPECIALLY SURPRISING THOUGH WAS NOT WELL ACCOUNTED
FOR IN THE GRIDS. UPPED SKY COVER MORE INTO PCLDY RANGE. THESE
CLOUDS MIGHT JUST BE TRANSIENT BUT MORE PATCHY CLOUDS COULD DEVELOP
BEFORE STRATUS FORM LATER IN THE NIGHT. ALSO REVISED HRLY
TEMPS/DEWPTS PER SHORT-TERM CONSENSUS PRODUCT...THOUGH NEW LOW TEMPS
ARE NOT FAR OFF FROM THE EARLIER PACKAGE. RH VALUES AND PROFILES ARE
NOT VERY SUPPORTIVE OF FOG...SO ROLLED BACK MENTION EXCEPT NEAR THE
BLUE RIDGE.

AS OF 220 PM EDT SUNDAY...ANOTHER PLEASANT EVENING IN STORE FOR
NORTHEAST GA AND THE WESTERN CAROLINAS AS DEEP LAYER RIDGING
PREVAILS. SOUTHEAST FLOW AROUND SURFACE HIGH OFF THE MID ATLANTIC
COAST WILL CONTINUE THROUGH THE PERIOD ALL THE WHILE ADVECTING IN
ATLANTIC MOISTURE.  THUS...MODELS FAVOR INCREASING CLOUDINESS OVER
THE REGION BY MORNING MONDAY...WITH MOSTLY CLOUDY SKIES PREVAILING
ON THE WESTERN PERIPHERY OF THE HIGH OVER NORTHEAST GA...SOUTHWEST
NC...AND THE WESTERN UPSTATE OF SC.  THE FCST REMAINS DRY THROUGH
MID MORNING BEFORE FLOW VEERS FURTHER SOUTH AND INCREASES...THEREBY
ALLOWING FOR BETTER UPSLOPE POTENTIAL ACROSS THE UPPER FRENCH BROAD
REGION.  IN RESPONSE...SLIGHT CHANCE POPS WILL INCREASE AROUND THE
15Z TIMEFRAME OVER THESE AREAS...BEFORE INCREASING/SPREADING FURTHER
EAST INTO THE NC FOOTHILLS AND CENTRAL UPSTATE FOR THE AFTERNOON AS
MOISTURE IMPROVES AND HEATING STEEPENS LAPSE RATES.  WITH
THAT...SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE WITH LITTLE
ORGANIZATION EXPECTED TO SUPPORT STRONG/SEVERE CONVECTION.
TEMPERATURES THROUGH THE PERIOD WILL GRADUALLY MODERATE WITH HIGHS
ON MONDAY RETURNING TO NEAR NORMAL AMONGST INCREASED HUMIDITY LEVELS.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
AS OF 215 PM SUNDAY...WHAT APPEARED A FEW DAYS AGO AS A SIMPLE
DIURNAL CONVECTIVE PERIOD FOR TUESDAY AND WEDNESDAY LOOKS A BIT MORE
COMPLICATED NOW. THE UPPER PATTERN SHOULD EVOLVE SLOWLY WITH AN
UPPER RIDGE/ANTICYCLONE OFF THE SOUTHEAST COAST ELONGATING AND
BECOMING POSITIVELY TILTED...THUS MAINTAINING A MOIST SW FLOW ALOFT
THAT WILL TRANSPORT MOISTURE FROM THE GULF TO THE WRN CAROLINAS.
THERE IS A SUBTLE TREND IN THE GFS THAT SHOWS THE RIDGE AXIS A BIT
FARTHER OFFSHORE...WHICH ESSENTIALLY WOULD MEAN THAT THE EASTERN
EXTENT OF THE DEEP CONVECTION WOULD BE TO THE EAST OF THE FCST AREA.
THE COMPLICATION COMES ABOUT BECAUSE OF JET STREAKS LIFTING NWD OUT
OF THE UPPER TROF AND WEAK CONVECTIVELY INDUCED VORT CENTERS THAT
MOVE UP FROM THE SW THRU THE PERIOD. THE PASSAGE OF THESE FEATURES
IS DIFFICULT TO PIN DOWN...HOWEVER...THE PATTERN ALSO FAVORS A WEAK
MOIST ATLANTIC UPSLOPE FLOW AT LOW LEVELS. THIS MEANS THAT EVEN
THOUGH THERE WILL BE SOME ENHANCEMENT OF PRECIP CHANCES DURING PEAK
HEATING...THE CHANCE OF SHOWERS AND STORMS WILL PROBABLY NEVER
REALLY GO AWAY EITHER TUESDAY NIGHT OR WEDNESDAY NIGHT. PRECIP
CHANCES WERE NUDGED UPWARD A BIT THRU THE PERIOD...AS WAS SKY
COVER...AND THAT SHOULD SERVE TO KEEP TEMPS A FEW DEGREES COOLER
THAN PREVIOUSLY THOUGHT. PERHAPS THE COVERAGE OF SHOWERS AND STORMS
WILL BE NUMEROUS ENOUGH THAT IT WILL NOT FEEL SO SUMMER-LIKE AFTER
ALL.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 2 PM EDT SUNDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
THURSDAY WITH MULTIPLE UPPER SHORTWAVES MOVING ACROSS THE GREAT
LAKES AND JUST TO OUR NORTH AS THE UPPER RIDGE AXIS SLIDES OFF THE
EAST COAST. SIMLUTANEOULSY A CLOSED UPPER LOW DEVELOPS WELL OFFSHORE
HOWEVER...COMPARED TO PREVIOUS MODEL RUNS...THE LOW APPEARS TO
REMAIN FARTHER OFFSHORE AND BECOME WEAKER TOWARDS THE END OF THE
MEDIUM RANGE. IN THE MEANTIME...THE OVERALL SYNOPTIC PATTERN DOES
NOT CHANGE SIG FOR THE REMAINDER OF THE PERIOD WITH BROAD RIDGING
PERSISTING OVER THE AREA AND TO OUR EAST.

AT THE SFC...WE WILL BE UNDER THE INFLUENCE OF THE SUMMERTIME
BERMUDA HIGH THRU MOST OF THE PERIOD. THIS WILL KEEP MOIST SLY LOW
LVL FLOW OVER THE REGION WITH THE GOOD CHANCE OF WIDESPREAD
CONVECTION EACH DAY/EVENING. SOME MINOR LOW TO MID LVL DRYING IS
POSSIBLE ON FRI AND SAT...YET ITS LOOKING LESS SUBSTANTIAL COMPARED
TO PREVIOUS MODEL GUIDANCE. THE MODELS GENERATE AN ELONGATED COLD
FRONT TO OUR NW ON SAT. THIS FRONT IS ASSOCIATED WITH A SFC LOW THAT
DEEPENS AS IT MOVES WELL NE OF THE GREAT LAKES. THE FRONTAL ZONE IS
SLOW TO REACH THE CWFA AND COULD ESSENTIALLY JUST LAY ACROSS THE
NORTHERN FRINGE OF THE FCST AREA BY THE VERY END OF THE PERIOD LATE
SUN. AS FOR THE SENSIBLE FCST...WE CAN EXPECT A TYPICAL WARM
SUMMERTIME PATTERN WITH GOOD CHANCES FOR WIDESPREAD SHOWERS AND TS
EACH DAY WITH SOMEWHAT REDUCED CHANCES ON FRI AND SAT OVER THE
SOUTHEASTERN ZONES AS PROFILES SHOULD BE DRIER OVERALL...BUT WITH
GOOD AMOUNTS OF INSTABILITY STILL PRESENT.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AT KCLT...ALL GUIDANCE...EVEN THE USUALLY RELIABLE NAM...HAVE BACKED
OFF ON THE AMOUNT OF LOW LEVEL MOISTURE MOVING INTO THE AREA BY
DAYBREAK. THEREFORE...HAVE BACKED OFF ON THE AMOUNT OF LOW CLOUDS IN
THE TAF. THAT SAID...STILL CANNOT RULE OUT SOME LOW VFR CIGS
DEVELOPING AFTER DAYBREAK...BUT THE MAIN THREAT WILL BE DEVELOPING
DIURNAL CU. SUBSIDENCE INVERSION WEAKENS LATE IN THE DAY BUT APPEARS
LIKELY TO HOLD ON ENOUGH TO PRECLUDE ANY CONVECTION. GUIDANCE DOES
AGREE ON LOW CLOUDS DEVELOPING AROUND MIDNIGHT...SO HAVE GONE WITH
MVFR CIGS. GENERALLY SLY WINDS CONTINUE THRU THE PERIOD.

ELSEWHERE...AS WITH KCLT...GUIDANCE HAS BACKED OFF ON LOW CLOUDS
EXCEPT AT KAND...BUT DOES GO WITH LOW VFR CIGS FOR THE FOR ALL BUT
KHKY. HAVE FOLLOWED THESE TRENDS. EXPECT LOW VFR CIGS TO CONTINUE
THRU THE DAY AS CIGS LIFT WITH HEATING AND DIURNAL CU DEVELOPING.
PROB30 RETAINED FOR ALL BUT HKY WHERE INSTABILITY DOES NOT DEVELOP.
AS WITH KCLT...MVFR CIGS DEVELOP AROUND MIDNIGHT...WITH MVFR VSBY AT
KAVL AS WELL. S TO SE WINDS THRU THE PERIOD.

OUTLOOK...MOISTURE WILL CONTINUE TO RETURN OUT OF THE SOUTH THRU THE
MIDDLE OF THE WEEK. INCREASED MORNING STRATUS...AND BETTER THAN
CLIMATOLOGICAL CHANCES OF MAINLY AFTN/EVE SHRA/TSRA ARE EXPECTED
THRU THU. HOWEVER...PASSING UPPER LEVEL DISTURBANCES COULD DRIVE A
FEW STORMS AT NIGHT.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     LOW   55%     HIGH  89%     HIGH 100%
KAVL       HIGH 100%     HIGH  89%     HIGH  94%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     MED   61%     HIGH  94%     HIGH 100%
KAND       HIGH 100%     MED   61%     HIGH  83%     HIGH 100%

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_TABLES

&&

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

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...CDG/RWH/WIMBERLEY
SHORT TERM...PM
LONG TERM...JPT
AVIATION...RWH



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