Area Forecast Discussion
Issued by NWS Greer, SC

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171
FXUS62 KGSP 061741
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
141 PM EDT FRI MAY 6 2016

.SYNOPSIS...
THE WEATHER WILL REMAIN UNSETTLED TODAY AS A DEEP UPPER LOW CENTER
MOVES AWAY TO THE NORTHEAST. ANOTHER FRONT IS EXPECTED TO STALL JUST
TO OUR NORTH ON SATURDAY AND SUNDAY. THE FRONT SHOULD LIFT BACK TO
THE NORTH ON MONDAY...AS HIGH PRESSURE OFF THE SOUTHEAST COAST
EXPANDS AND WARM SOUTHERLY FLOW RETURNS.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 1230 PM...UPPER TROUGH REMAINS OVER THE EASTERN SEABOARD...WITH
EMBEDDED CLOSED LOW OVER THE DELMARVA PENINSULA. NAM/GFS RESOLVE
MESOSCALE LOBES OF VORTICITY SWINGING SOUTHWARD THRU THE CWFA THIS
AFTN. SPC MESOANALYSIS ALREADY SHOWS UPWARDS OF 250 J/KG SBCAPE
PRESENT OVER THE ERN HALF OF THE CWFA WHERE UPPER LEVELS ARE COOLEST
UNDER THE TROUGH...LOWER BUT NONZERO VALUES BEING PRESENT ELSEWHERE.
STRATOCU LINGER OVER THE MTNS AND A FEW SHRA ARE BEGINNING TO DEVELOP
WITHIN THEM...LIKELY IN RESPONSE TO THE DPVA ALOFT. PER CONSENSUS OF
SHORT RANGE GUIDANCE...FURTHER DESTABILIZATION AND SHRA ARE EXPECTED
OVER MAINLY THE ERN HALF OF THE AREA...TAPERING OFF DIURNALLY NEAR
SUNSET.

A COUPLE MORE VORT LOBES WILL CROSS THE AREA TONIGHT...THOUGH WITHOUT
MUCH MOISTURE AND WITH CONTINUING DOWNSLOPING WINDS ACRS MOST OF THE
CWFA...NO QPF WILL BE GENERATED. DURING THE DAY SATURDAY...THE OMEGA
BLOCK OVER THE CONUS WILL BREAK DOWN AS A POLAR TROUGH DIGS INTO THE
GREAT LAKES. THE PROGRESSION OF THE UPPER PATTERN LEADS TO HEIGHT
RISES OVER THE SOUTHEAST...WARMING THE MIDLEVELS. THIS WILL INHIBIT
DEEP CONVECTION. AS WINDS BACK TO A MORE WESTERLY DIRECTION...THEY
INITIATE WAA WHICH WILL BRING TEMPERATURES BACK TO MORE SEASONABLE
VALUES.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
AS OF 255 AM FRIDAY...THE ISSUE FOR THE WEEKEND IS HOW FAR TO THE
SOUTH A BACK DOOR COLD FRONT MAKES IT BEFORE STALLING...AND HOW MUCH
PRECIP ACTIVITY WILL DEVELOP ALONG THE BOUNDARY. THE OPERATIONAL
MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT WITH DROPPING THE BACK
DOOR BOUNDARY ONLY AS FAR SOUTH AS THE VA/NC BORDER ON SUNDAY. THE
DIFFERENCE IS IN THE DETAILS...WHERE THE GFS AND SREF DEVELOP MORE
PRECIP SOUTH OF THE BOUNDARY SUNDAY AND SUNDAY NIGHT. THE FCST
FOLLOWS MORE IN LINE WITH THE NAM/ECMWF IN KEEPING THE BETTER
PRECIP CHANCES TO OUR N WITH ONLY A TOKEN SLIGHT CHANCE/CHANCE ON
THE N AND NW FRINGE OF THE FCST AREA. UNLESS THERE IS MORE UPPER
FORCING THAN INDICATED...PRECIP SEEMS UNLIKELY E OF THE BLUE RIDGE
ACROSS NORTHEAST GA AND UPSTATE SC BECAUSE OF DOWNSLOPE DRYING.
FURTHERMORE...THE UPPER RIDGE WILL BUILD IN FROM THE WEST DURING
THE DAY WHICH SHOULD MAKE THE SITUATION LESS FAVORABLE FOR PRECIP
WITH TIME. TEMPS WILL REBOUND TO NEAR NORMAL ON SATURDAY...THEN
GUIDANCE HAS HIGH TEMPS CLIMBING 5-10 DEG ABOVE NORMAL FOR SUNDAY.
CONFIDENCE IS NOT GREAT THAT WE WILL WARM UP THAT QUICKLY...BUT
THE WARMUP IS GENERALLY IN LINE WITH THE WESTERLY DOWNSLOPE BY
SUNDAY AFTERNOON.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 330 AM FRIDAY...NEXT WEEK LOOKS LIKE A RETURN TO SOMETHING
MORE TYPICAL OF LATE SPRING WITH TEMPS ABOVE NORMAL AND DIURNALLY
DRIVEN CONVECTIVE PRECIP. MONDAY LOOKS LIKE THE DAY WITH THE
SMALLEST CHANCE FOR SHOWERS AS A FLAT UPPER RIDGE MOVES ACROSS THE
REGION AND WE LACK ANY MEANINGFUL MID/UPPER FORCING.  AFTER MONDAY
THOUGH...WE END UP WITH WHAT AMOUNTS TO A NEARLY ZONAL UPPER FLOW
ACROSS MOST OF THE SOUTH. HIGH PRESSURE OVER THE WESTERN ATLANTIC
WILL ALLOW FOR MOISTURE TO RETURN FROM THE GULF THROUGH MID-WEEK...
WHICH SHOULD PROVIDE THE FUEL FOR DIURNAL PRECIP DEVELOPMENT. THE
MAIN PROBLEM WILL BE THE TIMING OF ANY WEAK SHORT WAVES CAUGHT UP IN
THE ZONAL FLOW THAT WOULD MOVE THROUGH AND ENHANCE PRECIP CHANCES.
THE GFS HAS ONE MOVING THRU WEDNESDAY AND ANOTHER LATE THURSDAY...
WITH SOME SHORT WAVE RIDGING IN BETWEEN. THE ECMWF REMAINS A BIT
MORE SUBDUED IN THAT REGARD. THE PATTERN FAVORS A PRECIP CHANCE
CLOSE TO CLIMATOLOGY FOR LATE SPRING...MEANING A CHANCE OF SHOWERS
AND STORMS MAINLY IN THE AFTERNOON AND EVENING OVER THE MOUNTAINS
AND FOOTHILLS...AND A SLIGHT CHANCE OVER THE PIEDMONT. OVERALL...
FEW CHANGES WERE MADE TO THE ONGOING FORECAST. MAINLY...TEMPS WERE
RAISED A BIT LATE IN THE PERIOD.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT AND ELSEWHERE...EXPECTING VFR TO PREVAIL THRU SATURDAY
MRNG...WITH EVEN THE ISOLD-SCTD SHRA THIS AFTN APPEARING UNLIKELY
TO PRODUCE RESTRICTIONS SAVE PERHAPS FOR BRIEF MVFR VSBY. THESE
SHOWERS ARE DEVELOPING IN THE UNSTABLE ENVIRONMENT FOSTERED BY
AN UPPER LOW OVER THE MID-ATLANTIC COAST...WHICH WILL DRIFT OFF
TO THE EAST TONIGHT. A POCKET OF MIDLEVEL MOISTURE MOVING THROUGH
MAY BRING A PERIOD OF VFR CIGS OVERNIGHT. THE MAIN IMPACT WEATHER
WILL BE WINDS...WHICH REMAIN RATHER GUSTY THIS AFTN WITHIN THE
GRADIENT AROUND THE SFC LOW TO THE NE OF THE REGION. THIS GRADIENT
WILL BE ALMOST AS STRONG SATURDAY...SO WINDS ARE EXPECTED TO PICK
UP QUICKLY AFTER DAYBREAK AND GUST ONCE AGAIN...SIMILAR TO TODAY.

OUTLOOK...DRYING WILL CONTINUE INTO SATURDAY. A COLD FRONT WILL
APPROACH FROM THE NORTH SUNDAY...WITH ASSOCIATED PRECIPITATION
LIKELY REMAINING NORTH OF ALL THE TERMINALS BEFORE THE FRONT
STALLS. WARMING CONDITIONS WITH A RETURN TO SW FLOW ARE EXPECTED
THROUGH EARLY NEXT WEEK.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-12Z
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.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

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

&&

$$
SYNOPSIS...PM
NEAR TERM...WIMBERLEY
SHORT TERM...PM
LONG TERM...PM
AVIATION...WIMBERLEY



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