Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 010619
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
219 AM EDT MON JUN 1 2015

.SYNOPSIS...
BERMUDA HIGH PRESSURE WILL PERSIST ACROSS THE REGION INTO THE EARLY
HALF OF THE WEEK.  A SERIES OF LOW PRESSURES WILL MOVE NORTHEAST
ALONG A STALLED OUT FRONT FROM LOUISIANA TO THE VIRGINIAS EARLY IN
THE WEEK.  AN UPPER LOW IS EXPECTED TO FORM OVER THE MID SOUTHEAST
EITHER MONDAY OR TUESDAY AND REMAIN FOR MUCH OF THE WEEK.  THIS WILL
MAKE IT A WETTER THAN NORMAL WEEK FOR OUR REGION.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 115 AM...RECENT RADAR IMAGES SHOW NEW SHRA/TSRA WERE
DEVELOPING ALONG A OUTFLOW BOUNDARY SOUTH OF KHKY. THE CONVECTION
SHOULD LIFT NORTH ACROSS THE I-40 CORRIDOR THROUGH 9Z. A LARGE PATCH
OF SHRA WILL CONTINUE ACROSS KGSP AND KGMU UNTIL 8Z. THE PRIMARY
FORECAST CHALLENGE WILL BE THE FORMATION OF FOG AND LOW CLOUDS OVER
WET GROUND. GUIDANCE REMAINS QUITE MIXED AT THIS
TIME...HOWEVER...BASED ON THE NAM AND PERSISTENCE I WILL MENTION LOW
CEILINGS AND FOG DURING THE EARLY DAYLIGHT HOURS THIS MORNING. IN
ADDITION...REMNANT CONVECTION NEAR THE GA/AL LINE MAY REACH THE NC
MTNS AND UPSTATE AROUND 12Z.

AS OF 1215 AM...RECENT COMPOSITE RADAR IMAGES INDICATED AN INCREASE
IN TSRA AND SHRA COVERAGE ACROSS THE LAKELANDS AND PIEDMONT AREAS.
THESE STORMS HAVE DEVELOPED WITHIN A SFC TROF...FAVORING THE
PIEDMONT AREAS FOR NEW CELLS. BASED ON THE LATEST TRENDS...I WILL
UPDATE THE FORECAST TO INCREASE POPS EAST OF I-85. IN ADDITION...I
WILL INCREASE CLOUD COVER AROUND THE CURRENT CONVECTION...REDUCING
IT ACROSS THE UPPER I-77 CORRIDOR BASED ON SATELLITE.

AS OF 1030 PM EDT SUNDAY...LATEST MESO MODELS CONTINUE TO FAVOR
SLOWLY WEAKENING CONVECTION THROUGH THE NEXT FEW HOURS ACROSS THE
SOUTHERN UPSTATE WHERE 02Z SPC MESOANALYSIS INDICATES WEAK SBCAPE
GRADIENT.  FURTHER NORTH THE LOW LEVELS HAVE BEEN FAIRLY WORKED OVER
BY EARLIER CONVECTION...THUS CONFIDENCE IS NOT THAT HIGH THAT ANY
NEW ACTIVITY...OR INCOMING ACTIVITY FROM NORTHEAST GA WILL
OCCUR/SURVIVE.  NEWLY ARRIVING 00Z NAM12 FAVORS A SIMILAR TRACK FOR
CONVECTION THROUGH 1-2AM BEFORE DEPLETION OCCURS.  THUS POPS WERE
LOWERED ALONG AND NORTH OF THE I40 CORRIDOR...WITH A GRADUALLY
INCREASING GRADIENT INTO THE SOUTHERN UPSTATE WHERE LIKELY POPS ARE
FEATURED SOUTH OF I85.  POPS WILL THEN LOWER AS THIS ROUND OF
CONVECTION WAINS INTO EARLY MORNING...AHEAD OF A GRADUAL INCREASE IN
POPS FURTHER WEST ALONG THE SOUTHERN ESCARPMENT WHERE WEAK NOCTURNAL
LLJ COULD PROVIDE ENOUGH SUPPORT FOR UPSLOPE SHOWERS.
OTHERWISE...THE POP TRENDS ON MONDAY REMAIN UNCHANGED WITH THIS
UPDATE.  THAT SAID...SHOULD NOTE THAT THE 00Z NAM12 CAME IN LESS
UNSTABLE THAN PREVIOUS RUNS THEREFORE WOULDNT BE SURPRISED IF POPS
WERE LOWERED SOMEWHAT FOR MONDAY AFTERNOON.  TEMPERATURE TRENDS WERE
UPDATED TO REFLECT LATEST OBSERVATIONS WITH NO OTHER SIGNIFICANT
CHANGES NEEDED/MADE AT THIS TIME.

PREVIOUS DISCUSSION...

ISOLATED TO WIDELY SCT CONVECTION IS DEVELOPING ACROSS THE AREA THIS
AFTERNOON...BUT HAS BECOME NUMEROUS TO WIDESPREAD ACROSS THE TENN
VALLEY/NORTH GA/TENN MTNS. LIKELY POPS STILL LOOK VERY GOOD ACROSS
OUR ZONES BORDERING TENN AND ACROSS THE NORTHEAST GA MTNS. CELLS
HAVE BEEN WELL-BEHAVED THUS FAR...BUT INSTABILITY SHOULD BE
SUFFICIENT TO SUPPORT A COUPLE OF BRIEF/PULSE SEVERE STORMS...
ALTHOUGH THE MAIN CONCERN SHOULD CONTINUE TO BE LOCALLY
HEAVY/POSSIBLY EXCESSIVE RAINFALL WITH TRAINING/BACK-BUILDING CELLS.

CONVECTION SHOULD GRADUALLY DIMINISH THIS EVENING...ALTHOUGH
INCREASINGLY DIFFLUENT FLOW ALOFT DOWNSTREAM OF DEVELOPING UPPER LOW
AND INCREASING DEEP LAYER MOISTURE MAY ENSURE THAT CONVECTIVE
COVERAGE NEVER COMPLETELY DIMINISHES. IN FACT...SW WINDS IN THE 925-
850 HPA LAYER ARE FORECAST TO ACCELERATE TO 15-20 KTS...SIMILAR TO
LAST NIGHT. THIS EXTRA BOOST OF UPSLOPE FLOW/TERRAIN CONVERGENCE
RESULTED IN SCT/NUM SHOWERS NEAR THE BLUE RIDGE THIS MORNING...AND
WOULD NOT BE SURPRISED TO SEE SOMETHING SIMILAR HAPPEN MONDAY
MORNING. THUS...A TREND OF SLIGHTLY INCREASING POPS IS DEPICTED NEAR
THE HIGH TERRAIN BETWEEN MIDNIGHT AND SUNRISE.

HEIGHTS CONTINUE TO FALL MONDAY AS WEAK SURFACE FRONT FINALLY
MEANDERS INTO THE SOUTHERN APPALACHIANS. A PLUME OF DEEP LAYER
MOISTURE ASSOCIATED WITH THE FRONTAL ZONE WILL GRADUALLY OVERSPREAD
THE FORECAST AREA THROUGH THE DAY. MEANWHILE...FORECAST SOUNDINGS
ARE QUITE BUOYANT BY AFTERNOON...WITH CAPE LIKELY MAXIMIZING IN THE
1500-2500 J/KG RANGE. IMPROVING WIND FIELDS DOWNSTREAM OF THE UPPER
TROUGH IS RESULTING IN 0-3 KM SHEAR IN EXCESS OF 20 KTS IN FORECAST
SOUNDINGS...WITH SUFFICIENT DCAPE TO LAY DOWN PLENTY OF OUTFLOW
BOUNDARIES THAT COULD INTERACT WITH THE DECENT LOW LEVEL SHEAR TO
PROMOTE SOME UPSCALE ORGANIZATION. ALL OF THESE FACTORS WILL SUPPORT
LIKELY POPS ACROSS THE WESTERN HALF OR SO OF THE FORECAST AREA...
WITH SOLID CHANCES TO THE EAST. LOCALIZED SEVERE WEATHER WILL BE
POSSIBLE...ESP WITH ANY CONVECTION THAT MANAGES TO GROW UPSCALE.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
AT 2 PM EDT SUNDAY...ON MONDAY EVENING THE MODELS HAVE AN UPPER LOW
TO OUR WEST....WITH THE ECMWF LOW OVER WESTERN TN...WHILE THE GFS
LOW IS OVER THE LOWER TN RIVER VALLEY. AN ATLANTIC SURFACE RIDGE
INITIALLY EXTENDING OVER THE CAROLINAS AND GA WILL PROGRESS SLOWLY
EASTWARD INTO MONDAY AND MONDAY NIGHT...WHILE THE TROUGH UPSTREAM
DOES LIKEWISE. BY WEDNESDAY THE ECMWF LOW REACHES EAST TN...WHILE
THE GFS LOW REACHES SOUTHERN MS.

AT THE SURFACE...A WEAKENING AND NEARLY STATIONARY FRONT WILL BE
OVER THE WESTERN PIEDMONT ON MONDAY EVENING. SUBSTANTIAL MOISTURE
WILL EXTEND EITHER SIDE OF THIS BOUNDARY. THE FRONT...OR ITS
REMNANTS...WILL MOVE VERY LITTLE THROUGH TUESDAY. BY WEDNESDAY THE
MODELS SUGGEST COLD AIR DAMMING AS HIGH PRESSURE NOSES DONE THE
EASTERN SEABOARD FROM NEW ENGLAND.

ENOUGH INSTABILITY AND SHEAR WILL BE PRESENT FROM MONDAY NIGHT
THROUGH TUESDAY TO SUPPORT ROBUST CONVECTION...PERHAPS ORGANIZED. ON
TUESDAY NIGHT AND WEDNESDAY INSTABILITY AND SHEAR WILL BE MUCH MORE
LIMITED...BUT STEERING FLOW WILL BE WEAK...AND FLOODING COULD BECOME
MORE OF A CONCERN. MINIMUM TEMPERATURES WILL RUN ABOVE NORMAL DUE TO
MOISTURE...WHILE MAXIMUM TEMPERATURES LOWER FORM NEAR NORMAL TO
BELOW NORMAL DUE TO CLOUDS...PRECIPITATION...AND POSSIBLE COLD AIR
DAMMING.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 135 PM SUNDAY AFTERNOON...THE MEDIUM RANGE FCST STARTS AT
00Z THURSDAY WITH A 500MB CUTOFF LOW SOMEWHERE AROUND ALABAMA.  THIS
CUTOFF LOW IS FORECAST TO DRIFT EITHER SOUTH ACROSS THE GULF OR SE
OVER FLORIDA AT THE END OF THE WEEK. WHILE THE CUTOFF LOW DOES
THIS IT IS FORECAST TO OPEN UP INTO GENERAL TROFINESS OVER THE EAST
COAST WITH AN UPPER RIDGE BUILDING OVER TEXAS.

AT THE SFC...A LARGE PLUME OF PERSISTENT DEEP LYR MOISTURE
ASSOCIATED WITH A DISSIPATING FRONTAL ZONE WILL KEEP THE FCST AREA
UNDER FAVORABLE CONDITIONS FOR WIDESPREAD SHOWERS AND MAINLY PM
THUNDER FOR THE SECOND HALF OF THE WEEK.  THIS PATTERN WEAKENS
SOME BY SUNDAY WITH THE RIDGE TO OUR WEST NOSING IN A BIT PRIOR TO
ANOTHER 500MB REENFORCING TROUGH DIPPING DOWN FROM MID CANADA.
ALSO NEXT WEEKEND...SURFACE HIGH PRESSURE IS EXPECTED TO DROP SE
FROM CANADA TO BE OVER NEW ENGLAND CREATING A TRANSIENT WEDGE OF
COOL AIR OVER OUR REGION.  THE LATEST GFS HAS A 500MB CUTOFF LOW
FORM DIRECTLY OVER OUR AREA SUNDAY THEN DRIFTING A BIT EAST GOING
INTO NEXT MONDAY. THIS WOULD ENHANCE THE COOLING EFFECT OF COMBINED
NE FLOW FROM SURFACE HIGH PRESSSURE NEAR NEW ENGLAND WITH THE DEEPER
COOLING AND LOWER FREEZING LEVEL WITH THE H5 LOW.  CAPE
VALUES FOR THE FOOTHILLS AND PIEDMONT EACH DAY SHOULD BE GREATER
THAN 1500 ACCORDING TO ALL MODELS WHICH WILL SUPPORT PM THUNDER.
HIGH TEMPERATURES WILL BE COOLER THAN NORMAL AND MAY TREND COOLER IF
THE INFLUENCE OF THE CUTOFF LOWS AND WEDGE BECOME GREATER.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AT KCLT...A CLUSTER OF SHOWERS AND THUNDERSTORMS WITHIN A SFC TROF
WILL LIKELY TRACK OVER THE TERMINAL BETWEEN 8Z TO 10Z. I WILL
HIGHLIGHT THE CONVECTION WITH A TEMPO FOR SHRA. FORECAST SOUNDINGS
AND PERSISTENCE FOR RECENT MORNINGS SUPPORT THE FORMATION OF MVFR
STRATUS AROUND DAYBREAK...DISSIPATING BY 14Z. THE SFC TROF WILL
REMAIN THROUGH THE DAYLIGHT HOURS...RESULTING IN SOUTHWEST WINDS
THROUGH THE DAY. CAM MODELS INDICATE THAT A LINE OF TSRA WILL
DEVELOP OVER NRN GA THIS AFTERNOON...TRACKING TO THE
NORTHEAST...SIMILAR TO EARLY THIS MORNING. I WILL HIGHLIGHT THE
POTENTIAL FOR TSRA WITH A PROB30 FROM 18Z-24Z.

ELSEWHERE...RECENT RADAR IMAGES SHOW NEW SHRA/TSRA WERE DEVELOPING
ALONG A OUTFLOW BOUNDARY SOUTH OF KHKY. THE CONVECTION SHOULD LIFT
NORTH ACROSS THE TERMINAL THROUGH 9Z. A LARGE PATCH OF SHRA WILL
CONTINUE ACROSS KGSP AND KGMU UNTIL 8Z. THE PRIMARY FORECAST
CHALLENGE WILL BE THE FORMATION OF FOG AND LOW CLOUDS OVER WET
GROUND...AT EACH TAF SITE. GUIDANCE REMAINS QUITE MIXED AT THIS
TIME...HOWEVER...BASED ON THE NAM AND PERSISTENCE I WILL MENTION
MVFR CEILINGS DURING THE EARLY DAYLIGHT HOURS THIS MORNING. IN
ADDITION...REMNANT CONVECTION NEAR THE GA/AL LINE MAY REACH THE NC
MTNS AND UPSTATE AROUND 12Z. SOUTHWEST WINDS AROUND 5 TO 10 KTS AND
CUR BASED AROUND 050 SHOULD OCCUR THIS AFTERNOON. ANOTHER ROUND OF
EVENING TSRA APPEARS POSSIBLE DURING THE FINAL HOURS OF THE 6Z
TAF...HIGHLIGHTED WITH A PROB30.

OUTLOOK...A MID LEVEL LOW IS FORECAST TO REMAIN ACROSS THE DEEP
SOUTH THROUGH THE WORK WEEK. DEEP MOISTURE WILL LINGER ACROSS
THE SOUTHEAST CONUS THROUGH THE WEEK. SHOWERS AND THUNDERSTORMS MAY
DEVELOP EACH AFTERNOON AND EVENING. MORNING STRATUS AND FOG WILL
REMAIN A POSSIBILITY...ESPECIALLY OVER WET GROUND.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH  96%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH  99%     HIGH  92%     HIGH  99%     HIGH 100%
KAVL       HIGH 100%     HIGH  95%     HIGH  97%     HIGH 100%
KHKY       HIGH 100%     HIGH  97%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH  89%     HIGH  96%     HIGH 100%
KAND       HIGH  90%     HIGH  84%     HIGH  97%     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...DEO
NEAR TERM...NED
SHORT TERM...JPT
LONG TERM...DEO
AVIATION...NED


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