Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS62 KGSP 172347
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
747 PM EDT FRI APR 17 2015

.SYNOPSIS...
DRIER AND WARMER AIR WILL SPREAD INTO THE REGION THROUGH SATURDAY. A
WARM FRONT WILL LIFT NORTHEAST ACROSS THE AREA SATURDAY NIGHT INTO
SUNDAY...ACCOMPANIED BY ABUNDANT MOISTURE AND MORE RAINFALL. A COLD
FRONT WILL CROSS THE AREA ON MONDAY...USHERING IN SEASONABLE
TEMPERATURES AND DRY CONDITIONS.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 730 PM EDT FRIDAY...HAVE BUMPED UP POPS ACROSS MOST OF THE
AREA THIS EVENING INTO THE OVERNIGHT PERIOD TO ACCOUNT FOR FAIRLY
WIDESPREAD LIGHT RAIN/SHOWERS MOVING ACROSS THE AREA...FORCED BY THE
RELATIVELY STRONG SHORTWAVE MOVING ACROSS THE SOUTHEAST THIS
EVENING. IF THE HRRR IS TO BE BELIEVED...THESE SHOWERS COULD LINGER
OVERNIGHT AND PAST SUNRISE...AND WILL EVALUATE FURTHER FOR THE LATE
EVENING UPDATE. BEST MOISTURE REMAINS ACROSS THE UPSTATE AND
NORTHEAST GEORGIA BUT STILL SEEING SOME LIGHT RAIN ACROSS THE
MOUNTAINS AND FOOTHILLS. STILL SEEING SOME SBCAPE VALUES HOLDING ON
ACROSS THE PIEDMONT BUT THESE SHOULD BEGIN DROPPING RAPIDLY WITH
SUNSET...SO HAVE PULLED BACK ON THUNDER WORDING THIS EVENING AND
OVERNIGHT. OTHER GRIDS IN GOOD SHAPE FOR THE MOST PART...WITH ONLY
MINOR TWEAKS TO ACCOUNT FOR HOURLY TRENDS.

AS OF 430 PM EDT FRIDAY...VERY LITTLE CHANGE TO PREVIOUS THINKING
FOR THE NEAR TERM. PRECIPITATION BEGINNING TO OVERSPREAD WESTERN AND
SOUTHWESTERN ZONES AS EXPECTED. NEW GUIDANCE BEGINNING TO PULL BACK
A LITTLE ON CONVECTIVE POTENTIAL...WITH INCREASING CLOUD COVER AND
MOISTENING ATMOSPHERE WHAT LITTLE SBCAPE WAS BEGINNING TO CREEP INTO
THE MESOANALYSES OVER THE PAST COUPLE OF HOURS IS ONCE AGAIN FALLING
OFF. LOOKING AT HI-RES REFLECTIVITY FORECASTS...DEFINITELY STARTING
TO LOOK LIKE MORE STRATIFORM RAIN OR SHOWERS WITH THE POSSIBILITY OF
EMBEDDED THUNDER. HAVE LEFT WEATHER WORDING AS IS FOR NOW SINCE
CURRENTLY ADVERTISED THUNDER IS CHANCE AT BEST...BUT WILL REEVALUATE
MORE THOROUGHLY FOR NEXT NEAR-TERM UPDATE. ONLY MINOR TWEAKS TO
TEMPS AND DEWPOINTS TO UPDATE TRENDS.

AS OF 245 PM EDT FRIDAY...THE SYNOPTIC PATTERN HAS NOT CHANGED ALL
THAT MUCH FROM YESTERDAY...OR DAYS PAST FOR THAT MATTER.  IT STILL
FEATURES ROTATING CLOSE UPPER LOW OVER THE FOUR CORNERS WHILE DEEP
SOUTHWEST WAA PREVAILS ACROSS THE SOUTHEAST UNITED STATES.  AT
THE SURFACE...SPRINGTIME WEDGE STARTING TO ERODE AS EXPECTED THIS
AFTERNOON AS WINDS HAVE VEERED SOUTHERLY ACROSS NORTHEAST GA AND THE
UPSTATE...ALONG WITH A FEW LOCATIONS OVER THE NC PIEDMONT.
FURTHERMORE...H5 SHORT WAVE AND ASSOCIATED VORTICITY MAXIMA
CONTINUES TO SLIDE EAST ACROSS THE DEEP SOUTH WITH A BROAD AREA OF
PRECIPITATION ACCOMPANYING.  LATEST SPC MESO ANALYSIS NOT ALL THAT
IMPRESSIVE AS INSTABILITY REMAINS NEARLY NONEXISTENT ACROSS THE FCST
AREA.  MODELS FAVOR IMPROVING LAPSE RATES WITH HEATING THIS
AFTERNOON...HOWEVER STILL SKEPTICAL AS PRECIP SHIELD AND ASSOCIATED
LOW OVERCAST SKY COVER WILL LIMIT HEATING.  NEVERTHELESS...THE FCST
DOES FEATURE INCREASING POPS THROUGH THE AFTERNOON/EVENING HOURS
WITH CHANCES FOR THUNDER MENTIONED...AND WILL CONTINUE WITH SUCH IN
THE HWO.  POPS WILL LOWER AFTER MIDNIGHT AS THE PRIMARY UPPER WAVE
EJECTS TO THE EAST...AND A WEAK/DRY BACK DOOR FRONT SLIDES SOUTHWARD
ACROSS THE REGION.  HELD ON TO TOKEN SLIGHT/CHANCE POPS THROUGH
MORNING TO ACCOUNT FOR ANY RESIDUAL SHRA ALONG THE BOUNDARY.  LATEST
SOUNDINGS DO NOT SUGGEST AS MUCH MID DRYING AS THE PREVIOUS
RUN...THEREFORE NOT ALL THAT CONFIDENT IN AREAS OF DENSE FOG
OVERNIGHT.  THAT SAID...WOULDNT BE SURPRISED TO SEE ISOLATED CASES OF
SUCH ACROSS THE NC PIEDMONT/FOOTHILLS JUST AHEAD OF THE INTRUDING
BOUNDARY WHEN WINDS ARE CALMEST AND THE PBL IS DECOUPLED.

SATURDAY WILL BE HIGHLIGHTED BY DECREASING CLOUDINESS AS DOWNSLOPING
FLOW PREVAILS AMONGST INCREASING HEIGHTS ALOFT AS AXIS OF SHORTWAVE
RIDGE SHIFTS OVERHEAD.  POPS WILL INCREASE YET AGAIN THROUGH THE DAY
AS FCST SOUNDINGS INDICATE MODEST DESTABILIZATION WITH HEATING.
HOWEVER EXPECTING UPPER RIDGING TO PROVIDE SOME SUBSIDENCE THEREFORE
KEPT POPS AT OR BELOW CHANCE LEVELS THROUGH THE DAY.  TEMPERATURES
ON SATURDAY WILL DEPEND HIGHLY ON HOW SOON THE SKY COVER SCT OUT.
TOOK A MIDDLE OF THE ROAD APPROACH AS IT PERTAINS TO GUIDANCE...WITH
THE FCST FEATURING HIGHS 3-5 DEGREES ABOVE NORMAL.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM FRIDAY...TWO AREAS OF CONCERN TO DEAL WITH IN THE SHORT
TERM. THE FIRST WILL BE A PERIOD OF HEAVY RAIN ON SUNDAY AND THEN A
RISK OF SEVERE STORMS ON MONDAY.

THE UPPER RIDGE OVER THE SOUTHEAST U.S. WILL TRANSLATE EASTWARD
SATURDAY NIGHT AS THE UPPER LOW THAT HAS BEEN OVER THE 4-CORNERS
BEGINS TO MOVE EAST THANKS TO A DIGGING TROUGH MOVING SE OUT OF THE
CANADIAN PRAIRIE. A SHORT WAVE OUT AHEAD OF THE UPPER LOW WILL
MOVE NE FROM THE GULF COAST AND ACROSS THE WESTERN CAROLINAS AND
NE GA ON SUNDAY. AT THE SURFACE...A WARM FRONT WILL APPROACH FROM
THE SW ON SUNDAY. ALL OF THIS WILL RESULT IN ALL TYPES OF FORCING
ACROSS THE REGION ON SUNDAY. PWATS WILL BE IN THE 1.5-1.7" RANGE
WITH A 35-45 KT SELY 850 MB JET INTO THE BLUE RIDGE. WILL RAMP
POPS UP QUICKLY TO CATEGORICAL FROM WEST TO EAST BY MIDDAY
SUNDAY...THEN DECREASE RAPIDLY FROM WEST TO EAST LATE SUNDAY AS
THE AXIS OF DEEP MOISTURE AND FORCING SHIFT EAST. HEAVY RAIN LOOKS
TO BE A GOOD BET...BUT THE RELATIVELY QUICK MOVEMENT OF THE SYSTEM
SHOULD PRECLUDE ANY SERIOUS HYDRO ISSUES. BLENDING THE MODEL
CONSENSUS AND WPC QPF GUIDANCE... RESULTS IN GENERALLY 1.5"-2.0"
FROM LATE SATURDAY NIGHT INTO SUNDAY NIGHT. THE HIGHEST AMOUNTS AS
USUAL ARE EXPECTED TO BE NEAR THE BLUE RIDGE ESCARPMENT WHERE 2-3"
OF RAIN CAN BE EXPECTED. THESE VALUES ARE UNDER THE 12 TO 24 HOUR
FFG. THERE MAY BE SOME LOCALIZED FLOODING BUT WIDESPREAD FLOODING
IS UNLIKELY. HOWEVER...WILL CONTINUE TO MENTION HEAVY RAIN IN THE
HWO. AN IN SITU WEDGE WILL RESULT IN COOL TEMPS ON SUNDAY AND WILL
THEREFORE TREND TOWARD CONSRAW GUIDANCE TEMPS.

SOME DEGREE OF CLEARING SHOULD OCCUR SUNDAY NIGHT AS THE AXIS OF
DEEP MOISTURE SHIFTS NE AND A DOWNSLOPE WIND COMPONENT THROUGH THE
COLUMN DEVELOPS. ON MONDAY...A COLD FRONT WILL MOVE ACROSS THE
REGION FROM WEST TO EAST. BOTH THE NAM AND GFS INDICATE THAT THE
ATMOSPHERE WILL DESTABILIZE BY AFTERNOON WITH CAPES MOST LIKELY
INCREASING TO BETWEEN 1000 AND 1500 J/KG PER GFS AND ECM.
ALSO...0-6KM SHEAR INCREASES TO ABOUT 40KT. THIS MAY SUPPORT SOME
ORGANIZATION TO THE CONVECTION AS THE COLD FRONT MOVES THROUGH.
THE 12Z NAM MODEL REFLECTIVITY SUGGESTS THAT A BROKEN LINE OF
CONVECTION WILL ACCOMPANY THE FRONT ACROSS THE AREA ON MONDAY WITH
A FEW SEVERE STORMS POSSIBLE. WITH THE AREA SOLIDLY IN THE WARM
SECTOR ON MONDAY...MAX TEMPS ARE EXPECTED TO BE ABOUT 5 DEGREES
ABOVE CLIMO.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 245 PM FRIDAY...MONDAY NIGHT...SFC HIGH PRESSURE WILL BUILD
OVER THE FORECAST AREA IN THE WAKE OF A PASSING COLD FRONT. 12Z GFS
INDICATES THAT H85 TEMPERATURES WILL COOL BY 5 C FROM 0Z TO 12Z
TUESDAY...A LITTLE LESS COOLING ON THE ECMWF. USING A BLEND OF
GUIDANCE...I WILL FORECAST LOW TEMPERATURES FROM THE UPPER 40S
WITHIN THE MTN VALLEYS TO MID 50S EAST. ON TUESDAY...BROAD HIGH
PRESSURE WILL REMAIN ACROSS THE CWA. THE REGION SHOULD SEE MOSTLY
SUNNY CONDITIONS WITH A LIGHT SOUTHWEST WIND. TEMPERATURES SHOULD
RESPOND TO THE LATE APRIL SUN AND WEAK DOWNSLOPING...FORECAST TUES
HIGHS SLIGHTLY ABOVE NORMAL.

WEDNESDAY THROUGH FRIDAY...THE GFS AND ECMWF GENERALLY AGREE THAT A
LARGE CLOSED MID LEVEL LOW WILL REMAIN ACROSS THE NORTHEAST AND
EASTERN CANADA...AS A RIDGE LINGERS OVER THE SOUTHERN PLAINS. THE
HEIGHTS ACROSS THE CWA WILL LIKELY REMAIN NW TO SE THROUGH THE
PERIOD. THE MODELS ARE IN LESS AGREEMENT WITH THE PLACEMENT AND
TIMING OF SFC FEATURES...PRIMARILY WEAK FRONTS AND PRESSURE CENTERS.
I AM MORE CONFIDENT TIMING MID LEVEL FEATURES WITHIN THE NW FLOW
ACROSS THE SOUTHERN APPALACHIANS...I WILL FAVOR THE ECMWF.
OVERALL...I WILL KEEP CONDITIONS DRY ON WED...BUT MOISTURE WILL
INCREASE THROUGH THE DAY. A SHORT SERIES OF MID LEVEL S/W ARE
FORECAST TO RIPPLE ACROSS THE CWA THURSDAY THROUGH FRIDAY.
TEMPERATURES SHOULD RANGE CLOSE TO NORMAL WITH AFTERNOON DEWPOINTS
ONLY IN THE 40S. GIVEN THE TRACK OF THE MID LEVEL DISTURBANCES AND
WEAK DIURNAL INSTABILITY...I WILL INDICATE ONLY SCHC POPS ACROSS THE
MTNS ON THURSDAY. FORECAST SOUNDINGS SHOW GREATER INSTABILITY FRIDAY
AFTERNOON...FROM THE MTNS TO THE PIEDMONT. THE COMBINATION OF THE
PASSING DISTURBANCE AND INSTABILITY SHOULD SUPPORT SCT COVERAGE
ACROSS THE MTNS AND ISO EAST.


&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...EXPECT -SHRA TO SLOWLY SPREAD TOWARD THE AIRPORT AS
ANOTHER UPPER WAVE PUSHES ACROSS THE REGION. VFR CONDITIONS STILL
HANGING ON IN THE MEANTIME...BUT ONCE THE DEEPER MOISTURE ARRIVES...
CIGS SHOULD DROP TO MVFR IN THE NEXT COUPLE OF HOURS. AS WINDS
DECOUPLE OVERNIGHT...VSBYS SHOULD DROP TO MVFR AND POTENTIALLY LOWER
EITHER BRIEFLY OR IN ISOLATED LOCATIONS...WITH CIGS DROPPING TO IFR.
SLOW IMPROVING TREND ON SATURDAY WITH MVFR CIGS THROUGH THE
PERIOD...THOUGH KCLT MAY BEGIN TO SEE SOME SCATTERING TOWARD THE END
OF THE PERIOD. SW WINDS TO START WITH WEDGE CONTINUING TO ERODE...
AND WINDS SHIFTING NNE AND NE SATURDAY IN THE WAKE OF THE UPPER WAVE
AS A SURFACE HIGH PRESSURE AXIS PUSHES EAST OVER THE OHIO RIVER
VALLEY.

ELSEWHERE...AT KGSP/KGMU/KAND EXPECT AN OVERALL SIMILAR TREND TO
KCLT BUT WITH -SHRA IN AT TAF INITIALIZATION AND CIGS DROPPING A
LITTLE FASTER OVERNIGHT. KAVL/KHKY WILL SEE FEWER RESTRICTIONS BEING
A LITTLE FARTHER NORTH FROM THE DEEP MOISTURE...AND IT IS POSSIBLE
THAT KHKY MAY KEEP VFR CIGS THROUGH THE NIGHT THOUGH HAVE CONTINUED
MVFR TREND WITH THIS ISSUANCE. MVFR VSBYS STILL LIKELY WITH SURFACE
WINDS DROPPING OFF. ANY -TSRA TOO ISOLATED TO INCLUDE IN THE TAF AT
THIS TIME.

OUTLOOK...DRIER WEATHER IS FAVORED SATURDAY AFTERNOON. DEEPER
MOISTURE WILL RETURN ALONG A WARM FRONT SAT NIGHT THROUGH
SUNDAY...WITH HEAVY RAINFALL AND WIDESPREAD RESTRICTIONS LIKELY ONCE
AGAIN. THUNDERSTORMS WILL THEN BE POSSIBLE THROUGH MONDAY AS A COLD
FRONT REACHES THE AREA FROM THE WEST.

CONFIDENCE TABLE...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       MED   64%     MED   62%     MED   64%     HIGH  80%
KGSP       MED   71%     MED   69%     LOW   46%     HIGH  90%
KAVL       HIGH  93%     MED   62%     MED   60%     HIGH 100%
KHKY       LOW   57%     HIGH 100%     MED   64%     HIGH 100%
KGMU       MED   78%     MED   69%     MED   64%     HIGH  90%
KAND       LOW   57%     MED   69%     MED   78%     HIGH  80%

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...CSH
NEAR TERM...CDG/TDP
SHORT TERM...LG
LONG TERM...NED
AVIATION...TDP


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