Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 200021
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
821 PM EDT SUN APR 19 2015

.SYNOPSIS...
A MOIST WARM FRONT LIFTS THROUGH THE AREA THIS EVENING...BRINGING
MORE ROUNDS OF HEAVY RAIN. A COLD FRONT WILL THEN CROSS THE AREA ON
MONDAY...USHERING IN SEASONABLE TEMPERATURES AND DRY CONDITIONS
THROUGH MIDWEEK. ANOTHER COLD FRONT WILL PUSH IN FROM THE NORTHWEST
ON THURSDAY...POSSIBLY BRINGING SHOWERS BACK TO THE AREA...BEFORE
DRIER HIGH PRESSURE RETURNS FRIDAY.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 750 PM...I WILL ISSUE A QUICK UPDATE TO REMOVE HEADLINES FOR
THE FLASH FLOOD WATCH AND TORNADO WATCH. SEVERAL ROUNDS OF HEAVY
RAIN WILL REMAIN POSSIBLE ACROSS THE INTERSTATE 77 CORRIDOR NORTH OF
THE CHARLOTTE METRO AREA THROUGH 9 PM. ANOTHER WEAKENING BAND OF
THUNDERSTORMS WILL APPROACH THE WESTERN ZONES THROUGH THE LATE
EVENING HOURS.

AS OF 530 PM...A LINE OF MODERATE TO HEAVY RAIN WILL SWEEP ACROSS
THE CLT METRO AREA BY 6 PM. RAINFALL RATES WILL APPROACH 2 INCHES
PER HOUR...CLT METRO STREAMS HAVE PREVIOUSLY PEAKED AND STREAM FLOWS
REMAIN HIGH. HOWEVER...THE COMING RAINFALL WILL LIKELY RESULT IN
FLASH FLOODING ACROSS THE METRO AREA...WITH MALLARD
CREEK...BRIAR...AND LONG CREEK POISED FOR THE QUICKEST RISE TO FLOOD
STAGE. IN ADDITION...SVR WINDS MAY OCCUR WITH THE MAIN LINE SECTION
LIFTING FROM THE MID LANDS. SVR THREAT EAST OF LAURENS CO HAS PASSED
AND REMOVED FROM TORNADO WATCH 79.

AS OF 245 PM EDT SUNDAY...PRIMARY UPPER LOW THAT HAS BEEN CENTERED
OVER THE FOUR CORNERS FOR NEARLY A WEEK HAS FINALLY OPENED UP...AND
IT SLIDING NORTHEAST THROUGH THE CENTRAL PLAINS.  A POTENT SHORTWAVE
THAT EJECTED FROM SAID H5 LOW IS MOVING THROUGH THE TN VALLEY REGION
AT THIS TIME.  AT THE SURFACE...A WEAK CYCLONE MIGRATING THROUGH THE
OHIO VALLEY CONTINUES TO PUSH A WARM FRONT ACROSS THE SOUTHEAST.
LATEST SFC ANALYSIS INDICATES THE WARM FRONT ADVECTING EAST THROUGH
NORTH GEORGIA WITH A VAST PRECIP SHIELD EXTENDING INTO THE WESTERN
CAROLINAS.  MODELS CONTINUE TO PROG CONVECTION MOVING ACROSS THE
FCST AREA THIS AFTERNOON THUS POPS REMAIN AT CAT LEVELS.  AS FOR
SEVERE...LATEST SPC MESO ANALYSIS INDICATES MODEST DESTABILIZATION
TO THE SOUTH ALONG THE I20 CORRIDOR WITH A FRINGE OF ENHANCED SBCAPE
EXTENDING NORTHWARD INTO PORTIONS OF NORTHEAST GEORGIA AND THE
WESTERN UPSTATE.  SHEAR PROFILES REMAIN SUPPORTIVE OF AT LEAST AN
ISOLATED TORNADO THREAT IF ANY UPDRAFTS BECOME WELL ORGANIZED.  THAT
SAID...THE WINDOW FOR SUCH ENHANCEMENT IS NARROW...AND WILL CLOSE AS
THE PRIMARY SHORTWAVE EJECTS NORTH.  CURRENT THINKING IS THAT ANY
FLOODING CONCERNS WILL REMAIN ISOLATED AND CONFINED TO ANY OF THE
HEAVIEST CONVECTIVE ELEMENTS.  POPS WILL DECREASE INTO THE EVENING
AFTER THE CURRENT FLOOD WATCH EXPIRES AT 8PM.

FOR MONDAY...THE PRIMARY FOCUS CONTINUES TO BE A COLD FRONT PASSAGE
ASSOCIATED WITH A POTENT NEGATIVELY TILTED UPPER TROF AXIS.
GUIDANCE HAS CONVERGED ON A FAIRLY GOOD CONSENSUS THAT THE FRONT WILL
SLIDE INTO THE MOUNTAINS BY MID/LATE MORNING WITH MODEST
DESTABILIZATION IN THE WARM SECTOR ACROSS NORTHEAST GA AND THE NC/SC
PIEDMONT AND FOOTHILLS.  FCST SOUNDINGS FEATURE IMPRESSIVE THERMAL
PROFILES WITH STEEP LAPSE RATES SUPPORTED BY AMPLE DRY AIR ALOFT.
ALTHOUGH LOW LEVEL FLOW IS NOT AS BACKED ON MONDAY AS IT IS
TODAY...LONG RIGHT TURNING HODOGRAPHS ARE STILL IN PLACE.  THUS THE FCST
FEATURES SOLID CHANCE POPS ACROSS THE ENTIRE FCST AREA TO ACCOUNT
FOR AFTERNOON CONVECTION.  EXPECTING STORM MODES TO REMAIN LINEAR
FOR THE MOST PART...BUT CANT RULE OUT A FEW DISCRETE CELLS AHEAD OF
THE MAIN LINE.  WITH ANY OF THESE STRONGER STORMS EXPECTING THE
PRIMARY THREATS TO DAMAGING WINDS...LARGE HAIL...AND ISOLATED
TORNADOES.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 1240 PM SUNDAY...CONVECTIVE CHANCES WILL LINGER INTO MID-
EVENING OR SO ON MONDAY...MAINLY ACROSS EASTERN AREAS...AS COLD
FRONT SLIDES TOWARD CENTRAL NC/THE SC MIDLANDS...AND ACROSS THE NC
MTNS...WHERE A DEVELOPING NW FLOW COULD RESULT IN A FEW STRAGGLING
SHOWERS NEAR THE TENN BORDER. AFTER THAT...THE REMAINDER OF THE
SHORT TERM PERIOD WILL OFFER A WELCOME CHANGE FROM THE PAST WEEK OR
SO: SEASONABLY MILD...AND MORE IMPORTANTLY...DRY...AS A BROAD/LOW
AMPLITUDE LONG WAVE TROUGH BECOMES ESTABLISHED OVER THE EASTERN
CONUS. A SHORT WAVE TROUGH ROUNDING THE BASE OF AN UPPER LOW OVER
THE GREAT LAKES REGION IS EXPECTED TO INTRODUCE A FRONTAL BOUNDARY
TO THE REGION BY THE END OF THE PERIOD...RESULTING IN INCREASING
POPS BY WED AFTERNOON...BUT IT DOES NOT APPEAR THAT ANYTHING MORE
THAN SLIGHT/LOW CHANCES ARE WARRANTED ATTM.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF MIDDAY SUNDAY...LONGWAVE UPPER TROUGH WITH EMBEDDED CLOSED LOW
WILL PERSIST OVER ERN CANADA AND THE NRN TIER OF THE ERN CONUS
THROUGH THE MED RANGE PERIOD. A VORT LOBE ROTATING AROUND THE LOW
WILL ALLOW A WEAK SFC LOW TO SPIN UP OVER THE NE CONUS AND DRAG A
FAIRLY WEAK COLD FRONT SWD THRU THE SRN APPALACHIANS ON THU.
MOISTURE IS GENERALLY LACKING...BUT LAPSE RATES ARE MARGINAL. SOME
CONVECTIVE ACTIVITY COULD DEVELOP AHEAD OF THE FRONT...AND ON
ACCOUNT OF THE SHARP HEIGHT GRADIENT AROUND THE TROUGH PRODUCING
DECENT SHEAR PARAMETERS...AND WITH DRY UPPER LEVELS...SEVERE WX IS
NOT OUT OF THE QUESTION WITH CELLS THAT DO FIRE. COVERAGE HOWEVER
WILL LIKELY BE LOW.

HIGH PRESSURE BRIEFLY RETURNS TO THE AREA FRI BEFORE A SHORTWAVE
CROSSES THE SRN ROCKIES...AND MOISTURE RETURNS TO THE SOUTHEAST
AHEAD OF THE ENSUING SFC SYSTEM. PWATS AGAIN SURGE TO NEAR RECORD
VALUES SAT MRNG OVER THE UPSTATE...BEING SIGNIFICANTLY ELEVATED
THROUGHOUT THE CWFA. A JET STREAK ON THE SRN FRINGE OF THE UPPER
TROUGH CONCURRENTLY BRINGS SIGNIFICANT UPPER DIVERGENCE ACROSS THE
AREA. WIDESPREAD HEAVY RAIN WILL LIKELY BE OF SOME CONCERN. PRECIP
MAY CONTINUE INTO SATURDAY NIGHT BEFORE TAPERING OFF...ESP WITH THE
19/00Z EC DEPICTING A TRAILING SHORTWAVE BRINGING ANOTHER ROUND OF
PRECIP AT THAT TIME. HIGH PRESSURE SHOULD RETURN TO THE AREA SUNDAY
AND KEEP US DRY INTO MONDAY.

TEMPS WILL GENERALLY BE AT OR BELOW NORMAL THRU THE PERIOD WITH
ABNORMALLY LOW THICKNESSES UNDER THE TROUGH.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...BRIEF PERIODS OF MVFR CEILINGS EXPECTED IN
THE WAKE OF PASSING HEAVY RAIN. FORECAST SOUNDINGS AND MOS INDICATE
THAT CEILINGS WILL LOWER STEADY THROUGH THIS EVENING...REACHING IFR.
IFR CEILINGS SHOULD REMAIN THROUGH THE SUNRISE...THE RISE TO VFR BY
MID DAY. A ROUND OF THUNDERSTORMS ARE EXPECTED TO DEVELOP DURING THE
AFTERNOON HOURS...SWEEPING EAST. I WILL HIGHLIGHT THE TSRA WITH A
PROB30. WINDS WILL REMAIN FROM THE SSW THROUGH THE PERIOD.

OUTLOOK...HIGH PRESSURE WILL BUILD IN BEHIND THE COLD FRONT LEADING
TO LOWER PRECIP/RESTRICTION CHANCES.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       LOW   55%     MED   66%     MED   66%     HIGH  93%
KGSP       MED   69%     LOW   47%     MED   70%     HIGH  93%
KAVL       HIGH  85%     MED   61%     HIGH  86%     HIGH 100%
KHKY       MED   64%     LOW   35%     LOW   55%     HIGH  93%
KGMU       HIGH  87%     MED   76%     HIGH  82%     HIGH  91%
KAND       HIGH  91%     MED   69%     HIGH  81%     HIGH  91%

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...JPT
NEAR TERM...NED
SHORT TERM...JDL
LONG TERM...WIMBERLEY
AVIATION...NED



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