Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 191429
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1029 AM EDT SUN APR 19 2015

.SYNOPSIS...
A VERY MOIST WARM FRONT WILL LIFT NORTHEAST ACROSS THE AREA TODAY. A
COLD FRONT WILL THEN CROSS THE AREA ON MONDAY...USHERING IN
SEASONABLE TEMPERATURES AND DRY CONDITIONS THROUGH MIDWEEK. ANOTHER
COLD FRONT WILL CROSS THE AREA FROM THE NORTHWEST ON THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1015 AM EDT SUNDAY...FIRST ROUND OF HEAVY SHOWERS SLIDING
THROUGH THE EASTERN UPSTATE INTO THE NC PIEDMONT AT THIS TIME.
MODERATE TO HEAVY RAINFALL IS LIKELY OVER THE NEXT FEW HOURS ACROSS
THESE ZONES WITH RATES LIKELY AT OR GREATER THAN AN INCH PER HOUR AT
TIMES.  FORTUNATELY...FORWARD PROPAGATION REMAINS SUFFICIENT TO
ALLEVIATE ANY SIG FLOODING CONCERNS.  THAT SAID...ANTECEDENT
CONDITIONS CONTINUE TO DEGRADE WITH ADDITIONAL PRECIP LIKELY LATER
IN THE MORNING/AFTERNOON.  LATEST NAM12 HAS ARRIVED WITH INDICATIONS
THAT THIS AFTERNOON COULD BE RATHER ACTIVE WITH BOTH HYDRO AND
SEVERE CONCERNS.  THE WARM FRONT IS CURRENTLY SLIDING THROUGH NORTH
CENTRAL GA...WITH SURFACE BASE CONVECTION JUST BEHIND THE BOUNDARY.
EXPECTING EARLIER/CURRENT UPGLIDE PRECIP TO BE REPLACED BY
CONVECTIVE PRECIP LATER IN THE DAY AS THE WARM SECTOR INTRUDES
BEHIND THE FRONT.  MODELS CONTINUE TO PROG SUFFICIENT INSTABILITY
AMONGST HIGHLY SHEARED PROFILES WHICH CONTINUES TO SUGGEST POSSIBLE
ORGANIZED SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING WITH DAMAGING
WINDS AND ISOLATED TORNADOES BEING THE PRIMARY THREATS...IN ADDITION
TO HEAVY RAINFALL.  THUS FOR THE FCST...ADJUSTED BOTH POPS AND QPF
TO BETTER ALIGN WITH MOST RECENT OBS AND LATEST GUIDANCE.  NO OTHER
SIG CHANGES WERE MADE AT THIS TIME.

PREVIOUS DISCUSSION...

AS OF 715 AM...WIDESPREAD SHRA DEVELOPING NEARLY ON SCHEDULE...AND
WILL CONTINUE THRU THE DAY. HAVE SLOWED THE ONSET OF TSRA AS THERE
IS NOT EVEN ANY IN CLOUD LIGHTNING SHOWING UP TO THE WEST.
OTHERWISE...GOING FCST ON TRACK WITH UPDATES MAINLY FOR CURRENT
CONDITIONS.

AS OF 335 AM...PRIMARY FCST CONCERN THROUGH THE NEAR TERM REMAINS
THE POTENTIAL FOR HEAVY RAIN ACROSS MUCH OF THE AREA TODAY. THE
CURRENT WATCH LOOKS TO BE WELL PLACED WITH QPF UP TO 3 INCHES
POSSIBLE IN THE WATCH AREA. SHRA ARE DEVELOPING ACROSS THE CWFA AND
WILL CONTINUE TO EXPAND IN COVERAGE AND INCREASE IN INTENSITY THRU
THE MORNING...WITH WIDESPREAD COVERAGE BY MIDDAY. IN ADDITION TO THE
HEAVY RAIN POTENTIAL... GUIDANCE SHOWS WEAK INSTABILITY WILL DEVELOP
ACROSS THE AREA TODAY. THE GUIDANCE ALSO SHOWS MODERATE BULK SHEAR
ALONG WITH HIGH LEVELS OF 0-1KM HELICITY. THE FCST HODOGRAPHS ARE
GREATLY CURVED AS WELL. ALL THIS WOULD INDICATE A HIGH SHEAR/LOW
CAPE ENVIRONMENT DEVELOPING TODAY AS THE WARM FRONT TO OUR SOUTH
MOVES ACROSS THE AREA. THAT SAID...FCST SHERB VALUES REMAIN BELOW 1
TODAY. WE ARE IN A SLIGHT RISK FOR SEVERE STORMS TODAY...SO THIS
WILL NEED TO BE WATCHED THRU THE DAY. SHOULD SEE GUSTY WINDS
DEVELOPING ACROSS THE AREA IN ANY CASE AS THE FRONT MOVES THRU.

CONVECTION WILL MOVE EAST OF THE AREA DURING THE EVENING WITH A
DIMINISHING POP TREND. HOWEVER...SOME GUIDANCE SHOWS A SECONDARY
LINE OF CONVECTION MOVING THRU EARLY IN THE EVENING...THEN A
TERTIARY LINE OF CONVECTION MOVING IN TOWARD DAYBREAK AS SHORT WAVES
ROTATE ACROSS THE AREA. KEEP HIGHER POP EARLY EVENING DIMINISHING
AROUND MIDNIGHT...THEN PICKING BACK UP THRU DAYBREAK. COULD BE SOME
LINGERING HEAVY RAIN DURING THE EVENING...WITH MUCH LOWER QPF
EXPECTED AFTER MIDNIGHT. GUST WINDS WILL DIMINISH THRU THE EVENING.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...MODELS IN GOOD AGREEMENT ON A COLD FRONT
CROSSING THE AREA DURING THE DAY ON MONDAY. THE FRONT SHUD HAVE
SOLID 1500-2000 J/KG OF SBCAPE AND 35-45 KT OF GENERALLY
UNIDIRECTIONAL SHEAR TO WORK WITH. THE NEW DAY 2 SPC CONVECTIVE
OUTLOOK HAS EXPANDED THE SLGT AND MRGL RISK AREAS A BIT FURTHER WEST
OVER OUR AREA TO LINE UP WITH THE EXPECTED FRONTAL TIMING. THERE
WILL BE ANOTHER LOBE OF VORTICITY TO HELP SUPPORT CONVECTION...BUT
DEEP LAYER MOISTURE WILL BE THINNING DUE TO A STRONG DRY SLOT OVER
THE AREA. SO WILL GO WITH GENERALLY HIGH-END CHC TO LOW LIKELY POPS
MONDAY AFTN ACRS THE ENTIRE CWFA. THE MAIN THREATS LOOK TO BE
DAMAGING WIND GUSTS AND AN ISOLD TORNADO THREAT EAST OF THE MTNS.
LARGE HAIL WILL ALSO BE POSSIBLE. HIGHS WILL BE ABOUT 8-10 DEG ABOVE
NORMAL.

THE FRONT AND ASSOCIATED CONVECTION SHUD EXIT EAST OF THE AREA BY
MID EVENING...WITH A LINGERING SHWR THREAT ALONG THE TN BORDER
WITHIN NW FLOW. TEMPS WILL BE A CATEGORY OR TWO ABOVE NORMAL.

TUESDAY THRU TUESDAY NIGHT LOOKS DRY...AS SFC HIGH PRES BUILDS IN
UNDER QUASI-ZONAL FLOW ALOFT. TEMPS WILL BE BACK TO AROUND NORMAL.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 315 AM SUNDAY...THE UPPER PATTERN WILL CHANGE LITTLE OVER THE
MEDIUM RANGE...WITH A LOW SPINNING OVER THE GREAT LAKES...AND SPLIT
FLOW UPSTREAM ACRS MOST OF THE CONUS. A SOUTHERN STREAM SHORTWAVE
TROF IS EXPECTED TO EVENTUALLY EJECT OUT ACRS THE PLAINS AND BRING A
RETURN OF MORE UNSETTLED WX FOR THE CWFA. THE LATEST WPC GUIDANCE
WAS BLENDED INTO THE FCST WITH THIS PACKAGE. THIS RESULTS IN NEAR
NORMAL TEMPS FOR WEDNESDAY AND THURSDAY...WITH A SLGT CHC TO LOW-END
CHC POP FOR THURSDAY WITH A REINFORCING COLD FRONT FROM THE NW.
BELOW NORMAL TEMPS FOR FRIDAY AND SATURDAY WITH AN INCREASE IN POPS
TO MID CHC TO LOW LIKELY BY SATURDAY.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
AT KCLT...SHRA AND MVFR TEMPO IFR RESTRICTIONS WILL CONTINUE EARLY
THIS MORNING WITH IFR FOR THE LATE MORNING/EARLY AFTERNOON. IFR AND
PROB30 TSRA FROM LATE AFTERNOON INTO THE EVENING. EXPECT MVFR TO
DEVELOP WITH PRECIP ENDING NEAR MIDNIGHT...THEN IFR CIGS TOWARD
DAYBREAK. SE WIND TODAY BECOME GUSTY FOR THE AFTERNOON THEN SW WIND
TONIGHT.

ELSEWHERE...GENERALLY SIMILAR TREND TO KCLT THOUGH AN EARLIER ONSET.
ALSO...LESS CHC OF TSRA KHKY. KAVL WILL SEE SLY WIND THRU THE PERIOD.

OUTLOOK...A COLD FRONT WILL SWEEP THROUGH THE REGION ON MONDAY WITH
STRONG TO SEVERE THUNDERSTORMS BEING A POSSIBILITY. RESTRICTIONS
WILL BE LIKELY AT TIMES ON MONDAY FOR ALL SITES. HIGH PRESSURE WILL
BUILD IN BEHIND THE COLD FRONT LEADING TO LOWER PRECIP/RESTRICTION
CHANCES.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       MED   61%     MED   62%     LOW   55%     HIGH  90%
KGSP       MED   70%     MED   72%     MED   75%     HIGH  95%
KAVL       HIGH  86%     MED   75%     HIGH  88%     LOW   58%
KHKY       MED   61%     MED   71%     LOW   58%     HIGH  81%
KGMU       MED   70%     MED   73%     MED   65%     HIGH  90%
KAND       MED   63%     MED   68%     MED   73%     MED   65%

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...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR GAZ010-017-018-026-
     028.
NC...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR NCZ033-035>037-049-
     050-053-056-057-062>065-068>072-501>510.
SC...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR SCZ001>010.

&&

$$
SYNOPSIS...ARK
NEAR TERM...CDG/RWH
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...RWH


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