Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 211525
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1125 AM EDT MON JUL 21 2014

.SYNOPSIS...
THE COMBINATION OF WEAK LOW PRESSURE ACROSS THE DEEP SOUTH AND HIGH
PRESSURE ACROSS THE MID ATLANTIC STATES WILL PUMP DEEP MOISTURE
ACROSS THE REGION THROUGH TUESDAY. A COLD FRONT WILL APPROACH FROM
THE NORTH DURING MID WEEK AND THEN STALL OVER THE REGION DURING THE
LATE WEEK. THIS BOUNDARY SHOULD WASH OUT BY THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 1120 AM EDT MONDAY... UPDATED FORECASTS TO INCREASE POPS AND QPF
IN NORTHERN PORTIONS OF UPSTATE SC AND NEARBY AREAS IN NC. 12Z NAM
CONTAINS A VERY WELL-DEFINED REGION OF BOUNDARY LAYER CONFLUENCE AND
LOTS OF MOISTURE. IN ADDITION... UPSLOPE FLOW COULD ENHANCE
PRECIPITATION. EXCESSIVE RAINFALL IS POSSIBLE DURING THE NEXT FEW
HOURS.

PREVIOUS DISCUSSIONS...
AT 1030 AM EDT MONDAY... POPS HAVE BEEN BUMPED UPWARD IN ARC FROM
UPSTATE SC ACROSS NC/SC BORDER TO VICINITY CHARLOTTE. CONVECTIVE
STORMS ARE INCREASING IN AXIS OF HIGH PRECIPITABLE WATER EXTENDING
FROM COASTAL SC WEST INTO NORTH GEORGIA. CAPES ARE FAIRLY HIGH IN
THIS SAME AREA... 1000 TO 2000 J/KG FROM NEAR GSP TO CLT. THERMAL
GRADIENT HAS BEEN TIGHTENING A BIT DUE TO SOME HEATING OCCURRING
JUST TO THE SOUTH OF THE ACTIVE CONVECTION. VERTICAL WIND STRUCTURE
FAVORS SLOWLY MOVING STORMS AND PERHAPS SOME BACKBUILDING. EXCESSIVE
RAINFALL WILL BE A POSSIBILITY DURING THE NEXT SEVERAL HOURS. ACROSS
NORTHERN AND FAR WESTERN ZONES... EXPECT CONTINUED SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS THIS AFTERNOON.

AS OF 645 AM...SHOWER COVERAGE ACROSS THE PIEDMONT HAS EXPANDED
OVER THE PAST HOUR...AS ANTICIPATED. I WILL FORECAST TO ALIGN TEMPS
TO LATEST OBS. OVERALL...THE FORECAST APPEARS IN GOOD SHAPE.

AS OF 530 AM...WIDELY SCATTERED SHOWERS AND THUNDERSTORMS REMAINED
ACROSS THE PIEDMONT AND SC/GA FOOTHILLS. RADAR TRENDS INDICATE THAT
ANOTHER ROUND OF CONVECTION MAY ARRIVE FROM THE MIDLANDS OVER THE
NEXT TWO HOURS. THE FORECAST REMAINS IN GOOD CONDITIONS...I WILL
UPDATE TO MAKE HRLY ADJUSTMENTS TOWARD OBSERVATIONS.

AS OF 330 AM...LATEST MESOSCALE ANALYSIS INDICATED BETWEEN 300-900
J/KG OF CAPE ACROSS THE REGION...CAPPED BY 100-200 J/KG OF CIN.
RADAR INDICATED SEVERAL PATCHES OF SHRAS ACROSS THE PIEDMONT AND
FOOTHILLS. SHRAS AND TSRAS MAY INCREASE IN COVERAGE THROUGH SUNRISE
AS A WEAK S/W APPROACHES FROM THE SOUTHEAST. CAMS INDICATE THAT
COVERAGE MAY DECREASE DURING THE DAYLIGHT MORNING HOURS AS LLVL FLOW
VEERS NORTHEAST AND UPPER SUPPORT WEAKENS. HOWEVER...DURING THE
AFTERNOON...LLVL CIN WILL ERODE UNDER A FIELD OF CAPES AROUND 1000
J/KG. I WILL FORECAST 40 POPS ACROSS THE MTNS WITH 50 POPS EAST OF
I-85. SKY COVER IS ANTICIPATED TO REMAIN SLIGHTLY GREATER THAN
SUNDAY AFTERNOON. HOWEVER...TEMPERATURES ARE FORECAST TO PEAK WITHIN
TWO DEGREES OF VALUES OBSERVED ON SUNDAY.

TONIGHT...H5 LOW WILL REMAIN CENTERED OVER THE MS/AL GULF COAST. THE
MID LEVEL PATTERN WILL LIKELY YIELD THE PASSAGE OF WEAK S/W. THE
PASSING FORCING AND DEEP MOISTURE SHOULD SUPPORT AT LEAST SCT SHRA
THROUGH THE NIGHT. OTHERWISE...IT APPEARS THAT CONDITIONS WILL
FEATURE MOSTLY CLOUDY SKY WITH PATCHY FOG. A BLEND OF PREFERRED
GUIDANCE SUPPORTS MIN TEMPERATURES VERY CLOSE TO NORMAL.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 230 AM EDT MONDAY...THE SHORT RANGE LOOKS LIKE A SLOW
TRANSITION BETWEEN A WEAK UPPER LOW OVER THE SOUTHEAST ON TUESDAY
AND A DIGGING UPPER TROF INTO THE EAST ON THURSDAY. THIS SHOULD
FAVOR A RETURN TO MORE OF A DIURNAL TREND IN THE PRECIP BY LATE
WEEK...BUT THE APPROACH OF A COLD FRONT FROM THE NORTH IS A
COMPLICATING FACTOR. TUESDAY LOOKS LIKE THE LAST DAY THAT WILL
FEATURE A LOW LEVEL SOUTHEAST TO SOUTH UPSLOPE FLOW AS THE UPPER LOW
REMAINS FAIRLY CLOSE. THE UPSLOPE FLOW AND DEEP MOISTURE SHOULD
EASILY SUPPORT SCATTERED SHOWERS AND THUNDERSTORMS WITH MINIMAL
HEATING. A LIKELY POP WAS KEPT NEAR THE NC BLUE RIDGE WHERE FORCING
MIGHT BE BEST. KEPT TEMPS ON THE COOL SIDE OF GUIDANCE WITH PRECIP
AND EXTENSIVE CLOUD COVER. THE FLOW AT 850 MB IS FCST TO VEER
SUBSTANTIALLY TUESDAY NIGHT WHICH SHOULD BRING AN END TO THE
NOCTURNAL SHOWERS THAT WE HAVE SEEN FOR THE LAST SEVERAL DAYS. THE
PRECIP CHANCE DROPS OFF TO SLIGHT DURING THE EARLY MORNING HOURS ON
WEDNESDAY BUT SUSPECT THIS IS STILL TOO HIGH. FINALLY ON WEDNESDAY
EXPECT THAT WE WILL BREAK OUT AND SEE SOME SUN...WHICH SHOULD LEAD
TO MORE INSTABILITY...WHICH SHOULD ALLOW FOR SCATTERED STORMS TO
DEVELOP ACROSS THE ENTIRE AREA IN THE AFTERNOON. DIURNAL WEAKENING
SHOULD HAPPEN WEDNESDAY EVENING...BUT THE APPROACH OF THE FRONTAL
ZONE FROM THE N WARRANTS KEEPING A CHANCE ALL NIGHT OVER THE NRN
HALF OF THE FCST AREA.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 320 AM MONDAY...HARD TO FIND MANY TARGETS OF OPPORTUNITY WITH
THE MEDIUM RANGE PART OF THE FCST. FEW CHANGES WERE SUGGESTED WITH
THE NEW GUIDANCE GENERALLY IN FAVOR OF THE ONGOING FCST. THE MAIN
PROBLEM WILL BE THURSDAY. THE MODELS ARE IN DECENT AGREEMENT WITH
BRINGING A COLD FRONT DOWN FROM THE N INTO THE FCST AREA IN THE
AFTERNOON WHICH SHOULD BE A DECENT FOCUS FOR AT LEAST SCATTERED
SHOWERS AND STORMS...A FEW OF WHICH SHOULD BE STRONG TO SEVERE.
PRECIP CHANCES WERE RAISED EARLIER IN THE DAY AND TOP OUT IN THE
LIKELY RANGE OVER THE NRN ZONES IN THE AFTERNOON. THE BOUNDARY IS
STILL EXPECTED TO ESSENTIALLY STALL AND WASH OUT ACROSS THE REGION
THURSDAY NIGHT AND FRIDAY.

NO SIGNIFICANT CHANGES WERE MADE FOR NEXT WEEKEND WITH WEAK HIGH
PRESSURE.

&&

.AVIATION /16Z MONDAY THROUGH FRIDAY/...
AT KCLT... RESTRICTIONS IN SHOWERS AND THUNDERSTORMS LIKELY TO
CONTINUE INTO EARLY AFTERNOON AS SLOWLY MOVING AND BACKBUILDING
CONVECTIVE STORMS FORM ALONG A GENERALLY EAST TO WEST BOUNDARY.
DURING MID TO LATE AFTERNOON... MVFR CLOUDS SHOULD REMAIN...WITH
WINDS BETWEEN 060-080 DEGREES. THE WINDOW BETWEEN 21Z-24Z WILL
LIKELY BE THE MOSTLY LIKELY PERIOD FOR ADDITIONAL TSRA..
TONIGHT...CONDITIONS WILL REMAIN VERY SIMILAR TO THIS MORNING...THE
12Z TAF WILL BE MODELED AFTER THIS MORNINGS OBS.

ELSEWHERE...RESTRICTIONS IN SHOWERS AND THUNDERSTORMS WILL BE MOST
COMMON VICINITY KGMU AND KGSP INTO EARLY AFTERNOON WITH SCATTERED
CONVECTIVE STORMS NEAR KAND... KAVL... AND KHKY. MVFR CEILINGS
SHOULD BECOME MORE PREDOMINANT DURING MID TO LATE AFTERNOON...
ALTHOUGH ISOLATED TO SCATTERED THUNDERSTORMS CAN OCCUR. WINDS SHOULD
BETWEEN 060-090 DEGREES THROUGH THE PERIOD. TONIGHT...CONDITIONS
WILL REMAIN VERY SIMILAR TO THIS MORNING...THE 12Z TAF WILL BE
MODELED AFTER THIS MORNINGS OBS.

OUTLOOK...A GRADUAL RETURN TO A MORE TYPICAL PATTERN WITH DIURNAL
SHOWERS AND STORMS IS EXPECTED STARTING THROUGH MID WEEK. A FRONTAL
SYSTEM IS EXPECTED TO CROSS THE REGION THURSDAY NIGHT...BRINGING
STRONGER CONVECTION AND POSSIBLE FLIGHT RESTRICTIONS INTO MID
MORNING FRIDAY.

CONFIDENCE TABLE...

            15-21Z        21-03Z        03-09Z        09-15Z
KCLT       HIGH  84%     HIGH  87%     MED   77%     HIGH  83%
KGSP       HIGH  88%     HIGH  98%     MED   71%     HIGH  87%
KAVL       HIGH  83%     HIGH  84%     HIGH  85%     HIGH  89%
KHKY       HIGH  83%     HIGH  83%     MED   73%     HIGH  87%
KGMU       HIGH  86%     HIGH  97%     MED   71%     HIGH  83%
KAND       HIGH  94%     HIGH  98%     MED   77%     MED   72%

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...PM
NEAR TERM...LGL/NED
SHORT TERM...PM
LONG TERM...PM
AVIATION...LGL/NED






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