Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 272019
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
419 PM EDT MON JUL 27 2015

.SYNOPSIS...
HIGH PRESSURE WILL PERSIST OVER THE REGION THROUGH MID WEEK...WITH
CONTINUED WARM TEMPERATURES. A WEAK COLD FRONT WILL APPROACH THE
AREA FROM THE NORTHWEST ON THURSDAY AND SETTLE SOUTHWARD OF THE
REGION ON FRIDAY. THE FRONT WILL LIKELY REMAIN STALLED JUST SOUTH OF
THE AREA THROUGH THE WEEKEND...WITH COOLER TEMPERATURES EXPECTED AND
BETTER CHANCES FOR WIDESPREAD SHOWERS AND THUNDERSTORMS.

&&

.NEAR TERM /THROUGH TUESDAY/...
1620 UTC UPDATE...POPS AND QPF HAVE BEEN ADJUSTED UP FARTHER EAST
FROM THE BLUE RIDGE PER RADAR TRENDS...ESPECIALLY IN THE NC
FOOTHILLS AND PIEDMONT. SKY COVER WAS UPDATED FROM SATELLITE IMAGERY.

AS OF 230 PM...SCATTERED CONVECTION SHUD CONTINUE TO FIRE ACRS THE
HIGH TERRAIN THRU THE REST OF THE AFTN...AS A MID LVL VORT MAX
ENTERS THE MTNS. INSTBY IS STILL ON THE WEAK SIDE...WITH SPC
MESOANALYSIS PAGE SHOWING MOST OF THE AREA IN A CAPE  MINIMUM
BETWEEN 500-1000 J/KG. SO FAR...THE CONVECTION THAT HAS DEVELOPED
HAS NOT BEEN PRODUCING CG-LIGHTNING IN THE CWFA. THIS IS INDICATE OF
THE SHALLOW NATURE OF THE CAPE. I TWEAKED THE POPS FOR THE AFTN/EVE
WITH THE LATEST CAMPOP. COVERAGE WAS BUMPED UP...BUT I THINK MOST OF
THAT WILL BE SHOWERS. SEVERE THREAT IS VERY LOW.

TONIGHT...CONVECTION SHUD WANE AFTER SUNSET...AS VORT MAX EXITS TO
THE EAST AND WE LOSE INSTBY. SOME OF THE CAMS...PARTICULARLY THE
HRRR...WANT TO LINGER CONVECTION THRU THE EVENING ACRS THE NC
PIEDMONT. I/M NOT SURE WHAT THAT IS KEYING ON...UNLESS THE VORT MAX
IS STILL A FACTOR. OTHERWISE...EXPECT PLENTY OF LINGERING MID AND
HIGH CLOUDS AND LIGHT WINDS. PATCHY FOG EXPECTED IN THE MTNS AND
WHEREVER A DECENT DOWNPOUR OCCURS. TEMPS ABOUT A CATEGORY ABOVE
NORMAL.

TUESDAY...LARGE UPPER RIDGE ACRS THE PLAINS WILL BEGIN TO BUILD IN
SOMEWHAT ACRS THE GREAT LAKES AND OHIO VALLEY. SUBTLE VORT MAXES
WILL DRIFT SWD ACRS THE CWFA. IN SPITE OF THIS...FCST SNDGS SHOW
SLIGHTLY BETTER MID LVL LAPSE RATES AND MUCH MORE CAPE THAN LAST
COUPLE DAYS. TO ADD TO THIS...DEWPTS ARE FCST TO REMAIN A LITTLE
MORE ELEVATED...AS WEAK FLOW DOESN/T MIX THEM OUT AS MUCH. SO EXPECT
SCATTERED TO NUMEROUS SHWRS AND STORMS ACRS THE AREA. THE SEVERE
THREAT LOOKS LIMITED TO HOW MUCH DCAPE WILL DEVELOP. THE NAM FCST
SNDGS SHOW A FAIR AMOUNT OF MID LVL MOISTURE. SO I EXPECT A LOW
SEVERE THREAT.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
AS OF 220 PM MONDAY...VERY LITTLE CHANGE OF SUBSTANCE IS ANTICIPATED
IN THE SYNOPTIC PATTERN THROUGH THE PERIOD. THE SUBTROPICAL RIDGE
WILL REMAIN CENTERED OVER OKLAHOMA...PERHAPS UNDERGOING A SLIGHT
STRENGTHENING EARLY IN THE PERIOD. BY THE END OF THE PERIOD...THERE
MAY BE A BIT OF RETROGRADE EFFECT...AS A SUBSTANTIAL SHORT WAVE
TROUGH PROGRESSES ACROSS THE NORTHERN CONUS...WHICH WILL INTRODUCE
HEIGHT FALLS TO MUCH OF THE EASTERN HALF OF THE CONUS. CLOSER TO
HOME...A GRADUAL INCREASE IN LOW LEVEL MOISTURE IS ANTICIPATED
THROUGH THE PERIOD...WHICH IS EXPECTED TO RESULT IN MODEST
IMPROVEMENT IN BUOYANCY EACH DAY. THIS SHOULD ALLOW DIURNAL POPS TO
REMAIN AT OR JUST ABOVE CLIMO THROUGH THE PERIOD. CONVECTIVE CHANCES
COULD BE FURTHER ENHANCED BY THE END OF THE PERIOD...AS HEIGHT FALLS
ALLOW A WEAK FRONTAL BOUNDARY TO SAG INTO THE AREA.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 210 PM MONDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
FRIDAY WITH A BROAD NORTHERN STREAM UPPER TROF MOVING ACROSS ONTARIO
AND VERY BROAD UPPER RIDGING IN PLACE OVER THE WESTERN CONUS. THIS
BROAD UPPER TROFFING IS EXPECTED TO REMAIN IN PLACE OVER THE NE
CONUS FOR MOST OF THE PERIOD WITH THE UPPER RIDGE STRENGHTENING OVER
THE WEST AND PERSISTING BEYOND DAY 7. AT THE SFC...IN THE WAKE OF A
WEAK FROPA ON THURS...SFC RIDGING WILL SPREAD BACK OVER THE CWFA
FROM THE NW ON FRI AND LINGER INTO THE WEEKEND. FOR THE REMAINDER OF
THE PERIOD THE SYNOPTIC PATTERN REMAINS FAIRLY UNCERTAIN WITH A SFC
LOW TRYING TO DEVELOP TO OUR SOUTH OVER THE WEEKEND...YET AT PRESENT
BOTH THE GFS AND ECMWF REMAIN LUKE WARM WITH ITS ORGANIZATION. THEY
CONTINUE TO KEEP A HEALTHY AMOUNT OF DEEP LYR MOISTURE OVER THE
EXTREME SE THRU DAY 7...SO THIS SHOULD PROVIDE BETTER CHANCES FOR
WIDESPREAD SH AND TS EACH DAY/EVENING. AS FOR THE SENSIBLE FCST...WE
CAN EXPECT MOSTLY DIURNAL CHANCES FOR SCT TO WIDESPREAD CONVECTION
EACH DAY/EVENING WITH THE BEST CHANCES OVER THE SE ZONES. TEMPS WILL
START OUT RIGHT AROUND NORMAL AND ARE EXPECTED TO DROP JUST BELOW
NORMAL OVER THE WEEKEND.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
AT KCLT...GENERALLY VFR CONDITIONS EXPECTED THROUGH THE 18Z TAF
PERIOD. CONVECTION IS FIRING ALONG THE BLUE RIDGE AT THE TIME OF THE
18Z TAF ISSUANCE. THE STEERING FLOW WILL TAKE THE SHRA/TSRA TO THE
SE TOWARD THE TERMINAL. HOWEVER...THERE IS WEAK INSTABILITY ACRS THE
PIEDMONT TODAY. SO MOST OF THE ACTIVITY WILL LIKELY DISSIPATE BEFORE
REACHING KCLT. WITH THAT SAID...WILL HAVE A TEMPO FROM 21-24Z FOR
TS. THE MOST LIKELY IMPACT WILL BE OUTFLOW THAT WILL COME OUT OF THE
NW OR N. SOME OF THE GUIDANCE KEEPS A N TO NE WIND THRU THE
EVENING...WHILE OTHER GUIDANCE PREVAILS SE. I THINK THERE WILL BE A
PERIOD OF LIGHT NE...BUT THEN SHUD FAVOR SE OVERNIGHT. EITHER
WAY...SHUD BE UNDER 5 KTS. OTHERWISE...EXPECT A FAIR AMOUNT OF
DEBRIS MID/HIGH CLOUDS...WHICH MAY LIMIT FOG POTENTIAL. UNLESS RAIN
IS MORE WIDESPREAD THAN EXPECTED...I THINK IT WILL REMAIN VFR. ON
TUESDAY...GUIDANCE IN GOOD AGREEMENT ON BETTER COVERAGE OF
CONVECTION STARTING AROUND MIDDAY. WILL LIKELY NEED A PROB30 WITH
THE 00Z TAF FOR TOMORROW AFTN.

ELSEWHERE...SO FAR CONVECTION IS FIRING ACROSS THE HIGH TERRAIN...AS
EXPECTED. INSTABILITY REMAINS WEAK EAST OF THE MTNS...SO EXPECT MOST
OF THE ACTIVITY TO REMAIN CONFINED TO THE MTNS. WILL PLACE KAVL AND
KHKY WITH VCTS FOR THIS AFTN. THE UPSTATE SITES WILL STRUGGLE TO SEE
CONVECTION TOO CLOSE...SO NO MENTION. WINDS WILL BE LIGHT AND CLOUDS
GENERALLY 5000 FT OR HIGHER THRU TONIGHT. THEN ON
TUESDAY...INCREASED LLVL MOISTURE WILL ALLOW FOR QUICK CUMULUS
DEVELOPMENT BELOW 5000 FT. SHRA/TSRA COVERAGE WILL INCREASE TOWARD
END OF 18Z TAF PERIOD. WILL MENTION PROB30 AT KAVL...WHERE
CONVECTION WILL DEVELOP EARLIEST. FOG POTENTIAL LOOKS LIMITED TO
KAVL AND KHKY...WHERE THEY ARE EXPECTED TO RECEIVE SOME RAINFALL
TODAY.

OUTLOOK...DECENT COVERAGE OF AFTN/EVE SHRA/TSRA EXPECTED EACH DAY
THRU THE END OF THIS WEEK...AS MOIST AIR MASS REMAINS IN PLACE.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH  91%     HIGH  92%
KGSP       HIGH 100%     HIGH 100%     HIGH  96%     HIGH  95%
KAVL       HIGH 100%     HIGH 100%     HIGH  93%     HIGH  97%
KHKY       HIGH 100%     HIGH 100%     HIGH  81%     HIGH  95%
KGMU       HIGH 100%     HIGH 100%     HIGH  96%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  98%     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...JPT
NEAR TERM...ARK
SHORT TERM...JAT/JDL
LONG TERM...JPT
AVIATION...ARK



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