Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 280603
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
203 AM EDT TUE JUL 28 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 TODAY/...
AS OF 155 AM...I WILL UPDATE THE FORECAST TO REDUCE POPS...BASED ON
LATEST RADAR TRENDS. I WILL ALSO INCREASE THE MENTION OF MTN VALLEY
AND NC FOOTHILLS FOG...BASED ON RECENT RAINFALL AND OBSERVED LOW
DEWPOINT DEPRESSIONS.

0245 UTC...POPS AND QPF WERE AGAIN ADJUSTED TO ACCOUNT FOR
INCREASING ACTIVITY EAST OF CHARLOTTE.

0215 UTC UPDATE...POPS HAVE BEEN ADJUSTED PER RADAR TRENDS...
FAVORING THE SC COUNTIES SOUTH OF CHARLOTTE. OVERALL...A DECREASING
TREND HAD BEEN ACCOUNTED FOR.

0130 UTC UPDATE...POPS WERE ADJUSTED TO FAVOR THE NORTHERN SC
PIEDMONT PER RADAR TRENDS...AND WERE LOWERED ELSEWHERE. SKY COVER
WAS UPDATED FROM INFRARED SATELLITE IMAGERY.

0015 UTC UPDATE...POPS AND QPF WERE RAISED IN THE PIEDMONT AND THE
NC MOUNTAINS...AND LOWERED ELSEWHERE...PER RADAR TRENDS.

2315 UTC UPDATE...POPS AND QPF HAVE BEEN INCREASED OVER AND EAST OF
INTERSTATE 85 CORRIDOR PER RADAR TRENDS. WINDS WERE UPDATED WITH
THE LATEST NAM GUIDANCE. SKY COVER WAS UPDATED FROM SATELLITE
IMAGERY.

2020 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 /TONIGHT 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 /06Z TUESDAY THROUGH SATURDAY/...
AT KCLT...RECENT SATELLITE IMAGES AND OBSERVATIONS INDICATED
WIDESPREAD MID LEVEL CLOUDS ACROSS THE I-77 CORRIDOR. THE THICK MID
LEVEL CLOUD COVER SHOULD GRADUALLY DISSIPATE THROUGH SUNRISE.
FORECAST SOUNDINGS AND SEVERAL MOS MEMBER INDICATE THAT MVFR
CEILINGS MAY DEVELOP ONE TO TWO HOURS AFTER SUNRISE...REMAINING
THROUGH MOST OF THE MORNING. I WILL USE A TEMPO DURING THE 12Z TO
15Z FORMATION PERIOD...FOLLOWED BY A FM GROUND FOR BKN030 AT 15Z.
CAMS AND PERSISTENCE SUPPORT A PROB30 BETWEEN 19Z TO 23Z FOR TSRA.
WINDS SHOULD REMAIN BETWEEN 140-170 DEGREES AROUND 5 KTS THROUGH THE
PERIOD.

ELSEWHERE...MOSTLY CLEAR SKY...CALM WINDS...AND 2 DEGREE DEWPOINT
DEPRESSIONS MAY YIELD IFR FOG AT KAVL BY SUNRISE. I WILL INCLUDE A
TEMPO IN THE KAVL TAF FROM 10Z TO 13Z FOR IFR FOG AND MVFR CEILINGS.
KHKY MAY ALSO SEE IFR CONDITIONS AROUND SUNRISE. OTHERWISE...I WILL
MONITOR TRENDS THIS MORNING...BUT WILL SIDE WITH VFR AT THIS TIME.
THE AFTERNOON APPROACH OF A WEAK MID LEVEL DISTURBANCE SHOULD YIELD
A ROUND OF SHRA/TSRA LATE THIS AFTERNOON AND EVENING. I WILL INCLUDE
A PROB30 IN EACH TAF...GENERALLY BETWEEN 20Z TO 24Z.

OUTLOOK...A MID LEVEL RIDGE WILL REMAIN ACROSS THE WESTERN CAROLINAS
THROUGH MID WEEK. A LONGWAVE TROUGH WILL AMPLIFY ACROSS THE ATLANTIC
STATE LATE IN THE WEEK...WITH THE LIKELY PASSAGE OF A COLD FRONT ON
FRIDAY. THE POTENTIAL FOR CONVECTION WILL INCREASE EACH DAY THIS
WEEK.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH  97%     MED   69%     HIGH 100%     HIGH 100%
KGSP       HIGH  94%     HIGH  94%     HIGH 100%     HIGH 100%
KAVL       HIGH  82%     HIGH  82%     HIGH 100%     HIGH 100%
KHKY       HIGH  86%     MED   76%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH  97%     HIGH 100%     HIGH 100%
KAND       HIGH  94%     HIGH  94%     HIGH 100%     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...NED
SHORT TERM...JAT/JDL
LONG TERM...JPT
AVIATION...NED



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