AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
115 AM EDT WED MAY 22 2013
.SYNOPSIS...
AN APPROACHING UPPER LEVEL TROUGH WILL CONTINUE TO INFLUENCE THE
REGION THROUGH MIDWEEK. SOUTHERLY FLOW WILL KEEP THE AREA WARM AND
GENERALLY UNSETTLED WITH STORM CHANCES EACH AFTERNOON. A COOLER AND
DRIER AIRMASS SETTLES IN FOR THE WEEKEND AFTER A COLD FRONT MOVES
THROUGH THURSDAY.
&&
.NEAR TERM /THROUGH TODAY/...
0515 UTC UPDATE...POPS HAVE BEEN RAISED IN THE NORTHERN NC MOUNTAINS
AND THE NE GA MOUNTAINS BASED ON RADAR TRENDS...EVEN THROUGH
CONVECTION IN THOSE AREAS IS DIMINISHING. WINDS WERE UPDATE TO
INCLUDE THE 00Z NAM. SKY COVER WAS INCREASED PER SATELLITE IMAGERY.
AS OF 1030 PM...CONVECTION CONTINUES TO GRADUALLY WANE WITH LOSS OF
DAYTIME HEATING. A FEW LINGERING SUB-SEVERE STORMS WILL CONTINUE TO
AFFECT MAINLY THE NRN MTNS AND NRN NC FOOTHILLS...BUT EXPECTING ALL
ACTIVITY TO DIE OFF BY AROUND 06Z. EXPECTING SIMILAR CONDITIONS TO
LAST NIGHT WITH PATCHY FOG DEVELOPING IN THE MTN VLYS AND LWR
PIEDMONT WHERE THE RAIN WAS HEAVIEST. MAY BE LOCALLY DENSE. TEMPS
LOOK ON TRACK.
AS OF 800 PM...A LITTLE BIT OF SHORTWAVE ENERGY CROSSING THE WRN
THIRD OF THE CWFA IS WORKING TO ENHANCE CONVECTION.
FORTUNATELY...SHEAR IS STILL WEAK AND THE LAST OF THE UN-OVERNTURNED
AIR MASS IS CURRENTLY BEING WORKED OVER. SO STILL EXPECT THINGS TO
WIND DOWN OVER THE NEXT 2-4 HOURS. THE REST OF THE CWFA SHUD REMAIN
TRANQUIL. POPS WERE ADJUSTED ACCORDINGLY...WITH OTHER CHANGES BEING
FOR 00Z AVIATION GRIDS.
AS OF 530 PM...CONVECTION HAS BEEN FAVORING THE WESTERN SITE OF THE
CWFA IN THE LAST HOUR OR SO...AS DECENT WWD PROPAGATING OUTFLOW
BNDRYS ARE WORKING INTO 3500 J/KG CAPE AIR MASS. THE PULSE
CONVECTION HAS BEEN FAIRLY ROBUST...WITH LARGE HAIL AND DAMAGING
WIND THREATS. HAVE UPDATED THE POPS...BLENDING IN THE 18Z NAM AND
LATEST HRRR...WHICH AGREE ON CONVECTION WORKING OVER THE UPPER
SAVANNAH VALLEY AND SW NC MTNS DURING THE EARLY EVENING HOURS.
MEANWHILE...CONVECTION IS TRYING TO ORGANIZE OVER ERN TN WHERE THE
BETTER UPPER FORCING AND DEEP LAYER SHEAR EXISTS. I/M EXPECTING MOST
OF THIS TO STRUGGLE TO REACH THE SRN APPALACHIANS...DUE TO THE LACK
OF SHEAR AND FORCING OVER OUR AREA.
AT 230 PM EST TUESDAY...STILL SEEING AN EVOLVING CONVECTIVE
SITUATION ACROSS THE CWFA AS WEAK FORCING IS MAINTAINED WITHIN A
VERY BROAD H5 TROF. STILL EXPECT PULSE SEVERE LATER THIS AFTERNOON
MAINLY ACROSS THE ERN UPSTATE ALIGNED WITH A LINE OF VORT ENERGY AND
ACROSS NC MTNS WHERE RATHER STEEP LAPSE RATES ARE MOVING IN FROM THE
WEST. THESE STORMS WILL BE MAINLY DIURNALLY DRIVEN...BUT SOME -SHRA
WILL BE MAINTAINED ACROSS THE NC MTNS IN UPSLOPE FLOW THROUGH THE
MID MORNING. DEBRIS CLOUDS WILL PERSIST OVERNIGHT...BUT ENOUGH
CLEARING SHOULD BE HAD TO ENABLE MORNING FG...AND PATCHY/AREAS OF
DENSE FG THROUGH 13Z OR SO. NOT MUCH CHANGE IS IN STORE WITH THE
SYNOPTIC PATTERN WED. THE WRN UPPER TROF IMPINGES UPON THE AREA AND
THE WRN ZONES WILL HAVE A BETTER CHANCE FOR AFTERNOON PRECIP/CONV
THAN THE ERN ZONES AND HAVE MAINTAINED HIGH END CHANCES ACROSS THE
MTNS. A GOOD HEATING DAY IN SW/LY FLOW WITH MAXES A COUPLE DEGREES
ABOVE NORMAL WILL SET THE STAGE FOR ANOTHER HIGH CAPE ENVIRONMENT
AND PULSE SEVERE STORMS POSSIBLE.
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY/...
AS OF 210 PM TUESDAY...MODEL GUIDANCE REMAINS IN FAIRLY GOOD
AGREEMENT WITH REGARDS TO THE WEATHER ACROSS NORTHEAST GEORGIA AND
THE CAROLINAS FOR THE REMAINDER OF THE WORK WEEK. DEEP UPPER LEVEL
TROF AND AN ASSOCIATED SURFACE COLD FRONT WILL SLOWLY MIGRATE
EASTWARD OVER THE NEXT 24 HOURS. SURFACE RIDGING TO THE SOUTHEAST
WILL ALLOW FOR SOUTHERLY FLOW...THUS SETTING UP A MODEST WARM SECTOR
ACROSS THE REGION ON THURSDAY LEADING TO ABOVE NORMAL TEMPERATURES.
EXPECTING COLD FRONT TO MOVE INTO FAR WESTERN PORTIONS OF THE CWA BY
AROUND 12Z THURSDAY MORNING. PRECIPITATION CHANCES WILL INCREASE
NEAR AND ALONG THIS BOUNDARY AS IT MOVES ACROSS THE NORTH CAROLINA
MOUNTAINS...AND THEN SPREADS EASTWARD ACROSS THE PIEDMONTS. HIGHEST
POPS WILL BE ACROSS THE NORTH CAROLINA FOOTHILLS/PIEDMONT DUE TO
CLOSER PROXIMITY TO BOTH UPPER AND SFC LOWS. EXPECTING ANY ACTIVITY
ACROSS THE ABOVE MENTIONED REGIONS DURING THE MID TO LATE MORNING
HOURS ON THURSDAY TO REMAIN SUBSEVERE AS LOW LEVEL INVERSION REMAINS
IN PLACE. LATER IN THE AFTERNOON AS SURFACE TEMPS INCREASE INTO THE
80S NEAR AND ALONG THE I85 CORRIDOR...AND SHEAR PROFILES IMPROVE
SOMEWHAT ALONG THE PASSING FRONTAL BOUNDARY...A SVR STORM OR TWO
CANNOT BE RULED OUT. CONDITIONS WILL IMPROVE ACROSS THE REGION LATE
ON THURSDAY AS DIURNAL HEATING IS LOST...AND DRIER AIR BEGINS TO
ADVECT IN BEHIND THE FRONT.
SLIGHT CHANCE POPS REMAIN IN THE FCST ACROSS THE HIGHER TERRAIN
DURING THE EARLY MORNING HOURS ON FRIDAY MORNING. BY DAYBREAK...ALL
PRECIPITATION SHOULD HAVE DISSIPATED AND SKIES WILL BEGIN TO CLEAR
AS HIGH PRESSURE BUILDS. UPPER LEVEL RIDGING ACROSS THE MIDWEST
WILL ADVECT TO THE EAST DURING THE DAY ON FRIDAY ALLOWING HEIGHTS TO
BUILD OVER NORTHEAST GEORGIA AND THE CAROLINAS...LEADING TO PLEASANT
WEATHER CONDITIONS FOR THE REMAINDER OF FRIDAY EVENING.
TEMPERATURES ON FRIDAY WILL BE ON AVERAGE ABOUT TEN DEGREES COOLER
THAN PREVIOUS DAYS AS NORTHWEST FLOW USHERS IN A COOLER/DRIER
AIRMASS.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 220 PM TUESDAY...THE SHORTWAVE TROUGH MOVES OFF THE EAST COAST
FRIDAY NIGHT AND DRIER COOLER AIR FILTERS IN FROM THE NORTHWEST.
DRIEST AIR VARIES PER MODEL FROM FRIDAY NIGHT THROUGH THE DAY
SATURDAY. AS THE UPPER RIDGE SLOWLY BUILDS FROM THE WEST AND WARM
FRONT CHANNELS SHOWERS CLOSER TO THE NC MTNS TO START THE NEW
WEEK...POPS WILL INCREASE AT LEAST INTO THE SLIGHT RANGE. BASED ON
THE BLEND OF THE MODELS...LOOKS LIKE THE BEST TIME FOR RAIN WILL BE
GOING INTO MID WEEK. SEEMS BEST ORGANIZED BANDS OF CONVECTION WOULD
BE LATE TUESDAY. CONSIDERED GOING TO LOW CHANCE POPS AT THAT
TIME...BUT THAT IS A WEEK AWAY AND MUCH COULD CHANGE. CAPES ON THE
GFS FOR TUES PM ARE 1100 TO 1400 AND WINDS GOING UP FROM SURFACE NOT
TOO BAD FOR THAT TIME. TEMPERATURES...HIGHS NEAR NORMAL OR SLIGHTLY
BELOW AND LOWS COOLER THAN NORMAL EARLY IN WEEKEND AND GOING ABOVE
INTO NEW WEEK.
&&
.AVIATION /05Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...A BLEND OF THE ADJMAV AND ADJMET SUPPORTS AN MVFR CIG
BRIEFLY AROUND DAWN...OTHERWISE A LOW VFR CIG WILL PERSIST UNTIL
THIS EVENING...WHEN GUIDANCE WOULD SUGGEST A MID LEVEL CIG. GUIDANCE
ONLY SUPPORTS LOW VFR VSBY AT DAYBREAK...WHICH SEEMS REASONABLE
BASED ON THE ABSENCE OF PRECIPITATION AT THE FIELD. VFR SHOULD
RETURN BY MID MORNING. ONCE AGAIN...MODEL SOUNDINGS SUPPORT ROBUST
CONVECTION... AND MODEL DATA SHOWS MOISTURE MOVING IN FROM THE
SOUTH. A MENTION OF THUNDERSTORMS WILL BE MADE IN THE TAF LATE THIS
AFTERNOON AND EARLY THIS EVENING. SOUTHERLY WINDS WILL APPROACH 10
KNOTS THIS AFTERNOON.
ELSEWHERE...GUIDANCE SUPPORTS MVFR CIGS AT FOOTHILL SITES TOWARD
DAWN...AND MVFR VSBY AT ALL SITES BUT KGSP AND KGMU...WHERE LOW VFR
VSBY IS SUPPORTED. IF KAVL CAN FOG UP TO IFR...A LOW CIG WOULD
PROBABLY FORM. VFR RETURNS BY MID MORNING. ANOTHER AFTERNOON OF
ROBUST CONVECTION IS EXPECTED AS AN UPPER TROUGH APPROACHES...WITH
THE BEST COVERAGE IN THE MOUNTAINS. CONVECTION MAY DIMINISH SOME IN
THE EVENING WITH THE LOSS OF HEATING...BUT NOT ENTIRELY...AS COLD
FRONT ARRIVES FROM THE WEST. SSW WINDS WILL APPROACH 10 KNOTS THIS
AFTERNOON.
OUTLOOK... CEILING AND VISIBILITY RESTRICTIONS IN SCATTERED SHOWERS
AND THUNDERSTORMS AGAIN THURSDAY AFTN/EVE. GENERALLY VFR WEATHER
FRIDAY AND SATURDAY.
CONFIDENCE TABLE...
05-11Z 11-17Z 17-23Z 23-05Z
KCLT HIGH 94% HIGH 94% HIGH 100% HIGH 100%
KGSP HIGH 94% HIGH 88% HIGH 100% HIGH 100%
KAVL HIGH 97% HIGH 97% HIGH 100% HIGH 91%
KHKY HIGH 91% HIGH 81% HIGH 100% HIGH 100%
KGMU HIGH 82% HIGH 95% HIGH 100% HIGH 100%
KAND HIGH 94% HIGH 86% HIGH 100% HIGH 97%
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...LEV
NEAR TERM...ARK/JAT/SBK
SHORT TERM...CDG
LONG TERM...DEO
AVIATION...ARK/JAT
