Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 271752
AFDGSP

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

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

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 145 PM...CONVECTION IS FIRING A LITTLE MORE READILY THAN
CURRENT FCST TRENDS...AS A MID LVL SHORTWAVE APPROACHES THE SOUTHERN
APPALACHAINS. CAPE IS STILL PRETTY LIMITED...WITH SPC MESO ANALYSIS
PAGE SHOWING GENERALLY 500-1000 J/KG OF SBCAPE. CAPE IS AT A MINIMUM
ACRS THE PIEDMONT...WHERE DEWPTS HAVE MIXED OUT TO THE MID 60S. THE
HRRR IS STILL PRETTY BULLISH ON CONVECTION THIS AFTN AND EVENING
ACRS THE ENTIRE AREA. I WILL TAKE ANOTHER LOOK AT GRIDS FOR NEXT
UPDATE...BUT HAVE LEFT POPS AS IS FOR NOW.

AS OF 1030 AM...EMBEDDED SHORTWAVES CAN BE SEEN ROUNDING THE
NORTHERN AND EASTERN PERIPHERY OF A LARGE UPPER LEVEL ANTICYCLONE
CENTERED OVER THE SOUTHERN PLAINS. MOST OF THIS ENERGY LOOKS TO
REMAIN NORTH OF THE AREA. AT THE SFC...CONDITIONS LOOK SIMILAR TO
YESTERDAY...WITH WEAK AXIS OF HIGH PRES STRETCHING ACRS THE
SOUTHEAST STATES. THE LATEST GUIDANCE GENERALLY AGREES ON DEWPTS
MIXING OUT ACRS THE PIEDMONT...INTO THE LWR-MID 60S. THIS COUPLED
WITH WARM MID LVL TEMPS SHUD LIMIT CAPE TO GENERALLY LESS THAN 1000
J/KG. IN THE MTNS...CAPE IS PROGGED TO BE A LITTLE HIGHER. DESPITE
THE WEAK BUOYANCY AND SHEAR...THE MAJORITY OF THE HIGH RES MODELS AS
WELL AS THE NAM AND RAP SHOW FAIRLY STOUT COVERAGE OF CONVECTION
THIS AFTN...ROLLING OFF THE BLUE RIDGE INTO THE PIEDMONT. THE GFS
KEEPS THE BULK OF THE CONVECTION IN THE HIGH TERRAIN AND ADJACENT
FOOTHILLS...LIKE THE LAST COUPLE DAYS. BASED ON THE CURRENT DEWPT
TRENDS AND THE 12Z GSO/FFC SOUNDINGS...I THINK THE GFS IS MORE
REALISTIC...AND THAT LINES UP WITH THE CURRENT FCST...WHICH IS CHC
POPS ACROSS THE HIGH ELEVATIONS AND THE I-40 CORRIDOR OF THE NC
FOOTHILLS AND PIEDMONT. THE REST OF THE FCST IS ON TRACK AS WELL.
HIGH TEMPERATURES ARE FORECAST TO PEAK AROUND 1 DEGREE COOLER THAN
YESTERDAY.

TONIGHT...THE VORT SHOULD SLIDE SE OF THE FA...AS H5 HEIGHTS REMAIN
ABOVE 590 DM. FORECAST SOUNDINGS INDICATE THAT CONDITIONS SHOULD
GRADUALLY STABILIZE AFTER SUNSET. I WILL INDICATE A SLOW DECREASE IN
POPS OVERNIGHT...REMAINING SCHC ACROSS THE NRN NC MTNS AND FOOTHILLS
THROUGH SUNRISE TUESDAY. LOW TEMPERATURES ARE FORECAST TO RANGE FROM
THE U60S WITHIN THE MTN VALLEYS TO LOW 70S EAST.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 245 AM EDT MONDAY...A BROAD UPPER RIDGE WILL BE IN PLACE
ACROSS THE CENTRAL AND EASTERN CONUS TUESDAY THROUGH WEDNESDAY.
WINDS WILL BE LIGHT UNDER THE RIDGE...BUT WITH WEAK LOW LEVEL
CONVERGENCE DEVELOPING EACH DAY ALONG THE ERN SLOPES OF THE SRN
APPALACHIANS. DESPITE THE RIDGING ALOFT...THE NAM GENERATES
CONSIDERABLE INSTABILITY BOTH TUE AND WED AFTERNOONS...ESPECIALLY
OVER THE MTNS...WHILE THE GFS PROFILES ARE MORE RESERVED. A BLENDED
APPROACH SUGGESTS SCATTERED CONVECTION FOCUSING PRIMARILY ON THE
MTNS WITH SOME LATE DAY BLEEDOVER INTO THE ADJACENT FOOTHILLS AND
POSSIBLY OUT ACROSS THE INTERSTATE 40 CORRIDOR. MAXES SHOULD BE
ABOUT A CATEGORY ABOVE CLIMO...WITH MILD MINS SOME TWO CATEGORIES
ABOVE CLIMO.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 245 AM EDT MONDAY...HEIGHTS WILL FALL THURSDAY THROUGH FRIDAY
AS THE UPPER RIDGE RETROGRADES TO THE DESERT SOUTHWEST. THIS WILL
PERMIT A COLD FRONT TO PUSH SOUTHEAST INTO THE APPALACHIANS THURSDAY
EVENING AND SETTLE ACROSS THE SOUTHERN HALF OF THE AREA THROUGH
FRIDAY. INSTABILITY MAY POOL ALONG AND AHEAD OF THE APPROACHING COLD
FRONT ON THURSDAY...WITH THE BEST CHANCE OF STRONG TO SEVERE
THUNDERSTORMS THURSDAY AFTERNOON AND EVENING. AFTER A NIGHTTIME LULL
IN CONVECTION...THE BEST COVERAGE ON FRIDAY SHOULD BE ALONG THE SRN
TIER CLOSER TO THE BOUNDARY.

TROUGHINESS WILL DEVELOP OVER THE EAST AS A DEEP VORTEX SETS UP OVER
ONTARIO AND QUEBEC THROUGH THE WEEKEND. AT LOW LEVELS...WEAK
SOUTHEAST RETURN FLOW MAY DEVELOP AS THE BOUNDARY LIKELY REMAINS
STALLED JUST SOUTH OF THE REGION. A FAIRLY SHARP POP GRADIENT WILL
BE NEEDED WITH MUCH BETTER VALUES ACROSS THE SRN TIER SATURDAY AND
SUNDAY. COOLER TEMPERATURES ARE EXPECTED...WITH HIGHS IN THE 80S
BOTH DAYS AND 70S IN THE HIGH MOUNTAIN VALLEYS.

&&

.AVIATION /18Z 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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH  93%     HIGH  92%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  94%
KAVL       HIGH 100%     HIGH 100%     HIGH  83%     HIGH  80%
KHKY       HIGH 100%     HIGH 100%     MED   79%     HIGH  91%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  98%
KAND       HIGH 100%     HIGH 100%     HIGH  97%     HIGH  94%

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...HG
NEAR TERM...ARK/NED
SHORT TERM...HG
LONG TERM...HG
AVIATION...ARK



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