Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 270957
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
557 AM 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 545 AM...THE FORECAST REMAINS ON TRACK. I WILL UPDATE THE SKY
AND TEMP/DWPT TO MATCH OBSERVATIONS.

AS OF 3 AM...A STRONG MID LEVEL RIDGE WILL REMAIN CENTERED OVER THE
SOUTHERN PLAINS AS A LONG WAVE TROUGH BEGINS TO AMPLIFY ACROSS THE
MID ATLANTIC STATES. A WEST TO EAST RIDGE AXIS IS FORECAST TO REMAIN
ACROSS THE I-20 CORRIDOR...REACHING AS FAR EAST AS GA. THE WEAK
RIDGING WILL RESULT IN A SUBSIDENCE INVERSION AT H5...WITH SHALLOW
LAPSE RATE ALOFT. IN ADDITION...MIXING DEWPOINTS ARE FORECAST TO
FALL INTO THE LOW TO MID 60S THIS AFTERNOON. THE COMBINATION OF THE
POOR LAPSE RATES AND RELATIVELY LOW DEWPOINTS SHOULD RESULT IN WEAK
INSTABILITY ACROSS THE CWA THIS AFTERNOON AND EVENING. HOWEVER...WV
LOOP AND NEAR TERM MODELS INDICATE THAT A VORT MAX WILL LIKELY PASS
ACROSS WESTERN VA LATE THIS AFTERNOON AND EVENING. FORCING
ASSOCIATED WITH THE MID LEVEL DISTURBANCE SHOULD YIELD A CLUSTER OF
SE MOVING TSRA. I WILL FORECAST CHC POPS ACROSS THE HIGH ELEVATIONS
AND THE I-40 CORRIDOR OF THE NC FOOTHILLS AND PIEDMONT. HIGH
TEMPERATURES ARE FORECAST TO PEAK AROUND 1 DEGREE COOLER THAN SUNDAY.

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 /10Z MONDAY THROUGH FRIDAY/...
AT KCLT...VFR CONDITIONS EXPECTED THROUGH THE 6Z TAF PERIOD. RECENT
OBSERVATIONS INDICATES THAT KCLT AREA HAD A 8 TO 9 DEWPOINT
DEPRESSION. LATEST MOS AND FORECAST SOUNDINGS INDICATE THAT
DEPRESSIONS MAY CLOSE TO 3 TO 4 DEGREES BY SUNRISE...TOO WIDE TO
MENTION FOG. LIGHT SOUTH WINDS SHOULD DEVELOP WITH MIXING THIS
MORNING...THEN STRENGTHENING TO 6 KTS DURING THE HEAT OF THE
AFTERNOON. INSTABILITY APPEARS LIMITED TO LESS THAN 500 J/KG THIS
AFTERNOON. HOWEVER...CAMS INDICATE THAT A TSRA CLUSTER MAY DEVELOP
NEAR KGSO LATE THIS AFTERNOON...THEN SLIDE SE THROUGH EARLY THIS
EVENING. COVERAGE OF ANY CONVECTION SHOULD REMAIN EAST OF KCLT...SO
NO MENTION WILL BE INCLUDED IN THE TAF.

ELSEWHERE...WIDE DEWPOINT DEPRESSION ACROSS THE WESTERN CAROLINAS
WILL LIMIT FOG DEVELOPMENT THIS MORNING. LATEST OBS AND MOS SHOW THE
CLOSEST DEPRESSIONS WITHIN THE MTN VALLEYS. I WILL INCLUDE A TEMPO
FROM 10Z TO 12Z AT KAVL FOR MVFR FOG...ELSEWHERE NO RESTRICTIONS
EXPECTED. MIXING TO 5 TO 6KFT THIS AFTERNOON SHOULD RESULT IN
DEWPOINTS FALLING IN THE LOW TO MID 60S. INSTABILITY ACROSS THE
REGION SHOULD REMAIN WEAK...WITH THE GREATEST VALUES OVER THE MTNS.
I WILL GIVE KAVL A MID TO LATE AFTERNOON PROB30...ELSEWHERE
TERMINALS APPEAR DRY. WINDS SHOULD FAVOR A LIGHT SOUTH WIND DURING
THE DAYLIGHT HOURS...KAVL NNW.

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...

            10-16Z        16-22Z        22-04Z        04-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     MED   75%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     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...HG
NEAR TERM...NED
SHORT TERM...HG
LONG TERM...HG
AVIATION...NED


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