Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 120642
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
242 AM EDT SAT JUL 12 2014

.SYNOPSIS...
WEAK HIGH PRESSURE IN CONTROL OF OUR WEATHER THIS WEEKEND. AN
UNSEASONABLY STRONG COLD FRONT IS THEN EXPECTED TO REACH THE WESTERN
CAROLINAS BY TUESDAY INCREASING THE POSSIBILITY OF WIDESPREAD
THUNDERSTORMS. EXPECT COOLER THAN NORMAL TEMPERATURES FOR MUCH OF
THE LAST HALF OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 3 AM EDT SATURDAY...A DEAMPLIFYING UPPER TROUGH WAS LOCATED ALONG
THE EAST COAST...WHILE A FLAT UPPER RIDGE WAS LOCATED OVER THE
PLAINS. A SLOW MOVING SHORTWAVE WAS MOVING SOUTH EAST THROUGH THE
BASE OF THE TROUGH OVER GA. THE UPPER TROUGH IS EXPECTED OT CONTINUE
TO WEAKEN AND PROGRESS OFFSHORE TODAY...WHILE THE UPPER RIDGE
EXTENDS EAST OVER THE SOUTHERN APPALACHIANS. THE RIDGE WEAKENS
TONIGHT...AS TROUGH AMPLIFIES SOUTH OF A STRONG CLOSED UPPER LOW
OVER CENTRAL CANADA.

A STATIONARY FRONT WILL PERSIST IN OUR VICINITY TODAY AND TONIGHT.
MODEL TIME HEIGHTS SHOW A PERSISTENT MOIST LAYER FROM 850 TO 750
MB...WITH VERY LITTLE MOISTURE ABOVE. CONVECTIVE ACTIVITY ALONG THE
NORTHERN BLUE RIDGE IS EXPECTED TO WANE TOWARD DAWN. GUIDANCE
SUPPORTS FOG ACROSS MUCH OF THE AREA THIS MORNING...BUT DENSE FOG
ONLY IN MOUNTAIN VALLEYS. MODEL SOUNDINGS SHOW A WARM NOSE AT AROUND
650 MB THAT PROVIDES A WEAK CAP TO LIFT THIS AFTERNOON...LIMITING
CONVECTIVE CHANCES. THE GREATEST CHANCE FOR CONVECTION WILL BE IN
THE MOUNTAINS...WHERE OROGRAPHIC EFFECTS WILL ENHANCE LIFT.
TEMPERATURES WILL BE NEAR NORMAL TODAY AND TONIGHT.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 235 AM SAT...MODELS STILL INDICATE LIGHT LOW LEVEL WIND
DIRECTIONAL CONVERGENCE FOCUSING ON THE MTNS SUNDAY WHICH SHOULD
HELP IN THE GENERATION OF CONVECTION IN THAT AREA. VERY LITTLE
CONVECTION EXPECTED OUTSIDE OF THE MTNS SUNDAY. INSTABILITY HAS 750
TO 1000 CAPE ALONG THE I-85 CORRIDOR SUNDAY ON THE GFS AND 1200 TO
1400 CAPE OVER MTNS AT 00Z MONDAY. AS THE BOWLING BALL 500MB CLOSED
LOW MOVES SE FROM NRN MINNESOTA SUNDAY NIGHT TO LAKE MICHIGAN MONDAY
NIGHT...THE UPPER TROUGH WILL BE ACCOMPANIED BY THE ADVANCING
SURFACE COLD FRONT CROSSING THE OHIO VALLEY AND TN VALLEY.
PREFRONTAL CONVECTION IS MOST NOTICEABLE ON THE SREF MODEL FOR LATE
MONDAY. GFS HAS POCKETS OF GREATER THAN 2500 CAPE OVER THE NC
PIEDMONT AND JUST WEST OF OUR NC AND GA MTNS AT 00Z TUES. 925MB FLOW
LATE MONDAY MAINLY SW AT 10 TO 20KTS AND 700MB FLOW MAINLY WEST AT
15 TO 25KTS. CERTAINLY SOME CONCERN FOR STRONG CONVECTION WITH THE
GREATER INSTABILITY. TEMPS WILL BE A DEGREE OR TWO ABOVE CLIMO
NORMALS SUNDAY AND MONDAY.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 150 AM SAT...ALL MODELS ARE IN AGREEMENT ON A DISTINCT UPPER
LEVEL PATTERN CHANGE THAT IS FORECAST TO OCCUR IN THE EARLY TO MID
WEEK PERIOD ACROSS THE EASTERN PART OF THE NATION. A DEEP UPPER LOW
IS STILL FORECAST TO SWING SOUTH OUT OF NORTHERN CANADA AND
ESTABLISH AN ANOMALOUS UPPER TROUGH OVER THE EAST BY MIDWEEK. ALL
MODELS HAVE THE CLOSED 500MB LOW ROUGHLY OVER THE NE GREAT LAKES AT
12Z TUESDAY...THEN MOVE IT OVER QUEBEC BY WED NIGHT AND THURSDAY.
THE BROAD UPPER TROUGH CREATED OVER THE EASTERN PART OF THE NATION
ON TUES AND WED WILL GRADUALLY DEAMPLIFY THURS AND FRI AS THE LOW
REACHES FAR EASTERN CANADA.  MODELS HAVE THE FRONT ON AVERAGE MOVING
THROUGH OUR REGION A BIT FASTER THAN PREVIOUS RUNS.
HOWEVER...NATIONAL GUIDANCE NOW HAS THE FRONT STALLING OUT JUST
SOUTH OF OUR AREA BY LATE WED AND GRADUALLY DISSIPATING IT THROUGH
THE END OF THE WEEK. INSTABILITY TUES PM WILL LIKELY BE MOST
IMPRESSIVE ALONG AND SOUTH OF I-85 WHERE CAPES SHOULD BE AROUND
2000. LOW LEVEL 925MB WIND SHOULD BE LIGHT AND VARIABLE TUES WHILE
700MB WIND WILL BE FROM THE WEST 15 TO 20KTS. THIS 700MB WIND IS
LESS THAN THE 25 TO 30KT WIND FORECAST IN PREVIOUS RUNS. AS THE
FRONT MOVES SOUTH OVER GA THEN STALLS...WE SHOULD HAVE LOW COVERAGE
OF CONVECTION ON WED MAINLY OVER THE PIEDMONT. EXPECT MORE
CONVECTION THURS AND FRI AS WAVES MOVE EAST ALONG FRONT AND FRONT
MAY WOBBLE NORTH AHEAD OF THE PASSAGE OF THESE WAVES. EXPECT LIGHT
AND VARIABLE SURFACE WIND IN THE LAST HALF OF THE WEEK WITH NO
PRESSURE GRADIENT INDUCED WIND FIELDS.

TEMPS ARE CURRENTLY FORECAST TO BE 5 TO 8 DEGREES BELOW NORMAL AFTER
THE FRONT PASSES FROM WED THROUGH END OF WEEK. CONSRAW GUIDANCE
CONTINUES TO BE THE COLDEST OF THE VARIOUS MODEL DATA AND HAS HIGHS
ON THURS IN THE 70S FROM MTN VALLEYS TO I-85 CORRIDOR.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...MODEL GUIDANCE IS SUPPORTIVE OF AN MVFR FOG RESTRICTION
BEFORE DAWN. ALTHOUGH MODEL TIME HEIGHTS SHOW VERY LOW LEVEL
MOISTURE...CONFIDENCE ON SUFFICIENT CLOUD COVER FOR A CIG IS
LOW....SO ONLY SCATTERED LOW CLOUDS WILL BE CARRIED AT DAWN. VFR
RETURNS BY MID MORNING...WITH LIGHT SE WINDS PERSISTING. WINDS VEER
SOUTH THIS EVENING. CONVECTIVE CHANCES ARE QUITE LOW TODAY AS A MID
LEVEL WARM NOSE IS EXPECTED TO LIMIT LIFT.

ELSEWHERE...GUIDANCE SUPPORTS MVFR VSBY IN FOG BY DAYBREAK AT SC
SITES...IFR AT KHKY...AND LIFR TO VLIFR IN MOUNTAIN VALLEYS...
INCLUDING KAVL. CIG RESTRICITONS APPEAR MOST LIKELY IN MOUNTAIN
VALLEYS...WHERE IFR WILL BE CARRIED. CONFIDENCE IS LIMITED FOR LOW
CLOUDS IN THE FOOTHILLS...GIVEN CURRENT OBSERVATIONS. WITH GUIDANCE
SHOWING MOIST LOW LEVELS...SCATTERED LOW CLOUDS WILL BE CARRIED AT
DAYBREAK AT KGSP AND KGMU...WITH MVFR AT KAND WHERE A CIG EXISTS
ALREADY. CONVECTIVE CHANCES WILL BE BEST IN THE MOUNTAINS...BUT TOO
LOW TO MENTION AT KAVL.

OUTLOOK...HIGH PRESSURE WILL SLOWLY SETTLE OVER THE AREA THIS
WEEKEND. ANY RESTRICTIONS SHOULD MAINLY BE CONFINED TO DIURNAL TSTMS
AND MORNING VALLEY FOG EACH DAY.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       MED   74%     HIGH  90%     HIGH 100%     HIGH 100%
KGSP       MED   74%     HIGH  94%     HIGH 100%     HIGH 100%
KAVL       LOW   49%     LOW   50%     HIGH 100%     HIGH 100%
KHKY       MED   72%     HIGH  89%     HIGH 100%     HIGH 100%
KGMU       MED   66%     HIGH  88%     HIGH 100%     HIGH 100%
KAND       MED   74%     HIGH  92%     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...DEO
NEAR TERM...JAT
SHORT TERM...DEO
LONG TERM...DEO
AVIATION...JAT






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