Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 300556
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
156 AM EDT TUE SEP 30 2014

.SYNOPSIS...
RAINFALL WILL TAPER OFF LATER TONIGHT AND EARLY TOMORROW. DRIER HIGH
PRESSURE WILL THEN BUILD BACK OVER THE REGION ON TUESDAY AND LINGER
THROUGH THURSDAY. A COLD FRONT WILL ARRIVE FROM THE NORTHWEST ON
FRIDAY WITH A COOL AND DRY AIR MASS MOVING BACK INTO THE REGION OVER
THE WEEKEND.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 1 AM...THINK IT BEST TO HOIST THE DENSE FOG ADVISORY ACROSS
THE AREA FROM THE FRENCH BROAD VALLEY...ACROSS THE NC FOOTHILLS...TO
THE NW PIEDMONT. VISIBILITY HAS BEEN VARIABLE AT SEVERAL OF THE OBS
SITES BUT KEEPS COMING BACK TO 1/2 MILE OR LESS. THE VARIABILITY
WILL PROBABLY NOT END THROUGH DAYBREAK...BUT THAT MIGHT JUST MAKE IT
WORSE AS DRIVERS ENCOUNTER FOG BANKS THAT SHARPLY REDUCE VISIBILITY
TO NEAR ZERO. WILL KEEP ON EYE TOWARD EXPANSION THROUGH THE PRE-DAWN
HOURS...IN PARTICULAR DOWN INTO THE CHARLOTTE METRO AREA...WHICH THE
NAM GUIDANCE SUGGESTS MIGHT HAPPEN. TEMPS LOOK OK. ALL PRECIP HAS
ENDED.

REMAINDER OF PREVIOUS DISCUSSION...
AS OF 1025 PM...PRECIP HAS MOVED EAST OF THE AREA AND SKIES ARE
SLOWLY CLEARING. THIS IS ALLOWING FOG AND LOW CLOUDS TO FORM. ALMOST
A CERTAINTY NOW THAT AREAS OF DENSE MTN VALLEY FOG WILL FORM
OVERNIGHT. HOWEVER...EVEN WITH THE FOG DEVELOPING OUTSIDE OF THE
MTNS...IT IS STILL UNCLEAR WHETHER DENSE FOG OR LOW CLOUDS WILL WIN
OUT. EVEN IF THE LOW CLOUDS ARE PREDOMINANT...THERE WILL LIKELY BE
PATCHY DENSE FOG IN THE NORMALLY MORE FOGGY AREAS...ESPECIALLY NEAR
BODIES OF WATER. WILL UPDATE THE HWO FOR NOW AND LET THE NEXT SHIFT
ISSUE A DENSE FOG ADV IF IT BECOMES MORE THAN PATCHY.

AN UPPER TROUGH AXIS WILL MOVE OFF THE COAST BY LATE TUESDAY.
MEANWHILE...AND UPPER RIDGE WILL PROGRESS FROM THE PLAINS TO THE MS
RIVER VALLEY. ON TUESDAY...WITH ONLY LIGHT WINDS EXPECTED TO COME UP
FORM THE NE...MORNING FOG MAY TAKE SOME TIME TO BURN OFF. WINDS WILL
GRADUALLY VEER FROM TO THE SE DURING THE DAY...REMAINING LIGHT. WITH
MORE SUNSHINE AND RISING HEIGHTS ALOFT...HIGH TEMPERATURES ARE
EXPECTED TO RUN SEVERAL DEGREES ABOVE NORMAL. PRECIPITATION IS NOT
EXPECTED ON TUESDAY DUE TO THE DRIER AIR MASS...AND A WARM NOSE
ALOFT BETWEEN 600 AND 400 MB.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
AS OF 215 PM MONDAY...AN UPPER RIDGE IS FORECAST TO BUILD ACROSS THE
EASTERN U.S. DURING THE MIDWEEK TIMEFRAME IN RESPONSE TO A
SIGNIFICANT UPPER TROUGH DIGGING SOUTH THROUGH THE ROCKIES. SURFACE
HIGH PRESSURE INTIALLY OVER THE WESTERN GREAT LAKES IS FORECAST TO
RIDGE SOUTHWARD OVER THE REGION. THIS WILL PROVIDE A WARM AND
GENERALLY DRY STRETCH OF WEATHER THROUGH THURSDAY. THE EXCEPTION MAY
BE OVER PORTIONS OF THE MOUNTAINS WHERE UPSLOPE FLOW MAY TRIGGER
SOME ISOLATED SHOWERS EACH AFTERNOON. TEMPERATURES WILL BE ABOVE
CLIMO THROUGH THU.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 210 PM MONDAY AFTERNOON...THE MEDIUM RANGE FCST PICKS UP AT 00Z
ON FRIDAY WITH WEAK UPPER RIDGING IN PLACE OVER THE SE REGION AND A
FAIRLY POTENT LOOKING SOUTHERN STREAM UPPER SHORTWAVE DIGGING DOWN
OVER THE SOUTHERN PLAINS. OVER THE NEXT 24HRS...THE SHORT IS
EXPECTED TO MOVE ACROSS THE FCST AREA AND SIMULTANEOUSLY BECOME
ABSORBED BACK INTO THE NORTHERN STREAM UPPER TROF. BEYOND THIS
POINT...THE LONG RANGE MODELS STILL DIFFER WRT THE EVOLUTION OF THE
MAIN UPPER TROF. THE ECMWF REAMPLIFIES THE TROF MULTIPLE TIMES FROM
SAT THRU EARLY NEXT WEEK AND KEEPS THE TROF AXIS ORIENTED TO OUR
NORTH. ON THE OTHER HAND...THE LATEST RUN OF THE GFS MAINTAINS A
MUCH BROADER LONGWAVE TROF OVER THE EASTERN CONUS THRU NEW DAY 7.

AT THE SFC...WARM SLY LOW LVL FLOW WILL BE IN PLACE AT THE START OF
THE PERIOD EARLY FRI. OVER THE NEXT 12 TO 24 HRS...A ROBUST COLD
FRONT WILL MOVE OVER THE CAROLINAS AND SHOULD MOVE OFF THE CAROLINA
COAST BY SAT MORNING. IT ITS WAKE...COOL AND DRY HIGH PRESSURE WILL
SPREAD OVER THE CWFA AND REMAIN THRU THE WEEKEND. THE MODELS ARE
SUGGESTING THAT ANOTHER LOW WILL DEVELOP OVER THE GREAT LAKES EARLY
NEXT WEEK AND MOVE A SECOND COLD FRONT OVER OUR AREA. AT THIS POINT
HOWEVER...THE TIMING BETWEEN MODELS IS INCONSISTENT AND THEY SUGGEST
THAT THE FROPA WILL BE ESSENTIALLY DRY. AS FOR THE SENSIBLE FCST...I
STEADILY RAMP POPS UP FORM WEST TO EAST ON FRI WITH THE HIGHEST
VALUES BETWEEN ROUGHLY 12Z AND 18Z. BY 12Z SAT...POPS DROP BACK
BELOW 20% FOR MOST OF THE CWFA. THE REST OF THE MEDIUM RANGE SHOULD
BE DRY. TEMPS WILL COOL AFTER THE FROPA WITH HIGHS IN THE LOW 70S
OVER THE WEEKEND FOR THE LOWER ELEVATIONS AND LOWS IN THE LOWER TO
MID 50S.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AT KCLT...VFR FOR THE TIME BEING...BUT CONDITIONS ARE RIGHT FOR THE
FORMATION OF FOG IF THE HIGH BASED STRATOCU CEILING MOVES OFF TO THE
EAST...WHICH SHOULD HAPPEN IN THE PRE-DAWN HOURS. DENSE FOG HAS
ALREADY DEVELOPED ACROSS THE NW PIEDMONT TO SRN FOOTHILLS AND EXPECT
THE FOG AREA TO EXPAND S INTO METRO CLT THROUGH SUNRISE. WILL GO
MORE PESSIMISTIC THAN LAMP GUIDANCE AND INCLUDE A TEMPO FOR MVFR
VISIBILITY THROUGH 09Z...THEN PREVAILING MVFR WITH A TEMPO IFR FROM
09Z TO 13Z AS THE FOG EXPANDS. THIS COULD VERY EASILY GO TO LIFR OR
VLIFR IN THE 09Z TO 13Z TIME FRAME. THE FOG SHOULD LIFT AND
DISSIPATE BY 13Z OR SO...LEAVING BEHIND VFR CONDITIONS WITH ONLY A
FEW STRATOCU AND A LIGHT N WIND THROUGH THE REST OF THE PERIOD.

ELSEWHERE...WILL BE WATCHING FOR DENSE FOG DEVELOPMENT. THIS WAS
ALREADY MOST PREVALENT IN THE MTN VALLEYS WHERE CONDITIONS WILL BE
VARIABLE BETWEEN MVFR AND VLIFR THROUGH DAYBREAK. THE IFR HAD
ALREADY SURROUNDED KHKY AT ISSUANCE TIME AND SHOULD CLOSE IN BY 09Z.
THE OTHER TAF SITES GET A LONG TEMPO PERIOD FOR IFR VISIBILITY IN
FOG THROUGH DAYBREAK AT LEAST. THE FOG SHOULD LIFT AND DISSIPATE BY
MID MORNING AT THE VERY LATEST. AFTER THAT...VFR WITH LIGHT N WIND.
EXPECT MORE FOG TO START DEVELOPING IN THE MTN VALLEYS BY LATE
TUESDAY EVENING.

OUTLOOK...VFR CONDITIONS WILL PREVAIL WED THROUGH FRIDAY MORNING...
WITH FOG/VSBY CONCERNS REMAINING ACROSS THE MTNS AND FOOTHILLS EARLY
EACH MORNING. A FRONT WILL APPROACH ON FRIDAY WHICH COULD TRIGGER
SOME SHOWERS AND THUNDERSTORMS...WITH ASSOCIATED RESTRICTIONS
POSSIBLE.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH  94%     HIGH  92%     HIGH 100%     HIGH 100%
KGSP       MED   76%     HIGH  97%     HIGH 100%     HIGH 100%
KAVL       MED   71%     MED   74%     HIGH 100%     HIGH  91%
KHKY       MED   66%     HIGH  92%     HIGH 100%     HIGH  87%
KGMU       MED   78%     HIGH  86%     HIGH 100%     HIGH 100%
KAND       HIGH  80%     HIGH  89%     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...DENSE FOG ADVISORY UNTIL 9 AM EDT THIS MORNING FOR NCZ035>037-
     053-056-057-065-068-069-501>510.
SC...NONE.

&&

$$
SYNOPSIS...JPT
NEAR TERM...JAT/PM/RWH
SHORT TERM...LG
LONG TERM...JPT
AVIATION...PM





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