Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 212346
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
746 PM EDT TUE OCT 21 2014

.SYNOPSIS...
NORTHWEST FLOW WILL KEEPS CLOUDS AND ISOLATED SHOWERS ACROSS THE
NORTH CAROLINA MOUNTAINS TONIGHT...WITH DRY CONDITIONS ELSEHWERE.
HIGH PRESSURE RETURNS FOR THE REST OF THE WEEK AND CONTINUES INTO
THE THE WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 745 PM...NO MAJOR CHANGES TO THE FCST WITH THIS UPDATE. I
TWEAKED WINDS/SKY FOR THE 00Z TAFS. I LEFT THE SLGT CHC POP ALONG
THE TN BORDER FOR TONIGHT...BUT SO FAR...THERE IS LITTLE SEEN ON
RADAR UPSTREAM. TEMPS/DWPTS ARE ON TRACK.

AS OF 240 PM EDT TUESDAY...HIGH AMPLITUDE UPPER TROF CONTINUES TO
SWING THROUGH THE EAST/CENTRAL GREAT LAKES REGION.  MEANWHILE AT THE
SURFACE...A WEAK CYCLONE SLIDING SOUTHEAST INTO THE MIDATLANTIC
PUSHES A COLD FRONT SOUTHWARD ACROSS WESTERN NC AND INTO PORTIONS OF
NORTHEAST GA AND THE WESTERN UPSTATE.  HIGH PRESSURE BUILDING TO THE
WEST WILL CONTINUE PUSHING EAST EFFECTIVELY INCREASING PRESSURE
GRADIENT FORCES ACROSS THE ENTIRE FORECAST AREA THIS AFTERNOON. THIS
COMBINED WITH A DEEPENING MIXED LAYER WILL YIELD GUSTY CONDITIONS
THROUGH THE REMAINDER OF THE AFTERNOON BEFORE SUBSIDING AFTER
SUNSET.  THAT SAID...CHANNELING EFFECTS AND CONTINUED MODERATE NW
FLOW ALOFT WILL YIELD PERSISTENT GUSTS THROUGH THE THE OVERNIGHT
ACROSS THE WESTERN NC MOUNTAINS.  AS FOR PRECIP CHANCES...CARRIED
EARLIER FORECAST ISOLATED POPS ACROSS THE NORTHERN MOUNTAINS THIS
EVENING/OVERNIGHT DUE TO WEAK UPSLOPE FLOW POTENTIAL.  MOISTURE WILL
LIKELY REMAIN TRAPPED BENEATH A DEVELOPING INVERSION OVERNIGHT
ALLOWING FOR MOUNTAIN VALLEY STRATUS FORMATION.  CONDITIONS WILL
IMPROVE ON WEDNESDAY AS THE PRESSURE GRADIENT SLOWLY RELAXES AND
UPPER TROF EJECTS TO THE EAST.  ABOVE MENTIONED HIGH PRESSURE WILL
CONTINUE ADVECTING OVERHEAD WITH UPPER HEIGHTS ALSO RISING LEADING
TO A DRY FORECAST.  DESPITE THE FROPA AND WEAK COLD ADVECTION
PATTERN...NOT EXPECTING TEMPERATURES TO COOL SUBSTANTIALLY.  HOWEVER
FORECAST DOES FEATURE BOTH MAX/MIN TEMPERATURES THROUGH THE PERIOD A
FEW DEGREES BELOW NORMAL.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 205 PM EDT TUESDAY...THE DEEP UPPER LOW ALONG THE MID-ATLANTIC
COAST WILL MOVE NORTHEAST ALLOWING SHORT WAVE RIDGING TO DEVELOP OVER
THE SE STATES ON THU. A SHORT WAVE OVER THE NORTHERN PLAINS IS
FORECAST TO DIVE QUICKLY SE AND MOVE INTO THE MID-ATLANTIC STATES
LATE FRIDAY. THE 12Z GFS HAS TRENDED FASTER...FARTHER NORTH AND LESS
AMPLIFIED WITH THE UPPER WAVE FOR FRIDAY AS OPPOSED TO THE 00Z EC
AND NOW THE 12Z CMC WHICH ARE SLOWER AND CLOSE OFF AN UPPER LOW OVER
THE OHIO VALLEY. THE ONLY ISSUE WITH THIS SYSTEM IS WHETHER THE
UPPER FORCING AND NW UPSLOPE FLOW WILL BE ENOUGH TO SQEEZE OUT ANY
LIGHT SHOWERS OVER THE NORTHERN MOUNTAINS FRIDAY AFTERNOON. THE 12Z
GFS/NAM SUPPORT MAINTAINING A DRY FORECAST FOR THE MOUNTAINS ON
FRIDAY WITH PERHAPS JUST SOME MID-HIGH LEVEL CLOUDINESS. HENCE...
WILL KEEP MENTIONALB EPOPS OUT OF THE FORECAST.

BACKING UP IN TIME...WITH THE DEAMPLIFYING FLOW AND RISING HEIGHTS
OVER THE REGION ON THURSDAY...TEMPS SHOULD REBOUND BUT STILL REMAIN
SHY OF CLIMO. WED NIGHT WILL BE A CHILLY WITH MID 30S COMMON OVER
THE MOUNTAINS AND EVEN SOME POCKETS OF UPPER 30S POSSIBLE IN
PIEDMONT. POCKETS OF FREEZING TEMPS ARE LIKELY IN THE LITTLE TN
VALLEY WHERE THE FROST/FREEZE PROGRAM HAS ENDED. WINDS ESPECIALLY IN
THE CENTRAL/NORTHERN MOUNTAINS LOOK TO STAY HIGH ENOUGH TO PRECLUDE
WIDESPREAD FROST FORMATION AND FREEZING TEMPS. MAX TEMPS ON FRIDAY
ARE FORECAST TO WARM A COUPLE MORE DEGREES IN THE DOWNSLOPE FLOW.
DEEP LAYERED DRY AIR SHOULD ALLOW FOR GENERALLY CLEAR CONDITIONS WED
NIGHT THROUGH THU NIGHT...WITH SOME JUST PATCHY HIGH CLOUDS ON
FRIDAY AHEAD THE UPPER WAVE.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 205 PM TUESDAY...GUIDANCE IN GENERAL AGREEMENT FOR THE MEDIUM
RANGE. AN UPPER TROF CROSSES THE AREA FRI NITE LEAVING NW FLOW OVER
THE AREA THRU SUN. UPPER RIDGE BUILDS INTO THE AREA MON...THEN RIDGE
AXIS SLIDES EAST ON TUE...WITH NEXT POTENTIAL WX SYSTEM REMAINING
WEST OF THE AREA UNTIL AFTER THIS PERIOD. CANNOT RULE OUT SOME SHRA
ACROSS THE MTNS SAT NITE AS THE TROF MOVES THRU...BUT GUIDANCE BLEND
KEEPS FCST DRY. A DRY COLD FRONT BRUSHES THE AREA SAT NITE...THEN
HIGH PRESSURE BUILDS IN SUN AND SLOWLY SLIDES EAST MON AND TUE. NEAR
NORMAL TEMPS ON SAT RISE A LITTLE ABOVE NORMAL THRU THE PERIOD...
WHILE LOWS START OUT A LITTLE BELOW NORMAL AND RISE TO A LITTLE
ABOVE NORMAL THRU THE PERIOD.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...VFR CONDITIONS EXPECTED THRU THE PERIOD. VFR LVL STRATOCU
SHUD GENERALLY DISSIPATE ACRS THE PIEDMONT WITH LOSS OF HEATING AND
INCREASING LLVL CAA. THE CAA MAY HELP KEEP A SMALL CHC OF A FEW
GUSTS THIS EVENING. GUIDANCE SEEMS OVERDONE...AND EVEN A TEMPO SEEMS
UNWARRANTED...SO NO MENTION OF GUSTS THIS EVENING. ON
WEDNESDAY...LOW PRES WILL CONTINUE TO SLIDE FURTHER EAST ACRS THE
MID ATLANTIC...ALLOWING LLVL FLOW TO VEER MORE NLY WITH CONTINUED
CAA. SO EXPECT LOW-END GUSTS OF 15-20 KTS WITH A N/NW WIND WED AFTN.
THERE LOOKS TO BE LESS MOISTURE TO ALLOW FOR ANY CU DEVELOPMENT.

ELSEWHERE...A N OR NW WIND EXPECTED THRU THE PERIOD AT ALL SITES
WITH GENERALLY CLEAR SKIES. THE EXCEPTION WILL BE KAVL WHERE A LARGE
AREA OF STRATOCU WILL CONTINUE TO BANK UP AGAINST THE NC MTNS AND
WILL OCCASIONALLY WORK UP THE FRENCH BROAD VALLEY INTO WEDNESDAY
MORNING. GUIDANCE IS MIXED ON HOW MUCH CLOUD COVER AND AT WHAT
HEIGHT. I THINK IT WILL BE GENERALLY 3000-4000 FT...BUT MAY BE
LOWER. ALSO...WINDS WILL PERIODICALLY BE GUSTY AT KAVL...WITH BEST
POTENTIAL DURING THE DAY ON WEDNESDAY. SOME GUSTS WILL BE POSSIBLE
AT KHKY WHICH IS CLOSER TO THE LOW PRES TO THE NE.

OUTLOOK...QUIET WEATHER WILL CONTINUE ACRS THE REGION...AS DEEP
LAYER RIDGING SETTLES IN THRU THIS WEEKEND.

CONFIDENCE TABLE...

            23-05Z        05-11Z        11-17Z        17-23Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  87%     MED   77%     HIGH 100%
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...RWH
NEAR TERM...ARK/CDG
SHORT TERM...LG
LONG TERM...RWH
AVIATION...ARK






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