Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 211750
AFDGSP

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

.SYNOPSIS...
A WEAK COLD FRONT WILL CROSS THE REGION FROM THE NORTHWEST TODAY
FOLLOWED BY DRY NORTHWEST FLOW ON WEDNESDAY. DRY HIGH PRESSURE WILL
THEN RETURN ON THURSDAY AND LINGER INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 140 PM EDT TUESDAY...WEAK/DRY COLD FRONT CONTINUES TO SLIDE
THROUGH THE REGION AT THIS TIME AS EVIDENT BY DEVELOPING CU FIELD
ALONG THE BOUNDARY ACROSS THE NC PIEDMONT...SOUTHWARD INTO THE SC
UPSTATE.  NORTHWESTERLY VEERING WINDS CONTINUE TO INCREASE WITH
15-20KT GUSTS DEVELOPING REGIONWIDE AMONGST DEEPENING MIXED LAYER
AND INCREASED PRESSURE GRADIENT FORCES. NO SIGNIFICANT CHANGES MADE
TO THE EXTREME NEAR TERM PORTION OF THE FORECAST.  FULL FORECAST
DISCUSSION TO FOLLOW WITHIN THE HOUR.

PREVIOUS DISCUSSION...

AS OF 245 AM...AN UPPER LEVEL TROF REMAINS PROGRESSIVE THROUGH THE
PERIOD...BRINGING A CLIPPER LOW ACROSS THE MID ATL THROUGH THE DAY.
PREFRONTAL MOISTURE WILL BE GLAKES ENHANCED BRINGING INCREASING
CLOUD COVER TO THE NC MTN SPINE AND NRN MTN COUNTIES THIS
AFTERNOON/EVENING. ALONG WITH GOOD MECH LIFT...THERE WILL BE THE
PRESENCE OF ULVL DIV ACROSS THE MTNS AIDING IN STRATIFORM PRECIP
GENERATION. THUS HAVE BUMPED POPS UP TO THE CHANCE RANGE CENTERING
ON 18Z FOR A FEW HRS. WITH THE PROGRESSIVE NATURE OF THE PARENT
LOW...HAVE ALLOWED POPS TO DROP TO ISOL LATE AFTERNOON AND EVENING
AS UPSTREAM MOISTURE BECOMES SHALLOW AND LESS AVAILABLE. MIXING TO
H8 WILL PRODUCE LOW END TO MODERATE WIND GUSTS THIS AFTERNOON ACROSS
THE MTNS AND FTHILLS. MAX TEMPS WILL BE RIGHT AROUND NORMAL OVER THE
MTN VALLEYS AND A FEW DEGREES ABOVE NORMAL NON/MTNS IN DOWNSLOPE
ENHANCED WARMING.

THERE WILL BE AN INCREASING PGRAD WITH THE CLIPPER TROF LATE
AFTERNOON ACROSS THE MTNS DEVELOPING EAST THROUGH THE CWFA
OVERNIGHT. BUFKIT TIME HEIGHTS SHOW REINFORCING SIGMA CAA BEGINNING
ARND 02Z WITH GUSTS REACHING 30 KTS OR SO OVER THE MTN VALLEYS...AND
LIKELY 40-45 KT GUSTS ACROSS THE HIGHER ELEVATIONS. EXPECT THESE
WINDS TO CONTINUE THROUGH THE OVERNIGHT AS A CA AIRMASS MIXES
IN...DIMINISHING SOMEWHAT ARND DAYBREAK. NO WIND ADV WILL BE ISSUED
AS THE CRITERIA NEEDED IS ABOUT 8-10 KTS HIGHER FOR SUSTAINED WINDS
AND GUSTS. MIN TEMPS WILL DROP TO ABOUT 5 DEGREES F BELOW NORMAL
WITH MT MITCHELL LIKELY DROPPING BELOW FREEZING. TEMPS AND TDS WILL
APPROACH THE FROST RANGE OVER SOME HIGHER MTN ELEVATIONS...BUT
CONTINUED MOMENTUM TRANSFERS WILL PRECLUDE THE NEED FOR A FR.Y.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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
MUCH IN THE WAY OF 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 THROUGH MONDAY/...
AS OF 225 AM TUESDAY...MEDIUM RANGE MODELS DEPICT LITTLE IN THE WAY
SENSIBLE WX ACRS THE SE CONUS TO ROUND OUT THE WORKWEEK WITH A
DEVELOPING WEAKLY FORCED S/WV TROUGH ALOFT AND BROAD SFC LEE
TROUGHING. MAX TEMPERATURES WILL CONTINUE TO REBOUND...NEARING
CLIMO. A DEGREE OR TWO WARMER THAN PERSISTENCE WILL BE FEATURED FOR
SATURDAY WITHIN DRY NW FLOW ALOFT...AND YET WARMER FOR SUNDAY AS
DEEP LAYERED RIDGING NOSES EASTWARD. AT THIS JUNCTURE...IT STILL
LOOKS LIKE RIDGING WILL HANG ON THROUGH DAY 7...DRY AND CONTINUED
MILD FOR MONDAY.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.  DRY COLD
FRONT WILL SLIDE THROUGH THE REGION THIS AFTERNOON LEADING TO
INCREASING LOW LEVEL CLOUDINESS ACROSS THE NC PIEDMONT.
LIKEWISE...INCREASING PRESSURE GRADIENT AND DEEPENED MIXED LAYER
WILL YIELD GUSTY NORTHWESTERLY VEERING FLOW AT THE SURFACE.
THUS...INITIALIZED TAF WITH WNW WINDS AT 06KTS UNDER FEW LOW CU AND
HIGH LEVEL CIRRUS.  INCREASED SKY BY MID AFTERNOON TO SCT LEVELS
WITH A 4HR TEMPO FOR BKN045 CIGS.  CONDITIONS IMPROVE BEHIND THE
FRONT THIS EVENING WITH SKIES SCT TO SKC WITH GUSTY WINDS GIVING WAY
TO SUSTAINED 6-10KT NW FLOW.

ELSEWHERE...MUCH THE SAME AS KCLT ABOVE AS VFR CONDITIONS WILL
PREVAIL AT ALL SITES WITH THE POSSIBLE EXCEPTION OF IFR/MVFR CIGS
OVERNIGHT AT KAVL.  ALL SITES WERE INITIALIZED WITH GUSTY WNW WINDS
AS THE WEAK/DRY COLD FRONT SLIDES THROUGH THE REGION.  FEW/SCT LOW
LEVEL CU IS FEATURED FOR SKIES AT ALL SITES THROUGH THE AFTERNOON
WITH IMPROVEMENT FORECAST BY 00Z ASIDE FOR AT KAVL.  AS FOR
KAVL...MOISTURE POOLING ALONG THE TERRAIN AMONGST NW FLOW PATTERN
WILL LIKELY BECOME TRAPPED BENEATH THE DEVELOPING INVERSION LEADING
TO POSSIBLE MOUNTAIN VALLEY STRATUS OVERNIGHT.  A FEW GUIDANCE
SOURCES WERE HINTING AT POSSIBLE IFR CONDITIONS...HOWEVER HELD CIGS
AT LOW MVFR FOR THIS TAF ISSUANCE THROUGH MORNING.  GUSTY WINDS WILL
SUBSIDE WITH 6-10KT NW FLOW PREVAILING THROUGH THE OVERNIGHT AT ALL
SITES EXCEPT FOR KAVL WHERE CHANNELING YIELDS CONTINUED 20-25KT
GUSTS THROUGH THE REMAINDER OF THE TAF CYCLE.

OUTLOOK...BLUSTERY AND COOLER FOR THE MIDDLE PART OF THE WEEK...THEN
WARMING BY WEEKS END INTO THE WEEKEND AS DEEP LAYER RIDGING SETTLES
IN.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-17Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     MED   79%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     MED   79%
KAVL       HIGH 100%     HIGH 100%     HIGH  87%     LOW   58%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     MED   79%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     MED   79%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     MED   79%

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...CSH
NEAR TERM...CDG/SBK
SHORT TERM...CSH
LONG TERM...CSH
AVIATION...CDG






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