Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 290749
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
349 AM EDT WED OCT 29 2014

.SYNOPSIS...
A COLD FRONT WILL CROSS THE REGION TODAY. FOLLOWED BY A COOL AREA OF
HIGH PRESSURE BUILDING IN BEHIND THE FRONT FOR THURSDAY INTO FRIDAY.
THEN A COLDER HIGH PRESSURE SYSTEM WILL BUILD IN FROM THE NORTHWEST
FRIDAY NIGHT THROUGH SUNDAY...RESULTING IN MUCH BELOW NORMAL
TEMPERATURES.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 330 AM...LATEST REGIONAL RADAR COMPOSITE INDICATED A SLOW
MOVING RAIN BAN ACROSS EASTERN TN. THE GREATEST MOTION WITHIN THE
BAND REMAINS ALONG THE AL/TN LINE...APPEARS PARTIALLY SUPPORTED BY A
MID LEVEL S/W. BASED ON THE LATEST RADAR...SAT...AND MODEL
TRENDS...I WILL DELAY -RA REACHING THE NC LINE UNTIL AROUND DAWN.
AFTER SUNRISE...THE SFC COLD FRONT IS EXPECTED TO SWEEP EAST ACROSS
THE SOUTHERN APPALACHIANS...PUSHING ACROSS THE FOOTHILLS AND
PIEDMONT DURING THE EARLY TO MID AFTERNOON. CAMS INDICATE THAT
SHALLOW CONVECTION MAY DEVELOP ALONG AND AHEAD OF THE FRONT. I WILL
INDICATE LIKELY POPS ACROSS THE TN BORDER COUNTIES...WITH CHC POPS
TIMED EASTWARD WITH THE FRONTAL PASSAGE THIS AFTERNOON. QPF AMOUNTS
WILL REMAIN LIGHT ACROSS THE CWA...GREATEST VALUES APPROACHING A
QUARTER OF AN INCH ALONG THE TN LINE. A FEW THUNDERSTORMS COULD
DEVELOP ACROSS THE FOOTHILLS AND PIEDMONT THIS AFTERNOON...THREATS
LIMITED TO LIGHTNING. HIGH TEMPERATURES ARE FORECAST TO RANGE CLOSE
TO NORMAL...MID 60S WITHIN THE MTN VALLEYS TO AROUND 70 EAST.

TONIGHT...CLOUD COVER WILL DECREASE...WINDS WILL WEAKEN...AND CAA
WILL CONTINUE ACROSS THE CWA. THE CENTER OF SFC HIGH PRESSURE WILL
REACH WESTERN KY/TN...WITH RIDGING ACROSS THE FORECAST AREA. A BLEND
OF MOS INDICATES THAT INVERSE LAPSE RATES ARE POSSIBLE ACROSS THE
MTNS. MIN TEMPERATURES ARE FORECAST TO RANGE FROM THE LOW TO MID 30S
WITHIN THE MTN VALLEYS TO MID 40S EAST. AREAS OF FROST APPEARS
LIKELY ACROSS THE NRN MTNS AND PORTIONS OF THE CENTRAL AND SOUTHERN
MTN COUNTIES. I WILL HIGHLIGHT THE AREAS WITH A REMAINING GROWING
SEASON WITH A FROST ADVISORY.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 315 AM WEDNESDAY...WEAK DRY SFC HIGH PRES WILL BUILD INTO THE
AREA BEHIND THE DEPARTING COLD FRONT ON THURSDAY...AS A 500 MB TROF
DIGS ACRS THE GREAT LAKES AND OHIO VALLEY. TEMPS WILL BE 2-3
CATEGORIES COOLER THAN WEDNESDAY...DESPITE SUNNY SKIES AND LIGHT
WINDS. ANOTHER COOL NIGHT WILL BE IN STORE...AS GOOD RADIATIONAL
COOLING CONDITIONS WILL EXIST ACRS THE CWFA THURSDAY NIGHT. THERE
WILL BE SOME INCREASE IN HIGH CLOUDS AS A POTENT SHORTWAVE AND
CLIPPER SYSTEM APPROACH FROM THE NORTHWEST. STILL...WITH MIN TEMPS
IN THE 30S IN THE MTNS MTNS...COULD SEE PATCHY FROST...ESP IN THE
VALLEYS. LOWS WILL BE ABOUT 5-8 DEG BELOW NORMAL.

FRIDAY AND FRIDAY NIGHT...MODELS SEEM TO BE COMING INTO BETTER
AGREEMENT ON A VERY ENERGETIC/COMPACT VORT MAX/CLOSED 500 MB
LOW...DIVING SE THRU THE WESTERN GREAT LAKES TO THE OHIO VALLEY. THE
00Z/29 GFS LOOKED VERY SIMILAR TO THE 12Z/ECMWF...TAKING THE LOW
ACRS THE NRN NC MTNS TO NEAR CHARLOTTE BY 12Z SATURDAY. PER THE
WPC/S MODEL DISCUSSION...WITH HEIGHT ANOMALIES 5.5 STANDARD
DEVIATIONS BELOW NORMAL (CENTER OF 533-535 DAM) AND A 50-YEAR RETURN
PERIOD. AT 850 MB...TEMPS PLUMMET TO -5 TO -8C UNDER THE UPPER
LOW...WITH NW WINDS OF 40-55 KTS AND STRONG CAA. THE 00Z/29 ECMWF
HAS BACKED OFF THIS A BIT...BUT STILL SHOWS VERY COLD TEMPS AND
STRONG WINDS. DESPITE SOME DIFFERENCES WITH THE EXACT DEPTH AND
TRACK OF THE LOW...IT LOOKS LIKE CONFIDENCE IS INCREASING ON A
PERIOD OF NW FLOW SNOW SHWRS AND WIND ADV TO HIGH WIND WARNING WINDS
IN THE MTNS. WITH SO MUCH ENERGY AND STEEP LAPSE RATES...PROBABLY
WILL BE A FEW SHWRS OUTSIDE THE MTNS...ESP IN THE NC PIEDMONT FRIDAY
NIGHT. AS FOR SNOW AMOUNTS...THERE/S STILL A LOT OF UNCERTAINTY. BUT
AT LEAST 1-3" IN THE USUAL NW FLOW UPSLOPE AREAS LOOKS
LIKELY...HEADING INTO SATURDAY. TEMPS WILL BE SIMILAR TO THURSDAY/S
READING DURING THE DAY ON FRIDAY...BUT SHUD BE COOLER FRIDAY
NIGHT...AS STRONG CAA CRANKS UP. TEMPS IN THE 20S MTNS AND 30S BELOW
ABOUT 3500 FT.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 330 AM WEDNESDAY...STRONG CAA...GUSTY WINDS AND MTN NW FLOW
SNOW SHWRS WILL LINGER THRU THE DAY ON SATURDAY...WITH HIGHS 10-15
DEG BELOW NORMAL. SATURDAY NIGHT/SUNDAY MORNING STILL LOOKS LIKE THE
COLDEST OF THE SEASON SO FAR...WITH SOME LINGERING WIND/MIXING TO
MAKE IT FEEL EVEN COLDER. WPC MIN TEMPS LOOK A LITTLE TOO COLD...BUT
EVEN JUST A 50/50 BLEND RESULTS IN FREEZING TEMPS ACRS NEARLY THE
ENTIRE CWFA. CONFIDENCE IS STILL LOW ON A FREEZE ACRS THE USUAL
THERMAL BELT FROM GSP TO THE UPPER SAVANNAH VALLEY. IN ANY CASE...I
THINK I WILL CHANGE THE FROST MENTION IN THE HWO TO FREEZE
POSSIBLE...GIVEN EVEN WITH MID 30S...FROST WILL BE UNLIKELY GIVEN
THE VERY DRY AIR AND STILL SOME WINDS.

FROM SUNDAY THRU TUESDAY...THE CENTER OF THE CANADIAN HIGH PRES WILL
SETTLE OVER THE REGION AND GRADUALLY MODERATE...AS AN UPPER RIDGE
QUICKLY BUILDS OVER THE EASTERN STATES IN THE WAKE OF THE EXITING
DEEP TROF. GOING WITH A DRY FCST WITH GRADUALLY WARMING TEMPS.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...BANDS OF HIGH CLOUDS AND LIGHT SW WINDS WILL CONTINUE
ACROSS THE TERMINAL THROUGH THE MORNING HOURS. SOUTHWEST WINDS ARE
FORECAST TO STRENGTHEN TO AROUND 10 KTS BY LATE MORNING. THE SFC
COLD FRONT MAY PUSH WEST TO EAST ACROSS THE TERMINAL BETWEEN 17Z TO
21Z. AS THE FRONT APPROACHES...CLOUD BASES WILL LIKELY LOWER TO
SCT020 BKN035 WITH ISOLATED SHOWERS. IT IS POSSIBLE THAT PERIODS OF
MVFR CEILINGS MAY OCCUR NEAR THE FRONT. AFTER 23Z...WINDS SHOULD
STEADILY VEER FROM THE NNW WITH VFR CLOUDS.

ELSEWHERE...A SLOW MOVING BAND OF RAIN MAY REACH THE TN/NC LINE BY
12Z. THE BAND SHOULD REMAIN OVER THE MTNS THROUGH THE
MORNING...SHIFTING EAST ACROSS THE FOOTHILLS AND PIEDMONT WHILE
THINNING THROUGH THE AFTERNOON. I WILL TIME VCSH OR -SHRA AS THE
COLD FRONT APPROACHES FROM THE WEST. TIMING OF THE -SHRA ACROSS THE
MTNS IS 16 TO 18Z...TO 18-20Z ACROSS THE I-85 CORRIDOR. AFTER
FROPA...WINDS SHOULD VEER FROM THE NNW AND CLOUDS WILL DISSIPATE.

OUTLOOK...HIGH PRESSURE AND VFR CONDITIONS RETURN FOR THURSDAY.
ANOTHER FRONT APPROACHES ON FRIDAY...BRINGING CLOUDS COVER OVER THE
AREA THROUGH SATURDAY...BUT CONFIDENCE IS MARGINAL ON RESTRICTIONS
ASSOCIATED WITH THIS SYSTEM.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...FROST ADVISORY FROM 2 AM TO 9 AM EDT THURSDAY FOR NCZ033-049-
     050-053.
SC...NONE.

&&

$$
SYNOPSIS...ARK
NEAR TERM...NED
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...NED



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