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Area Forecast Discussion

861
FXUS62 KGSP 272347
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
647 PM EST THU NOV 27 2014

.SYNOPSIS...
DRY HIGH PRESSURE WILL BUILD ACROSS THE REGION TODAY AND LINGER
THROUGH THE WEEKEND. A COLD FRONT IS EXPECTED TO APPROACH THE
FORECAST AREA FROM THE NORTH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 630 PM...THE FCST CONTINUES TO BE IN GOOD SHAPE WITH LITTLE TO
SUGGEST ANY MID-COURSE CORRECTIONS. STILL EXTENSIVE LOW CLOUDINESS
ON THE TN SIDE OF THE MTNS...BEING FORCED UPSLOPE BY A NW WIND. SOME
OF THE CLOUDS WILL CONTINUE TO RUN UP AND OVER THE MTNS THROUGH THE
EVENING. RADAR IMAGERY SUGGESTS THAT MEASUREABLE PRECIP WILL BE
CONFINED TO AREAS CLOSER TO THE TN BORDER...SO A MINOR CHANGE WAS
MADE TO PUSH THE CHANCE POP BACK CLOSER TO THE BORDER.

PREVIOUS DISCUSSION...

AS OF 205 PM...LINGERING LIGHT SNOW SHOWERS ACROSS THE MTNS WILL
SLOWLY DIMINISH THIS EVENING AND DISSIPATE BY DAYBREAK. NO
SIGNIFICANT ADDITIONAL ACCUMULATIONS ARE EXPECTED. CLOUDS WILL
LINGER ACROSS THE MTNS THRU MOST OF THE NITE BEFORE DISSIPATING
AROUND DAYBREAK. GUSTY NWLY WINDS WILL FOLLOW A SIMILAR PATTERN.
OUTSIDE OF THE MTNS...CLOUDS AND GUSTY NWLY WINDS WILL DISSIPATE
THIS EVENING. LOWS TONIGHT WILL BE AROUND 10 DEGREES BELOW NORMAL.

FRIDAY...HEIGHTS BEGIN TO RISE AS THE UPPER TROF AXIS OVER THE AREA
MOVES EAST. AT THE SFC...HIGH PRESSURE BUILDS INTO THE AREA AS THE
EDGE OF A WEAK WARM FRONT BRUSHES BY TO THE NW. EXPECT QUITE A BIT
OF MID AND HIGH CLOUDS TO MOVE IN WHICH WILL LIMIT SOME OF THE
INSOLATION AND COUNTERACT THE SLOWLY INCREASING THICKNESSES. NLY
WINDS TO START THE DAY WILL BECOME LIGHT AND VARIABLE OR TURN LIGHT
SLY THRU THE AFTERNOON. HIGHS WILL BE 10 TO 15 DEGREES BELOW NORMAL.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 130 PM EST THURSDAY...THE SHORT RANGE PERIOD INITIALIZES
FRIDAY EVENING AMIDST INCREASINGLY ZONAL FLOW ALOFT AS LONGWAVE
UPPER TROF EJECTS OVER THE WESTERN ATLANTIC.  AT THE SURFACE...HIGH
PRESSURE WILL REPOSITION ITSELF ALONG THE SOUTHEAST COASTLINE
LEADING TO LIGHT...YET INCREASING SOUTHERLY WAA.  A WEAK IMPULSE
SLIDING THROUGH THE MEAN UPPER FLOW WILL MIGRATE SOUTHEAST THROUGH
THE OH VALLEY INTO THE CENTRAL/SOUTHERN APPS OVERNIGHT INTO SATURDAY
MORNING.  MOISTURE PROFILES REMAIN DRY ENOUGH IN THE LOW/MID LEVELS
TO PROHIBIT ANY SIGNIFICANT IMPACTS AS A RESULT OF THIS PASSING
WAVE.  THUS FCST FEATURES ONLY TEMPORARY INCREASES IN MID/HIGH LEVEL
CLOUDINESS WITH SKIES SCT OUT BY MIDDAY SATURDAY.

THROUGH THE REMAINDER OF THE PERIOD...BROAD SCALE LOW LEVEL FLOW
WILL CONTINUE TO BE INFLUENCED BY ABOVE MENTIONED SOUTHEAST RIDGE
AND LOW PRESSURE SLIDING OUT OF THE CENTRAL ROCKIES.  IN
RESPONSE...UPGLIDE REGIME WILL EXPAND NORTHWARD AHEAD OF APPROACHING
COLD FRONT THROUGH THE LOWER MISSISSIPPI RIVER VALLEY BEFORE SLIDING
EAST INTO THE TN VALLEY. LOW LEVEL CLOUDINESS WILL INCREASE FROM THE
SOUTHWEST ON SATURDAY AFTERNOON/EVENING AS REGION OF ENHANCED LIFT
MOVES OVER THE MTNS OF NORTHEAST GA AND SOUTHWEST NC.  EXPECTING
ADDITIONAL LOW LEVEL CLOUDINESS TO SPREAD THROUGH MUCH OF THE FCST
AREA ON SUNDAY WITH POPS GRADUALLY RAMPING UP TO SLIGHT CHANCE
LEVELS BY EVENING FOR PORTIONS OF THE SOUTHWEST MTNS AS THE ABOVE
MENTIONED SFC LOW/FRONT SLIDE SLOWLY EASTWARD.  TEMPERATURES WILL
GRADUALLY MODERATE TO ABOVE NORMAL LEVELS THROUGH THE PERIOD AS WAA
PATTERN PREVAILS.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 245 PM EST THURSDAY...LATEST GLOBAL MODELS ARE IN GOOD
AGREEMENT WITH REGARD TO THE OVERALL SYNOPTIC PATTERN SUN NIGHT THRU
TUE...BUT BEGIN TO DIVERGE CONSIDERABLY BY WED. HENCE...A BLEND OF
THE 12Z GFS/ECMWF WAS PREFERRED FOR THE AFTERNOON MEDIUM RANGE FCST
UPDATE.

UPPER PATTERN...A WEAK UPPER RIDGE AXIS WILL BE PUSHED OFF THE
ATLANTIC COAST BY SUN NIGHT WITH SWLY FLOW ALOFT SETTING UP BY MON
AS A POSITIVELY TILTED UPPER TROUGH QUICKLY APPROACHES FROM THE
WEST. THE TROUGH AXIS IS PROGGED TO CROSS THE REGION MON NIGHT INTO
EARLY TUE...FOLLOWED BY WESTERLY FLOW ALOFT TUE AND TUE NIGHT. THE
GFS KEEPS NEARLY ZONAL FLOW ALOFT THRU FRI WHILE THE ECMWF BRINGS
ANOTHER UPPER TROUGH TO THE EASTERN CONUS WED AND THU.

AT THE SURFACE...HIGH PRESSURE CENTERED OVER THE WESTERN ATLANTIC
WILL CONTINUE TO RIDGE WESTWARD INTO THE FORECAST AREA SUN NIGHT
THROUGH MON...LEADING TO DRY CONDITIONS WITH WARMER TEMPS.
MEANWHILE...A NE TO SW ORIENTED COLD FRONT WILL SLOWLY APPROACH THE
APPALACHIANS FROM THE NW THROUGH MON AS A COLD CANADIAN HIGH
PRESSURE CENTERED OVER THE GREAT PLAINS EXPANDS EASTWARD. THE FRONT
IS FORECAST TO REACH OUR MTNS ZONES BY MON NIGHT AND SLIPS THROUGH
THE REGION THRU TUE MORNING AS A BACK DOOR COLD FRONT IN
RESPONSE TO THE HIGH PRESSURE MIGRATING EAST ACROSS THE GREAT LAKES
REGION AND INTO THE OHIO VALLEY. AS THE HIGH SETTLES OVER THE
NORTHEAST STATES...A CAD WILL SET UP OVER THE REGION BY TUE.
HOWEVER...THE ECMWF BREAKS DOWN THE CAD BY TUE NIGHT IN LIGHT OF
ANOTHER COLD FRONT PUSHING THRU THE REGION WED WHILE THE GFS
KEEPS THE CAD THRU DAY 7. DUE TO THE UNCERTAINTY...POPS REMAIN ON
THE LOW SIDE MON THRU WED...FEATURING 20/30 POPS ACROSS MUCH OF THE
CWA. TEMPS ON MONDAY WILL BE AROUND 5-7 DEGREES ABOVE NORMAL...WITH
NEAR NORMAL RANGE TUE THRU THU.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AT KCLT...VFR THROUGH THE PERIOD. STILL SOME LINGERING HIGH BASED
STRATOCU CEILINGS AROUND THE WRN PIEDMONT AT ISSUANCE TIME...ALONG
WITH AN OCCASIONALLY GUSTY NW WIND. WILL ACCOUNT FOR THIS WITH THE
INITIAL FCST PERIOD BUT SCATTER OUT THE CLOUDS AND DIMINISH THE
GUSTS NO LATER THAN 02Z. IN REALITY THIS COULD HAPPEN WELL BEFORE
01Z. WIND SHOULD BECOME LIGHT NW OR N TOWARD DAYBREAK AS THE CENTER
OF HIGH PRESSURE SETTLES IN. THE GUIDANCE SUGGESTS THE HIGH CENTER
WILL DRIFT E ENOUGH TO ALLOW THE WIND DIRECTION TO COME AROUND TO SW
IN THE AFTERNOON FRIDAY...ALTHO THE SPEED SHOULD BE UNDER 5KT.

ELSEWHERE...SIMILAR TO KCLT E OF THE MTNS. KAVL IS STILL A SPECIAL
CASE AS MOISTURE BLOWS UP THE FR BROAD VALLEY. CEILING IS CURRENTLY
AT THE BOTTOM END OF VFR AND THINK THIS WILL PREVAIL...BUT BOUNDARY
LAYER COOLING MAY ALLOW THE CEILING TO DROP DOWN INTO THE MVFR
CATEGORY THROUGH THE EARLY MORNING HOURS. INCLUDED A TEMPO FOR THAT
POSSIBILITY. THINK BY 06Z THE LOW CLOUDS WILL START TO SCATTER OUT
AND GUSTINESS TO THE WIND WILL START TO ABATE. EVEN KAVL BECOMES
MOSTLY CLEAR BY DAYBREAK WITH LIGHT WIND AS THE HIGH CENTER REACHES
THE MTNS.

OUTLOOK...DRY HIGH PRESSURE WILL SET UP OVER THE AREA THROUGH THE
WEEKEND. A COLD FRONT WILL APPROACH FROM THE NORTHWEST EARLY NEXT
WEEK.

CONFIDENCE TABLE...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     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...SBK
NEAR TERM...PM/RWH
SHORT TERM...CDG
LONG TERM...JOH
AVIATION...PM



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