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Area Forecast Discussion

058
FXUS62 KGSP 221440
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
940 AM EST MON DEC 22 2014

.SYNOPSIS...
A MOIST AIR MASS WILL REMAIN ACROSS THE REGION BEFORE A COLD FRONT
CROSSES THE AREA ON WEDNESDAY. DRY HIGH PRESSURE ARRIVE FOR THURSDAY
AND FRIDAY. ANOTHER COLD FRONT WILL CROSS THE AREA ON SATURDAY...
FOLLOWED BY HIGH PRESSURE ON SUNDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 935 AM...LIGHT RAIN QUICKLY ENDING ACROSS THE CWFA. HOWEVER...
WIDESPREAD DRIZZLE AND LOW CLOUDS REMAIN. SHOULD ONLY SEE PATCHY
VERY LIGHT RAIN FOR THE REST OF THE DAY...BUT LOW CLOUDS AND DRIZZLE
WILL LINGER...WITH PATCHY FOG OF VARYING VISIBILITY DEPENDING ON
THE AMOUNT OF DRIZZLE. NELY WIND WITH OCCASIONAL LOW END GUSTS WILL
CONTINUE OUTSIDE OF THE MTNS...WITH GENERALLY LIGHT SLY WINDS ACROSS
THE MTNS. MAY SEE SOME BREAKS IN THE CLOUDS NEAR THE TN BORDER THRU
THE DAY WHICH WOULD ALLOW TEMPS TO INCREASE SIGNIFICANTLY THERE.
ELSEWHERE...ONLY A SMALL INCREASE IN TEMPS IS EXPECTED WITH THE
CONTINUED LOW CLOUDS AND DRIZZLE. THAT SAID...TEMPS COULD RISE A
LITTLE HIGHER IF DRIZZLE ENDS...ALLOWING A LITTLE MORE INSOLATION
EVEN WITH THE CLOUDS REMAINING.

AS OF 630 AM EST...FAIRLY HIGH COVERAGE OF MAINLY VERY LIGHT RAIN
AND DRIZZLE ARE INDICATED ON RADAR AND IN OBS AROUND DAYBREAK ACROSS
THE AREA. PRECIP INTENSITY/COVERAGE WILL LIKELY CONTINUE TO SLOWLY
DWINDLE THROUGH THE DAY AS WEAK UPGLIDE RELAXES OVER THE CAD
STRETCHING FROM 1027 MB HIGH PRES CENTERED OVER ERN NY DOWN THROUGH
THE WRN CAROLINAS. ANY LINGERING SPOTTY FREEZING DRIZZLE ALONG THE
NRN BLUE RIDGE SHOULD BE ENDING AS TEMPS RISE THROUGH THE MIDDLE
30S. THE CAD WILL REMAIN IN PLACE THROUGH THE DAY DESPITE THE
GRADUALLY WEAKENING ISENTROPIC LIFT. THIS SHOULD HOLD TEMPERATURES
IN THE UPPER 30S TO MIDDLE 40S THROUGHOUT THE REGION TODAY...EXCEPT
FOR SOME LOWER 50S IN THE SW MTNS OUTSIDE THE CAD REGIME.

MEANWHILE...A DEEP TROUGH STRETCHING FROM THE NRN PLAINS TO E TX
WILL SEE HEIGHTS CLOSING OFF OVER THE CENTRAL CONUS THROUGH TONIGHT.
THE MAIN DOWNSTREAM RESULT OF THIS WILL BE RESURGENT UPGLIDE TONIGHT
ALONG WITH SLIGHTLY DEEPER MOISTURE. WILL ALLOW POPS TO REBOUND TO
HIGH CHC TO LIKELY FOR MAINLY LIGHT RAIN...AND TEMPERATURES WILL
GENERALLY REMAIN STEADY THROUGH THE NIGHT.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AT 230 AM EST MONDAY...ON TUESDAY MORNING A CLOSED UPPER LOW WILL BE
MOVING FROM THE CENTRAL PLAINS TO THE MID MS RIVER VALLEY...WITH A
TROUGH EXTENDING SOUTH INTO NE MEXICO...AND RIDGING DOWNSTREAM OFF
THE EAST COAST. THE UPPER LOW MOVES NE ACROSS THE GREAT LAKES BY
WEDNESDAY...WHILE THE TROUGH AXIS MOVES VERY LITTLE. THE TROUGH THE
RAPIDLY PROGRESSES ACROSS THE MS RIVER VALLEY TO THE APPALACHIANS
LATE WEDNESDAY NIGHT.

A COLD AIR DAMMING SCENARIO WILL EXIST OVER THE WESTERN CAROLINAS
AND N GA ON TUESDAY...WHILE A COLD FRONT SLOWLY CROSSES THE TN VALLEY
AND GULF STATES. ISENTROPIC UPGLIDE OVER AN EAST COAST SURFACE HIGH
WILL SUPPORT WIDESPREAD AND PROLONGED PRECIPITATION.

A SURFACE WAVE DEVELOPS MOVES NORTH ALONG THE FRONT IN THE GULF
STATES AND TN TUESDAY NIGHT...WHILE THE CAD WEDGE WEAKENS. ROBUST
MOIST SOUTHERLY LOW LEVEL FLOW SETS UP INTO THE SOUTHERN
APPALACHIANS. AT THIS POINT THERE REMAINS SOME UNCERTAINTY AS TO HOW
MUCH INSTABILITY AND SHEAR WILL BE PRESENT OVER OUR AREA AHEAD OF
THE COLD FRONT AND WEDNESDAY...BUT THE BEST SUPPORT FOR SEVERE
WEATHER APPEARS TO BE TO OUR SOUTH. THE FRONT MOVES THROUGH ON
WEDNESDAY...FOLLOWED BY COLD ADVECTION AND NW FLOW SNOW SHOWERS OVER
THE NC MOUNTAINS.

TEMPERATURES WILL EXHIBIT A VERY LOW DIURNAL RANGE ON TUESDAY AND
TUESDAY NIGHT...AS CLOUD COVER AND MOISTURE HOLD MAXIMUMS BELOW
NORMAL AND MINIMUMS ABOVE NORMAL. WARMING IMMEDIATELY AHEAD OF THE
FRONT WILL BRING HIGH TEMPERATURES ABOVE NORMAL ON WEDNESDAY. COLD
ADVECTION BEHIND THE FRONT WILL BE PARTIALLY OFFSET BY DOWNSLOPE
WARMING EAST OF THE MOUNTAINS...AND MINIMUM TEMPERATURES WILL BE
SLIGHTLY ABOVE NORMAL.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AT 230 AM EST MONDAY...ON THURSDAY MORNING UPPER TROUGHS WILL BE
OVER THE EAST AND THE WEST...WITH A LOW AMPLITUDE UPPER RIDGE OVER
THE PLAINS. BY FRIDAY MORNING THE RIDGE AXIS WILL HAVE PROGRESSED TO
THE EAST COAST...WHILE THE TROUGH UPSTREAM WILL HAVE REACHED THE
EAST SLOPES OF THE ROCKIES. THE TROUGH WILL CROSS THE PLAINS ON
SATURDAY. BY SUNDAY THE ECMWF AND GFS ARE OUT OF PHASE...WITH THE
FORMER PLACING ITS HIGHLY AMPLIFIED TROUGH OVER THE MS RIVER VALLEY
     AND THE LATER HAVING ITS DEAMPLIFIED TROUGH OVER THE EAST
COAST...WITH A LOW AMPLITUDE RIDGE OVER THE MS RIVER VALLEY...AND
ANOTHER LOW AMPLITUDE TROUGH OVER THE PLAINS...WITH NEARLY ZONAL
FLOW OVER THE SOUTHERN TIER OF STATES.

A COLD FRONT WILL BE DEPARTING THE EAST COAST ON THURSDAY...WITH
DRYING DOWNSLOPE FLOW IN THE LEE OF THE MOUNTAINS...AND SOME
LINGERING UPSLOPE FLOW SNOW SHOWERS IN THE NC MOUNTAINS BORDERING
TN. THE UPSLOPE/DOWNSLOPE REGIME ENDS LATE THURSDAY AS HIGH PRESSURE
CROSSES THE GULF...AND BY FRIDAY MORNING....GULF INFLOW SETS UP ON
THE BACK SIDE OF THIS HIGH AHEAD OF THE NEXT FRONT. THIS FRONT
CROSSES THE MOUNTAINS LATE FRIDAY NIGHT...BUT GULF INFLOW WEAKENS
BEFORE IT ARRIVES...LIMITING PRECIPITATION. THE FRONT MOVES OFF THE
EAST COAST BY SUNDAY MORNING....WITH ANOTHER ROUND OF NW UPSLOPE
FLOW INTO THE NC MOUNTAINS...SUPPORTING ANOTHER BATCH OF SNOW
SHOWERS. BY MONDAY...DRY HIGH PRESSURE MOVES INTO THE TN VALLEY.

TEMPERATURES WILL WARM FROM NEAR NORMAL THURSDAY TO SLIGHTLY ABOVE
NORMAL FRIDAY IN WARM ADVECTION AHEAD OF THE NEXT FRONT...COOLING TO
SLIGHTLY BELOW NORMAL BEHIND THE FRONT.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
AT KCLT...LITTLE IN THE WAY OF ADDITIONAL RAIN IS EXPECTED...BUT
DRIZZLE SHOULD CONTINUE IN THE UPGLIDE OVER THE SFC CAD LAYER
THROUGH MUCH OF THE DAY. IFR CIGS LOOK TO BE FAIRLY LOCKED INTO THE
600 TO 800 FEET RANGE FOR THE BULK OF THE DAY...BUT 500 OR EVEN 400
IS POSSIBLE. EXPECT A STEADY NE FLOW AT 10 KT OR LESS THROUGH THE
PERIOD. DRIZZLE OR LIGHT RAIN WILL RETURN WITH RESURGENT UPGLIDE BY
LATE EVENING AND BECOME STEADIER OVERNIGHT ALONG WITH DEVELOPING
LIFR CIGS.

ELSEWHERE...UPGLIDE MOISTURE OVER THE SFC CAD LAYER WILL YIELD
DRIZZLE THROUGHOUT THE REGION THROUGH MOST OF THE DAY EVEN AS RAIN
HAS TAPERED OFF. SOLID IFR CIGS SHOULD CONTINUE UNTIL AT LEAST EARLY
AFTN. SOME BRIEF RECOVERY TO LOWER END MVFR IS POSSIBLE THIS AFTN IF
THE DRIZZLE WANES. EXPECT CONTINUED NE FLOW AT 10 KT OR LESS THROUGH
THE PERIOD AT THE FOOTHILL SITES...EXCEPT SLY WINDS AT KAVL. DRIZZLE
AND LIGHT RAIN WILL RETURN THIS EVENING ALONG WITH IFR CIGS...WITH
STEADIER RAIN AND LIFR CIGS LIKELY OVERNIGHT ALONG WITH LOWERING
VSBY.

OUTLOOK...MOISTURE WILL DEEPEN LATE TONIGHT THROUGH TUESDAY NIGHT
AHEAD OF THE NEXT APPROACHING COLD FRONT. LOW RESTRICTIONS AND
WIDESPREAD RAIN SHOWERS ARE EXPECTED. A COLD FRONT WILL CROSS THE
REGION FROM THE WEST ON WED. DRY HIGH PRESSURE WILL RETURN THROUGH
LATE WEEK.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       MED   61%     MED   65%     MED   78%     HIGH  83%
KGSP       MED   75%     MED   74%     HIGH  80%     HIGH  83%
KAVL       MED   69%     MED   76%     HIGH  85%     HIGH  91%
KHKY       MED   71%     MED   66%     HIGH  83%     HIGH  85%
KGMU       MED   70%     MED   66%     HIGH  80%     HIGH  83%
KAND       MED   70%     MED   69%     MED   75%     HIGH  83%

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...JAT
NEAR TERM...HG/RWH
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...HG/RWH



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