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Area Forecast Discussion

142
FXUS62 KGSP 302346
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
746 PM EDT THU OCT 30 2014

.SYNOPSIS...
MOISTURE WILL INCREASE ON FRIDAY OUT AHEAD OF AN APPROACHING COLD
FRONT. THIS FRONT...AND A STRONG MID LEVEL AREA OF LOW PRESSURE IS
FORECAST TO TRACK ACROSS THE REGION FRIDAY NIGHT INTO SATURDAY. A
STRONG SURFACE LOW PRESSURE SYSTEM WILL DEVELOP OFFSHORE ON
SATURDAY...THEN TRACK QUICKLY NORTH BY SATURDAY NIGHT. CIRCULATION
AROUND THE COASTAL LOW WILL BRING A CANADIAN AIR MASS TO THE REGION
INTO MONDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 745 PM...FCST REMAINS ON TRACK WITH LIGHT WINDS AND CLEAR
SKIES ACROSS THE AREA. CIRRUS WILL BE ON THE INCREASE OVERNIGHT WITH
LOW AND MID CLOUDS INCREASING FRI. BEST CHC FOR ANY MTN VALLEY FOG
WILL AGAIN BE THE LITTLE TN BASIN. UPDATES WERE MAINLY FOR CURRENT
CONDITIONS.

AS OF 425 PM...SKIES ARE CLEAR AND WINDS ARE GENERALLY LIGHT AND
VARIABLE ACROSS THE CWFA THIS AFTERNOON. HAVE UPDATED FCST TO SHOW
THESE TRENDS AND LATEST OBSERVATIONS. OTHERWISE...LITTLE CHANGE TO
GOING FCST.

AT 230 PM EDT THURSDAY...AN UPPER TROUGH WILL AMPLIFY OVER THE
EASTERN USA THROUGH FRIDAY...WHILE A RIDGE UPSTREAM PROGRESSES FROM
THE ROCKY MOUNTAINS TO THE PLAINS. A SHORTWAVE ROUNDING THE BASE OF
THIS TROUGH WILL CROSS THE SOUTHERN APPALACHIANS BY DAYBREAK...WHILE
AN UPPER LOW CLOSES OFF OVER THE GREAT LAKES. THIS DEEPENING LOW
WILL MOVE INTO THE OH RIVER VALLEY BY LATE FRIDAY.

A NEARLY STATIONARY FRONT WILL REMAIN NEAR THE CAROLINA AND GA
COASTS TONIGHT...THEN BEGINS MOVING SLOWLY EAST ON FRIDAY AS A
SURFACE WAVE MOVES NE UP THE BOUNDARY. MEANWHILE...A SURFACE LOW
WILL FILL AS IT MOVES FROM THE SOUTHERN PLAINS TO THE TN VALLEY.
MOISTURE AHEAD OF THIS LOW WILL REACH THE SOUTHERN APPALACHIANS BY
DAYBREAK...BUT PRECIPITATION ASSOCIATED WITH THE SYSTEM WILL LIKELY
NOT ARRIVE UNTIL MIDDAY...WHEN A COLD FRONT REACHES THE MOUNTAINS
FROM THE NW. THE FRONT MOVES ACROSS OUR AREA DURING THE AFTERNOON...
ACCOMPANIED BY MODEST PRECIPITATION WITH LIMITED LIFT ALONG THE
BOUNDARY. VERY LIMITED INSTABILITY WILL BE PRESENT IN THE
PIEDMONT...AND CONVECTION CANNOT BE TOTALLY RULED OUT...BUT
THUNDERSTORMS WILL NOT BE MENTIONED AT THIS TIME.

THE BETTER PRECIPITATION WILL FOLLOW THE FRONT IN THE MOUNTAINS...
WHERE ROBUST MOST UPSLOPE FLOW WILL SETUP FROM THE NW. WITH
SUFFICIENT COLD ADVECTION BEHIND THE FRONT...PRECIPITATION WILL
CHANGE OVER TO A MIX OF RAIN AND SNOW AT HIGHER ELEVATIONS DURING
AFTERNOON...AND ALL SNOW ON THE VERY HIGHEST PEAKS TOWARD EVENING...
BUT DURATION APPEARS TOO SHORT FOR ACCUMULATIONS BEFORE DUSK.

MINIMUM TEMPERATURES WILL RUN A FEW DEGREES BELOW NORMAL TONIGHT IN
A COOL NW FLOW BEHIND THE COASTAL FRONT. HIGH TEMPERATURES ON FRIDAY
WILL RUN AROUND FIVE DEGREES BELOW NORMAL DUE TO CLOUD COVER AND
PRECIPITATION.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
DDHHMM
WRKSHT

AS OF 230 PM THURSDAY...12Z GUIDANCE PACKAGE REMAINS CONSISTENT IN
MOVING AN ANOMALOUS UPPER LOW RAPIDLY SE FROM THE GREAT LAKES INTO
THE CAROLINAS ON SAT. THIS LOW IS IN THE NEIGHBORHOOD OF 5 SD`S
BELOW NORMAL. SO WE DO NOT SEE THIS TYPE OF SYSTEM VERY OFTEN.
THUS...WE WILL BE ONGUARD IN REGARD TO THE UNEXPECTED. WITH THE VERY
GOOD RUN TO RUN MODEL CONSISTENCY...WE ARE CONFIDENT ENOUGH TO GO
AHEAD A UPGRADE THE WINTER STORM WATCH IN THE NC MOUNTAINS TO A
WARNING FOR FRIDAY NIGHT AND SAT...EXCEPT FOR BUNCOMBE...NORTHERN
JACKSON AND GRAHAM COUNTIES WHERE A WINTER WEATHER ADVISORY WILL BE
ISSUED.

THE VERY POTENT COMPACT VORTMAX/CLOSED 500 MB LOW WILL INDUCE
CYCLOGENESIS EAST OF THE OUTER BANKS DURING THE DAY ON SAT... WITH A
DEFORMATION ZONE SETTING UP FROM CENTRAL VA/NC EXTENDING AS FAR WEST
AS THE I-77 CORRIDOR ON SAT. AN ASSOCIATED COLD FRONT MOVING ACROSS
THE AREA FRIDAY NIGHT WILL BRING A SURGE OF VERY COLD AIR WITH 850
MB TEMPS PLUMMETING TO -6 TO -8C ALONG THE TN LINE AND GENERALLY 0
TO -4C ACRS THE PIEDMONT.  THE COLD TEMPS ALOFT ALONG ALONG WITH THE
RAPIDLY COOLING BOUNDARY LAYER WILL ALLOW RAIN TO CHANGE TO SNOW BY
MIDNIGHT FRIDAY NIGHT IN THE MOUTNAINS...WITH A RAIN/SNOW MIX
SPREADING EASTWARD ACROSS THE FOOTHILLS INTO THE I-85 CORRIDOR
TOWARD SR ON SAT. IN THE MOUNTAINS...UPSLOPE FLOW WILL CONTINUE TO
PRODUCE SNOW SHOWERS INTO SAT EVENING. STORM TOTAL SNOW AMOUNTS IN
THE TN BORDER COUNTIES WILL BE ON THE ORDER OF 4-8 INCHES WITH
POSSIBLY AS MUCH AS 10 INCHES IN THE HIGHER PEAKS OF THE SMOKIES.
OTHER MOUNTAINS LOCATIONS WILL SEE ANYWHERE FROM A DUSTING TO UP TO
3 INCHES.

ON SATURDAY THE BOMBING LOW ALONG THE COAST WILL GENERATE STRONG
LLVL WINDS ON THE ORDER OF 40-50 KTS OUT OF THE NW. OUR WIND GUST
ALGORITHM HITS THE UPSTATE AND NE GA WITH THE HIGHEST GUSTS ON THE
ORDER OF 35 TO 45 MPH...WHICH WOULD BE BELOW HIGH WIND WATCH
CRITERIA. PRECIP ENDS FOR THE MOST PART BY SAT EVENING...EXCEPT FOR
SOME LINGERING SNOW SHOWERS IN THE NC MOUTNAINS ADJACENT TO TN.
CLEARING CONDITIONS WILL OCCUR SAT NIGHT BUT ATMOSPHERE MAY STAY
MIXED ENOUGH TO PREVENT WIDESPREAD FREEZING TEMPS OUTSIDE THE
MOUNTAINS...SO NO FREEZE WATCH FOR NOW. TEMPS STAY WELL BELOW CLIMO
FOR SUN EVEN WITH FULL SUNSHINE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 100 PM THURSDAY...MEDIUM RANGE MODELS ARE IN DECENT AGREEMENT
IN BUILDING DEEP LAYERED RIDGING ATOP THE SE CONUS ON MONDAY AND
TRANSLATING RIDGE CENTER OFFSHORE ON TUESDAY. IT NOW LOOKS LIKE MAX
TEMPERATURES WILL CREEP BACK TO WITHIN 5 DEG F OF CLIMO BY TUESDAY.
IT REMAINS TO BE SEEN JUST HOW MUCH IF ANY DEEPER CONVECTION DEVELOPS
WITHIN THE WARM SECTOR ON WEDNESDAY WITH THE BEST MODEL RESPONSE
STILL WEST OF THE MTNS BY THE EVENING HOURS. FOR NOW...WILL MAINTAIN
TOKEN SMALL OR SLIGHT SHOWER CHANCES AND CONTINUE TO MODERATE
TEMPERATURES.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AT KCLT..A LIGHT NNE WIND AND INCREASING CIRRUS EXPECTED OVERNIGHT.
LOW VFR AND MID CLOUDS WILL INCREASE AFTER DAYBREAK...BUT EXPECT ANY
LOW VFR CIGS TO HOLD OFF UNTIL EITHER LATE IN THE PERIOD OR AFTER
THE PERIOD. THE WINDS WILL TURN SWLY...BUT REMAIN GENERALLY LIGHT
AHEAD OF AN APPROACHING COLD FRONT FRI AFTERNOON. ALTHOUGH AN
ISOLATED SHRA IS POSSIBLE LATE IN THE PERIOD...ANY SIGNIFICANT
PRECIP SHOULD HOLD OFF UNTIL AFTER THE PERIOD.

ELSEWHERE...VFR. LIGHT AND VARIABLE WINDS AND INCREASING CIRRUS
EXPECTED OVERNIGHT. LOW VFR AND MID CLOUDS INCREASE THRU THE DAY FRI
WITH LOW VFR CIGS EXPECTED BY AFTERNOON AT KAVL. WINDS TURN WSW FRI
AFTERNOON AHEAD OF THE APPROACHING COLD FRONT. HOWEVER...WINDS
REMAIN NLY AT KAVL. KAVL ALSO HAS THE BEST CHC OF SEEING ANY SHRA BY
LATE IN THE AFTERNOON. HOWEVER...CHC TOO LOW FOR TAF ATTM. ISOLATED
SHRA POSSIBLE ELSEWHERE...BUT ANY SIGNIFICANT PRECIP SHUD HOLD OFF
UNTIL AFTER THE PERIOD.

OUTLOOK...A CHANCE FOR SHOWERS DEVELOPS FRIDAY EVENING AS A COLD
FRONT MOVES THRU. SOME RESTRICTIONS ARE POSSIBLE...ESPECIALLY IN THE
MOUNTAINS WHERE EVEN SOME SNOW SHOWERS ARE EXPECTED FRIDAY NIGHT AND
SATURDAY.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WINTER STORM WARNING FROM 8 PM FRIDAY TO 8 PM EDT SATURDAY FOR
     NCZ033-048>052.
     WINTER WEATHER ADVISORY FROM 8 PM FRIDAY TO 8 PM EDT SATURDAY
     FOR NCZ053-058-059.
SC...NONE.

&&

$$
SYNOPSIS...CSH
NEAR TERM...JAT/RWH
SHORT TERM...ARK/LG
LONG TERM...CSH
AVIATION...RWH



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