Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 300602
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
202 AM EDT THU OCT 30 2014

.SYNOPSIS...
A COLD FRONT WILL EXIT THE REGION TODAY...FOLLOWED BY COOL HIGH
PRESSURE FOR THURSDAY INTO FRIDAY. COLDER HIGH PRESSURE WILL BUILD
IN FROM THE NORTHWEST FRIDAY NIGHT THROUGH SUNDAY...RESULTING IN
TEMPERATURES WELL BELOW NORMAL.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 2 AM...MID LEVEL CLOUDS WILL CONDITIONS TO MOVE EAST EARLY
THIS MORNING...RESULTING IN CLEARING CONDITIONS FROM WEST TO EAST.
TEMPERATURES WILL CONTINUE TO GRADUALLY COOL THROUGH SUNRISE.
OVERALL...THE CURRENT FORECAST AND PRODUCTS APPEAR ON TRACK.

AS OF 1025 PM...A FEW LINGERING SHRA WILL END BEFORE MIDNIGHT AS
THE COLD FRONT MOVES EAST OF THE AREA. LOW CLOUDS HAVE LINGERED
LONGER THAN EXPECTED OUTSIDE OF THE MTNS...SO HAVE SLOWED THE
CLEARING THIS EVENING. STILL EXPECT SKIES TO CLEAR OVERNIGHT.
HOWEVER...WINDS HAVE DROPPED OFF FASTER THAN EXPECTED...SO HAVE
MODIFIED THOSE AS WELL. LOWS STILL LOOK TO BE ON TRACK...BUT HAVE
MODIFIED THE TEMP AND DEW POINT CURVE BASED ON LATEST TRENDS.

AS OF 745 PM...THE COLD FRONT IS MOVING INTO THE NC PIEDMONT AND SC
UPSTATE ATTM. A FEW SHRA DID DEVELOP ALONG THE FRONT...BUT WILL MOVE
EAST OF THE AREA BEFORE MIDNIGHT. LOW CLOUDS ALONG THE FRONT WILL
MOVE EAST AS WELL...LEAVING MOSTLY CLEAR SKIES OVERNIGHT. WINDS WILL
SHIFT WITH THE FRONT...THEN SLOWLY DIMINISH OVERNIGHT...EXCEPT
ACROSS THE MTNS WHERE GUSTY WINDS WILL LINGER LONGER. HAVE ADJUSTED
THE TEMPS AND DEW POINTS AGAIN BASED ON LATEST TRENDS AND FRONTAL
MOVEMENT...BUT OVERNIGHT LOWS STILL LOOK ON TRACK.

AS OF 435 PM...PRECIP HAS DISSIPATED RAPIDLY AS FROM MAKES ITS WAY
THRU THE CWFA. THEREFORE...HAVE BACKED OFF GREATLY ON POP...KEEPING
ONLY AN ISOLATED MENTION FOR THE NC PIEDMONT AND ERN UPSTATE WHERE
BEST INSTABILITY AND FORCING LINGER. HAVE ALSO MADE SIGNIFICANT
ADJUSTMENTS TO SKY CONDITION GIVEN LATEST SAT PIX...FRONTAL MOVEMENT
AND LATEST GUIDANCE. HAVE ALSO SLOWED THE COOLDOWN AND DRYING
OUTSIDE OF THE MTNS FOR LATE AFTERNOON AND EARLY EVENING IN LINE
WITH LATEST OBS AND FRONTAL MOVEMENT.

AS OF 200 PM...COLD FRONT IS SLOWLY MAKING ITS WAY ACROSS THE AREA
THIS AFTERNOON AND WAS ROUGHLY IN THE VICINITY I-85 AS I WRITE.
RADAR STILL INDICATES ONLY SCT LIGHT SHOWERS ARE ASSOCIATED WITH IT.
STRONGER CONVECTION IS NOTED WELL TO THE SW OVER EASTERN GA MOVING
TOWARD THE SC MIDLANDS. THE GOING LOW POP FORECAST IS STILL WORKING
OUT AND IF ANY THUNDER DOES DEVELOP IT WILL BE OVER THE SOUTHERN
PIEDMONT. THE SPC MESOANAL SHOWS AROUND 500J/KG OF CAPE IN THAT AREA
AND THE 12Z NAM MAX`S IT OUT AROUND 800J/KG.

THE FRONT WILL MOVE OUT OF THE AREA BY 00Z ALONG WITH ANY LINGERING
SHOWERS. CLOUDS SHOULD CLEAR THE ENTIRE AREA BY MIDNIGHT. MODERATE
COLD ADVECTION AND DECOUPLING WINDS LATE TONIGHT WILL ALLOW FOR SOME
FROST FORMATION ACROSS THE MOUNTAINS. WILL MAINTAIN THE FROST
ADVISORY FOR TONIGHT IN AVERY...MITCHELL...YANCEY AND BUNCOMBE
COUNTIES. THE REST OF THE CENTRAL AND SW MOUNTAINS HAVE ALREADY HAD
A FREEZE...SO THE FROST/FREEZE PROGRAM HAS ENDED FOR THAT REGION.

ON THURSDAY...WEAK HIGH PRESSURE WILL BUILD ACROSS THE AREA
PROVIDING GENERALLY CLEAR CONDITIONS AND MAX TEMPS A LITTLE SHY OF
CLIMO.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
ALL
TTAA00 KCAE 291915

THE MAIN SHORT TERM CONCERN WILL REVOLVE AROUND EXTREMELY
DYNAMIC/NEG TILT MID-LEVEL SHORT WAVE TROUGH/SPEED MAX THAT WILL
DIVE RAPIDLY OUT OF THE MIDWEST AND TOWARD THE SOUTHEAST AND
MID-ATLANTIC FRIDAY THROUGH EARLY SATURDAY. THIS FEATURE WILL BLAST
THROUGH OUR AREA FRI NIGHT/EARLY SATURDAY...INTRODUCING THE COLDEST
AIR MASS OF THE SEASON THUS FAR. HOWEVER...PERHAPS THE MORE
IMMEDIATE CONCERN WILL BE THE AREA OF VERY STRONG MID/UPPER FORCING
ACCOMPANYING THE INTENSIFYING WAVE...ALONG WITH AN INCREASE IN LOWER
LEVEL FORCING AS SURFACE CYCLOGENESIS GETS UNDER WAY ACROSS THE
CENTRAL CAROLINAS FRI NIGHT. FORCING WILL BE MORE THAN SUFFICIENT TO
SUPPORT LIKELY/CAT POPS ACROSS THE MTNS DURING THIS TIME...WHILE
EVEN THE NC PIEDMONT SHOULD SEE AT LEAST A SOLID CHANCE FOR SHOWERS
IN LIGHT OF THE INTENSITY OF THE FORCING. MEANWHILE...TEMPS WILL BE
PLUMMETING RAPIDLY ACROSS THE MTNS...SETTING THE STAGE FOR AN
EXTENDED NW FLOW SNOW EVENT...WITH SOME SYNOPTIC ENHANCEMENT AT THE
OUTSET. PRECIP RATES COULD BE QUITE IMPRESSIVE FRI NIGHT IN THE HIGH
ELEVATIONS ALONG THE TENN BORDER...WHICH SHOULD SEE VIRTUALLY ALL
SNOW DURING THIS EVENT.

BASED UPON THE STRENGTH OF THE NW FLOW (GREATER THAN 40 KTS AT
H8)...ACCUMULATING SNOWFALL WILL CONTINUE ACROSS THE USUAL NW FLOW
AREAS THROUGH THE DAY SATURDAY. WHILE IT/S TOO EARLY TO GET TALK
ABOUT SNOWFALL ACCUMULATION SPECIFICS... CONFIDENCE IS HIGH THAT
SIGNIFICANT (I.E. AT LEAST ADVISORY-LEVEL) SNOWFALL WILL OCCUR
ACROSS PORTIONS OF THE MTNS FRI NIGHT INTO SATURDAY. EVEN IN THE NC
PIEDMONT...AS DEFORMATION ZONE GRADUALLY BECOMES ESTABLISHED IN
RESPONSE TO CYCLOGENESIS...ENOUGH COLD AIR MAY TRICKLE IN TO ALLOW
FOR A BRIEF TRANSITION TO LIGHT SNOW SHOWERS BEFORE PRECIP COMES TO
AN END.

THE OTHER CONCERN WILL BE THE WIND...AS THE PRESSURE GRADIENT
INTENSIFIES IN THE WAKE OF THE DEEPENING LOW. A CONSENSUS OF MODEL
GUIDANCE DEPICTS A 7-10 MG GRADIENT WITHIN STRONG COLD ADVECTION
FLOW...ALONG WITH H8 WINDS AS HIGH AS 55 KTS. THESE INGREDIENTS ARE
TYPICALLY INDICATIVE OF A HIGH WIND EVENT ACROSS PORTIONS OF THE
HIGH TERRAIN...AND THIS WILL HAVE TO BE WATCHED CLOSELY. TEMPS BY
SATURDAY WILL BE 10-15 DEGREES BELOW NORMAL ACROSS THE AREA.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AT 230 PM EDT WEDNESDAY...ON SATURDAY EVENING...A STRONG...ANOMALOUS
UPPER LOW WILL BE LOCATED OFF THE NC COAST...WHILE AN UPPER RIDGE
WILL BE OVER THE PLAINS. THE UPPER LOW WILL WEAKEN AND FILL AS IT
LIFTS NE OFF THE NEW ENGLAND COAST ON SUNDAY. BY MONDAY THE UPPER
RIDGE REACHED THE OH AND TN RIVER VALLEYS...AND ON TUESDAY THIS
RIDGE CROSSES THE EAST COAST. AN UPPER TROUGH PROGRESSES FROM THE
GREAT LAKES TO THE SOUTHERN AND CENTRAL APPALACHIANS BY WEDNESDAY IN
THE GFS...BUT IS LESS PROGRESSIVE IN THE ECMWF.

DRY HIGH PRESSURE WILL BUILD SOUTHEAST ACROSS OUR AREA FROM SATURDAY
NIGHT THROUGH MONDAY. AS A RESULT...VERY TIGHT PRESSURE GRADIENT
WILL GRADUALLY RELAX ON SATURDAY NIGHT AND SUNDAY. BY LATE
TUESDAY...A LIGHT MOIST UPSLOPE FLOW ON THE BACK SIDE OF THE
DEPARTING SURFACE HIGH WILL REACH OUR AREA...STARTING IN THE
MOUNTAINS...WHILE A COLD FRONT MOVES INTO THE OH AND MID MS RIVER
VALLEY. THIS COLD FRONT IS EXPECTED TO STALL TO OUR WEST BY
WEDNESDAY MORNING. POPS WILL BE ALLOWED TO RAMP UP LATE TUESDAY INTO
WEDNESDAY... HOWEVER PRECIPITATION ACCUMULATIONS WILL BE LIGHT...AND
MAINLY LIMITED TO THE MOUNTAINS.

TEMPERATURES WILL START OUT AROUND 15 DEGREES OR SO BELOW NORMAL IN
A COLD AIR MASS BEHIND THE DEPARTING UPPER LOW AND AN ASSOCIATED
COLD FRONT. TEMPERATURES WILL MODERATE TO NEAR NORMAL VALUES BY
MIDWEEK AHEAD OF THE NEXT FRONT.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS EXPECTED THROUGH THE
TAF PERIOD ACROSS THE WESTERN CAROLINAS. BROAD HIGH PRESSURE WILL
BUILD ACROSS THE REGION...RESULTING IN LIGHT NNE WINDS AND DRY
CONDITIONS. CIRRUS LEVEL MOISTURE WILL BEGIN TO INCREASE LATE THIS
EVENING AS MID LEVEL TROF AMPLIFIES ACROSS THE REGION.

OUTLOOK...ANOTHER COLD FRONT APPROACHES ON FRIDAY AFTERNOON BRINGING
CLOUDS AND A CHANCE FOR SHOWERS AS IT MOVES THROUGH BY FRIDAY
EVENING. 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...FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR NCZ033-049-050-
     053.
SC...NONE.

&&

$$
SYNOPSIS...JAT
NEAR TERM...NED
SHORT TERM...JDL
LONG TERM...JAT
AVIATION...NED



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