Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 170541
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
141 AM EDT THU APR 17 2014

.SYNOPSIS...
AN UNSEASONABLY COLD AIR MASS WILL REMAIN OVER THE REGION INTO
FRIDAY. A SUBTROPICAL LOW WILL DEVELOP TO OUR SOUTH ON FRIDAY AND
SATURDAY BUT IS EXPECTED TO REMAIN TO OUR SOUTH AND EAST. A DEEP UPPER
TROUGH ARRIVES FROM THE WEST TO START THE WEEKEND. BY EARLY NEXT
WEEK...TEMPERATURES SHOULD RANGE CLOSE TO NORMAL AHEAD OF AN
APPROACHING COLD FRONT.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 140 AM...CURRENT FORECAST GENERALLY ON TRACK. MAINLY THIN
CIRRUS MOVING IN FASTER THAN EXPECTED...SO UPDATED FOR THESE TRENDS.
OTHERWISE...UPDATES FOR CURRENT CONDITIONS.

AS OF 930 PM EDT WEDNESDAY...LATEST GUIDANCE CONSENSUS HAS NOT
CHANGED MUCH REGARDING FROST/FREEZE POTENTIAL TONIGHT THEREFORE
UPDATED RELEVANT PRODUCTS FOR THE EVENING.  OTHERWISE...TWEAKED
TEMPERATURE AND DEWPOINT TRENDS TO REFLECT LATEST OBSERVATIONS AND
LEFT THE REMAINDER OF THE FORECAST AS IS.

PREVIOUS DISCUSSION...

AS OF 215 PM...SKIES REMAIN CLEAR ACRS THE FA AS COLD HIGH PRESSURE
RIDGES DOWN THE EAST COAST. CONFLUENCE AHEAD OF UPPER TROUGH WILL
ALLOW THIS HIGH TO PERSIST THRU THURSDAY. HOWEVER...AS THE HIGH
DRIFTS FURTHER NE...EASTERLY FLOW OFF THE ATLANTIC WILL INCREASE
TONIGHT. EARLIER GUIDANCE RUNS INDICATED ENOUGH MOISTURE ACCOMPANIED
THIS FLOW TO EXPECT LOW CLOUDS TO REACH THE ERN ZONES AROUND
DAYBREAK THU. THIS IS NO LONGER THE FAVORED SOLUTION. PROG SOUNDINGS
HOWEVER DO NOT SUPPORT CLOUDS OR FOG MAKING IT THIS FAR INLAND...AND
MODELS DO NOT GENERATE CLOUD COVER IN LLVLS.

A FEW CIRRUS WILL BEGIN TO FILTER IN AHEAD OF THE INCOMING UPPER
TROUGH...BUT OTHERWISE SKIES SHOULD BE CLEAR. PARTIAL THICKNESSES
INCREASE SLIGHTLY AND THE PRESSURE GRADIENT BUILDS SLIGHTLY
OVERNIGHT. THUS...I EXPECT TEMPS GENERALLY JUST SLIGHTLY WARMER THAN
THOSE THIS MRNG. TRIED TO USE THIS MRNG/S MINS TO CAPTURE LOCAL
EFFECTS BY BLENDING THESE WITH FAVORED GUIDANCE BLEND. THIS BRINGS
TEMPS DOWN TO 31-32F IN PORTIONS OF THE ZONES FROM
GREENVILLE/GREENWOOD EAST. HAVE EXPANDED FREEZE WRNG TO THOSE
ZONES...AND TO HABERSHAM. CONDITIONS IN THE SAVANNAH VALLEY ARE NOT
PARTICULARLY FROSTY DUE TO THE CONTINUED BREEZES AND SOMEWHAT DRY
DEWPOINTS. NONETHELESS SOME PATCHY FROST IS LIKELY SO THEY WILL
REMAIN IN THE FROST ADVY.

THE EASTERLY FLOW OVER THE WEDGELIKE SFC HIGH DOES BRING SOME
LOW-MID CLOUDINESS INTO THE LOWER PIEDMONT BY THU AFTN. SOME
ENHANCED LIFT ALONG THE BLUE RIDGE MIGHT DRIVE SOME ADDITIONAL CLOUD
DEVELOPMENT LATER IN THE DAY. THE MOISTURE REMAINS SHALLOW AND
PRECIP CHANCES REMAIN TOO SMALL TO MENTION. HIGHS SHOULD REBOUND A
BIT...BUT WILL REMAIN TWO OR THREE CATEGORIES BELOW NORMAL WITH THE
COLD AIRMASS STILL IN PLAY.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
AS OF 230 PM WEDNESDAY...A STUBBORN AREA OF SURFACE HIGH PRESSURE
WILL REMAIN SITUATED FROM MAINE...THROUGH THE VIRGINIA`S AND THE
CAROLINA`S THURSDAY NIGHT...BEFORE EASING OFF INTO THE ATLANTIC.

MEANWHILE SOUTHERN STREAM ENERGY WILL WORK ACROSS TEXAS THURSDAY
NIGHT AND INTO THE NORTHERN GULF OF MEXICO FRIDAY AND FRIDAY NIGHT.
IT APPEARS THIS STREAM OF ENERGY WILL BE OUT OF PHASE WITH ITS
PARENT NORTHERN STREAM ENERGY. NEVERTHELESS...THE SUITE OF MODELS
CONTINUE TO INDICATE THIS SOUTHERN STREAM FEATURE WILL BE A
SIGNIFICANT WEATHER MAKER AS THE UPPER (H5) LOW CUTS OFF AND A
SURFACE LOW PRESSURE REFLECTION MOVES EAST ACROSS THE NORTHERN PARTS
OF THE GULF OF MEXICO AND INTO FLORIDA.

INITIALLY TIME HEIGHT CROSS SECTIONS AND BUFKIT DATA SUGGEST THAT
SFC TO 850 MB MOISTURE ON THE BACK SIDE OF THE RETREATING HIGH WILL
ALLOW LOW CLOUDS TO ENTRAIN INTO OUR REGION THURSDAY NIGHT AND
FRIDAY. BOTH THE NAM AND GFS (AND EVEN THE CANADIAN) HAVE TRENDED TO
THE SOUTH WITH THE CUTTING OFF OF THE UPPER LOW AND ULTIMATE TRACK
OF THE SURFACE REFLECTION. HOWEVER...EVEN WITH THESE EVENTS THE
CANADIAN MODEL CONTINUES TO BRING COPIOUS AMOUNTS OF PRECIPITATION
NORTH INTO OUR COUNTY WARNING AREA (CWA) FRIDAY INTO SATURDAY
MORNING. THIS APPEARS UNREASONABLE CONSIDERING THE FORECAST
SOUTHWARD SHIFT...AND AN APPARENT CONFLUENT ZONE SETTING UP TO THE
NORTH. THIS CONFLUENT ZONE WOULD "MORE OR LESS" GIVE US A HINT AT
THE NORTHWARD EXTENT OF THE PRECIPITATION FIELD. I CAN NOT SAY WITH
A HIGH DEGREE OF CONFIDENCE THAT WE WILL NOT HAVE ANY PATCHY LIGHT
RAIN OR SPRINKLES...SINCE A HAND FULL OF THE GFS ENSEMBLES DO BRING
A CHANCE OF RAIN INTO THE UPSTATE AT THE END OF THE WORK WEEK.
HOWEVER...ENOUGH EVIDENCE IN THE MODELS IS CURRENTLY SWAYING ME TO
KEEP THOSE SLIGHT CHANCE POPS OUT OF THE FORECAST FOR NOW...AND TO
CONTINUE TO HAVE A BEEFY CLOUD COVER. JUDGING BY SOME OF OUR
SURROUNDING NEIGHBORS WE ARE NOT FAR OFF.

WE SHOULD START TO SEE A GRADUAL RECOVERY IN TEMPERATURES (UPWARD
SWING) PARTICULARLY SATURDAY...AND EVEN MORE SO IF THE BULK OF THE
CLOUD AND PRECIPITATION SHIELD REMAINS TO OUR SOUTH.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 145 PM WEDNESDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
SUNDAY WITH A SOUTHERN STREAM H5 LOW HAVING CLOSED OFF OVER FLORIDA
AND OTHERWISE WEAK UPPER RIDGING JUST TO ITS WEST. THE LONG RANGE
MODELS INDICATE THAT THE LOW WILL SLOWLY DRIFT EASTWARD AND
EVENTUALLY OPEN BACK UP BY EARLY NEXT WEEK. AT THE SAME TIME...A
COUPLE OF WELL DEFINED UPPER SHORTWAVES WILL DRIFT ACROSS THE
SOUTHERN PLAINS AND TO OUR DOORSTEP BY LATE MON/EARLY TUES. BEYOND
THIS...ITS LOOKING LIKE ANOTHER ROUND OF UPPER RIDGING WILL MOVE
BACK OVER THE REGION FOR DAY 7 AND BEYOND.

AT THE SFC...THERE APPEARS TO BE MORE UNCERTAINTY AMONG THE MODEL
SOLUTIONS WRT ROUGHLY THE FIRST HALF OF THE FCST PERIOD. THE LATEST
GFS MAINTAINS STRONGER CANADIAN HIGH PRESSURE TO OUR NORTH AND KEEPS
ANY DEEPER MOISTURE ASSOCIATED WITH A SFC LOW THAT TRIES TO SPIN UP
TO OUR SOUTH...TO OUR SOUTH AND EAST. ON THE OTHER HAND...THE ECMWF
DEVELOPS A STRONGER LOW BY THE START OF THE PERIOD 00Z SUN AND
SPREADS ITS ASSOCIATED MOISTURE SHIELD INTO OUR SOUTHERN ZONES. THE
ECMWF IS ALSO QUITE A BIT SLOWER MOVING THE LOW NE AND AWAY FROM THE
CAROLINAS COMPARED TO THE GFS WHICH I HAVE PLACED MORE CONFIDENCE IN
FOR THE TIME BEING. AS FOR THE SENSIBLE FCST...THE FCST IS DRY ON
SUN WITH POPS RAMPING UP SLOWLY ON MON TO SLIGHT CHANCE ACROSS THE
CWFA AND THEN SLIGHT CHANCE TO SOLID CHANCE ON TUES. WED IS LOOKING
MOSTLY DRY AT THIS POINT. TEMPS SHOULD START OUT AROUND NORMAL AND
SLOWLY WARM ON DAYS 6 AND 7.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS WILL PREVAIL THROUGH THE
PERIOD AS HIGH PRESSURE DOMINATES ACROSS THE REGION. MAINLY THIN
CIRRUS MOVES IN THRU THE DAY. NELY WIND CONTINUES THRU THE DAY AS
WELL...WITH GUSTS DEVELOPING WITH MIXING BY MID MORNING FOR THE SC
SITES. KAVL THE EXCEPTION WHERE LIGHT WIND BECOMES SLY AFTER
DAYBREAK THEN SSE AND GUSTY FOR THE AFTERNOON. VFR STRATOCU MOVES IN
FROM THE SW LATE AFTERNOON OR EARLY EVENING WITH BKN CIRRUS
DEVELOPING. BEST CHC FOR LOW VFR CIGS IS KAND. GUSTS TAPER OFF
DURING THE AFTERNOON TURNING ENE. RELATIVELY LIGHT NE WIND CONTINUES
THRU THE EVENING. KAVL WILL SEE LIGHTER SLY WIND FOR THE EARLY
EVENING THEN TURNING NLY BEFORE MIDNIGHT.

OUTLOOK...CEILING AND VISIBILITY RESTRICTIONS WILL RETURN FRIDAY AND
SATURDAY AS A COLD FRONT APPROACHES FROM THE WEST AND A LOW PRESSURE
SYSTEM DEVELOPS ALONG THE COAST.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-05Z
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...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR GAZ010-017.
     FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR GAZ018-026-028-
     029.
NC...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR NCZ035>037-048-
     051>053-056>059-062>065-068>072-082-501>510.
SC...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR SCZ003-006>009-
     011>014-019.
     FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR SCZ001-002-004-
     005-010.

&&

$$
SYNOPSIS...JPT
NEAR TERM...CDG/RWH/WIMBERLEY
SHORT TERM...TS
LONG TERM...JPT
AVIATION...RWH






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