Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KGSP 221213
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
813 AM EDT WED APR 22 2015

.SYNOPSIS...
A COLD FRONT MOVES INTO THE AREA FROM THE NORTHWEST TODAY WITH GUSTY
WINDS AND LOW PRECIPITATION CHANCES. THE FRONT MOVES SOUTH OF THE
AREA TONIGHT WITH DRY HIGH PRESSURE PREVAILING BRIEFLY IN ITS WAKE.
A WARM FRONT BRINGS BETTER CHANCES FOR RAINFALL TO THE AREA OVER THE
WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 810 AM...TEMPS A LITTLE COOLER THAN EXPECTED SO ADJUSTED
TEMP GRID USING OBSERVATIONS AND USED LATEST CONSHORT FOR
TEMP/DEWPOINTS TREND THROUGH TODAY. ALSO...BLENDED IN THE LATEST
CONSHORT POPS WHICH BRINGS SCT SHOWERS/STORMS IN THE MOUNTAINS
CIRCA 18Z MAXIMIZING DURING THE LATE AFTERNOON. THIS LOOKS
REASONABLE BASED ON REGIONAL RADARS TO THE NW. GUSTY WINDS ARE
STILL EXPECTED IN ADVANCE OF THE COLD FRONT AS PRESSURE GRADIENT
TIGHTENS. WIND ADVISORY LOOKS WELL PLACED FOR THE NORTHERN
MOUNTAINS.

AS OF 645 AM...NO SIGNIFICANT CHANGES NEEDED FOR THIS UPDATE...AS
LATEST GUIDANCE IN LINE WITH THE CURRENT FCST.

AS OF 315 AM...A MID LVL WESTERLY JET WILL STRENGTHEN AROUND THE
BASE OF A BROAD UPPER LOW SPINNING OVER THE GREAT LAKES TODAY. AT
THE SFC...A RELATIVELY DRY COLD FRONT WILL CROSS THE OHIO VALLEY
THIS MORNING...THEN PUSH ACRS THE APPALACHIANS THIS AFTN. THE MAIN
CONCERN FOR TODAY LOOKS TO BE GUSTY WIND POTENTIAL...ESP IN THE NRN
MTNS WHERE THE WESTERLY LLVL FLOW WILL BE STRONGEST. THE 00Z GFS IS
STRONGER WITH WINDS AND GUSTS THAN THE NAM. BOTH SHOW DEEP MIXING OF
7-10 KFT AGL. TAKING A BLEND OF THE TWO RESULTS IN WINDS JUST BELOW
WIND ADVISORY CRITERIA. HOWEVER...PORTIONS OF THE NRN MTNS WILL BE
CLOSE...AND GIVEN THE WET SOILS FROM RECENT HEAVY RAINS...THINK EVEN
20-30 MPH WINDS WITH 35-45 MPH GUSTS MAY DOWN A FEW TREES. SO AFTER
COLLABORATION WITH RNK...WILL HOIST A WIND ADVISORY FOR THE NRN MTNS
FOR TODAY.

THE OTHER FCST CHALLENGE FOR TODAY WILL BE CONVECTION...WHICH WHAT
DOES DEVELOP WILL HAVE POTENTIAL TO TAP INTO VERY STRONG WINDS. THE
NEW DAY 1 SPC CONVECTIVE OUTLOOK HAS PAINTED A MRGL RISK FOR MAINLY
DAMAGING WIND GUSTS ACRS THE NC MTNS. THE MAJORITY OF HIGH-RES/CAMS
DO SHOW SCATTERED CONVECTION DEVELOPING ALONG AND AHEAD OF THE
COLD FRONT THIS AFTN...PUSHING INTO WESTERN NC. I THINK THE SLGT CHC
TO LOW-END CHC POPS LOOKS GOOD...WITH AN ISOLD CHC OF SEVERE TSTMS.
THE WESTERLY DOWNSLOPE FLOW ACRS THE PIEDMONT SHUD LIMIT MOISTURE
CONVERGENCE FOR ANYTHING MORE THAN ISOLD CONVECTION. SO THERE IS A
GRADIENT OF POP TAPERING TO SLGT CHC POP ACRS NE GA AND THE UPSTATE.
UNDER GRADUALLY INCREASING CLOUDINESS...TEMPS SHUD BE ABLE TO WARM
INTO THE 60S IN THE MTNS AND MID-UPR 70S ACRS THE PIEDMONT.

TONIGHT...THE LLVL CAA AND DRYING SHUD RAMP UP THIS EVENING...SO
POPS WILL TAPER OFF. WINDS SHUD ALSO SUBSIDE AND LOSE GUSTINESS BY
LATE EVENING AS WE LOSE THE DEEP MIXING. TEMPS WILL DIP BACK INTO
THE UPR 30S TO LWR 40S IN THE MTNS...AND MID 40S TO MID 50 ACRS THE
PIEDMONT.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 210 AM WED...A BROAD LOW AMPLITUDE UPPER TROF MOVES EAST OF
THE AREA THU WITH SHORT WAVE RIDGING MOVING ON ON FRI. A SHORT WAVE
UNDERCUTS THE RIDGE AND MOVES INTO THE AREA FRI NITE ALONG WITH THE
RIDGE AXIS. CLOUDS WILL DIMINISH THU AS A COLD FRONT MOVES SOUTH OF
THE AREA AND HIGH PRESSURE BUILDS IN FROM THE NW. ALTHOUGH LIGHTER
THAN WED...WILL STILL SEE SOME GUSTY WINDS THRU THE DAY AS WELL.
HIGH PRESSURE REMAINS OVER THE AREA FRI. DEEP MOISTURE AND LOW LEVEL
ISENTROPIC LIFT MOVE IN FROM THE WEST BRINGING CLOUDS AND EVENTUALLY
PRECIP. KEPT POP IN THE CHC RANGE AS THERE IS STILL SOME
DISAGREEMENT ON TIMING...WITH HIGHEST POP OVER THE SWRN MTNS INTO
THE UPPER SAVANNAH RIVER VALLEY. THE AIR MASS MOVING IN WITH THE
HIGH IS QUITE COOL. TEMPS THU AND THU NITE WILL BE AROUND 5 DEGREES
BELOW NORMAL...BUT COULD BE EVEN COOLER THU NITE IF RADIATIONAL
COOLING CONDITIONS IMPROVE. THIS COULD BRING FROSTY CONDITIONS OT
THE I-40 CORRIDOR...AND FROST/FREEZE CONCERNS TO THE CENTRAL AND SRN
NC MTNS. HIGHS RISE A FEW DEGREES FRI...WITH LOWS RISING UP TO 5
DEGREES ABOVE NORMAL FRI NITE WITH WAA AND INCREASING CLOUDS.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 400 AM WED...GUIDANCE IN PRETTY GOOD AGREEMENT FOR THE FIRST
HALF OF THE MEDIUM RANGE...BUT DIVERGES FOR THE LATTER HALF. A SHORT
WAVE MOVES INTO THE AREA SAT NITE THEN BECOMES ENVELOPED INTO THE
UPPER LOW CIRCULATION NEAR THE NEW ENGLAND COAST. THIS LOW KEEPS
CYCLONIC FLOW ACROSS MUCH OF THE EAST COAST UNTIL MONDAY. THE GFS
AND ECMWF BRING A LOW PRESSURE SYSTEM INTO THE AREA SAT THEN OFF
SHORE SAT NITE. THIS KEEPS DEEP MOISTURE AND LOW LEVEL ISENTROPIC
LIFT ACROSS THE AREA SAT WITH THE LIFT DIMINISHING SAT NITE.
HOWEVER...A BOUNDARY REMAINS ACROSS THE AREA SUN AND A WAVE MAY FORM
ALONG THE BOUNDARY AND MOVE ACROSS THE AREA. THIS WILL KEEP A THREAT
OF PRECIP OVER THE CWFA DURING THE DAY. COULD SEE UP TO 1.5 INCHES
OF RAIN WITH THIS SYSTEM. WILL HAVE TO SEE HOW THE GROUND AND
STREAMS RESPOND THE THE DRY DAYS BEFORE THIS EVENT DEVELOPS TO SEE
IF THIS WOULD BE ENOUGH QPF TO CAUSE A SIGNIFICANT RESPONSE. HIGHS
AROUND 5 DEGREES BELOW NORMAL SAT RISE TO NEAR NORMAL SUN. LOWS WILL
START AROUND 5 DEGREES ABOVE NORMAL THEN FALL TO NEAR NORMAL.

DRY WX FORECAST MONDAY EVEN WITH THE MDL DIFFERENCES AS GFS HAS HIGH
PRESSURE MOVING IN...AND THE ECMWF HAS CYCLONIC BUT DRY FLOW OVER
THE AREA. HIGHS WILL BE NEAR NORMAL WHILE LOWS WILL BE AROUND 5
DEGREES ABOVE NORMAL.

THE ECMWF DAMPENS A SRN STREAM UPPER LOW AS IT MOVES INTO THE AREA
AND INTERACTS WITH THE CYCLONIC FLOW ACROSS THE EAST COAST. THE GFS
THE GFS MOVES SHORT WAVE RIDGING OVER THE AREA AS STRONG NRN AND SRN
STREAM LOWS MERGE OVER THE MID MS VALLEY. AT THE SFC...THE ECMWF HAS
A MILLER-A LOW MOVING IT ALONG THE GULF COAST TO THE SERN ATLANTIC
COAST. THE GFS HAS MORE OF A MILLER-B LOW AND BRINGS IT IN FASTER.
EITHER WAY...PRECIP CHC WILL BE ON THE INCREASE THRU THE DAY AND
CONTINUING INTO THE EVENING. HOWEVER...QPF WOULD BE DRAMATICALLY
DIFFERENT. HIGHS TUE WILL BE AROUND 5 DEGREES BELOW NORMAL.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT AND ELSEWHERE... GUSTY WEST-SOUTHWEST (WEST-NORTHWEST AT
KAVL) WINDS BY 15-16Z...WITH POTENTIAL FOR 25-30 KT GUSTS AT TIMES
THIS AFTN. A COLD FRONT WILL PUSH INTO THE AREA THIS AFTN...BRINGING
MAINLY MID AND UPR LVL MOISTURE. A ISOLD TO SCATTERED SHRA AND TSRA
ARE EXPECTED TO MOVE INTO THE NC MTNS TO THE FOOTHILLS FROM THE
NORTH. WILL MENTION VCTS AT KAVL AND KHKY...WHERE THE HIGHEST CHC OF
IMPACT WILL BE. COVERAGE LOOKS TOO LIMITED AT THE OTHER SITES. WINDS
WILL SUBSIDE AFTER SUNSET THIS EVENING WITH MID TO HIGH CLOUD CIGS
LINGERING THRU THE EVENING.

OUTLOOK...A DRY HIGH PRES SYSTEM WILL BUILD IN THURSDAY THROUGH
FRIDAY...BEFORE ANOTHER WET STORM SYSTEM APPROACHES THE AREA FROM
THE WEST OVER THE WEEKEND.

CONFIDENCE TABLE...

            12-18Z        18-24Z        00-06Z        06-12Z
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...WIND ADVISORY UNTIL 7 PM EDT THIS EVENING FOR NCZ033-049-050.
SC...NONE.

&&

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.