Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 281429
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1029 AM EDT FRI AUG 28 2015

.SYNOPSIS...
WEAK HIGH PRESSURE WILL LINGER OVER THE EAST THROUGH THE UPCOMING
WEEKEND. MOISTURE WILL GRADUALLY RETURN FROM THE SOUTHWEST THROUGH
THE WEEKEND...ALONG WITH A PASSING UPPER LEVEL DISTURBANCE BY
SUNDAY. TROPICAL SYSTEM ERIKA WILL LIKELY BE SOMEWHERE IN THE
VICINITY OF FLORIDA MONDAY THROUGH TUESDAY...WITH HIGH UNCERTAINTY
ON HER LOCATION MID TO LATE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1025 AM EDT FRIDAY...A REGION OF BKN/OVC STRATUS
CONTINUES TO PREVAIL OVER THE UPPER SAVANNAH RIVER VALLEY PER
LATEST OBS AND VISIBLE SAT WHERE ENHANCED LLV MOISTURE RESIDES.
OTHERWISE...ASIDE FOR PATCHY HIGH LEVEL CIRRUS...SAT ALSO INDICATES
MOSTLY SUNNY SKIES ALONG THE I77 CORRIDOR AND MUCH OF THE WESTERN
NC FOOTHILLS/MOUNTAINS...WITH THE EXCEPTION OF LOW/MID CLOUDS
ALONG THE TN LINE.  12Z NAM GUID CONTINUES TO FAVOR EASTERLY
VEERED SFC FLOW BY EARLY AFTERNOON...WITH FURTHER SOUTHEASTERLY
VEERING BY EARLY EVENING.  LIKEWISE...NAM/CAMS CONTINUE TO SUGGEST
ISOLATED/SCATTERED SHOWERS ALONG THE MTN RIDGETOPS THIS AFTERNOON
WHERE DIFFERENTIAL HEATING AND THUS INSTABILITY WILL BE MAXIMIZED.
THAT SAID...SOUNDINGS REMAIN FIRM IN FAVORING STRONG WARM NOSE
IN THE LOW/MID LEVELS THEREFORE EXPECT ANY UNSTABLE LAYERS THAT
DO DEVELOP TO REMAIN SHALLOW THEREBY LIMITING THUNDER CHANCES.
AS FOR THE FCST...TWEAKED POPS A TAD TO BETTER ALIGN WITH RECENT
CAM GUID ALONG WITH MINOR ADJUSTMENTS TO SKY/TEMPS...ALL OF WHICH
YIELDED NO SIG CHANGES.

AS OF 315 AM...SFC HIGH PRESSURE WILL REMAIN CENTERED OVER NY/PA
TODAY...RIDGING SOUTH ACROSS THE WESTERN CAROLINAS. LLVL FLOW IS
FORECAST TO REMAIN FROM THE EAST...WITH SPEEDS GRADUALLY DECREASING
TO AFTERNOON VALUES BELOW 10 KTS. THE LLVL WINDS WILL LIKELY RESULT
IN UPSLOPE FLOW...YIELDING CLOUD COVER ACROSS THE MTNS THROUGH MOST
OF THE DAY. IN ADDITION...STRATUS OVER THE MIDLANDS ARE FORECAST TO
SLIDE OVER THE UPPER SAVANNAH RIVER VALLEY AND UPSTATE EARLY THIS
MORNING. CLOUD COVER SHOULD GRADUALLY THIN WITH THE DECREASE IN
LLVL EAST WINDS THIS AFTERNOON. FORECAST NAM SOUNDINGS AND PLAIN
VIEW OF CAPE INDICATE VERY WEAK VALUES ACROSS THE FORECAST AREA
THIS AFTERNOON. THE GREATEST CAPE VALUES SHOULD OCCUR ACROSS THE
MTNS...BUT LIKELY LESS THAN A 1000 J/KG. THE INSTABILITY WILL BE
LIMITED BY A SIGNIFICANT INVERSION AROUND H7. HOWEVER...FOLLOWING
THE NAM AND 4KM WRF...I WILL HIGHLIGHT THE MTN RIDGES WITH SCHC
TO LCHC POPS DURING THE HEAT OF THE AFTERNOON. OTHERWISE...THE
REGION WILL REMAIN DRY. HIGH TEMPERATURES SHOULD PEAK A DEGREE OR
TWO BELOW NORMALS.

TONIGHT...A BROAD MID LEVEL LOW IS EXPECTED TO REMAIN NEAR THE
MISSISSIPPI DELTA...AS A SLIGHT S/W RIDGE INCREASED FROM THE EAST
ACROSS THE CAROLINAS. H925 FLOW IS FORECAST TO VEER FROM SOUTHEAST
THIS EVENING TO SOUTH BY 12Z SAT. SKY COVER MAY INCREASE FROM
SOUTH TO NORTH DURING THE LATE NIGHT HOURS. I WILL KEEP POPS IN
THE SINGLE DIGITS TONIGHT. MIN TEMPERATURES ARE FORECAST TO RANGE
FROM 2 TO 4 DEGREES BELOW NORMAL.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 255 AM FRIDAY...NRN STREAM ENERGY WILL MOVE ACROSS THE GREAT
LAKES ON SATURDAY AND REACH NEW ENGLAND LATE IN THE WEEKEND.
MEANWHILE...A SRN STREAM TROUGH WILL LINGER OVER THE MID AND DEEP
SOUTH WEST OF THE APPALACHIANS. A PIECE OF THIS SRN STREAM LOW...AND
AN ASSOCIATED UPPER JETLET...WILL LIKELY LIFT NWD THROUGH THE BASE
OF THE SRN APPALACHIANS SAT NIGHT INTO SUNDAY. AHEAD OF THIS
FEATURE...MOISTURE WILL START INCREASING FROM THE SW LATE
SATURDAY...WITH THE DEEPEST MOISTURE AND FORCING THEN CROSSING THE
REGION SATURDAY NIGHT INTO SUNDAY. WILL ADVERTISE MAINLY INCREASING
CLOUDS ON SATURDAY...WITH THE BEST SHOWER CHANCES ARRIVING FROM THE
SW SAT NIGHT INTO SUNDAY MORNING. DEWPOINTS WILL STEADILY RECOVER
ALONG WITH THUNDER CHANCES THROUGH SUNDAY. WILL FEATURE A SLIGHTLY
SMALLER THAN GUIDANCE DIURNAL RANGE ON TEMPS GIVEN THE ANTICIPATED
CLOUDS OVER THE WEEKEND.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 255 AM FRIDAY...A RESURGENT RIDGE AXIS IS EXPECTED TO DEVELOP
EARLY NEXT WEEK FROM THE SRN SHORES OF THE GREAT LAKES TO THE MID
ATLANTIC COAST...AS NRN STREAM ENERGY DEPARTS NEW ENGLAND...AND THE
REMAINING SRN STREAM LOW RETROGRADES WEST INTO THE SRN PLAINS/TX.
THE RESULTING RIDGE AXIS OVER THE EASTERN UNITED STATES WILL MAKE
FOR HIGH UNCERTAINTY IN THE TRACK OF TROPICAL SYSTEM ERIKA THROUGH
THE MEDIUM RANGE PERIOD. THERE IS REASONABLY GOOD CLUSTERING OF THE
MODEL SOLUTIONS IN THE VICINITY OF FLORIDA MON INTO TUE...BUT THEN
HIGH UNCERTAINTY BEYOND THAT. WILL THUS KEEP A MAINLY DIURNAL
PATTERN OF SLIGHTLY ABOVE CLIMO POPS GOING MON THROUGH THU GIVEN THE
ANTICIPATED MID ATLANTIC BLOCKING RIDGE AND POSSIBILITY OF GRADUALLY
INCREASING TROPICAL MOISTURE WITH THE ERIKA CIRCULATION...BUT WITH
HIGH UNCERTAINTY AT THIS POINT.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
AT KCLT...VFR. THE LATEST RUN OF THE NAM12 INDICATES THAT LOW LEVEL
MOISTURE WILL SPREAD WEST FROM THE MIDLANDS THIS MORNING...FAVORING
THE UPSTATE OF SC AND NC FOOTHILLS. FORECAST SOUNDING OVER CLT DOES
NOT INDICATE A RESTRICTIVE CEILING THROUGH THE 12Z TAF PERIOD. WEAK
HIGH PRESSURE WILL CONTINUE TO RIDGE ACROSS THE PIEDMONT THROUGH THE
PERIOD. I EXPECT A EAST-NORTHEAST THROUGH THE DAYLIGHT
HOURS...SPEEDS 8 KTS OR LESS. THE TERMINAL IS FORECAST TO REMAIN
DRY.

ELSEWHERE...LATEST OBSERVATIONS INDICATED A PATCH OF MVFR CLOUDS
ACROSS THE UPSTATE OF SC AND HIGHER MTN RIDGES. FORECAST SOUNDINGS
AND 11U-3.9U SATELLITE INDICATED A SIGNIFICANT LAYER OF STRATUS
ACROSS KAND...KGMU...KGSP...AND POSSIBLY KAVL DURING THE EARLY
DAYLIGHT HOURS THROUGH MID TO LATE MORNING. THE CASE FOR
RESTRICTIVE...MVFR...CEILINGS REMAIN THE GREATEST FOR KAND AND KAVL.
I WILL INDICATE WINDS BACKING FROM AN EAST WIND BEFORE SUNRISE...TO
EAST-NORTHEAST THROUGH THE DAYLIGHT HOURS FRIDAY...SPEEDS 8 KTS OR
LESS. KAVL WINDS WILL REMAIN FROM THE SOUTH. THE TERMINALS ARE
FORECAST TO REMAIN DRY.

OUTLOOK...MOISTURE WILL SLOWLY INCREASE FROM THE SOUTH AND EAST
THROUGH THE WEEKEND AND THEREFORE ISOLATED TO SCATTERED AFTERNOON
AND EVENING SHRA/TSRA CHANCES WILL INCREASE.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  81%     HIGH 100%     HIGH 100%     HIGH  83%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  95%     HIGH 100%     HIGH 100%     MED   69%

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

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...HG
NEAR TERM...CDG/NED
SHORT TERM...HG
LONG TERM...HG
AVIATION...NED


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