Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 291053
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
653 AM EDT SAT AUG 29 2015

.SYNOPSIS...
WEAK SURFACE HIGH PRESSURE WILL LINGER OVER THE REGION THROUGH THE
WEEKEND...BUT WITH MOISTURE GRADUALLY INCREASING FROM THE SOUTHWEST.
TROPICAL SYSTEM ERIKA IS EXPECTED TO MOVE SLOWLY NORTHWARD THROUGH
THE EASTERN GULF OF MEXICO ON MONDAY AND TUESDAY. THE FATE OF ERIKA
WILL BECOME MUCH MORE UNCERTAIN FROM MID WEEK ONWARD...BUT TROPICAL
MOISTURE COULD GRADUALLY REACH THE WESTERN CAROLINAS AND NORTHEAST
GEORGIA THROUGH THE UPCOMING WORK WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 645 AM...I WILL ISSUE A QUICK UPDATE TO ADJUST WINDS TO
OBSERVATIONS. IN ADDITION...I WILL INCREASE EARLY HOUR SKY COVER AND
DECREASE ASSOCIATED POPS.

AS OF 5 AM...I WILL UPDATE THE FORECAST TO ACCOUNT FOR THE LATEST
CLOUD AND TEMPERATURE OBSERVATIONS. IN ADDITION...I WILL REDUCE
EARLY MORNING HOURLY POPS TO OR NEAR ZERO. OTHERWISE...NO CHANGES
WILL BE MADE TO THE FORECAST.

AS OF 3 AM...THE CENTER OF WEAK SFC HIGH PRESSURE WILL REMAIN NORTH
OF THE REGION TODAY...SLIGHT RIDGING WILL LIKELY CONTINUE ACROSS THE
CAROLINAS AND NE GA. SFC WINDS ARE FORECAST TO REMAIN LIGHT FROM THE
EAST-NORTHEAST. LATEST WATER VAPOR IMAGES SHOW THE CENTER OF A MID
LEVEL LOW OVER THE MISSISSIPPI RIVER DELTA...WITH RIDGING OVER THE
SOUTHEAST CONUS. THE CIRCULATION AROUND THE LOW WILL RESULT IN
MOISTURE ACROSS THE FORECAST AREA TO INCREASE FROM THE TOP-DOWN
THROUGH TONIGHT. I EXPECT THAT CIRRUS AND CONTRAILS WILL BECOME
THICKER THROUGH THIS AFTERNOON...THE MID AND HIGH CLOUDS SHOULD
SWEEP NORTH ACROSS THE REGION TONIGHT. FORECAST SOUNDINGS INDICATE
THAT THE LOW LEVEL ENVIRONMENT WILL REMAIN RATHER DRY THROUGH THIS
AFTERNOON. THE COMBINATION OF DRY LOW LEVELS...A SIGNIFICANT
INVERSION AROUND 675 MB...MILD TEMPERATURES WILL RESULT IN LITTLE TO
NO CAPE TODAY. I WILL KEEP POPS LIMITED TO SINGLE DIGITS EAST OF THE
MTNS...AND SCHC ACROSS THE WESTERN MTNS. HIGH TEMPERATURES ARE
FORECAST TO RANGE FROM 2 TO 3 DEGREES BELOW NORMAL.

TONIGHT...THE MID LEVEL LOW IS FORECAST TO SLOW LIFT NORTH OVER THE
DEEP SOUTH...BUT REMAINING SOUTH OF I-20 THROUGH 12Z SUN. A PLUME OF
MOISTURE WILL LIKELY LIFT ACROSS THE SOUTHERN APPALACHIAN REGION. IT
APPEARS THAT A FEW SHOWERS WILL DEVELOP OVER THE EASTERN UPSLOPE
REGION FIRST...THEN INCREASE ACROSS THE WESTERN MTNS THROUGH
SUNRISE. THE GFS IS SEVERAL HOURS FASTER THAN THE NAM WITH THE
ARRIVAL OF MEASURABLE RAINFALL SUN MORNING. I WILL SIDE WITH THE
NAM SINCE MODELS HAVE GENERALLY BEEN TRENDING SLOWER WITH THE MID
LEVEL LOW. I WILL KEEP POPS LIMITED TO A CHC ACROSS THE WESTERN
TIER...AND SCHC WEST OF HWY 321. I WILL FORECAST LOW TEMPERATURES
FROM THE LOW 60S ACROSS THE MTNS TO NEAR 70 AROUND KAND.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 230 AM EDT SATURDAY...A 250 MB JETLET WILL MOVE NWD OVER THE
FORECAST AREA ON SUNDAY AS A MID/UPPER LEVEL SHORTWAVE PHASES BACK
INTO THE NRN STREAM FLOW AND LIFTS NE ACROSS THE SRN APPALACHIANS.
THIS IMPROVED FORCING WILL BE COINCIDENT WITH DEEPER MOISTURE
ARRIVING IN PROFILES FROM THE SW TO WARRANT SOLID CHANCE POPS FOR
SHOWERS IN ALL BUT THE NW NC PIEDMONT THROUGH SUNDAY. THE ASSOCIATED
CLOUDINESS WILL LIMIT INSTABILITY AND THE DIURNAL TEMPERATURE RANGE
ON SUNDAY...WITH SOME WEAK IN SITU WEDGING POSSIBLE IF SHOWERS
BECOME A BIT MORE WIDESPREAD. DESPITE THE CLOUDS...BRIEFLY STEEPER
LAPSE RATES ALOFT UNDER THE PASSING TROUGH WILL WARRANT AN ISOLD TO
SCT THUNDER MENTION FOR SUNDAY AFTN...ESPECIALLY IN SRN SECTIONS.

AN UPPER RIDGE WILL THEN BUILD OVER THE SOUTHEAST MONDAY THROUGH
MONDAY NIGHT AS THE SHORTWAVE DEPARTS TO THE NE AND THE LINGERING
SRN TIER TROUGH RETROGRADES TO E TX. TEMPERATURES SHOULD REBOUND
CLOSER TO CLIMO FOR MON...WITH DIURNAL ISOLD TO SCATTERED
SHOWERS/TSTMS EXPECTED WITH WEAK INSTABILITY BUT WITH DEVELOPING SE
UPSLOPE FLOW. PRECIPITATION CHANCES MAY BE SLOW TO WANE MONDAY NIGHT
IF ANY TROPICAL MOISTURE FROM ERIKA STARTS TO ENTER THE PICTURE.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 230 AM EDT SATURDAY...THE EVENTUAL TRACK OF ERIKA AND THE
ASSOCIATED MOISTURE WILL PROVIDE PLENTY OF UNCERTAINTY IN THE
CURRENT MEDIUM RANGE FORECAST. HOWEVER...THE SURROUNDING SYNOPTIC
FEATURES LOOK A LITTLE BETTER RESOLVED. THE UPPER LEVEL TROUGH AXIS
NEAR THE MS RIVER VALLEY WILL STRENGTHEN A 250 MB JETLET FROM THE
GULF COAST TO JUST WEST OF THE APPALACHIANS TUE THROUGH THU. THIS
UPPER LEVEL FEATURE MAY BECOME COINCIDENT WITH A LOW LEVEL 925 TO
850 MB RIDGE OF EQUIVALENT POTENTIAL TEMPERATURE STRETCHED THROUGH
THE PIEDMONT OF THE CAROLINAS. THERE IS SLOWLY GROWING CONCERN THAT
THIS MIGHT PROVIDE A FAVORABLE SETUP FOR A PREDECESSOR RAINFALL
EVENT...PRE...SOMEWHERE OVER THE REGION BY MID WEEK AHEAD OF THE
TROPICAL SYSTEM EXPECTED TO MOVE SLOWLY NORTHWARD THROUGH THE
EASTERN GULF OF MEXICO. ONE LIMITING FACTOR MAY BE THE LOW LEVEL
BLOCKING RIDGE OVER THE MID ATLANTIC WHICH COULD INHIBIT MOISTURE
TRANSPORT NORTHWARD. THE COMBINATION OF ANY PRE ALONG WITH E TO SE
UPSLOPE FLOW INTO THE HIGHER TERRAIN OF THE SOUTHERN APPALACHIANS
COULD CREATE THE POTENTIAL FOR HEAVY RAINFALL THROUGH THE PERIOD.
THIS MIGHT BE BENEFICIAL GIVEN THE CURRENT DROUGHT STATUS...BUT IT
COULD ALSO BECOME EXCESSIVE BY MID TO LATE WEEK.

GIVEN THE UNCERTAINTY...WILL SIMPLY FEATURE ABOVE CLIMO POPS FOR THE
TUE THROUGH FRI PERIOD AS THE ERIKA REMNANTS MEANDER NORTHWARD. WILL
GIVE THE POP TRENDS A SLIGHTLY DIURNAL CHARACTER WITH AN ISOLD TO
SCT AFTN THUNDER MENTION...BUT WILL KEEP SOME COVERAGE GOING THROUGH
THE OVERNIGHT HOURS. AND...WILL SHADE THE DIURNAL TEMPERATURE
CHANGES TO A SMALLER RANGE GIVEN THE POTENTIAL FOR MORE
CLOUDS/PRECIP. WILL HOLD OFF ON ANY HWO MENTION OF HEAVY RAINFALL
UNTIL THE TROPICAL MOISTURE/PRE POTENTIAL IS BETTER RESOLVED.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...VFR. LATEST W/V IMAGES INDICATED THE CENTER OF A MID LEVEL
LOW OVER THE NORTHERN GULF OF MEXICO...LIFTING MOISTURE NORTH ACROSS
THE SOUTHEAST CONUS. FORECAST SOUNDINGS INDICATE THAT MOISTURE WILL
INCREASE FROM THE TOP DOWN THROUGH TONIGHT. CIRRUS AND CONTRAILS
SHOULD INCREASE THROUGH THE DAY...POSSIBLY A FEW CU. A SIGNIFICANT
INVERSION AROUND 675 MB SHOULD KEEP THE ENVIRONMENT CAPPED THROUGH
THIS AFTERNOON. WINDS WILL REMAIN LIGHT THROUGH THE
PERIOD...FAVORING A NORTH WIND THIS MORNING VEERING EAST-SOUTHEAST
BY MID DAY...SPEEDS 6KTS OR LESS.

ELSEWHERE...TERMINALS SHOULD OBSERVE VFR CONDITIONS THROUGH THE TAF
PERIOD. MODELS INDICATE THAT A STRONG 675 MB INVERSION AND A WIDE
LLVL DEWPOINT DEPRESSION WILL KEEP INSTABILITY LIMITED TODAY. AS
MENTIONED ABOVE...A MID LEVEL LOW WILL ADVECT HIGH LEVEL MOISTURE
ACROSS THE REGION THROUGH TONIGHT....RESULTING IN AN INCREASE IN
HIGH CLOUDS AND CONTRAILS. WINDS WILL REMAIN LIGHT THROUGH THE
PERIOD...FAVORING A NORTHHEAST DIRECTION TODAY...VEERING
SOTHEAST BY THIS EVENING ....SPEEDS 6KTS OR LESS.

OUTLOOK...THE SOUTHEAST REGION IS FORECAST TO REMAIN UNDER A PLUME
OF GULF AND ATLANTIC MOISTURE THROUGH THE MIDDLE OF NEXT WEEK. IN
ADDITION...MOISTURE ASSOCIATED WITH THE REMNANTS OF ERIKA COULD
REACH THE SOUTHERN APPALACHIANS DURING THE MID WEEK. RESTRICTIONS
ARE POSSIBLE DURING PERIODS OF RAIN AND WITHIN THE MTN VALLEYS
AROUND DAWN.

CONFIDENCE TABLE...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   75%     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

&&

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

&&

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



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