Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 291717
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
117 PM EDT MON SEP 29 2014

.SYNOPSIS...
MOISTURE WILL INCREASE ACROSS THE REGION TODAY AS LOW PRESSURE
DEVELOPS OFF CAROLINA COAST. DRY HIGH PRESSURE WILL THEN BUILD IN ON
TUESDAY AND LINGER THROUGH THURSDAY. A COLD FRONT WILL ARRIVE FROM
THE NORTHWEST ON FRIDAY. A DRY AND COOL AIR MASS IS EXPECTED TO
ARRIVE ACROSS THE REGION NEXT WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
1715 UTC UPDATE...POPS WERE UPDATED BASED ON RADAR TRENDS...FAVORING
THE PIEDMONT. WINDS WERE UPDATED WITH A BLEND OF THE LATEST NAM AND
ADJMAV. SKY COVER WAS UPDATED FROM VISIBLE SATELLITE IMAGERY.

AT 1000 AM EDT...AN UPPER TROUGH EXTENDED FROM THE GREAT LAKES TO
THE NE GULF OF MEXICO THIS MORNING...WITH SHORTWAVE MOVING THROUGH
IT OVER THE SOUTHERN APPALACHIANS AND THE MID MS RIVER VALLEY. A
SURFACE STATIONARY FRONT WAS LOCATED FROM THE CAROLINA AND GA COASTS
TO THE GULF COAST.

ALTHOUGH MODEL DATA SHOWS LITTLE TO NO ISENTROPIC UPGLIDE OVER THE
COASTAL FRONT...AS LEAST OVER OUR AREA... PRECIPIATION ASSOCIATED
WITH THE FIRST SHORTWAVE WAS NOTED CROSSING THE PIEDMONT...AND
ADDITIONAL ACTIVITY CAN BE EXPECTED AS THE SECOND SHORTWAVE ADVANCES
LATER TODAY. THE MODELS CONTINUE TO SHOW ENOUGH INSTABILITY OVER
THE NC MOUNTAINS FOR THUNDERSTORMS THIS AFTERNOON...BUT NOT ENOUGH
TO SUPPORT STRONG UPDRAFTS OR SEVERE WEATHER. PRECIPITATION AMOUNTS
ARE EXPECTED TO BE RATHER LIGHT.

PREVIOUS DISCUSSION...WHAT RAIN FALLS SHOULD GET PUSHED OFF TO THE
EAST BY LATE AFTERNOON AND EARLY EVENING BY THE PASSAGE OF THE SHORT
WAVE. WILL END PRECIP CHANCES STEADILY FROM THE WEST THROUGH THE
EVENING HOURS. THE REMAINING CONCERN WILL BE FOG IN THE PRE-DAWN
HOURS ON TUESDAY. WIND SHOULD BE FAIRLY LIGHT AND MID/UPPER LEVELS
SHOULD DRY OUT DRAMATICALLY. ASSUMING SOME LIGHT PRECIP FALLS
TODAY...THAT COULD PROVIDE FOR ENOUGH LOW LEVEL MOISTURE TO HELP
WIDESPREAD FOG TO DEVELOP BEFORE DAYBREAK TUESDAY...SO IT WILL BE
INCLUDED.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
AS OF 245 AM MONDAY...FAIR WEATHER EXPECTED TUESDAY THROUGH
WEDNESDAY. SHORT RANGE MODELS INDICATE THAT SHALLOW MID LEVEL
RIDGING WILL RIPPLE ACROSS THE REGION THROUGH THE PERIOD. AT THE
SFC...A WEAK LEE TROF WILL LIKELY DEVELOP DURING THE DAYLIGHT HOURS
EACH DAY. HIGH TEMPERATURES ON TUESDAY ARE FORECAST TO RANGE FROM
UPPER 70S WITHIN THE MTN VALLEYS AND FOOTHILLS WITH VALUES NEAR 80
ACROSS THE PIEDMONT. ON THURSDAY...INCREASING LLVL THICKNESSES AND
PLENTIFUL INSOLATION SHOULD RESULT IN HIGH TEMPERATURES 2 TO 3
DEGREES ABOVE TUESDAY/S VALUES. OTHERWISE...CONDITIONS WILL REMAIN
DRY WITH LIGHT WINDS.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 315 AM MONDAY...THURSDAY...MOISTURE WILL BEGIN TO INCREASE
ACROSS THE SOUTHERN APPALACHIAN REGION AHEAD OF AN APPROACHING L/W
TROUGH. THE AXIS OF THE MID LEVEL RIDGE WILL SLIDE OVER THE ATLANTIC
COAST...WITH H85 TEMPS ACROSS CWA UNCHANGED FROM TUESDAY. HIGH
TEMPERATURES ARE FORECAST TO RANGE FROM THE U70S WITHIN THE MTN
VALLEYS TO NEAR 80 EAST OF I-85.

ON FRIDAY INTO FRIDAY NIGHT...THE AXIS OF THE L/W TROUGH AND SFC
COLD FRONT WILL SWEEP QUICKLY ACROSS THE REGION. FORECAST SOUNDINGS
INDICATE THE SFC CAPE WILL REMAIN BETWEEN 100-300 J/KG AHEAD OF THE
FRONT. HOWEVER...PW VALUES WILL LIKELY SURGE TO 1.7 INCHES BY FRIDAY
AFTERNOON. THE COMBINATION OF THE PASSING FRONT AND TROUGH...WEAK
INSTABILITY...AND DEEP MOISTURE SHOULD SUPPORT A BAND OF LIGHT TO
MODERATE RAIN AND A FEW TSRA ON FRIDAY. PEAK COVERAGE IS EXPECTED
AROUND MID DAY FRIDAY...HIGHLIGHTED WITH LIKELY POPS ACROSS THE MTNS
AND CHC POPS EAST. HIGH TEMPERATURES SHOULD RANGE A FEW DEGREES
BELOW NORMAL,

NEXT WEEKEND...IN THE WAKE OF THE COLD FRONT...SFC HIGH PRESSURE IS
EXPECTED TO PUSH ACROSS THE SOUTHERN MISSISSIPPI RIVER ON
SATURDAY...REACHING THE SOUTHEAST U.S. ON SUNDAY. CONDITIONS SHOULD
REMAIN CLEAR AND DRY. TEMPERATURES WILL LIKELY RANGE SEVERAL DEGREES
BELOW NORMAL.

&&

.AVIATION /17Z MONDAY THROUGH FRIDAY/...
AT KCLT...PRECIPITATION IS EXPECTED TO DECREASE FROM THE WEST
TODAY AS MID AND UPPER LEVELS DRY OUT BEHIND A SHORTWAVE. GUIDANCE
DOES NOT FAVOR LOW CLOUDS OVERNIGHT...BUT MODEL TIME HEIGHTS
SUGGEST THE MAIN DECK WILL BE BELOW 3000 FT...ALBEIT WITH
DECLINING CLOUD COVER. IF CLOUDS ARE SLOWER TO SCATTER OUT...A
BRIEF MVFR CIG WOULD BE POSSIBLE AT DAYBREAK. GUIDANCE IS MORE
SUPPORTIVE OF A DAYBREAK VSBY RESTRICTION IN FOG. LIGHT NE WINDS
WILL GENERALLY PERSIST...WITH PERHAPS SOME BRIEF ESE WINDS THIS
EVENING.

ELSEWHERE...ALL SITES BUT KGSP HAVE ENOUGH LOW CLOUDS COVER FRO
TEMPO IFR CIGS WITH RAIN THIS AFTERNOON. RAINFALL WILL DECREASE FORM
THE WEST THIS AFTERNOON AS MID AND UPPER LEVEL DRY BEHIND A MID
LEVEL SHORTWAVE. GUIDANCE IS NOT VERY SUPPORTIVE OF LOW CLOUDS
OUTSIDE THE MOUNTAINS...DESPITE MODEL TIME HEIGHTS SUGGESTING
OTHERWISE. WITH CLOUD COVERAGE DECREASING...THE BEST BET FOR CIGS
WILL BE IN MOUNTAIN VALLEYS WHERE COL AIR WILL POOL. GUIDANCE
SUPPORTS WIDESPREAD FOG BY DAWN...BUT KEEPS ITS LOWEST VSBYS IN THE
MOUNTAIN VALLEYS. FOR NOW FOOTHILLS SITES WILL HAVE MVFR VSBY IN THE
TAFS...WHILE KAVL WILL HAVE IFR VSBY AND CIG. LIGHT WINDS WILL FAVOR
THE NE...EXCEPT AT KAVL WHERE THEY WILL CHANNEL UP VALLEY OR GO
LIGHT AND VARIABLE.

OUTLOOK...VFR CONDITIONS WILL PREVAIL TUESDAY THROUGH FRIDAY
MORNING...WITH FOG/VSBY CONCERNS REMAINING ACROSS THE MTNS AND
FOOTHILLS EARLY EACH MORNING. A FRONT WILL APPROACH ON FRIDAY WHICH
COULD TRIGGER SOME SHOWERS AND THUNDERSTORMS...WITH ASSOCIATED
RESTRICTIONS POSSIBLE.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-17Z
KCLT       HIGH 100%     HIGH 100%     MED   63%     MED   60%
KGSP       HIGH  84%     HIGH 100%     HIGH  88%     MED   63%
KAVL       HIGH  86%     HIGH  88%     HIGH  85%     MED   63%
KHKY       HIGH  95%     HIGH  97%     HIGH  86%     MED   60%
KGMU       HIGH  85%     HIGH 100%     HIGH  87%     LOW   59%
KAND       HIGH  89%     HIGH 100%     HIGH  80%     MED   63%

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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...NED
NEAR TERM...JAT/PM
SHORT TERM...NED
LONG TERM...NED
AVIATION...JAT





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