Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 251136
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
636 AM EST THU DEC 25 2014

.SYNOPSIS...
HIGH PRESSURE WILL ARRIVE FROM THE WEST TODAY AND LINGER INTO
SATURDAY. A PAIR OF COLD FRONTS WILL APPROACH THE AREA ON
SUNDAY...CROSSING THE AREA MONDAY. GUSTY WINDS WILL FOLLOW THE
FRONTS ON TUESDAY...DECREASING ON WEDNESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM EST...THE AXIS OF A 150 KT UPPER JET STREAK WAS
ORIENTED OVER THE ERN SLOPES OF THE APPALACHIANS AT DAYBREAK THIS
MORNING. THIS JETLET WILL SLIP EAST OF THE FORECAST AREA THROUGH
LATE MORNING...TAKING ALL THE HIGH CLOUDS WITH IT. BOUNDARY LAYER
MOISTURE IN THE ERN PIEDMONT HAS DRIED OUT...AND THE ONLY
SIGNIFICANT MOISTURE SOURCE IN THE PICTURE IS SHALLOW MOISTURE OVER
ERN TN BANKING UP AGAINST THE NC MTNS IN WESTERLY UPSLOPE FLOW. KMRX
RADAR RETURNS HAVE BEEN QUITE SPARSE THIS MORNING...BUT IR IMAGERY
DOES SHOW CLOUD TOPS AROUND MINUS TEN RIGHT ALONG THE SPINE OF THE
MTNS. ISOLD TO SCT LOWER VALLEY RAIN SHOWERS AND RIDGE TOP SNOW
SHOWERS WILL LINGER THROUGH THE MORNING BEFORE DISSIPATING. ONLY
VERY LIGHT ACCUMULATIONS APPEAR POSSIBLE ALONG THE HIGHEST RIDGES.

OTHERWISE...ANTICIPATE FLAT UPPER RIDGING THROUGH THE DAY AS THE
DEAMPLIFYING TROUGH PASSES TO THE EAST. A SFC LEE TROUGH SHOULD
DEVELOP AND KEEP WINDS SW THROUGH THE DAY...AT LEAST ACROSS THE SRN
TIER OF THE FORECAST AREA. THE COMBINATION OF GOOD INSOLATION FROM
MID MORNING ONWARD...A LIGHT DOWNSLOPING WESTERLY 850 MB FLOW...AND
THE LEE TROUGHING WILL CONTRIBUTE TO MAXES ONE TO TWO CATEGORIES
ABOVE NORMAL IN MOST LOCATIONS EAST OF THE MTNS. THE SFC HIGH
PRESSURE CENTER WILL THEN BUILD OVERHEAD TONIGHT...WITH SEASONABLE
MINS IN THE 20S MTNS TO 30S EAST.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
AT 230 AM EST THURSDAY...ON FRIDAY MORNING AN UPPER RIDGE WILL BE
OVER THE EASTERN USA....WHILE A TROUGH WILL BE OVER THE WEST WITH A
CLOSED LOW OVER THE CENTRAL ROCKIES. BY SATURDAY THE LOW OPENS UP
AND FILLS...AND THE WESTERN TROUGH TAKES ON A POSITIVE TILTS FROM
THE NORTHERN PLAINS TO THE SOUTHERN ROCKIES...WHILE THE EASTERN RIDGE
AXIS MOVES OFF THE COAST. THE RESULT IS A LONGER WAVELENGTH AND
DECREASING AMPLITUDE INTO SATURDAY NIGHT.

A DRY SURFACE RIDGE WILL BE CENTERED OVER THE CAROLINAS ON FRIDAY
MORNING. THE RIDGE CENTER MOVES OFF THE NC COAST BY FRIDAY
EVENING...WHILE GULF MOISTURE STARTS MOVING NORTH UP THE MS RIVER
VALLEY IN ADVANCE OF A FRONT IN THE SOUTHERN PLAINS. BY SATURDAY
MORNING GULF MOISTURE OVERSPREADS THE GULF STATES...AND BY LATE IN
THE DAY IT REACHES THE UPPER SAVANNAH RIVER VALLEY AND SOUTHERN
APPALACHIANS. ISENTROPIC UPGLIDE OVER A GULF WARM FRONT WILL RESULT
IN WIDESPREAD MOISTURE ACROSS OUR AREA...THOUGH LIFT AND RESULTANT
PRECIPITATION WILL BE RATHER LIMITED.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AT 230 AM EST THURSDAY...ON SUNDAY MORNING AN UPPER HIGH CENTERED
OVER THE CARIBBEAN WILL EXTEND NORTH OFF THE EAST COAST...WHILE A
HIGH AMPLITUDE TROUGH WILL BE OVER THE PLAINS. BY MONDAY...THE RIDGE
PROGRESSES SLIGHTLY...WHILE THE TROUGH UPSTREAM RETROGRESSES
SLIGHTLY AS UPPER LEVEL ENERGY DIVES SOUTH OVER THE ROCKIES...
RESULTING IN A LOWER AMPLITUDE PATTERN THAT PERSISTS INTO TUESDAY.
AN UPPER LOW CLOSES OFF INT THE SOUTHWEST BY WEDNESDAY...WHILE
NEARLY ZONAL FLOW EXTENDS DOWNSTREAM TO THE EAST COAST.

A COLD FRONT WILL SLOWLY CROSS THE WESTERN CAROLINAS AND NE GA FROM
THE WEST ON SUNDAY AND SUNDAY NIGHT. GULF INFLOW AHEAD OF THIS
BOUNDARY WILL BE LIMITED...BUT MODEST UPSLOPE FLOW AND ISENTROPIC
UPGLIDE WILL SUPPORT WIDESPREAD...GENERALLY LIGHT PRECIPITATION. BY
MONDAY MORNING THE FRONT WILL BE EXITING OUR AREA TO THE EAST...
WHILE ANOTHER COLD FRONT APPROACHES FROM THE NW. THE SECOND FRONT
MOVES THROUGH DURING THE DAY...FOLLOWED BY SOME MOIST NW UPSLOPE
FLOW INTO THE MOUNTAINS THAT WILL LAST INTO WEDNESDAY. ALTHOUGH
COLD ADVECTION WILL SET UP...IT APPEARS THAT CRITICAL THICKNESS
VALUES MAY BE LACKING EARLY ON...AND RAIN SHOWERS WILL BE THE
PREDOMINANT PRECIPITATION TYPE UNTIL EARLY WEDNESDAY. TEMPERATURES
WILL RUN ABOVE NORMAL AHEAD OF THE FRONT...FALLING TO NEAR NORMAL
BEHIND THE FRONTS AT MIDWEEK.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
AT KCLT...ANY LINGERING 925 MB MOISTURE HAS MOVED EAST OF THE
AIRFIELD AROUND DAYBREAK THIS MORNING. EXPECT MAINLY BKN
ALTOCUMULUS/CIRRUS THROUGH 15Z...THEN CLEARING AS THE UPPER JET
STREAK SLIDES OFF TO THE EAST. A BRIEF PERIOD OF WSW SFC WINDS ARE
EXPECTED UNTIL MIXING TURNS THE FLOW MORE SOLIDLY WNW FROM LATE
MORNING THROUGH THE AFTERNOON HOURS. CANNOT RULE OUT WINDS TOGGLING
BACK TO WSW FROM TIME TO TIME TODAY...BUT THE BETTER LEE TROUGHING
SHOULD BE CONFINED TO THE NRN/WRN SC UPSTATE AND AWAY FROM THE NC
PIEDMONT. EXPECT CLEAR AND CALM CONDITIONS TONIGHT AS SFC HIGH
PRESSURE BUILDS INTO THE AREA FROM THE WEST.

AT KAVL...WEST/NORTHWEST FLOW MOISTURE IS PUSHING INTO THE FRENCH
BROAD VALLEY...AND MVFR CIGS WILL RESULT THROUGH 14Z. EXPECT THE
CLOUDS TO SCATTER AS THE MOISTURE SHALLOWS AFTER 14Z...WITH A FEW
LOW END GUSTS DEVELOPING THROUGH LATE MORNING ON MIXING. NW FLOW
WILL SETTLE DOWN TO STEADY 10 KT THIS AFTN...AND SLACKEN FURTHER
TONIGHT...WITH NOTHING MORE THAN A FEW WISPY HIGH CLOUDS.

ELSEWHERE...ALTOCUMULUS/CIRRUS CEILINGS OVER THE FOOTHILLS WILL MOVE
EAST WITH THE AXIS OF THE UPPER JETLET THROUGH LATE MORNING. EXPECT
WSW TO SW FLOW TO CONTINUE AT THE UPSTATE TAF SITES AS A LEE TROUGH
HUGS THE ERN SLOOPES OF THE SC MTNS TODAY. KHKY MAY START OUT
WSW...BUT SHOULD TURN MORE WNW WITH MIXING FROM LATE MORNING THROUGH
THE AFTERNOON HOURS. EXPECT CLEAR AND CALM CONDITIONS TONIGHT AS THE
SFC HIGH PRES BUILDS IN.

OUTLOOK...DRY HIGH PRESSURE WILL PERSIST THROUGH FRIDAY. ANOTHER
COLD FRONT WILL ARRIVE FROM THE NW OVER THE WEEKEND AND MAY STALL
OVER THE MTNS. THAT MIGHT PERMIT RESTRICTIONS TO DEVELOP BY SUNDAY
MORNING...PERHAPS CONTINUING THROUGH THE MIDDLE OF NEXT WEEK.

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       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     MED   66%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       MED   60%     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...NONE.
SC...NONE.

&&

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


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