Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 251740
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1240 PM EST SUN JAN 25 2015

.SYNOPSIS...
HIGH PRESSURE WILL BUILD BACK INTO THE REGION TODAY...BEFORE ANOTHER
LOW PRESSURE AREA AND TRAILING UPPER LEVEL DISTURBANCE MOVE THROUGH
MONDAY AND TUESDAY. HIGH PRESSURE RETURNS DURING THE LATTER HALF OF
THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1240 PM...FIRST ROUND OF CIRRUS HAS MOVED EAST OF THE AREA
WITH ADDITIONAL CIRRUS HOLDING OFF UNTIL LATE AFTERNOON. S TO SW
WINDS HAVE INCREASED AND MAY BECOME GUSTY FOR THE REST OF THE
AFTERNOON. THICKER CLOUDS WILL NOT BE IN UNTIL NEAR SUNSET FOR THE
FAR WEST AND PRECIP CLOSER TO MIDNIGHT. FCST REMAINS ON TRACK WITH
UPDATES MAINLY FOR CURRENT CONDITIONS.

AS OF 935 AM...SUNNY SKIES WILL CONTINUE THRU MOST OF THE DAY AS THE
CIRRUS ACROSS THE NRN CWFA MOVES EAST OF THE AREA AND CIRRUS TO THE
WEST HOLDS OFF UNTIL AFTERNOON. TEMPS GOT OFF TO A COLD START BUT
ARE WARMING NICELY. S TO SW WINDS ALREADY DEVELOPING ACROSS THE AREA
AS WELL. THEREFORE...GOING FCST ON TRACK WITH ONLY MINOR ADJUSTMENTS
NEEDED...MAINLY FOR CURRENT CONDITIONS.

AS OF 630 AM...OTHER THAN SOME PATCHY THIN CIRRUS SWEEPING ACROSS
NORTHERN NC...SKIES ARE CLEAR ACROSS THE FORECAST AREA THIS MORNING.
BY THE END OF THE MORNING...SOUTHERLY WINDS WILL BEGIN TO INCREASE
AND TEMPS WILL WARM TO THE MID/UPPER 40S ACROSS MUCH OF THE AREA.

A RATHER PLEASANT DAY IS IN STORE FOR THE REGION...AS A S/SW FLOW
WILL BECOME ESTABLISHED IN THE LOW LEVELS. THICKNESS VALUES BENEATH
A TEMPORARILY FLATTENING LONG WAVE TROUGH WILL SUPPORT MAXES AROUND
5 DEGREES ABOVE CLIMO THIS AFTERNOON UNDER SUNNY/MOSTLY SUNNY SKIES.

THE WEATHER SITUATION WILL THEN CHANGE RATHER ABRUPTLY THIS
EVENING...AS POTENT UPPER SPEED MAX...CURRENTLY SEEN IN WATER VAPOR
IMAGERY DIGGING SOUTH ACROSS THE CENTRAL HIGH PLAINS...DIVES INTO
THE SOUTHEAST CONUS. THIS WILL BRING A RATHER HEALTHY AREA OF MID-
LEVEL FORCING INTO THE AREA...WITH SOME DEGREE OF LOW LEVEL
CONVERGENCE AND ISENTROPIC LIFT INTO THE TENN VALLEY AND SOUTHERN
APPALACHIANS IN ASSOCIATION WITH ATTENDANT COLD FRONT THIS EVENING.
THIS SUPPORTS LIKELY TO CATEGORICAL POPS ACROSS THE MTNS DURING THIS
TIME. MILLER-B SCENARIO OF WEAKENING OHIO VALLEY SURFACE LOW...AND
DEVELOPING COASTAL LOW PRESSURE WILL THEN DISRUPT LOW LEVEL FORCING
PATTERNS SUCH THAT POPS WILL DECREASE DRAMATICALLY TOWARD THE
PIEDMONT. HOWEVER...SOME LIGHT NC PIEDMONT PRECIP MAY DEVELOP IN
ASSOCIATION WITH COASTAL CYCLOGENESIS...ALTHOUGH POPS WILL BE MID-
RANGE CHANCE AT BEST.

WITH A RATHER RESPECTABLE /CROSS-HAIR/ SIGNATURE DEPICTED IN MODEL
CROSS-SECTIONS...THERMAL PROFILES WILL BE SUPPORTIVE OF SNOW ACROSS
THE MOUNTAINS. HOWEVER...IT APPEARS THIS WILL PRIMARILY BE FOR
ELEVATIONS ABOVE 3000 FEET OR SO...WITH THE LOWER ELEVATIONS MAYBE
SEEING A BRIEF CHANGEOVER AS DEVELOPING COLD ADVECTION BRINGS THE
SNOW LEVELS DOWN TO THE VALLEY FLOORS. HAVING SAID THAT...THIS
APPEARS TO BE QUITE A LOW QPF EVENT FOR THE AREA. IN FACT...THE ONLY
AREAS IN WHICH ADVISORY LEVEL SNOW IS BEING FORECAST THROUGH 12Z
MONDAY IS ACROSS THE HIGH ELEVATIONS OF THE SMOKIES...WITH MOST
OTHER AREAS EXPECTED TO SEE LITTLE MORE THAN AN INCH. AFTER
COLLABORATING WITH NEIGHBORING WFOS...THIS IS A SMALL ENOUGH AREA...
AND TIMING IS SUCH THAT WE CAN WAIT ANOTHER FORECAST CYCLE BEFORE
PULLING THE TRIGGER ON ANY ADVISORIES. CONTINUING THE HWO MENTION
SHOULD SUFFICE FOR NOW.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AT 230 AM EST SUNDAY...ON MONDAY MORNING AN UPPER TROUGH WILL BE
OVER EASTERN NORTH AMERICA...WITH A RIDGE OVER THE WEST. A STRONG
SHORTWAVE WILL BE CROSSING GA AND THE CAROLINAS ON MONDAY. THIS
SHORTWAVE MOVES OFF THE COAST BY MONDAY EVENING. CHANNELED VORTICITY
BEHIND FROM THE NW BEHIND THE DEPARTING SHORTWAVE PERSISTS INTO THE
SOUTHERN APPALACHIANS THROUGH TUESDAY NIGHT.

AT THE SURFACE...A COLD FRONT WILL BE MOVING OFF THE CAROLINA COAST
ON MONDAY MORNING...WHILE A SURFACE LOW WILL BE OVER THE CENTRAL
APPALACHIANS. MOISTURE ASSOCIATED WITH THE WEAKENING APPALACHIAN LOW
WILL SLOWLY MOVE EAST ACROSS OUR AREA DURING THE DAY. BY LATE IN THE
DAY...NW SURFACE FLOW SETS UP OVER OUR AREA BEHIND THE DEPARTING
COLD FRONT AND AN ASSOCIATED DEEPENING COASTAL LOW. THIS WILL AID IN
DRYING OUR THE LEE OF THE MOUNTAINS ON MONDAY NIGHT. MEANWHILE...A NW
FLOW SNOW EVENT WILL SETUP IN THE NC MOUNTAINS BORDERING TN THAT
WILL PERSIST INTO TUESDAY NIGHT. TEMPERATURES WILL RUN NEAR NORMAL
ON MONDAY AND MONDAY NIGHT...COOLING SLIGHTLY FOR TUESDAY AND
TUESDAY NIGHT.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AT 230 AM EST SUNDAY...ON WEDNESDAY MORNING AND UPPER TROUGH WILL BE
OFF THE EAST COAST....WHILE A RIDGE WILL BE OVER THE PLAINS. AS THE
TROUGH DEAMPLIFIES AND PROGRESSES FURTHER ON THURSDAY...A LOW
AMPLITUDE RIDGE REACHES THE EAST COAST...AND A LOW AMPLITUDE TROUGH
REACHES THE MS RIVER VALLEY. THIS TROUGH AMPLIFIES AND PROGRESSES TO
THE EASTERN USA BY FRIDAY...THOUGH THE MODELS DIFFER SLIGHTLY ON
PLACEMENT OF ITS AXIS. THE MODELS SHOW A BROADENING TROUGH BY
SATURDAY AS UPPER LEVEL ENERGY MOVES FROM CANADA TO THE NORTHERN US
PLAINS...AND HAVE A NEARLY ZONAL FLOW IN THE BASE OF THE TROUGH OVER
THE GULF STATES.

AT THE SURFACE...WEDNESDAY FEATURES HIGH PRESSURE MOVING FROM THE OH
AND TN RIVER VALLEYS ACROSS THE CENTRAL AND SOUTHERN APPALACHIANS.
BY THURSDAY THIS HIGH STRETCHES ALONG THE EAST COAST....WHILE A COLD
FRONT CROSSES THE MS RIVER VALLEY. THE FRONT MOVES QUICKLY THROUGH
OUR AREA LATE THURSDAY...AND OFF THE EAST COAST BY FRIDAY MORNING...
FOLLOWED BY ANOTHER ROUND OF NW UPSLOPE FLOW SNOW OVER THE NC
MOUNTAINS. ANOTHER SURFACE HIGH MOVES OVER THE MOUNTAINS BY EARLY
SATURDAY...ENDING THE MOUNTAIN SNOW EVENT. TEMPERATURES WILL WARM
FROM NEAR NORMAL ON WEDNESDAY...TO SLIGHTLY ABOVE NORMAL ON
THURSDAY...THEN WILL COOL TO SLIGHTLY BELOW NORMAL BY SATURDAY.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS EXPECTED THROUGH THE NEXT 12
HOURS OR SO. S TO SW WINDS WILL INCREASE AND MAY BECOME GUSTY THIS
AFTERNOON. MID LEVEL VFR CIGS EXPECTED TO OVERSPREAD THE AREA
QUICKLY DURING THE EVENING IN ADVANCE OF THE NEXT WEATHER SYSTEM.
PRECIP CHANCES WILL ALSO INCREASE BY AROUND 06Z...MAINLY ACROSS THE
MTNS...AND A -RA MENTION HAS BEEN INTRODUCED AT KAVL. RAIN CHANCES
ARE NON-ZERO...BUT MUCH LOWER AT OTHER TERMINALS. INCREASING
MOISTURE IS EXPECTED TO RESULT IN DEVELOPMENT OF MVFR CIGS BETWEEN
06Z AND 12Z AT MOST TERMINALS. SOME GUIDANCE IS EXTREMELY
PESSIMISTIC DURING THIS TIME...FEATURING WIDESPREAD IFR/LIFR CIGS.
ALTHOUGH I WOULDN/T RULE THIS OUT IN AREAS THAT SEE AT LEAST A
COUPLE OF HOURS OF RAIN...CONFIDENCE IN THAT IS VERY LOW ATTM...SO
HAVE OPTED TO HOLD CONDITIONS AT THE MVFR LEVEL FOR THE TIME BEING.
MVFR CIGS WILL LINGER THRU AT LEAST MID MORNING ACROSS THE NC SITES
WHILE CIGS LIFT OR EVEN SCATTER OUT BEFORE NOON ACROSS THE SC SITES.
CANNOT RULE OUT SOME RAIN AT KHKY/KCLT DURING THE DAY...BUT LOW CHC
AND HIGH UNCERTAINTY. KAVL COULD SEE RAIN OR SNOW DEVELOPING DURING
THE DAY...BUT AGAIN...LOW CHC HIGH UNCERTAINTY. WINDS WILL TURN SW
TO WSW OVERNIGHT...NW AT KAVL...THEN W TO WNW AFTER DAYBREAK MONDAY.
GUSTS ARE LIKELY AT KAVL/KAND AND ARE POSSIBLE ELSEWHERE.

OUTLOOK...A SERIES OF CLIPPER SYSTEMS WILL BRING PERIODIC CHANCES
FOR SNOW SHOWERS...MAINLY TO THE MOUNTAINS THROUGH THE WEEK. MOST OF
THESE SNOW SHOWERS WILL REMAIN WEST AND NORTH OF KAVL...BUT BRIEF
PERIODS OF RESTRICTIONS AND SNOW SHOWERS CANNOT BE RULED OUT THERE.
OTHERWISE...MAINLY VFR CONDITIONS ARE EXPECTED.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  80%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  80%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  80%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  80%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  80%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     MED   70%

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...JDL/RWH
SHORT TERM...ARK/JAT
LONG TERM...JAT/WIMBERLEY
AVIATION...RWH



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