Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 141051
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
651 AM EDT MON JUL 14 2014

.SYNOPSIS...
WEAK HIGH PRESSURE WILL LINGER OVER THE WESTERN CAROLINAS AND
NORTHEAST GEORGIA TODAY. AN UNSEASONABLY STRONG COLD FRONT WILL THEN
CROSS THE REGION ON TUESDAY. BEHIND THE FRONT...COOLER THAN
NORMAL TEMPERATURES WILL PREVAIL FOR THE SECOND HALF OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 640 AM UPDATE...HAVE UPDATED TEMPS/SKY COVER PER LATEST OBS
TREND. OTHERWISE...THE FORECAST REMAINS IN GOOD SHAPE.

AS OF 300 AM EDT MONDAY..AN UNSEASONABLY STRONG UPPER LOW PRESSURE
TROUGH WILL SWING SEWARD ACROSS THE UPPER MIDWEST TODAY. THIS WILL
GRADUALLY PUSH A TRAILING SURFACE COLD FRONT EXTENDING FROM THE OHIO
VALLEY TO MID MISSISSIPPI VALLEY SEWARD INTO THE TN VALLEY THROUGH
THIS AFTERNOON. AHEAD OF THIS FEATURE...THE REGION WILL EXPERIENCE
INCREASING SW/WSW FLOW IN LIGHT OF TIGHTENING SURFACE PRESSURE
GRADIENT. VARIOUS MODEL SOUNDINGS SUGGEST THAT WEAKLY CAPPED MID
LEVEL INVERSION LAYER WILL BE PRESENT AREAS EAST OF THE MTNS WITH
THE HELP OF INCREASING H85 DOWNSLOPE +15KTS SWLY WINDS. HENCE...THIS
WILL SOMEWHAT LIMIT THE COVERAGE OF DIURNALLY CONVECTION OVER THE
PIEDMONT. HOWEVER...THE MTN ZONES WILL SEE BETTER COVERAGE OF
CONVECTION DUE TO THE COMBINATION OF UPSLOPE FLOW REGIME AND BETTER
BUOYANCY. WE WILL THUS FEATURE 40-50 POPS IN THE MTNS WITH 20-30 POP
OVER THE PIEDMONT THIS AFTERNOON.

TONIGHT...AS A TRAILING COLD FRONT CONTINUES TO PROGRESS
SEWARD...MODELS AGREE THAT A LINE OF ORGANIZED CONVECTION AHEAD OF
THIS FRONT WILL REACH THE SOUTHERN APPALACHIANS BETWEEN 00Z AND 06Z.
HOWEVER...IT APPEARS THAT THIS FEATURE WILL WEAKEN CONSIDERABLY AS
IT CROSSES THE MTNS. IN FACT...THE SPC HAS BACKED OFF ON THE
COVERAGE OF SLIGHT RISK TO OUR WEST...THOUGH 5 PERCENT OF DAMAGING
WIND THREAT STILL COVERS MUCH OF THE CWA. WITH THAT SAID...POPS RAMP
UP TO LIKELY OVER THE NC MTNS WITH LOW END CHANCE OVER THE PIEDMONT
THROUGH THE OVERNIGHT HOURS. TEMPERATURES WILL RUN A FEW DEGREES
ABOVE CLIMO THROUGH THE PERIOD.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AT 230 AM EDT MONDAY...ON TUESDAY MORNING A CLOSED UPPER LOW WILL BE
OVER MI...WITH A TROUGH EXTENDING SOUTH TO THE GULF COAST. THE LOW
REACHES QUEBEC BY WEDNESDAY MORNING...WHILE THE TROUGH AXIS
PROGRESSES TO THE SOUTHERN APPALACHIANS.

A SHORTWAVE ROUNDING THE TROUGH WILL REACH THE TN VALLEY LATE IN THE
TUESDAY...AND CROSS THE SOUTHERN APPALACHIANS BY WEDNESDAY MORNING.
ANOTHER SHORTWAVE ROUNDING THE TROUGH ON WEDNESDAY WILL REACH THE
CENTRAL APPALACHIANS BY THURSDAY MORNING.

A COLD FRONT WILL BE CROSSING THE MOUNTAINS ON TUESDAY MORNING. THE
FRONT REACHES THE PIEDMONT BY TUESDAY EVENING...AND THE COAST BY
WEDNESDAY MORNING. INSTABILITY AND SHEAR MAY BE SUPPORTIVE OF SEVERE
WEATHER ALONG AND AHEAD OF THE BOUNDARY DURING THE DAY ON TUESDAY...
ESPECIALLY LATER IN THE DAY OVER THE PIEDMONT. QPF WILL BE LIMITED
BY THE SPEED OF THE SYSTEM.

COOL HIGH PRESSURE WILL BE SLOW TO BUILD IN BEHIND THE FRONT...AS
THE BOUNDARY DECELERATED OFF THE CAROLINA COAST AND OVER THE GULF
STATES. A RETURN FLOW FROM THE WESTERN GULF OVER THE STALLED FRONT
WILL PROVIDE MOIST LIFT TO CREATE WIDESPREAD CLOUDS THAT WILL SPREAD
IN NW GA BY THURSDAY MORNING.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AT 230 AM EDT MONDAY...ON THURSDAY MORNING A POSITIVELY TILTED UPPER
TROUGH WILL EXTEND FROM QUEBEC TO THE GULF COAST. THE NORTHERN AND
SOUTHERN STREAM GO OUT OF PHASE BY FRIDAY...WHEN THE NORTHERN STREAM
TROUGH REMAINS IN EASTERN CANADA...AND SHORTWAVE ENERGY MOVING OUT
OF THE PLAINS CAUSES A RETROGRESSION OF THE MEAN SOUTHERN STREAM
TROUGH TO THE LOWER MS RIVER VALLEY. A CLOSED LOW FORMS IN THE
SOUTHERN STREAM TROUGH OVER LAKE MI ON SATURDAY...WHILE THE TROUGH
AXIS MOVES SLOWLY INTO THE OH AND TN RIVER VALLEYS.

ON THURSDAY A COLD FRONT WILL BE OFF THE EAST COAST...WITH A
TRAILING STATIONARY FRONT ALONG THE GULF COAST...AND HIGH PRESSURE
TO THE NORTH FORM THE ROCKIES TO NEW ENGLAND. CLOUD COVER FORMED BY
ISENTROPIC ASCENT OVER THE WESTERN PART OF THE FRONT WILL WASTE NO
TIME SPREADING EAST TO THE SOUTHERN APPALACHIANS ON THURSDAY. BY
FRIDAY THE HIGH WEAKENS AND SHIFTS TO TO THE NORTHEAST...WHILE THE
STATIONARY FRONT REMAINS NEAR THE GULF COAST. HIGH PRESSURE BEGINS
TO BUILD DOWN THE EAST SIDE OF THE APPALACHIANS ON FRIDAY. WEAK
MOIST ASCENT OVER THE GULF FRONT AND SURFACE RIDGE WILL SUPPORT
CLOUD COVER AND PRECIPITATION OVER OUR AREA FRIDAY.

BY SATURDAY THE GULF FRONT MOVES NORTH ACROSS THE DEEP SOUTH...WHILE
THE HIGH PRESSURE EAST OF THE APPALACHIANS BEGINS TO WEAKEN. BY
SUNDAY THE SURFACE HIGH WILL HAVE RETREATED NORTH...AND A WARM
MOIST AIR FLOW FROM THE SOUTH WILL BRING MORE NORMAL WEATHER TO THE
AREA.

INITIALLY...BOTH MAXIMUM AND MINIMUM TEMPERATURES WILL RUN BELOW
NORMAL IN THE COOL AIR MASS BEHIND THE FRONT. BY SATURDAY THE
DIURNAL TEMPERATURE RANGE WILL BE LIMITED BY BOTH CLOUD COVER AND
MOISTURE. TEMPERATURES START TRENDING TOWARD NORMAL ON SUNDAY.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...FOR 12Z TAF...EXPECT VFR CONDITIONS TO
PERSIST OVER MUCH OF THE REGION THROUGH 12Z TUESDAY EXCEPT NC
MTNS/VALLEYS INCLUDING KAVL WHERE A BRIEF PERIOD OF IFR CIG/VSBY MAY
DEVELOP UNDER LLVL MOIST INVERSION LAYER TOWARD DAYBREAK ON TUESDAY.
A DEEPENING UPPER LOW PRESSURE TROUGH AND ASSOCIATED TRAILING
SURFACE COLD FRONT IS EXPECTED TO SLOWLY APPROACH FROM THE NW TODAY.
THUS...EXPECT SW WINDS TO INCREASE BY LATE THIS MORNING AND PERSIST
THAT WAY THROUGH TONIGHT. AS FOR OUR WEATHER...AREAS EAST OF THE
MTNS WILL REMAIN MOSTLY DRY THIS AFTERNOON...WITH THE HELP OF
INCREASING DOWNSLOPE W/WSW WINDS. HOWEVER...ISOLATED TO SCATTERED
THUNDERSTORMS CAN NOT BE RULED OUT. THE MTN ZONES WILL SEE BETTER
COVERAGE OF DIURNALLY DRIVEN CONVECTION DUE TO UPSLOPE FLOW REGIME
AND BETTER BUOYANCY. THUS HAVE MENTIONED TEMPO FOR TSRA FOR MOST
LOCATIONS DURING THE PEAK HEATING HOURS. LATEST SHORT RANGE MODELS
AGREE THAT A STRONG LINE OF CONVECTION WILL APPROACH THE SOUTHERN
APPALACHIANS FROM THE NW LATE THIS AFTERNOON AND EVENING.
HOWEVER...THIS FEATURE WILL WEAKEN CONSIDERABLY AS IT CROSSES THE
MTNS AND DISSIPATES WHEN IT REACHES THE PIEDMONT BY LATE TONIGHT.

OUTLOOK...RESTRICTIONS IN THUNDERSTORMS ARE POSSIBLE ON TUESDAY. VFR
WILL RETURN ON WEDNESDAY BEHIND A COLD FRONT.

CONFIDENCE TABLE...

            11-17Z        17-23Z        23-05Z        05-11Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  87%     HIGH 100%     HIGH 100%     HIGH  97%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  94%
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_TABLES

&&

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

&&

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






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