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Area Forecast Discussion

231
FXUS62 KGSP 302037
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
437 PM EDT WED JUL 30 2014

.SYNOPSIS...
CANADIAN HIGH PRESSURE WILL BEGIN TO SLIDE EAST OF THE AREA AND
WEAKEN THROUGH FRIDAY. AS THE HIGH WEAKENS...MOISTURE WILL RETURN
FOR THE WEEKEND INCREASING THE CHANCES OF WIDESPREAD SHOWERS AND
THUNDERSTORMS. CONDITIONS RETURN TO THOSE MORE TYPICAL OF LATE
SUMMER BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 415 PM...IN THE VERY NEAR TERM A QUIET AFTERNOON WILL CONTINUE
WITH GENERALLY MOSTLY SUNNY CONDITIONS AND PLEASNT MAX TEMPS MORE
LIKE MID TO LATE SEPTEMBER. ISOLD-SCT CONVECTION CONTINUES EAST AND
SOUTH OF THE AREA NEARER THE STATIONARY/SEA BREEZE FRONT. SOME OF
THE CU OVER THE BALSAMS ARE LOOKING FAIRLY CONGESTED...AND IT IS IN
THIS AREA THAT THE CONVECTIVE MODELS ARE IN BEST AGREEMENT SHOWERS
COULD FIRE. THUS...I EXPANDED THE SCHC POPS OVER A BIT WIDER AREA OF
THE SRN MTNS. OTHERWISE...FCST LOOKS GOOD.

AS OF 215 PM...IN REGARD TO THE BIG PICTURE....SOME CHANGES ARE
ANTICIPATED TO GRADUALLY TAKE PLACE BY LATE THU. THE UPPER TROUGH
AXIS OVER THE EASTERN U.S. IS FORECAST BY THE MODELS TO BECOME
RE-ESTABLISHED TO THE WEST OF THE APPALACHIANS AS ENERGY FROM THE
CENTRAL ROCKIES DIVES SE. AT THE SAME...A STATIONARY FRONT NEAR THE
COAST WILL BEGIN TO MOVE SLOWLY WESTWARD AS A WARM FRONT. HENCE BY
LATE TONIGHT...BOUNDARY LAYER WINDS WILL BEGIN TO VEER TO THE E-SE
WHICH WILL ADVECT ATLANTIC MOISTURE INTO THE AREA AND PROVIDE WEEK
MECHANICAL LIFT ACROSS THE HIGHER TERRAIN. PLUS BY THU AFTERNOON...A
VORT MAX IS FORECAST TO APPROACH FROM THE SW AND SWING ACROSS THE
MOUNTAINS THU AFTERNOON. ALL THIS COMBINED WILL GIVE US AN
INCREASING CHANCE FOR SHOWERS ON THU....WITH THE BEST COVERAGE OVER
THE NC MOUNTAINS DURING THE AFTERNOON HOURS. WILL LIMIT POPS TO THE
CHANCE RANGE AT THIS TIME AS INSTABILITY APPEARS LIMITED WITH ONLY A
COUPLE HUNDRED JOULES OF CAPE EXPECTED. ONLY WIDELY SCATTERED
SHOWERS ARE EXPECTED OUTSIDE THE MOUNTAINS. WITH INCREASING CLOUDS
TONIGHT...MIN TEMPS SHOULD BE SEVERAL DEGREES HIGHER THAN LAST
NIGHT. CONSIDERABLE CLOUDINESS IS ANTICIPATED ON THU WHICH WILL
CONTINUE TO HOLD MAX TEMPS BELOW CLIMO.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 220 PM...ON FRIDAY...MOISTURE ACROSS THE SOUTHEAST U.S. SHOULD
INCREASE SHARPLY AS ATLANTIC MOISTURE ADVECTS WEST AND MERGES WITH
MOISTURE ASSOCIATED WITH A FADING SOUTHERN PLAINS LOW. FORECAST
SOUNDINGS INDICATE THAT PW WILL INCREASE TO AROUND 1.75 INCHES BY
FRIDAY MORNING...WITH LCLS BELOW 2 KFT. NAM12 SHOWS ISENTROPIC LIFT
WILL STRENGTHEN BETWEEN 305K-315K FRI MORNING...PERSISTING THROUGH
THE AFTERNOON. LOW LEVEL LIFT WILL LIKELY BE AUGMENTED ALONG THE
EAST FACING SLOPES AS WINDS REMAIN FROM THE SOUTHEAST AROUND 20 KTS.
IN ADDITION...A BROAD AREA OF MID LEVEL Q-VECTOR CONVERGENCE WILL
REMAIN ACROSS THE SOUTHEAST...EAST OF AN AMPLIFYING L/W TROF CENTERED
ACROSS THE MISSISSIPPI RIVER VALLEY. THE COMBINATION OF THE DEEP
LIFT...ABUNDANT MOISTURE...AND WEAK INSTABILITY SHOULD SUPPORT
NUMEROUS SHOWERS AND THUNDERSTORMS ON FRIDAY... I WILL FORECAST
GENERALLY LIKELY POPS ALONG AND WEST OF I-85...HIGH CHC EAST. THE
LACK OF INSTABILITY ACROSS THE MTNS AND FOOTHILLS MAY SUPPORT ONLY
SHOWERS...THUNDERSTORMS APPEAR POSSIBLE ALONG AND EAST OF I-85.
PERIODS OF RAIN...ENE WINDS...AND THICK CLOUD COVER SHOULD LIMIT
DAYTIME HEATING...KEEPING HIGHS IN THE 70S ACROSS THE MTNS TO
WESTERN PIEDMONT.

ON SATURDAY...THE RIDGE OF SFC HIGH PRESSURE SHOULD TREND WEAKER
THROUGH THE DAY. HOWEVER...SHALLOW RIDGING IS EXPECTED TO LINGER
ALONG AND EAST OF THE HIGH TERRAIN. DEEP FORCING IS EXPECTED TO
CONTINUE ACROSS THE FORECAST AREA...AIDED BY THE APPROACH OF THE
AMPLIFYING MID LEVEL TROF. I WILL FORECAST A RANGE IN POPS...LIKELY
POPS ACROSS THE MTNS TO HIGH CHC EAST. LLVL WINDS ARE EXPECTED TO
VEER FROM THE SOUTHWEST...SUPPORTING TEMPERATURES 4 TO 6 DEGREES
WARMER THAN FRIDAY. FORECAST SOUNDINGS INDICATE WEAK INSTABILITY
ACROSS THE FORECAST AREA...SUPPORTING A MENTION OF THUNDERSTORMS FOR
ALL ZONES.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 200 PM WEDNESDAY...THE MEDIUM RANGE WILL START OUT WITH A
FAIRLY DEEP H5 TROF AXIS EXTENDING FROM THE GREAT LAKES SOUTH TO THE
LWR MS VLY AT 00Z SUNDAY. THE TROF WILL GRADUALLY WEAKEN/SHEAR OUT
EARLY NEXT WEEK...BUT SOME DEGREE OF TROFINESS WILL LINGER THRU
WEDNESDAY. A QUASI-STATIONARY FRONTAL ZONE WILL LINGER PARALLEL TO
THE SWLY UPR FLOW ALONG/JUST INLAND OF THE EAST COAST...KEEPING THE
CWFA IN A MOIST/UNSETTLED ENVIRONMENT INTO EARLY NEXT WEEK. THE
FRONT WILL WASH OUT BY WEDNESDAY...PER THE CONSENSUS OF THE MEDIUM
RANGE GUIDANCE.

SO BLENDING IN THE NEW GUIDANCE AND WPC GUIDANCE...I WILL FCST ABOVE
NORMAL POPS FOR SUNDAY AND MONDAY (HIGH-END CHC TO LIKELY)...AND
TAPERING SOMEWHAT TO SHOTGUN LOW-MID CHC FOR TUESDAY AND WEDNESDAY.
TEMPS WILL START OUT WITH BELOW NORMAL HIGHS (DUE TO
CLOUDS/PRECIP)...AND NEAR NORMAL LOWS THRU MONDAY...THEN AFTN HIGHS
WILL TREND TOWARD NORMAL BY WEDNESDAY WITH CONTINUED NEAR NORMAL
LOWS.

THE EXPECTED DECENT COVERAGE OF PRECIP OVER SEVERAL PERIODS LOOKS TO
BE MAINLY SUPPORTED BY PERSISTENT UPPER DIVERGENCE WITHIN RIGHT
ENTRANCE REGION OF A NEARLY STATIONARY JET STREAK ALONG THE
APPALACHIANS. HOWEVER...QG FORCING AND LLVL TRIGGERING WILL BE ONLY
MARGINALLY SUPPORTIVE...WITH THE BETTER MID LVL FORCING TO THE
NORTH...AND LLVL JET AND INSTBY TO THE EAST. SO CONFIDENCE IS LOW ON
ANY SEVERE WX OR HEAVY RAIN THREAT AT THIS TIME.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...VFR CIGS WILL LIKELY COME AND GO THRU LATE AFTN AS DIURNAL
CUMULUS CONTINUE TO BUBBLE. WINDS SHOULD BE NEARLY CALM BUT CONTINUE
TO PREVAIL NLY WHEN BLOWING. VFR CONDITIONS WILL PREVAIL THROUGH THE
PERIOD DESPITE INCREASING MOISTURE AS BOUNDARY LAYER WINDS TURN TO
THE SE. LOW VFR CIGS ARE A GOOD BET BY LATE TONIGHT. SFC WINDS WILL
BE LIGHT.

ELSEWHERE...MUCH THE SAME AS KCLT WITH VFR CONDITIONS PREVAILING
THROUGH THE PERIOD WITH THE EXCEPTION OF POSSIBLE MVFR FOG AT KAVL
EARLY THURSDAY MORNING. SHOWER CHANCES WILL BE INCREASING ON THU BUT
POPS TOO LOW BEFORE 18Z TO MENTION IN TAFS.

OUTLOOK...MOISTURE WILL CONTINUE TO INCREASE THROUGH THE REMAINDER
OF THE WORK WEEK AS A WARM FRONT APPROACHES FROM THE EAST AND
SOUTHEASTERLY FLOW CONTINUES. UNSETTLED WEATHER WITH ENHANCED
PRECIPITATION CHANCES ALONG WITH MORNING FOG/STRATUS THROUGH THE
WEEKEND.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-20Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  95%     HIGH  91%     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_TABLES

&&

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

&&

$$
SYNOPSIS...ARK
NEAR TERM...LG/WIMBERLEY
SHORT TERM...NED
LONG TERM...ARK
AVIATION...LG/WIMBERLEY







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