Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 041624
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1124 AM EST WED MAR 4 2015

.SYNOPSIS...
VERY WARM AND MOIST AIR WILL RETURN TO THE AREA TODAY AHEAD OF AN
APPROACHING COLD FRONT. THIS FRONT IS FORECAST TO PASS THROUGH THE
AREA ON THURSDAY...WITH COOL AND DRY HIGH PRESSURE RETURNING FOR
FRIDAY AND INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 1120 AM...MADE SOME ADJUSTMENTS TO SKY COVER IN THE MOUNTAINS AS
WELL AS TEMPS. A GOOD AMOUNT OF SUNSHINE HAS SPIKED TEMPS INTO THE
LOWER 70S IN THE FRENCH BROAD VALLEY. THEREFORE...HAVE BUMPED MAX
TEMPS UP CONSIDERABLY...BUT BELOW RECORD LEVELS. OUTSIDE THE
MOUNTAINS...COOL POOL GRADUALLY ERODING FROM THE NORTH. STILL EXPECT
ALL OF THE PIEMDONT AREAS TO EVENTUALLY MIX OUT IN THE EARLY TO MID
AFTERNOON TIMEFRAME. WHEN IT DOES...TEMPS WILL CLIMB RAPIDLY.

AS OF 0945AM...REMNANT COOL POOL STILL STUBBORNLY HANGING ON OUTSIDE
OF THE MOUNTAINS DESPITE SW WINDS. MOUNTAIN TEMPS STILL REMAIN CLOSE
TO 15 DEGREES WARNER THAN THE PIEDMONT. ALL SHORT TERM GUIDANCE
CONTINUES TO INDICATE THAT THE WARM AIR WILL EVENTUALLY PREVAIL
TODAY. STILL EXPECT THAT THE LOW STRATUS AND FOG WILL MIX OUT IN THE
EARLY AFTERNOON. WILL LET THE FOG ADVISORY EXPIRE AT 1000L BUT
FOLLOW IT UP WITH A SPS FOR PATCHY DENSE FOG UNTIL MIDDAY. STILL
LOOKS LIKE MAX TEMPS WILL TOP OUT IN THE UPPER 60S TO LOWER 70S
OUTSIDE THE MOUNTAINS WITH MID 60S MOUNTAIN VALLEYS. TRIMMED POPS
BACK SOME TODAY OVER THE MOUNTAINS BASED ON CURRENT RADAR.

AS OF 650 AM...QUITE THE FASCINATING SITUATION OVER THE FORECAST
AREA THIS MORNING...AS THE MTN VALLEYS ARE AS MUCH AS 20 DEGREES
WARMER THAN THE ADJACENT ERODING DAMMING AIR MASS OVER THE PIEDMONT.
SOME OF THIS WARMTH IS BEGINNING TO SPREAD INTO THE FOOTHILLS...
RESULTING IN IMPROVING VISBY (ALBEIT WITH STILL VERY LOW CEILINGS).
THE DENSE FOG ADVISORY WILL BE ALLOWED TO CONTINUE AS ADVERTISED...
BUT IT APPEARS THAT DENSE FOG WILL BE PATCHY AT WORST ACROSS THE
FOOTHILLS THROUGH THE REMAINDER OF THE MORNING. OTHERWISE...PATCHY
RAIN/SHOWERS CONTINUE NEAR THE TENN BORDER...WITH THE BULK OF
ACTIVITY REMAINING WEST OF THE FORECAST AREA.

DENSE FOG IS SLOWLY BUT SURELY EXPANDING ACROSS THE PIEDMONT THIS
MORNING WITHIN WARM/MOIST ADVECTIVE/DECAYING WEDGE REGIME. AS
SUCH...THE DENSE FOG ADVISORY APPEARS TO BE VERY WELL PLACED...AND
WILL REMAIN IN EFFECT UNTIL 15Z.

THE BULK OF SHOWER ACTIVITY CONTINUES TO DEVELOP ACROSS THE GREAT
TENN VALLEY AND CUMBERLAND PLATEAU AREAS THIS MORNING...LIFTING
PRIMARILY WEST OF THE APPALACHIANS WITHIN DEEP SW FLOW ALOFT. THIS
PROBABLY ISN/T GOING TO CHANGE A WHOLE LET OVER THE NEXT 12-18
HOURS...AS THIS IS WHERE THE BETTER FORCING AND MOISTURE PROFILES
WILL REMAIN THROUGH THE DAY...UNDER PERSISTENT DEEP SW FLOW.
STILL...CHANCE POPS APPEAR WARRANTED ALONG THE TENN BORDER THROUGH
THE DAY...WITH 50-60 POPS RESERVED PRIMARILY FOR THE SMOKIES AND
SURROUNDING AREAS...WHICH IS SLIGHTLY MORE ALONG THE TRAJECTORY OF
THE SHOWER GENERATION AREA...AND STANDS THE BEST CHANCE OF SEEING
SHOWERS INITIATE IN RESPONSE TO MECHANICAL LIFT ASSOCIATED WITH THE
SW FLOW.

THE AIR MASS ABOVE THE DRAINING COOL POOL IS VERY WARM...WITH H8
TEMPS OF +10 TO +13 REPORTED ACROSS THE REGION AT 00Z. ONCE THE FOG
AND LOW STRATUS BURN OFF...TEMPS WILL SOAR ACROSS THE AREA...LIKELY
REACHING THE 70S ACROSS MUCH OF THE PIEDMONT THIS AFTERNOON . IN
FACT...IF THE GRUNGE DISSIPATES EARLIER THAN CURRENTLY
ANTICIPATED...EVEN THIS MAY PROVE TO BE TOO COOL...AND WOULD NOT BE
SURPRISED TO SEE EXTREME SOUTHERN PIEDMONT AREAS TOP OUT NEAR 80.

POPS WILL GRADUALLY RAMP UP ACROSS THE MTNS THIS EVENING...AS
COLD/ANAFRONT GRADUALLY BUILDS INTO THE FORECAST AREA. DUE TO THE
ANAFRONT NATURE OF THE BOUNDARY...TIMING OF THE WIND SHIFT INTO THE
AREA WILL DICTATE HOW SOON LIKELY/CATEGORICAL CHANCES FOR RAIN WILL
DEVELOP OVER THE FORECAST AREA...AND THESE THINGS NEVER SEEM TO MOVE
AS FAST AS THE MODELS SUGGEST. THEREFORE...THE HIGHEST POPS HAVE
BEEN DELAYED UNTIL AFTER MIDNIGHT...CATEGORICAL ACROSS THE
MTNS...TAPERING TO HIGH CHANCE/LIKELY ACROSS THE PIEDMONT BY
DAYBREAK THU.

COLD AIR MAY BEGIN FILTERING INTO THE FAR WESTERN MTN VALLEYS BY
DAYBREAK THU...WITH PROFILES EXHIBITING A TREMENDOUS WARM NOSE...AND
FREEZING RAIN BEING THE PRIMARY WINTRY P-TYPE. WHILE IT APPEARS THAT
FREEZING RAIN WILL BE LIKELY AT SOME POINT DURING THIS EVENT ACROSS
THE WESTERN MTN VALLEYS...TIMING OF THE ARRIVAL OF COLD AIR IS STILL
HIGHLY UNCERTAIN...AND SUSPECT DAYBREAK THURSDAY IS THE
EARLIEST THAT THIS WOULD OCCUR. THEREFORE...NO ADVISORIES WERE
ENTERTAINED ON THIS SHIFT.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AT 300 AM EST WEDNESDAY...ON THURSDAY MORNING AN UPPER TROUGH WILL
EXTEND FRONT EASTERN CANADA TO THE SOUTHERN PLAINS...WITH A WELL
DEFINED SHORTWAVE MOVING THROUGH IT OVER THE UPPER MS RIVE VALLEY
AND SOUTHERN PLAINS. THE TROUGH DEAMPLIFIES SOMEWHAT BY
FRIDAY...WHILE AN UPPER LOW CLOSES OFF IN NW MEXICO. THE SHORTWAVE
MOVING THROUGH BECOMES MORE CHANNELED...APPROACHING THE SOUTHERN
APPALACHIANS IN THE MORNING. A SECOND AND MORE ROBUST SHORTWAVE
APPROACHES THE MOUNTAINS LATER IN THE DAY...CROSSING THE MOUNTAINS
BY FRIDAY EVENING...AND MOVING TO THE SOUTHERN EDGE OF OUR AREA LATE
SATURDAY NIGHT.

AT THE SURFACE...ON THURSDAY MORNING A STRONG COLD FRONT WILL BE
LOCATED JUST SE OF OUR AREA...WITH A SURFACE WAVE MOVING ALONG IT
OVER SC. MOISTURE WILL EXTEND WELL BEHIND THE FRONT INTO THE MS
RIVER VALLEY...AND POST FRONTAL PRECIPITATION. THE NAM EVEN SHOWS
SOME INSTABILITY AND SHEAR BEHIND THE BOUNDARY OVER UPSTATE SC AT
MIDDAY. AS THE FRONT MOVES SE DURING THE DAY...COLD ADVECTION WILL
SPREAD OVER THE NC MOUNTAINS. MODEL SOUNDINGS ARE INITIALLY TO WARM
AT THE TOP OF THE MOIST LAYER TO SUPPORT ICE NUCLEATION...AND
FREEZING RAIN IS EXPECTED BY LATE IN THE DAY. DRYING FROM THE TOP
DOWN WILL RAPIDLY LESSEN THE CHANCE OF PRECIPITATION IN THE
EVENING...BUT RAPID COOLING WILL BRING THE TOP OF THE MOIST LAYER TO
THE POINT OF ICE NUCLEATION...SUPPORTING A CHANGEOVER FROM FREEZING
RAIN TO SNOW BEFORE PRECIPITATION ENDS LATE THURSDAY NIGHT. FRIDAY
AND FRIDAY NIGHT FEATURE DRY AND COOL CONDITIONS.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AT 300 AM EST WEDNESDAY...ON SATURDAY MORNING A WELL AMPLIFIED UPPER
TROUGH WILL EXTEND FROM NE CANADA TO THE SOUTHERN APPALACHIANS...
WHILE A CLOSED UPPER LOW WILL BE OVER NW MEXICO. THE TROUGH LOSES
SOME AMPLITUDE BY SUNDAY...WHILE THE UPPER LOW FILLS AND CROSSES
NORTHERN MEXICO. THE REMAINS OF THE UPPER LOW CROSS THE SOUTHERN
PLAINS ON MONDAY...RESULTING IN LOW AMPLITUDE RIDGING OVER THE
SOUTHERN APPALACHIANS...WHILE NORTHERN STREAM FLOW BECOMES ZONAL. ON
TUESDAY THE ECMWF AND GFS DIVERGE...WITH THE FORMER HAVING ZONAL
FLOW OVER THE SE...AND THE LATER MAINTAINING A TROUGH IN THE LOWER
MS RIVER VALLEY AND A RIDGE TO THE EAST.

AT THE SURFACE...ON SATURDAY DRY HIGH PRESSURE WILL EXTEND FROM
CHESAPEAKE BAY TO TX...WHILE A STATIONARY FRONT WILL EXTEND FROM S FL
TO NEAR THE YUCATAN PENINSULA. MOISTURE AND PRECIPITATION ASSOCIATED
WITH THIS FRONT IS EXPECTED TO REMAIN SOUTH OF OUR AREA. A DRY COLD
FRONT RAPIDLY CROSSES OUR AREA SATURDAY NIGHT...REACHING THE GA
COAST BY SUNDAY MORNING...WHILE THE STATIONARY FRONT REMAIN OVER S
FL. ON MONDAY A SURFACE WAVE DEVELOPS ON THE STATIONARY FRONT IN THE
WESTERN GULF OF MEXICO. MOISTURE IS EXPECTED TO SPREAD FARTHER NORTH
OVER THE FRONT IN FL...PERHAPS SUPPORTING SMALL POPS AS FAR N AS OUR
AREA. BY TUESDAY THE SURFACE WAVE REACHES THE SC COAST...WITH
PRECIPITATION IN ISENTROPIC UPGLIDE EXTENDING BACK THE THE SOUTHERN
APPALACHIANS.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...LIFR CONDITIONS WILL CONTINUE UNTIL LATE MORNING.
CONDITIONS HAVE BEEN WELL-BEHAVED IN NOT FALLING BELOW AIRPORT
MINIMUMS...AND WILL TO KEEP THEM THAT WAY IN THE FORECAST. EXACT
TIMING OF LIFTING OF THE FOG/CIGS IS UNCERTAIN AS USUAL...BUT 16Z
SEEMS TO BE A REASONABLE GUESSTIMATE IN LIGHT OF THE SHALLOWNESS OF
THE MOISTURE DEPTH...AND THE WARMING THAT IS OCCURRING ACROSS THE
AREA. VFR CONDITIONS ARE EXPECTED BY EARLY AFTERNOON...ALONG WITH
GUSTY SW WINDS. GUSTS WILL DIMINISH THIS EVENING...BUT SW WINDS WILL
REMAIN AROUND 10 KTS THROUGH THE OVERNIGHT. CIGS SHOULD BEGIN TO
LOWER AGAIN LATE TONIGHT...IN ADVANCE OF AN APPROACHING COLD FRONT.
RAIN CHANCES WILL ALSO INCREASE...BUT THE BEST CHANCES ARE EXPECTED
TO HOLD OFF UNTIL AFTER THE END OF THE FORECAST PERIOD.

ELSEWHERE...WHILE PERIODS OF VLIFR VISBY ARE EXPECTED TO PERSIST AT
KAND THROUGH 14Z OR SO...SIGNIFICANT IMPROVEMENT HAS BEEN NOTED AT
THE FOOTHILLS SITES OVER THE PAST HOUR OR SO. NEVERTHELESS...LIFR
CIGS WILL PERSIST THROUGH LATE-MORNING OR SO AT THE PIEDMONT/FHILLS
TERMINALS. OTHERWISE...SIMILAR CONDITIONS TO KCLT . MEANWHILE...VFR
CONDITIONS ARE EXPECTED TO PERSIST AT KAVL THROUGH AT LEAST THE
DAYLIGHT HOURS...BEFORE LOWERING AGAIN TONIGHT IN ADVANCE OF A COLD
FRONT. RAIN MAY ALSO APPROACH LATE TONIGHT...AS THE COLD FRONT DRAWS
NEARER.

OUTLOOK...A COLD FRONT WILL REMAIN OVER THE REGION THROUGH
THURSDAY...BRINGING CHANCES FOR HEAVIER RAINFALL AND LOW CIGS/VSBYS
TO THE AREA. VFR CONDITIONS ARE EXPECTED TO RETURN FOR FRIDAY
THROUGH THE WEEKEND.

CONFIDENCE TABLE...

            13-19Z        19-01Z        01-07Z        07-12Z
KCLT       HIGH  95%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   74%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       MED   77%     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...WIMBERLEY
NEAR TERM...LG
SHORT TERM...JAT
LONG TERM...JAT/WIMBERLEY
AVIATION...JDL



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