Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 101043
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
643 AM EDT THU JUL 10 2014

.SYNOPSIS...
A SURFACE TROUGH AND AN APPROACHING FRONTAL BOUNDARY WILL PROVIDE
INCREASED CHANCES OF SHOWERS AND THUNDERSTORMS ACROSS THE AREA
TODAY. THE WEAK FRONT WILL PUSH INTO THE AREA ON FRIDAY AND
STALL...EVENTUALLY BECOMING DIFFUSE THIS WEEKEND. ANOTHER UPPER
TROUGH AND APPROACHING FRONT WILL BRING INCREASED CHANCES FOR RAIN
AGAIN EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
REGIONAL RADAR CONTINUES TO SHOW SCATTERED SHOWERS DEVELOPING IN
THE VICINITY OF A SURFACE TROUGH WITH WEAK MOIST LOW LEVEL
SOUTHWESTERLY FLOW. CONVECTION EARLIER HAD MORE OF A WEST TO EAST
MOTION WHILE RECENT IMAGERY SHOWS MORE OF A SOUTHWEST TO
NORTHEASTERLY MOTION. THIS IS RESULTING FROM THE GRADUAL
AMPLIFICATION OF THE UPPER TROUGH AXIS OVER THE OHIO AND TENNESSEE
VALLEYS AS SHORTWAVE ENERGY DROPS INTO THE BACK SIDE OF THE TROUGH
OVER THE GREAT PLAINS.

THE AMPLIFICATION OF THE UPPER TROUGH HAS RESULTED IN SLOWER
PROGRESSION OF THE SURFACE COLD FRONT EXTENDING FROM THE NORTHEAST
BACK THROUGH THE CENTRAL APPALACHIANS AND TO THE MID MISSISSIPPI
VALLEY. DESPITE SOME EARLY CONVECTIVE DEBRIS CLOUDS OVER THE
AREA...A GENERAL THINNING OF THESE CLOUDS IS EXPECTED AND MODERATE
INSTABILITY WILL AGAIN BE PRESENT THIS AFTERNOON WITH INCREASED
PRECIPITABLE WATER VALUES AROUND OR GREATER THAN 2 INCHES. THE
ADDITIONAL ATMOSPHERIC MOISTURE RESULTS IN A LOWER LEVEL OF FREE
CONVECTION AND SHALLOWER AND LESS PRONOUNCED LOW LEVEL INVERTED V
ON MODEL FORECAST SOUNDINGS...AND LOWER WINDEX VALUES.
HOWEVER...PROJECTED MODERATE INSTABILITIES COULD STILL PROVIDE AN
ISOLATED SEVERE WIND GUST THREAT. MAIN CONCERN TODAY MAY BE
LOCALLY HEAVY RAIN AND ISOLATED FLOODING POTENTIAL GIVEN HIGH PW
VALUES.

WILL CONTINUE THE LIKELY POPS ACROSS THE FORECAST AREA TODAY
BEGINNING AFTER 17Z AND CONTINUING INTO THE EVENING HOURS. CANNOT
TOTALLY RULE OUT POPS OVERNIGHT WITH A BOUNDARY IN THE AREA SO
WILL HOLD ON TO POPS ALL NIGHT THOUGH GRADUALLY LOWERING THEM
TOWARDS THE PREDAWN HOURS. HIGHS TODAY SHOULD BE COOLER THAN
YESTERDAY WITH MORE MOISTURE PRESENT AND ANTICIPATED WIDESPREAD
PRECIPITATION...IN THE UPPER 80S TO LOWER 90S. TEMPERATURES WILL
STRUGGLE TO FALL TONIGHT UNDER MOSTLY CLOUDY SKIES AND ELEVATED
DEWPOINTS...WITH LOWS EXPECTED IN THE LOWER 70S.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
THE FRONTAL BOUNDARY WILL MOVE INTO THE FORECAST AREA AND BECOME
STALLED OVER THE MIDLANDS ON FRIDAY AS THE UPPER TROUGH AXIS
SHIFTS OVERHEAD. THE AXIS OF HIGHEST PRECIPITABLE WATER VALUES
ALSO SHIFTS TOWARD THE COASTAL PLAIN BY FRIDAY. BY LATE FRIDAY
SOME DRIER AIR WILL ATTEMPT TO BUILD INTO THE REGION FROM THE WEST
AS A WEST TO EAST GRADIENT IN PRECIPITABLE WATER SETS UP WITH
VALUES CLOSE TO 2 INCHES IN THE EASTERN MIDLANDS AND DOWN TO
AROUND 1.5 IN THE WESTERN MIDLANDS. THIS WILL SUPPORT HIGHER POPS
IN THE EAST CLOSER TO THE BETTER MOISTURE AND THE FRONTAL BOUNDARY
WHICH WILL BECOME DIFFUSE. WILL CARRY HIGHER POPS IN THE EAST AND
LOWER CHANCE IN THE WEST. TEMPERATURES WILL AGAIN BE NEAR
CLIMATOLOGY IN THE LOWER 90S WITH MODERATE INSTABILITY. CANNOT
RULE OUT AN ISOLATED SEVERE STORM FRIDAY BUT THINK THE MAIN THREAT
WOULD BE POSSIBLE ISOLATED FLOODING IN THE EASTERN PART OF THE
FORECAST AREA WITH HIGH PW VALUES.

SATURDAY FEATURES A BIT DRIER AIRMASS IN PLACE AS PW VALUES FALL
BELOW 1.5 INCHES ACROSS MOST OF THE AREA AND THE ATMOSPHERE
BECOMES LESS UNSTABLE AS UPPER HEIGHTS ATTEMPT TO BUILD OVER THE
REGION. LOWERED POPS A BIT ACROSS THE FORECAST AREA BUT CONTINUING
TO SHOW A GRADIENT WITH SLIGHT CHANCE POPS IN THE NORTHWESTERN
MIDLANDS TO SOLID CHANCE POPS IN THE SOUTHEASTERN MIDLANDS.
TEMPERATURES WILL REBOUND A BIT ESPECIALLY IN THE WESTERN PART OF
THE AREA WITH HIGHS IN THE MID 90S...WHILE SLIGHTLY COOLER IN THE
EASTERN MIDLANDS.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
TYPICAL SUMMER TIME DIURNAL CONVECTION IS EXPECTED SUNDAY AND
MONDAY WITH THE UPPER RIDGE CENTERED OVER THE DEEP SOUTH RIDGING
EASTWARD OVER THE AREA ATOP A SHALLOW MOIST BOUNDARY LAYER WITH
SOUTHERLY FLOW AROUND THE BERMUDA HIGH. TEMPERATURES RETURNING
BACK ABOVE NORMAL SUN-TUE WITH HIGHS IN THE MID 90S. A DEEP CLOSED
UPPER LOW IS FORECAST TO DIG SOUTHWARD INTO THE GREAT LAKES REGION
MONDAY INTO TUESDAY RESULTING IN LOW PRESSURE TRACKING ACROSS THE
OHIO VALLEY AND PUSHING A COLD FRONT SOUTHEASTWARD INTO THE
FORECAST AREA ON TUESDAY AND STALLING OVER THE REGION ON
WEDNESDAY. HIGHER POPS WARRANTED FOR TUE-WED WITH THE APPROACHING
FRONT AND UPPER HEIGHT FALLS. PW VALUES RISE BACK ABOVE 2 INCHES
DURING THIS TIME SUPPORTING A HEAVY RAIN THREAT AS WELL AS
INCREASING THE INSTABILITY OF THE ATMOSPHERE. POSSIBLE SEVERE
WEATHER TUE OR WED CANNOT BE RULED OUT.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
AFTER MORNING FOG...WITH GENERALLY MVFR VSBYS...DISSIPATES
EARLY THIS MORNING...VFR CONDITIONS EXPECTED OUTSIDE DIURNAL
THUNDERSTORM ACTIVITY. FRONTAL BOUNDARY JUST TO OUR NORTH WILL
SLIP SLOWLY SOUTH TODAY. THE FRONT ALONG WITH A MOIST ATMOSPHERE
AND DAYTIME HEATING EXPECTED TO RESULT IN LIKELY CHANCES OF SHOWER
AND THUNDERSTORM ACTIVITY THIS AFTERNOON THROUGH EARLY TONIGHT.
HIGH RESOLUTION MODELS GENERALLY AGREE THAT SCATTERED
THUNDERSTORMS WILL DEVELOP THIS AFTERNOON ALONG THE BOUNDARY JUST
TO OUR NORTH...AND ALONG A SEA BREEZE JUST TO OUR SOUTH...THEN THE
TWO AREAS COULD CONVERGE OVER OUR FORECAST AREA....APPEARING TO
PROVIDE GOOD CONFIDENCE OF SH/TSRA AFFECTING THE TERMINALS AT SOME
POINT...MAINLY LATE AFTERNONO AND EVENING. FOR NOW...WILL CONVEY
THREAT WITH A VCSH GROUP FROM 18Z TO 02Z...WITH AN EMBEDDED TEMPO
TSRA FROM 21Z TO 24Z TO HIGHLIGHT BEST TIMING THREAT. AFTER
DIURNAL CONVECTION DISSIPATES...FOG MAY DEVELOP LATE TONIGHT INTO
EARLY FRIDAY MORNING...BUT UNCERTAINTIES WITH REGARDS TO EXTENT OF
LINGERING CONVECTIVE DEBRIS CLOUD COVER PRECLUDES MENTION IN THE
TAFS AT THIS TIME.

.EXTENDED AVIATION OUTLOOK...
SCATTERED AFTERNOON/EVENING THUNDERSTORMS.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&

$$







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