Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 260239
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
1039 PM EDT MON MAY 25 2015

.SYNOPSIS...
CONTINUED ONSHORE FLOW ASSOCIATED WITH HIGH PRESSURE OFF THE MID
ATLANTIC COAST WILL RESULT IN MODERATE TO HIGH MOISTURE THROUGH
MID WEEK. THIS WILL ALSO INCREASE THE CHANCE OF AFTERNOON AND
EVENING THUNDERSTORMS ACROSS THE AREA THROUGH THURSDAY. AN UPPER
RIDGE WILL BECOME ENTRENCHED OVER THE AREA AGAIN NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
SHOWERS HAVE MOVED OUT OF THE FORECAST AREA. MODELS INDICATE BEST
ISENTROPIC LIFT WILL REMAIN WEST AND NORTH OF THE MIDLANDS AND
CSRA OVERNIGHT.

THERE STILL APPEARS TO BE A GOOD CHANCE FOR LOW CLOUDS TO DEVELOP
WITH LOW LEVEL SE FLOW AND AMPLE MOISTURE...ESPECIALLY ACROSS THE
CSRA AND SOUTHEAST MIDLANDS. MODEL TIME SECTIONS SHOW PLENTY OF
LOW LEVEL MOISTURE AND GUIDANCE CONTINUE TO INDICATE LOW CLOUDS
DEVELOPING DURING THE EARLY MORNING HOURS.

GIVEN DEWPOINTS IN THE 60S AND WELL AS CLOUDS AND MIXING DUE TO A
LOW LEVEL JET...OVERNIGHT LOWS IN THE MID 60S TO AROUND 70 DEGREES
STILL LOOK GOOD.

&&

.SHORT TERM /7 AM TUESDAY MORNING THROUGH THURSDAY NIGHT/...
THE UPPER RIDGE AXIS WILL SHIFT EASTWARD AND WEAKEN A BIT ON
TUESDAY AS SHORTWAVE ENERGY MOVING THROUGH THE SOUTHWESTERLY FLOW
BENEATH THE MIDWEST UPPER TROUGH PUSHES INTO THE SOUTHERN
APPALACHIANS AND CAROLINAS. A PLUME OVER HIGHER PRECIPITABLE
WATER...AROUND 1.7 INCHES...THAT HAS BEEN SITUATED ACROSS THE
MS/TN VALLEYS WILL ALSO SHIFT EASTWARD ALLOWING DEEPER MOISTURE
TO FILL THE ATMOSPHERIC COLUMN OVER THE WESTERN MIDLANDS AND
CSRA. THIS INCREASE IN MOISTURE ALONG WITH INCREASED DEWPOINTS
FROM CONTINUED SOUTHEASTERLY LOW LEVEL FLOW OFF THE ATLANTIC
CIRCULATING AROUND THE BERMUDA HIGH WILL RESULT IN A MODERATELY
UNSTABLE AIRMASS TUESDAY AFTERNOON AND EVENING. WIND SHEAR REMAINS
QUITE WEAK WITH THE STRONGER FLOW OVER THE UPSTATE SO ORGANIZED
CONVECTION IS NOT EXPECTED BUT SCATTERED SHOWERS STORMS ARE
EXPECTED TO DEVELOP WITH DIURNAL HEATING. FOCUSED HIGHEST POPS IN
THE WESTERN MIDLANDS AND CSRA WITH A GRADIENT TO LOWER POPS EAST.
TEMPERATURES COULD BE IMPACTED BY INCREASED CLOUD COVER AND
SHOWERS BUT SHOULD STILL BE CLOSE TO NORMAL VALUES FOR THIS TIME
OF YEAR. CONVECTION MAY LINGER IN THE WESTERN MIDLANDS INTO THE
EVENING DUE TO THE WEAK SHORTWAVE ENERGY IN THE AREA BUT SHOULD
DIMINISH BY MIDNIGHT.

THE AXIS OF BEST MOISTURE SHIFTS A BIT FURTHER EAST OVER THE
MIDLANDS ON WEDNESDAY/THURSDAY...THOUGH THERE ARE SOME MODEL
DIFFERENCES IN HOW FAR EAST THE DEEP MOISTURE MIGRATES...SO
EXPECT A BETTER CHANCE OF CONVECTION WEDNESDAY WITH POSSIBLY MORE
ORGANIZATION AS SHORTWAVE ENERGY MOVING OVER THE AREA COULD
ENHANCE/SUPPORT THE CONVECTION. TEMPERATURES MAY BE SLIGHTLY
COOLER THAN ON TUESDAY DUE TO CLOUDS AND INCREASED SHOWER
CHANCES. THE SEA BREEZE COULD ALSO PROVIDE A FOCUS FOR STORMS
LATE EACH DAY.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
FRIDAY THROUGH MONDAY THE EXTENDED FORECAST WILL BE CHARACTERIZED BY
THE RETURN OF THE UPPER RIDGE OVER THE FORECAST AREA.  THE PLUME OF
ENHANCED ATMOSPHERIC MOISTURE WITH PRECIPITABLE WATER VALUES OVER
1.75 INCHES WILL RETREAT TO THE NORTHWEST ON FRIDAY GIVING WAY TO
THE UPPER RIDGE BUILDING WESTWARD OVER THE SOUTHEASTERN
STATES...CENTERED OVER THE WESTERN ATLANTIC. THE UPPER RIDGE WILL
CONTINUE TO BUILD OVER THE FORECAST AREA NEXT WEEKEND AS SHORTWAVE
ENERGY AND A COLD FRONT SINK SOUTHEASTWARD THROUGH NEW ENGLAND INTO
THE NORTH ATLANTIC. ANOTHER UPPER TROUGH OR CLOSED UPPER LOW
DEVELOPS OVER THE WESTERN PLAINS SAT/SUN BEFORE EJECTING EASTWARD ON
MONDAY. THE GFS IS DEEPER WITH THE UPPER LOW AND LESS PROGRESSIVE
THAN THE ECMWF WITH THE EJECTION OF THE LOW SUN/MON.

THE RESULTING SENSIBLE WEATHER FOR THE MIDLANDS AND CSRA WILL BE
ISOLATED DIURNAL CONVECTION MAINLY ACROSS THE WESTERN MIDLANDS ON
FRIDAY...THEN A RELATIVELY DRY DAY ON SATURDAY UNDER THE INFLUENCE
OF BUILDING HIGH PRESSURE ALOFT AND AT THE SURFACE WITH LOWER
MOISTURE AND PWAT VALUES AROUND AN INCH.  MOISTURE BEGINS TO SLOWLY
INCREASE AGAIN SUN/MON WITH DIURNAL CHANCES OF CONVECTION TYPICAL OF
SUMMER.  TEMPERATURES THROUGH THE PERIOD WILL BE NEAR TO SLIGHTLY
ABOVE NORMAL WITH HIGHS IN THE UPPER 80S TO AROUND 90 FRIDAY TO
LOWER 90S SAT-MON WITH LOWS IN THE 60S.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
LOW STRATUS AND PATCHY FOG POSSIBLE AT ALL TAF SITES EARLY
TUESDAY MORNING. MVFR CEILINGS LIKELY AT ALL TAF SITES IN THE
06Z-15Z TIME-FRAME. MODELS ALSO INDICATE A LOWER CHANCE FOR IFR
CIGS 09Z-14Z.

EASTERLY ONSHORE FLOW CONTINUES AND SHOULD PROMOTE LOW LEVEL
CLOUDS THROUGHOUT THE FA. ISENTROPIC LIFT APPEARS TO BE STRONGEST
ALONG THE MIDLANDS INTO THE UPSTATE OVERNIGHT ALLOWING FOR LOW
LEVEL MOISTURE AND STRATUS TO FORM. THE NAM AND GFS ARE IN BETTER
AGREEMENT THAN LAST NIGHT WITH BRINGING IN LOW CLOUDS. HIGHER
DEWPOINTS SUPPORT MODEL GUIDANCE. PATCHY FOG MAY ALSO FORM
OVERNIGHT AS WINDS BECOME LIGHT. THE GREATEST CHANCE OF FOG
FORMATION IS AT OGB AND ALONG THE COASTAL PLAIN WHERE MID LEVEL
DRY AIR WILL BE A FAVORABLE SET UP FOR FOG.

MVFR/IFR CIGS SHOULD LIFT AFTER SUNRISE ALLOWING VFR CONDITIONS
TO RETURN AROUND 15Z WITH SURFACE WINDS BECOMING SOUTHERLY 5 TO 10
KTS.

EXTENDED AVIATION OUTLOOK...EARLY MORNING RESTRICTIONS ARE
POSSIBLE THROUGH THE END OF THE WEEK. THERE WILL ALSO BE AN
INCREASED CHANCE OF AFTERNOON/EVENING SHOWERS AND THUNDERSTORMS
WHICH COULD REDUCE CEILINGS/VISIBILITIES AT TIMES.

&&

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

&&

$$


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