Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 202202
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
602 PM EDT WED AUG 20 2014

.SYNOPSIS...
DRIER AIR AND A BUILDING UPPER RIDGE JUST TO OUR WEST WILL REDUCE
THUNDERSTORM CHANCES THROUGH FRIDAY...AND LEAD TO HOTTER HIGH
TEMPERATURES. AN APPROACHING COLD FRONT AND INCREASING MOISTURE
WILL INCREASE THE THUNDERSTORM CHANCE OVER THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
A CLUSTER OF STRONG TO SEVERE THUNDERSTORMS CURRENTLY MOVING THROUGH
THE CSRA JUST WEST OF THE SAVANNAH RIVER WHERE THE GREATEST
INSTABILITY AND HIGHEST THETA-E IS LOCATED. ANOTHER AREA OF CONCERN
IS OVER THE UPSTATE WHERE ANOTHER CLUSTER OF STORMS IS MOVING SOUTH
TO SOUTHEAST...BUT THERE IS AN AREA OF DRY AIR BETWEEN THE UPSTATE
AND THE MIDLANDS SO THESE CELLS MAY WEAKEN OVER THE NEXT HOUR OR SO.
WILL KEEP MENTION OF CHANCE POPS FOR THE NW AND W COUNTIES FOR THE
NEXT COUPLE OF HOURS. STILL EXPECT CONVECTIVE ACTIVITY TO WEAKEN
DURING THE EVENING HOURS. THE THUNDERSTORM CHANCE SHOULD FURTHER
DIMINISH OVERNIGHT WITH THE LOSS OF HEATING AND MID-LEVEL SHORTWAVE
RIDGING. NOCTURNAL COOLING WITH DRY AIR ALOFT AND LIGHT WIND SHOULD
HELP SUPPORT AREAS OF FOG TOWARD SUNRISE. THE TEMPERATURE GUIDANCE
WAS CONSISTENT WITH LOWS IN THE LOWER AND MIDDLE 70S.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
UPPER RIDGE WILL BUILD JUST TO OUR WEST. THIS AND A LOW LEVEL
DOWNSLOPE FLOW WILL LEAD TO WARMING TEMPS. MODELS CONTINUE TO
INDICATE MAX TEMPS NEAR 100 DEGREES MOST AREAS...AND CONTINUE TO
INDICATES DEW POINTS MIXING DOWN INTO THE MID TO UPPER 60S ACROSS
THE NORTHERN AND WESTERN COUNTIES TO NEAR 70 OR LOWER 70S ACROSS
THE SOUTHEAST MIDLANDS. THIS KEEPS HEAT INDICES JUST BELOW OUR
HEAT ADVISORY CRITERIA OF 110F. ONLY SLIGHT CHANCE OF SHOWERS/TSTMS
EXPECTED DUE TO BUILDING RIDGE ALOFT...AND FAIRLY DRY LOW LEVEL
AIR LEADING TO AND HIGH LEVELS OF FREE CONVECTION/HIGH CONVECTIVE
TEMPS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
UPPER RIDGE TO OUR WEST WITH UPPER TROUGH AND CLOSED LOW TO OUR
NE...PROVIDING A NW FLOW ALOFT FOR OUR FA. SOME TIMING
UNCERTAINTIES WITH A BACK DOOR FRONT. MODELS TRENDING A LITTLE
SLOWER WITH IT OF LATE...WITH POSSIBILITY THAT IT MAY NOT MAKE IT
TO OUR FA UNTIL SATURDAY AFTERNOON OR EVENING...SLOWLY PUSHING
SOUTH THROUGH SUNDAY. INCREASING POPS/THUNDER CHANCE ALONG AND
SOUTH OF THE BOUNDARY...WITH COOLER TEMPS NORTH OF IT. FRONT TO
PUSH TO OUR SOUTH EARLY NEXT WEEK...WITH SURFACE AND UPPER RIDGE
OVER THE EASTERN SEABOARD.

&&

.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
EXPECT MAINLY VFR CONDITIONS THROUGH THE PERIOD.

THE LATEST ANALYSIS SHOWED SURFACE RIDGING TO OUR SOUTH WITH WEAK
TROUGHING IN THE FORECAST AREA. STRONG HEATING PLUS SOME SUPPORT
ASSOCIATED WITH THE SURFACE FEATURE AND A MID-LEVEL SHORTWAVE
TROUGH COULD HELP CAUSE THUNDERSTORMS. GIVEN CURRENT TRENDS
ANTICIPATE WIDELY SCATTERED/SCATTERED THUNDERSTORM COVERAGE INTO
THE EARLY EVENING HOURS WITH THE CHANCE TOO LOW TO INCLUDE IN THE
TERMINAL FORECASTS AT THIS TIME. MODERATE TO STRONG INSTABILITY
HAS DEVELOPED. SURFACE-BASED LI/S WERE -7 TO -8 EARLY THIS
AFTERNOON. THEREFORE...VERY STRONG WIND MAY OCCUR NEAR ANY
THUNDERSTORMS.

THE THUNDERSTORM CHANCE SHOULD FURTHER DIMINISH OVERNIGHT WITH THE
LOSS OF HEATING AND MID-LEVEL SHORTWAVE RIDGING. NOCTURNAL COOLING
WITH DRY AIR ALOFT AND LIGHT WIND SHOULD HELP SUPPORT AREAS OF FOG
TOWARD SUNRISE. THE NAM AND GFS MOS HAS TRENDED MORE OPTIMISTIC WITH
JUST MVFR FOG MAINLY AT THE RIVER VALLEY TERMINALS OF AGS AND
DNL. PREVIOUS RUNS INDICATED IFR CONDITIONS. WE CONTINUED THE
FORECAST OF A PERIOD OF IFR AT THE RIVER VALLEY TERMINALS AND MVFR
ELSEWHERE. HEATING AND MIXING SHOULD DISSIPATE ANY FOG BEGINNING
AROUND 13Z.

THE PRESSURE GRADIENT WILL REMAIN WEAK THROUGH THE TAF PERIOD.
GENERALLY LIGHT WIND WILL OCCUR.

EXTENDED AVIATION OUTLOOK...MVFR OR IFR CONDITIONS POSSIBLE IN LATE
NIGHT AND EARLY MORNING FOG THROUGH THE PERIOD. ISOLATED AFTERNOON
AND EVENING THUNDERSTORMS MAY ALSO BRING RESTRICTIONS.

&&

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

$$





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