Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 221721
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
121 PM EDT FRI AUG 22 2014

.SYNOPSIS...
A STRONG UPPER RIDGE WILL CONTINUE HOT CONDITIONS TODAY. A BACK
DOOR COLD FRONT WILL THROUGH THE NORTHERN AND CENTRAL MIDLANDS
SATURDAY...AND SHIFT TOWARDS THE CSRA SUNDAY. THIS WILL LEAD TO A
CHANCE OF THUNDERSTORMS ALONG AND AHEAD OF THE FRONT...WITH
TEMPERATURES RETURNING TO MORE NORMAL LEVELS BEHIND IT. THE FRONT
WILL LINGER SOUTH OF THE CSRA EARLY TO MID NEXT WEEK...LEADING TO
GENERALLY FAIR WEATHER WITH NEAR NORMAL TEMPERATURES.

&&

.NEAR TERM /THROUGH TONIGHT/...
SUNNY AND HOT THIS AFTERNOON.
UPPER LEVEL RIDGE REMAINS CENTERED OVER THE LOWER MISSISSIPPI
VALLEY. LOW LEVEL DOWNSLOPE/NORTHWEST FLOW CONTINUES ACROSS OUR
AREA. BOUNDARY LAYER AND 850MB TEMPERATURES SUPPORT AFTERNOON
TEMPERATURES NEAR 100 DEGREES. DEW POINTS MIXING DOWN INTO THE 60S
WILL RESULT IN HEAT INDEX VALUES AROUND 105. ALTHOUGH INSTABILITY
IS MODERATE...MODELS INDICATE A HIGH LFC AND LIMITED LIFT FOR
THUNDERSTORMS. BULK OF CONVECTION EXPECTED NORTH OF THE REGION
AROUND UPPER LEVEL RIDGE. ISOLATED THUNDERSTORMS STILL POSSIBLE
LATE THIS AFTERNOON AND EVENING AS WEAK SHORT WAVES CROSS THE AREA
IN NORTHWEST FLOW ALOFT. ANY EVENING CONVECTION WILL DIMINISH
TONIGHT.

SURFACE LOW PRESSURE ALONG THE VA COAST IS FORECAST TO MOVE
SOUTHWARD OVERNIGHT INTO EASTERN NC. THIS WILL ALLOW A BACKDOOR
COLD FRONT TO APPROACH THE NORTHERN MIDLANDS AROUND DAYBREAK
SATURDAY. KEPT OVERNIGHT LOWS NEAR CONSENSUS IN THE LOWER AND
MIDDLE 70S.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
MAIN ISSUE FOR SATURDAY AND INTO SUNDAY IS TIMING OF APPROACHING
BACK DOOR FRONT. THINK PRE-FRONTAL TROUGH SETS UP ACROSS SOUTHERN
CWA SATURDAY WITH FRONT IN EASTERN NORTH CAROLINA SHIFTING
SOUTHWEST DURING SATURDAY EVENING. MOS POP GUIDANCE LOW BUT SREF
AND MODEL QPF SUGGEST SCATTERED SHOWERS AND THUNDERSTORMS AHEAD
AND ALONG FRONT AS AIR MASS MODERATELY UNSTABLE AND MOISTURE
INCREASING...PRECIPITABLE WATER MAY RISE TO AROUND 2 INCHES.

WARM MAX TEMPS STILL POSSIBLE SAT AHEAD OF THE FRONT...WITH
WARMEST TEMPS FAVORING THE CSRA WHERE TEMPS COULD REACH 100 AGAIN.
WITH NAM BEING SLIGHTLY FASTER THAN GFS WITH THE BACK DOOR FRONT...THE
NAM MOS IS SLIGHTLY COOLER THAN THE GFS MOS FOR SAT MAX
TEMP...ESPECIALLY NORTH AND CENTRAL. EVEN IF TEMPS NEAR 100
REACHED AGAIN SAT...GUIDANCE STILL SUGGESTS DEWPOINTS LOW ENOUGH
TO PRECLUDE HEAT INDEX VALUES FROM REACHING OUR HEAT ADVISORY
CRITERIA OF 110F.

FRONT EXPECTED TO SHIFT SW THRU THE FA SAT NIGHT THRU SUN NIGHT.
EXPECT CHANCE POPS NEAR AND JUST AHEAD OF THE FRONT...WITH COOLING
TEMPS ALONG AND NORTH OF IT. SO...POPS SUN AFTERNOON FAVORING THE
CSRA WHERE INSTABILITY/LOW LEVEL CONVERGENCE STRONGER. HIGH TEMPS SUNDAY
SHOULD BE NOTICEABLY LESS BEHIND THE FRONT.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
MODELS IN GOOD AGREEMENT WITH MOVING THE FRONT SOUTH OF THE SAVANNAH
RIVER WITH UPPER LEVEL RIDGE BUILDING IN FOR THE WEEK.  WITH COOLER
DRY AIR SETTLING IN WILL BRING SLIGHTLY BELOW NORMAL TEMPS.  EXPECT
MAX TEMPS 85 TO 90 EARLY TO MID WEEK RISING BACK INTO THE LOWER 90S
LATER IN THE WEEK.  OVERNIGHT MINS WILL BE 65 TO 70 RISING INTO
THE LOWER 70S LATER IN THE WEEK.

&&

.AVIATION /17Z FRIDAY THROUGH TUESDAY/...
VFR CONDITIONS EXPECTED THROUGH THE PERIOD.

DIURNAL CUMULUS AOA 5 KFT DEVELOPING ACROSS THE REGION THIS
AFTERNOON. GIVEN FRONTAL BOUNDARY REMAINING WELL NORTH OF THE
AREA...CHANCE FOR CONVECTION TOO LOW TO INCLUDE IN TAFS ATTM.
NORTHWEST TO WEST WINDS 10 KNOTS OR LESS THIS AFTERNOON WILL
DIMINISH AND VEER NORTHERLY OVERNIGHT.

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

&&

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

$$





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