402  
FXUS62 KCAE 271432  
AFDCAE  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE COLUMBIA SC  
1032 AM EDT TUE JUN 27 2017  
   
SYNOPSIS
 
 
A FRONT LINGERING NEAR THE COAST WILL SHIFT FARTHER OFFSHORE  
TONIGHT. A PRESSURE RIDGE EXTENDING THROUGH THE OHIO RIVER  
VALLEY TODAY WILL BE IN THE MID-ATLANTIC REGION WEDNESDAY AND  
OFF THE EAST COAST THURSDAY. DIMINISHED RELATIVE HUMIDITY  
WILL BE ASSOCIATED WITH THIS PATTERN THROUGH WEDNESDAY BUT  
MOISTURE WILL BE ON THE INCREASE LATE IN THE WEEK AS THE  
OFFSHORE RIDGE DIRECTS AN ONSHORE FLOW INTO THE FORECAST AREA.  
THIS TREND WILL LEAD TO INCREASING CHANCES OF THUNDERSTORMS.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
MORNING ANALYSIS REVEALED A STALLED FRONTAL BOUNDARY JUST OFF  
THE COAST WITH A STRONG DEWPOINT GRADIENT ACROSS THE  
SOUTHEASTERN MIDLANDS WITH HIGH PRESSURE BUILDING INTO THE AREA  
FROM THE NORTHWEST. ALOFT, WATER VAPOR IMAGERY CONFIRMS A  
DIGGING SHORTWAVE TROUGH OVER THE WESTERN OHIO VALLEY AND  
MISSISSIPPI VALLEY REGION WHICH WILL SHIFT EASTWARD THROUGH THE  
AFTERNOON AND CROSS OUR REGION THIS EVENING. NUCAPS SOUNDINGS  
FROM AROUND 07Z SHOWED PRECIPITABLE WATER VALUES OVER THE  
MIDLANDS HAD DROPPED TO NEAR AN INCH WITH A GRADIENT IN MOISTURE  
TO THE SOUTHEAST WITH KCHS 12Z OBSERVED SOUNDING MEASURING A 1.43  
INCH PRECIPITABLE WATER VALUE.  
 
AS THE DIGGING SHORTWAVE TROUGH SHIFTS EASTWARD AND AMPLIFIES A  
BIT IT WILL PULL SOME OF THE DEEPER MOISTURE BACK TOWARDS THE  
MIDLANDS WITH FORECAST SOUNDINGS RAISING PRECIPITABLE WATER  
VALUES UP TO AROUND 1.4-1.5 INCHES. FORECAST INSTABILITY IS WEAK  
WITH LIFTED INDEX VALUES AROUND -3C TO -4C WITH THE MOISTURE  
GENERALLY SHALLOW IN THE 700-850MB LAYER. SURFACE WINDS WILL  
PICK UP FROM THE NORTH ACROSS THE FORECAST AREA WHILE A SEA  
BREEZE IS EXPECTED TO DEVELOP ALONG THE COAST WITH THE BEST  
MOISTURE CONVERGENCE AND LOW LEVEL FORCING ALONG THE COASTAL  
PLAIN AND FAR EASTERN MIDLANDS. GIVEN THE OVERALL LACK OF DEEP  
MOISTURE AND WEAK INSTABILITY AND FORCING ALONG WITH LOW MOS  
GUIDANCE POPS, WILL OPT TO CONTINUE SLIGHT CHANCE FOR AFTERNOON  
CONVECTION MAINLY EASTERN MIDLANDS AND PEE DEE REGION. DESPITE  
THE WIDELY SCATTERED NATURE OF EXPECTED CONVECTION, SOUNDINGS  
INDICATE AN INVERTED-V SIGNATURE AND IF A STORM IS ABLE TO  
STRENGTHEN WITH ANY DEPTH IT COULD POSE A STRONG WIND GUST  
THREAT.  
 
DRIER AND COOLER AIR WILL FILTER INTO THE REGION TONIGHT IN THE  
WAKE OF THE PASSING SHORTWAVE WITH CLEARING SKIES EXPECTED.  
TEMPERATURES THIS AFTERNOON ARE EXPECTED IN THE UPPER 80S TO  
AROUND 90 DEGREES WITH LOWS TONIGHT EXPECTED TO BE SEASONABLY  
COOL IN THE LOWER TO MID 60S WITH SOME POSSIBLE UPPER 50S IN  
OUTLYING SHELTERED AREAS OF THE NORTHERN MIDLANDS.  
 

 
   
SHORT TERM /WEDNESDAY THROUGH THURSDAY/
 
 
THE MODELS HAVE BEEN CONSISTENT WITH DRY HIGH PRESSURE  
DOMINATING WEDNESDAY AND WEDNESDAY NIGHT. MOISTURE SHOULD BE ON  
THE INCREASE THURSDAY ESPECIALLY IN THE SOUTH PART OF THE  
FORECAST AREA IN AN ONSHORE FLOW ASSOCIATED WITH THE RIDGE OFF  
THE EAST COAST AND A MID-LEVEL SHORTWAVE TROUGH MOVING INTO THE  
REGION. FOLLOWED THE GUIDANCE CONSENSUS AND FORECASTED CHANCE  
POPS. ALSO USED THE CONSENSUS FOR THE TEMPERATURE FORECAST.  
 

 
   
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
 
 
THE GFS AND ECWMF DISPLAY MOISTURE IN A SOUTHERLY FLOW  
ASSOCIATED WITH OFFSHORE HIGH PRESSURE AND BROAD UPPER  
TROUGHING DURING MUCH OF THE MEDIUM-RANGE PERIOD. THE PATTERN  
SUPPORTS SCATTERED MAINLY DIURNAL THUNDERSTORMS. THE GFS AND  
ECWMF MOS PLUS GFS ENSEMBLE MEAN INDICATE CHANCE POPS WITH  
TEMPERATURES NEAR CLIMATOLOGY.  
 

 
   
AVIATION /15Z TUESDAY THROUGH SATURDAY/
 
 
GENERALLY VFR CONDITIONS EXPECTED THROUGH THE 24 HR FORECAST  
PERIOD.  
 
AN UPPER TROUGH MOVING THROUGH THE OHIO/MISSISSIPPI VALLEYS WILL  
CROSS THE REGION LATE THIS AFTERNOON AND EVENING. WEAK HIGH  
PRESSURE IS IN PLACE AT THE SURFACE WITH A FRONTAL BOUNDARY  
STALLED JUST OFFSHORE. ATMOSPHERIC MOISTURE IS LIMITED WITH  
PRECIPITABLE WATER VALUES LESS THAN 1.25 INCHES. THE LACK OF  
SUFFICIENT MOISTURE AND LOW LEVEL CONVERGENCE ALONG WITH WEAK  
INSTABILITY PRESENT WILL LIMIT CONVECTIVE THREAT THIS AFTERNOON.  
SOME MID LEVEL CLOUDS THIS MORNING SHOULD GIVE WAY TO DEVELOPING  
CUMULUS WITH BASES AROUND 5-6KFT. CANNOT RULE OUT ISOLATED  
CONVECTION ACROSS EASTERN MIDLANDS BUT COVERAGE EXPECTED TO BE  
LOW ENOUGH TO NOT INCLUDE IN OGB TAF BUT WILL AMEND AS NEEDED.  
 
DRIER AIR WILL FILTER INTO THE REGION BEHIND THE SHORTWAVE  
TONIGHT WITH SKIES GENERALLY CLEARING OUT LATE.  
 
EXTENDED AVIATION OUTLOOK...NO SIGNIFICANT IMPACTS TO AVIATION  
EXPECTED THROUGH WEDNESDAY. A RETURN FLOW AND INCREASING LOW-LEVEL  
MOISTURE MAY PROVIDE A LATE NIGHT/EARLY MORNING STRATUS THREAT  
THU/FRI. SCATTERED THUNDERSTORMS EXPECTED FRI/SAT.  
 

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

 
 

 
 
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