976  
FXUS62 KCAE 160214  
AFDCAE  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE COLUMBIA SC  
914 PM EST FRI DEC 15 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL MOVE INTO THE FORECAST AREA FROM THE WEST  
TONIGHT. THE HIGH WILL BE OVER THE AREA SATURDAY AND SATURDAY  
NIGHT AND THEN SHIFT OFF THE SOUTHEAST COAST SUNDAY. THERE WILL  
BE INCREASED MOISTURE IN THE SOUTHERLY FLOW ON THE BACKSIDE OF  
THE OFFSHORE HIGH MONDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/
 
 
SKIES WILL BECOME MOSTLY CLEAR OVERNIGHT IN THE WAKE OF A  
SHORTWAVE TROUGH PLUS H5 CONFLUENT FLOW. SATELLITE TRENDS  
INDICATE DRYING FROM THE WEST. THE NEAR-SURFACE LAYER WILL  
REMAIN DRY ASSOCIATED WITH THE RIDGE MOVING INTO THE AREA FROM  
THE WEST. THE DRY AIR MASS SHOULD HELP PREVENT FOG DURING THE  
EARLY MORNING HOURS. FOLLOWED THE GUIDANCE CONSENSUS FOR THE  
TEMPERATURE FORECAST AND EXPECT LOWS MAINLY IN THE UPPER 20S AND  
LOWER 30S.  
 

 
   
SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/
 
 
THE FLOW ALOFT WILL BE NEARLY ZONAL ACROSS THE AREA, ALONG THE  
NORTHWESTERN PERIPHERY OF A STRONG UPPER RIDGE CENTERED OVER  
THE CARIBBEAN. MEANWHILE, SURFACE HIGH PRESSURE WILL SLOWLY  
SHIFT ACROSS THE AREA SATURDAY AND MOVE TOWARD THE COAST  
SATURDAY NIGHT. STRONG SUBSIDENCE AND LIMITED MOISTURE WILL KEEP  
RAIN-FREE CONDITIONS IN PLACE. CLOUDS WILL BE FEW ON SATURDAY,  
BUT START TO INCREASE SATURDAY NIGHT AS SOME WEAK MOISTURE  
ADVECTION TAKES PLACE ON THE BACK SIDE OF THE HIGH. HIGHS DURING  
THE DAY WILL BE IN THE MID TO UPPER 50S, WITH NIGHTTIME LOWS  
REACHING THE LOWER TO MID 30S MOST AREAS.  
 
ON SUNDAY, THE UPPER-LEVEL RIDGE WILL STRENGTHEN OVER THE  
REGION AS THE SURFACE HIGH SHIFTS INTO THE WESTERN ATLANTIC.  
MOISTURE WILL DEEPEN OVER THE AREA, RESULTING IN SKIES BECOMING  
MOSTLY CLOUDY. RAIN CHANCES LOOK TO HOLD OFF DURING THE DAYTIME  
HOURS, BUT A FRONT LIFTING FROM THE SOUTHWEST AND THE DEEPER  
MOISTURE COULD BRING SOME RAIN TO THE AREA BY LATER SUNDAY NIGHT  
AND THE FORECAST INDICATES CHANCE POPS ACROSS MUCH OF THE AREA  
AS A RESULT. EXPECT MILD TEMPERATURES BECAUSE OF THE SOUTHERLY  
FLOW DURING THE DAY AND CLOUD COVER AT NIGHT, WITH HIGHS IN THE  
LOWER TO MID 60S AND LOWS IN THE MID 40S TO LOWER 50S.  
 

 
   
LONG TERM /MONDAY THROUGH FRIDAY/
 
 
THERE IS CONSIDERABLE UNCERTAINTY IN THE LONG-TERM PERIOD DUE  
TO SIGNIFICANT MODEL DIFFERENCES AND SOMEWHAT POOR RUN-TO-RUN  
CONSISTENCY, LEADING TO A LOWER THAN NORMAL CONFIDENCE FORECAST.  
 
THE SURFACE BOUNDARY APPEARS TO BECOME NEARLY STATIONARY EITHER  
OVER OR IN CLOSE PROXIMITY TO THE AREA MONDAY AND MONDAY NIGHT,  
RESULTING IN PROBABLY THE GREATEST RAIN CHANCES OF THE WEEK  
WITH THE FORECAST SHOWING HIGH CHANCE OR LIKELY POPS. THEN,  
MODELS REALLY BEGIN TO DIFFER AS THE GFS HAS A MORE PROGRESSIVE  
SYNOPTIC PATTERN INTO MIDWEEK WHEREAS THE ECMWF IS MUCH MORE  
AMPLIFIED. IT SEEMS BEST TO TAKE SOMEWHAT OF A BLEND WHERE  
POSSIBLE, MAINTAINING CHANCE POPS INTO WEDNESDAY, THEN SHOW SOME  
DRIER CONDITIONS INTO THURSDAY BEFORE RAIN CHANCES INCREASE  
LATE WEEK AHEAD OF THE NEXT FRONT. TEMPERATURES GENERALLY APPEAR  
TO REMAIN ABOVE NORMAL THROUGH THE LONG-TERM PERIOD.  
 

 
   
AVIATION /02Z SATURDAY THROUGH WEDNESDAY/
 
 
HIGH CONFIDENCE IN VFR CONDITIONS AT ALL TERMINALS THROUGHOUT  
THE 24-HR TAF PERIOD.  
 
HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE AREA FROM THE WEST  
OVERNIGHT AS 500MB SHORTWAVE ENERGY CROSSING THE APPALACHIANS  
MOVES TO THE COAST. SATELLITE IMAGERY SHOWS A BLANKET OF HIGH  
CLOUDS CONTINUING TO STREAM OVER THE AREA FROM THE SOUTHWEST  
WHICH WILL REMAIN OVER THE TERMINALS THROUGH AROUND MIDNIGHT OR  
SO. THESE CLOUDS SHOULD SHIFT TO THE SOUTH LATER TONIGHT AS MID  
AND UPPER LEVEL FLOW BECOMES MORE NORTHWESTERLY. NO FOG  
EXPECTED TONIGHT DUE TO DRY AIR MASS. WESTERLY WINDS AROUND 5 TO  
10 KNOTS WILL CONTINUE THROUGH AROUND 03Z-05Z BEFORE SUBSIDING  
TO LESS THAN 5 KNOTS. WINDS WILL PICK UP AGAIN BY 16Z FROM THE  
SOUTHWEST AROUND 5 TO 8 KNOTS.  
 
EXTENDED AVIATION OUTLOOK...UNSETTLED CONDITIONS POSSIBLE EARLY  
NEXT WEEK WITH LOWER CEILINGS AND RESTRICTED VISIBILITIES  
POSSIBLE IN RAIN AT TIMES MONDAY THROUGH WEDNESDAY.  
 

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

 
 

 
SYNOPSIS...99  
NEAR TERM...99  
SHORT TERM...99  
LONG TERM...99  
AVIATION...99  
 
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