106  
FXUS62 KILM 210020  
AFDILM  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE WILMINGTON NC  
720 PM EST MON NOV 20 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL PREVAIL THROUGH TONIGHT. A WEAK TROUGH WILL  
DEVELOP JUST OFF THE COAST AND A COLD FRONT WILL APPROACH FROM THE  
NORTHWEST TUESDAY. THE FRONT WILL PASS OFF THE COAST EARLY WEDNESDAY  
FOLLOWED BY AN AREA OF WEAK HIGH PRESSURE. LOW PRESSURE WITH ORIGINS  
OVER THE EASTERN GULF OF MEXICO MAY BRING A LITTLE RAIN TO THE  
AREA WEDNESDAY NIGHT THROUGH THANKSGIVING DAY. THE LOW WILL  
ACCELERATE NORTHEAST AWAY FROM THE REGION BY FRIDAY WITH HIGH  
PRESSURE EXPECTED BY THE WEEKEND.  
 

 
   
NEAR TERM /THROUGH TUESDAY/
 
 
AS OF 730 PM MONDAY...YET ANOTHER QUIET NIGHT AS HIGH PRESSURE  
MOVES OFFSHORE AND CIRRUS STREAMS IN FROM THE WEST. STILL A  
QUESTION AS TO HOW MUCH THIS CIRRUS WILL HINDER RADIATIONAL  
COOLING, BUT SEE NO REASON FOR NOW TO CHANGES THE CURRENT  
FORECAST OF MID TO UPPER 30S MOST PLACES, WITH LOW 40S AT THE  
BEACHES. PREVIOUS DISCUSSION FROM THIS AFTERNOON FOLLOWS:  
 
SURFACE HIGH PRESSURE IS EXPECTED TO MOVE OFF THE NC COAST THIS  
EVENING AND A WEAK COASTAL TROUGH WILL DEVELOP. THE DRY COLUMN  
THAT HAS BEEN IN PLACE WILL GRADUALLY GIVE WAY TO INCREASING  
MOISTURE. INITIALLY, HIGH CLOUDS WILL BEGIN TO SPREAD ACROSS THE  
AREA TONIGHT, THEN RH WILL INCREASE IN THE LOWER LEVELS DURING  
TUESDAY. LOW TEMPERATURES TONIGHT COULD BECOME PROBLEMATIC AS  
SOME HIGH CLOUDS POSSIBLY LIMIT RADIATIONAL COOLING. AT THE  
MOMENT PREFER LEANING TOWARD THE COLDER GUIDANCE WITH THE  
TYPICAL COLD SPOTS POSSIBLY LIKELY REMAINING JUST ABOVE FREEZING  
(ESPECIALLY NORTHEAST ZONES). THE PRECIPITABLE WATER WILL  
INCREASE MORE-SO DURING TUESDAY AS LOW- LEVEL MOISTURE ADVECTION  
INCREASES ACROSS THE CAROLINAS. ISENTROPIC LIFT AT 295K ALONG  
WITH THE COASTAL FRONT COULD SPARK -RA, ESPECIALLY LATER IN THE  
DAY. OTHERWISE, FAVORED A BLEND OF MAV/MET/ECE.  
 

 
   
SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/
 
 
AS OF 245 PM MONDAY...BEST CHANCE FOR PRECIPITATION DURING THIS  
PERIOD APPEARS TO BE IN TUESDAY EVENING TIME FRAME, AS MOISTURE  
AHEAD OF A MID-LEVEL SHORTWAVE LIFTS OUT OF THE GULF OF MEXICO  
AND OVERRUNS SHALLOW, COOL AIR TO THE WEST OF A COASTAL TROUGH.  
THE 12Z NAM/ECMWF ARE WETTER THAN THE GFS, ALTHOUGH OVERALL QPF  
WOULD BE ON THE ORDER OF A TENTH OR TWO OF AN INCH. BY LATER  
TUESDAY NIGHT, A WAVE OF LOW PRESSURE WHICH IS EXPECTED TO  
DEVELOP ALONG THE OFFSHORE BOUNDARY WILL MOVE NORTHEAST, AND  
THIS WILL BRING AN END TO PRECIP CHANCES FOR THE NIGHT. THE  
CENTER OF SURFACE HIGH PRESSURE WILL REMAIN TO OUR WEST THROUGH  
THE PERIOD, AND WITH MID-LEVEL TROUGHINESS LINGERING WEST OF THE  
APPALACHIANS AND SOUTH INTO THE GULF, THE NAM WANTS TO BRING  
ANOTHER SURGE OF LIGHT, OVERRUNNING PRECIP INTO THE FORECAST  
AREA BY LATE WEDNESDAY NIGHT. AS THE NAM IS THE OUTLIER WITH  
THIS FOR THE MOMENT, WILL HOLD OFF ON INTRODUCING POPS FOR THAT  
PERIOD FOR NOW.  
 
TEMPS SLIGHTLY ABOVE CLIMO TUESDAY NIGHT, AND NEAR CLIMO  
WEDNESDAY WILL GIVE WAY WEDNESDAY NIGHT. COOLER AIR WILL GET  
PULLED SOUTHWARD ACROSS THE AREA BETWEEN SURFACE HIGH PRESSURE  
TO THE WEST, AND THE SURFACE-H8 LOW LIFTING NORTHEAST OFF THE  
MID-ATLANTIC COAST DURING THAT TIME FRAME.  
 

 
   
LONG TERM /THURSDAY THROUGH MONDAY/
 
 
AS OF 245 PM MONDAY...THE EXTENDED FORECAST WILL BE MOSTLY  
INFLUENCED BY AN ALMOST STANDING WAVE TROUGH ACROSS THE EASTERN  
THIRD OF THE CONUS. RIDGING WILL REMAIN FOCUSED ACROSS THE FOUR  
CORNERS REGION. THERE REMAINS SOME INDICATION OF A COUPLE OF  
SYSTEMS MOVING ACROSS THE BAROCLINIC ZONE TO THE EAST BUT THE 12  
UTC GUIDANCE HAS JOGGED EASTWARD. I DID TREND THE FORECAST IN  
THE EARLY PERIODS A LITTLE DRIER SO ITS ESSENTIALLY A DRY  
FORECAST THROUGHOUT. OVERALL TEMPERATURES WILL RUN A LITTLE  
BELOW NORMAL STARTING OUT ON THE COOLER SIDE OF CLIMATOLOGY WITH  
A BRIEF WARMUP FOR THE WEEKEND. THIS WILL BE FOLLOWED BY  
ANOTHER COLD SHOT EARLY NEXT WEEK.  
 

 
   
AVIATION /00Z TUESDAY THROUGH SATURDAY/
 
 
AS OF 00Z...VFR CONDITIONS AND LIGHT WINDS WILL CONTINUE  
THROUGH TONIGHT AS HIGH PRESSURE MOVES OVERHEAD, THEN OFFSHORE  
LATE. SOUTHERLY WINDS DEVELOPING ABOVE THE SURFACE WILL BEGIN TO  
BRING IN ATLANTIC MOISTURE IN THE FORM OF STRATOCUMULUS CLOUDS  
WITH BASES 3500-4000 FEET AGL IN THE MORNING BETWEEN 14-16Z. THE  
IS A SMALL CHANCE OF MVFR CIGS ASSOCIATED WITH LIGHT SHRA AFT  
20Z AT THE COASTAL TERMINALS BUT THAT CHANCE IS TOO SMALL TO  
INCLUDE IN THE TAFS ATTM.  
 
EXTENDED OUTLOOK...MVFR CONDITIONS MAY DEVELOP IN LOW CLOUDS  
AND LIGHT RAIN TUESDAY NIGHT THROUGH WEDNESDAY MORNING, THEN  
MVFR TO IFR CONDITIONS ARE POSSIBLE LATE FRIDAY INTO SATURDAY IN  
LOW CLOUDS AND RAIN.  
 

 
   
MARINE
 
 
NEAR TERM /THROUGH TUESDAY/...  
AS OF 730 PM MONDAY...LATEST OBS SHOW LIGHT NELY WINDS WITH SEAS  
OF AROUND 2 FT. HAVE THUS INITIALIZED WINDS TO A MORE NE  
DIRECTION WITH THE LATEST UPDATE, WITH WINDS VEERING E LATER  
OVERNIGHT. PREVIOUS DISCUSSION FROM THIS AFTERNOON FOLLOWS:  
 
HIGH PRESSURE WILL SHIFT OFF THE NC THIS EVENING ALLOWING A  
WEAK COASTAL TROUGH TO DEVELOP OVERNIGHT. AS A RESULT LATE  
TONIGHT INTO TUESDAY MORNING, EASTERLY WIND WILL BACK TO A LIGHT  
NORTHEAST DIRECTION ON THE WEST SIDE OF THE TROUGH AXIS WHILE  
THE FLOW EAST OF THE TROUGH AXIS BECOMES SOUTHEASTERLY. THE  
TROUGH WILL DRIFT CLOSER TO THE COAST TUESDAY AFTERNOON WITH  
LIGHT SOUTHEAST FLOW TO PREVAIL ACROSS THE BULK OF THE WATERS.  
SEAS ARE EXPECTED TO BE LESS THAN 3 FT THROUGH THE PERIOD AND A  
FEW SHOWERS ARE POSSIBLE TOMORROW.  
 
SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...  
AS OF 245 PM MONDAY...A TROUGH ALONG THE COAST TUESDAY EVENING  
WILL MAKE A CHALLENGING WIND DIRECTION FORECAST. IT IS EXPECTED  
TO BE CLOSE ENOUGH TO THE COAST IN THE EVENING TO YIELD ESE  
WINDS ACROSS THE WATERS, BUT AS A WAVE OF LOW PRESSURE TRACKS  
NORTHEAST OFFSHORE, WINDS WILL SHIFT AROUND TO THE NW AFTER  
MIDNIGHT. WEDNESDAY AND WEDNESDAY NIGHT, WINDS WILL VEER FROM N  
TO NE AS SURFACE HIGH PRESSURE EXTENDS FROM THE CENTRAL PLAINS  
STATES TO THE OHIO RIVER VALLEY. THE PERSISTENT NE FETCH BETWEEN  
THESE FEATURES WILL ALLOW SEAS TO BUILD TO THE BRINK OF SMALL  
CRAFT ADVISORY THRESHOLDS WEDNESDAY AFTERNOON AND NIGHT IN THE  
OUTER REACHES OF THE MARINE ZONES, ESPECIALLY NORTH OF LITTLE  
RIVER INLET.  
 
LONG TERM /THURSDAY THROUGH SATURDAY/...  
AS OF 245 PM MONDAY...NORTHEAST WINDS OF 10-15 KNOTS WILL  
PREVAIL THROUGH THE FIRST TWO DAYS OF THE EXTENDED MARINE  
FORECAST. THERE MAY BE A FEW HOURS OF 15-20 EARLY ON BUT OVERALL  
10-15 SHOULD DO IT. BY SATURDAY A MODEST SOUTHWEST FLOW WILL  
DEVELOP AHEAD OF ANOTHER COLD FRONT WHICH SHOULD MOVE ACROSS  
LATER IN THE WEEKEND. SIGNIFICANT SEAS WILL TREND DOWNWARD FROM  
3-5 FEET EARLY TO 2-4 AND POSSIBLY 1-3 FEET BY SATURDAY.  
 

 
   
ILM WATCHES/WARNINGS/ADVISORIES
 
 
SC...NONE.  
NC...NONE.  
MARINE...NONE.  
 

 
 

 
 
SYNOPSIS...SHK  
NEAR TERM...REK/SRP  
SHORT TERM...CRM  
LONG TERM...SHK  
AVIATION...RAN  
MARINE...REK/SHK/SRP/CRM  
 
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