858  
FXUS62 KILM 201028  
AFDILM  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE WILMINGTON NC  
630 AM EDT FRI APR 20 2018  
   
SYNOPSIS
 
 
TEMPERATURES WILL RUN 5 TO 10 DEGREES BELOW NORMAL TODAY THRU  
SUNDAY AS CANADIAN HIGH PRESSURE RIDGES ACROSS THE AREA FROM  
THE GREAT LAKES. WINDS WILL BE NOTICEABLY LOWER WHEN COMPARED  
TO THE PAST FEW DAYS. THE HIGH WILL GIVE WAY TO LOW PRESSURE  
MOVING OUT FROM THE GULF COAST STATES LATE SUNDAY. THIS LOW  
ACCOMPANIED BY BENEFICIAL STRATIFORM RAINS, WILL SLOWLY PUSH  
ACROSS THE REGION MONDAY THRU TUESDAY OF NEXT WEEK, AND  
POSSIBLY COULD PERSIST INTO WEDNESDAY OF NEXT WEEK.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 330 AM FRIDAY...VERY QUIET WEATHER WILL PREVAIL THROUGH  
THE NEAR TERM PERIOD AS SURFACE HIGH PRESSURE BUILDS IN FROM  
THE NORTHWEST. WITH A VERY DRY ATMOSPHERIC COLUMN, EVEN CLOUDS  
WILL BE AT A PREMIUM. HIGHS TODAY SHOULD BE IN THE LOWER TO  
MIDDLE 60S AS GUIDANCE HAS BEEN STABLE AT THESE VALUES. LOWS  
SATURDAY MORNING, WILL BE IN THE LOWER 40S ALONG THE COAST WITH  
SOME UPPER 30S NORTHWEST AND IN THE COLDER LOCATIONS AS IDEAL  
RADIATIONAL CONDITIONS WILL BE IN PLACE.  
 

 
   
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
 
 
AS OF 330 AM FRIDAY...THE FORECAST AREA WILL LIE BETWEEN 2  
"BOWLING BALLS", IE. BETWEEN 2 UPPER CLOSED LOWS AT THE START  
OF THIS PERIOD. THE 1 AFFECTING MAINE AND SOUTHEAST CANADA, WILL  
PROGRESS FURTHER AWAY FROM THE U.S. DURING THIS PERIOD.  
HOWEVER, THE OTHER CLOSED LOW WILL BE ABLE TO PROGRESS, MOVING  
SLOWLY EASTWARD ACROSS THE GULF COAST STATES THIS WEEKEND,  
AND REACHING THE ILM DOORSTEPS BY MON MORNING. AT THE SFC,  
MODELS IN DECENT AGREEMENT WITH CANADIAN HIGH PRESSURE RIDGING  
ACROSS THE AREA FROM THE GREAT LAKES DURING THIS WEEKEND, WITH  
THE HIGH RE-CENTERING ITSELF OVER THE NE STATES AT THE END OF  
THIS PERIOD. THIS WILL RESULT IN COOL NE TO ENE WINDS THRUOUT  
THIS PERIOD WHICH WILL HELP KEEP TEMPERATURES AT 5 TO 10 DEGREES  
BELOW NORMAL FOR BOTH MAXES AND MINS WITH THE EXCEPTION OF  
SUNDAY NIGHT/MONDAY MORNING LOWS WHICH WILL BE NEAR NORMAL DUE  
TO THE MODIFICATION OF THE AIR MASS AS WELL AS ONSHORE WINDS  
THAT MAY HAVE A SE COMPONENT BY THE END OF THIS PERIOD. CLOUDS  
SAT THRU SUN WILL BE IN THE FORM OF THIN CIRRUS SAT AND BECOMING  
MORE OPAQUE DURING THE DAY ON SUN. FOR LATE SUN THRU SUN NIGHT,  
MID-LEVEL ALTOSTRATUS WILL BECOME DOMINANT WITH LOW LEVEL  
STRATUS ACROSS THE FAR S TO SW PORTIONS OF THE FA AS THE UPPER  
LOW APPROACHES ALONG WITH THE THREAT FOR STRATIFORM RAINS.  
 

 
   
LONG TERM /MONDAY THROUGH THURSDAY/
 
 
AS OF 300 PM THURSDAY...VERY LARGE HIGH, MORE TYPICAL OF THE  
COOL SEASON, TO BE MOVING OFF THE COAST ON SUNDAY. MEANWHILE A  
CUTOFF UPPER LOW (ALSO NORMALLY A COOL SEASON FEATURE) TO BE  
CROSSING THE GULF STATES, LEADING TO CYCLOGENESIS. AS OFTEN THE  
CASE WITH A CUTOFF, THE TIMING IS OFTEN UNCERTAIN AND TOO FAST  
IN GUIDANCE. MUCH OF THE CLOUDINESS AND RAIN EXPECTED TO  
OVERSPREAD THE AREA SUNDAY NIGHT INTO MONDAY MAY NOW BE ABOUT  
12 HOURS SLOWER. ANOTHER CHANGE FROM THIS TIME YESTERDAY IS  
THAT GUIDANCE IS NOW SUPPRESSING THE HIGHEST RAINFALL AMOUNTS TO  
OUR SOUTH. GIVEN THE STRENGTH OF THE HIGH TO OUR NORTH THIS  
SEEMS PLAUSIBLE. EVEN SO, THE SYSTEM WILL BE SLOW MOVING AND  
KEEP RAIN IN THE FORECAST THROUGH AT LEAST WEDNESDAY.  
 

 
   
AVIATION /12Z FRIDAY THROUGH TUESDAY/
 
 
AS OF 12Z...VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD.  
HIGH PRESSURE CENTERED TO OUR NORTHWEST WILL BUILD IN THROUGH THIS  
EVENING. NORTHERLY WINDS MAY BUMP UP AFTER SUNRISE, BUT SHOULD STAY  
UNDER 15 KTS FOR THE MOST PART. LIGHT WINDS TONIGH WITH GOOD  
RADIATIONAL COOLING CONDITIONS.  
 
EXTENDED OUTLOOK...VFR. PERIODS OF MVFR/RA MONDAY/TUESDAY.  
 

 
   
MARINE
 
 
NEAR TERM /THROUGH FRIDAY/...  
AS OF 330 AM FRIDAY...WINDS STILL BLOWING FROM THE NORTH  
AT A FAIRLY BRISK RATE OF 20-25 KNOTS ACROSS THE WATERS THIS  
MORNING. HOWEVER MUCH LIGHTER WINDS ARE JUST UPSTREAM AND  
SHOULD MOVE ACROSS THE WATERS LATER THIS MORNING. AS WINDS FALL  
DOWN BELOW SMALL CRAFT CRITERIA, THE SEAS, WHICH ARE HOVERING  
JUST ABOVE THE SIX FOOT THRESHOLD WILL DROP AS WELL. OVERALL A  
MODEST NORTHEAST FLOW OF 10- 15 KNOTS WILL DEVELOP LATE MORNING  
AND PERSIST THROUGH MOST OF TONIGHT POSSIBLY INCREASING AGAIN  
VERY LATE. SEAS WILL DROP TO 3-5 FEET THIS MORNING AS WELL AND  
FURTHER TO 1-3 FEET BY EARLY SATURDAY.  
 
SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...  
AS OF 330 AM FRIDAY...THE AREA WATERS WILL REMAIN WITHIN A  
SEMI-TIGHTENED SFC PG SAT THAT WILL LIKELY FURTHER TIGHTEN SUN  
INTO SUN NIGHT. THIS DUE TO THE CLOSED LOW APPROACHING THE FA  
FROM THE GULF COAST STATES. HAVE RAMPED UP ENE TO E WINDS LATE  
SUN THRU SUN NIGHT AND HAVE THEM APPROACHING SCA THRESHOLDS BY  
MON DAYBREAK ALONG WITH BUILDING SEAS LIKELY BREACHING THE 6  
FOOT PLATEAU MON MORNING. SIGNIFICANT SEAS WILL PRIMARILY BE A  
FUNCTION OF WIND DRIVEN WAVES THAT COULD BE CONSIDERED A PSEUDO  
GROUND SWELL AS PROGGED PERIODS INCREASE TO 5 TO 7 SECONDS.  
 
LONG TERM /SUNDAY THROUGH TUESDAY/...  
AS OF 300 PM THURSDAY...ONSHORE FLOW ON SUNDAY THE RESULT OF A  
VERY LARGE AREA OF HIGH PRESSURE MOVING EASTWARD BUT REMAINING  
CENTERED WELL NORTH OF THE AREA. AT THE SAME TIME LOW PRESSURE  
WILL BE DEVELOPING OVER THE GULF STATES. THIS SETUP WILL  
INCREASINGLY SQUEEZE THE GRADIENT TO WHERE WIND AND SEAS BOTH  
REACH ADVISORY LEVELS. BOTH ENTITIES WILL BE VERY SLOW MOVING,  
KEEPING ADVISORY FLAGS FLYING FOR THE REMAINDER OF THE PERIOD.  
 

 
   
ILM WATCHES/WARNINGS/ADVISORIES
 
 
SC...NONE.  
NC...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 9 AM EDT THIS MORNING FOR AMZ250-  
252-254-256.  
 

 
 

 
SYNOPSIS...DCH  
NEAR TERM...SHK  
SHORT TERM...DCH  
LONG TERM...III  
AVIATION...43  
 
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