Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 220255 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1055 PM EDT TUE OCT 21 2014 .SYNOPSIS... A STRONG COLD FRONT WILL PUSH ACROSS THE AREA AND OFFSHORE LATE TONIGHT. COOLER THAN NORMAL AND DRY CONDITIONS WILL FOLLOW THROUGH THE MID TO LATE WEEK PERIOD AS THE FORECAST AREA REMAINS UNDER CYCLONIC FLOW SURFACE AND ALOFT. BROAD HIGH PRESSURE ACCOMPANIED WITH SEASONABLE TEMPERATURES AND CONTINUED DRY WEATHER WILL PREVAIL ACROSS THE FORECAST REGION FRIDAY THROUGH THE UPCOMING WEEKEND. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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AS OF 1030 PM TUESDAY...MAIN OBJECTIVE CONTINUES TO BE THE TIMING AND STRENGTH OF THE COLD FRONTAL PASSAGE. LATEST SFC PRESSURE PROG CONSENSUS INDICATES THE SFC FRONT TO DROP SE AND PUSH THROUGH AND OFF THE ILM CWA COAST BY MID-LATE EVENING. LIKE THE PREVIOUS CFP...THE CAA SURGE IS PROGGED TO LAG 3 TO 6 HRS BEHIND THE INITIAL CFP. THEREFORE...DURING THE PRE-DAWN WED HRS...THE SFC PG WILL TIGHTEN AND COMBINE WITH THE CAA SURGE TO PRODUCE A NW WIND AT 10 TO 15 MPH...WITH BRIEF GUSTS UP TO 20 MPH MAINLY ALONG THE IMMEDIATE COAST. THIS WILL KEEP THE ATM WELL MIXED WITH NO LIKELIHOOD OF FOG. THE MOISTURE PROFILES ACROSS THE ILM CWA WILL REMAIN SHALLOW AND LOW LEVEL...ENOUGH FOR CLOUD DEVELOPMENT BUT NO WHERE DEEP ENOUGH FOR ORGANIZED PCPN OCCURRENCE. THIS ILLUSTRATED WELL WITH VARIOUS MODEL TIME HEIGHT DISPLAYS FOR LOCATIONS ACROSS THE ILM CWA. OF NOTE...MODEST MID-LEVEL S/W TROFS WILL PUSH ACROSS THE FA AND RESULT IN SOME WEAK UVVS...JUST NOT ENUF MOISTURE TO SQUEEZE OUT FOR PCPN. TWEAKED MIN TEMPS AND OVERNIGHT SFC DEWPOINTS SLIGHTLY LOWER RESPECTIVELY DUE TO LATEST TRENDS. SUBSEQUENT SFC RH AND APPARENT TEMP FIELDS ADJUSTED.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... AS OF 230 PM TUESDAY...MID AND UPPER LOW WILL DOMINATE THE PICTURE WEDNESDAY/THURSDAY AS IT MOVES OFF THE VIRGINIA CAPES TO OFF THE JERSEY SHORE. TIME-HEIGHT CROSS SECTIONS SHOW A VERY DRY COLUMN ABOVE H85 WITH STRONG SUBSIDENCE WITH DEEP NORTHWEST FLOW THROUGH THE MID AND UPPER LEVELS. THE PRECIPITABLE WATER WILL ONLY REACH A HALF INCH WEDNESDAY FOLLOWED BY 0.4 INCHES THURSDAY. THIS PATTERN WILL HOLD MAX TEMPS TO JUST BELOW NORMAL WEDNESDAY...WHILE A SURGE IN COOL SFC-LOW LEVEL AIR WEDNESDAY NIGHT WILL SOMEWHAT HINDER RADIATIONAL COOLING. THINK RADIATIONAL COOLING WILL BE MORE OF A FACTOR THURSDAY NIGHT THUS MET/MAV MIGHT BE A CATEGORY TOO WARM MOST LOCATIONS BY THAT TIME. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 230 PM TUESDAY...THE DRY PERIOD WILL CONTINUE WITH PLEASANT FALL WEATHER ANTICIPATED THROUGH THE EXTENDED. AMPLIFIED MID-LEVEL PATTERN WILL GRADUALLY DE-AMPLIFY AS AN ANOMALOUSLY STRONG CUTOFF FILLS AND MOVES AWAY FROM NEW ENGLAND. LOCALLY...THIS LEAVES AN EXTENDED PERIOD OF NW FLOW ALOFT...WITH WEAK IMPULSES SERVING AS REINFORCING SHOTS OF COOL AIR INTO EARLY NEXT WEEK. THE AIR MASS WILL REMAIN EXCEEDINGLY DRY HOWEVER...WITH PWATS REMAINING BELOW 0.75 INCHES THE ENTIRE PERIOD...AND FALLING TO AS LOW AS 0.30 INCHES LATE IN THE WKND. IF THESE VERY LOW PWATS VERIFY...THEY WILL APPROACH ALL-TIME LOW THRESHOLDS FOR LATE OCTOBER ACROSS THE AREA. IN OTHER WORDS...NO PRECIP WILL BE POSSIBLE INTO EARLY NEXT WEEK. VERY LATE IN THE PERIOD THE SURFACE HIGH PRESSURE WILL PUSH OFFSHORE AS RIDGING BEGINS TO DEVELOP OVER THE SOUTHEAST...THIS WILL DRIVE SOME RETURN FLOW INTO THE CAROLINAS...BUT MOISTURE RETURN WILL REMAIN TOO LOW FOR ANY PRECIP. THE DRY AIR MASS IN PLACE WILL ALLOW FOR A LOT OF SUNSHINE...AND THUS WHILE HIGHS WILL RISE TO CLIMO OR ABOVE EACH DAY...OVERNIGHT MINS WILL DROP BELOW CLIMO INTO NEXT WEEK...WARMING BY TUESDAY. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 00Z...A WEAK RADIATIONAL INVERSION IS SETTING UP...BUT IT ONLY SHOULD LAST THROUGH ABOUT 05-06Z AS A DRY COLD FRONT PASSES THROUGH THE REGION. POST FRONTAL...EXPECT NORTHWEST WINDS TO PICK UP. WILL TAKE THE GUSTS OUT DUE TO THE DIURNAL NATURE OF THE PASSAGE. A BRIEF VFR STRATOCU CEILING IS POSSIBLE. WEDNESDAY...VFR WITH A GUSTY NORTHWEST FLOW. ONLY SCATTERED CU IS EXPECTED. EXTENDED OUTLOOK...EXPECT VFR.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1030 PM TUESDAY...WILL HOLD OFF WITH RAISING A SCEC THIS PACKAGE. BUT IN ALL LIKELIHOOD...A BRIEF SCEC MAY BE NEEDED COMMENCING LATER TONIGHT OR THE ENSUING 1 TO 2 PERIODS. MODEST CAA SURGE DELAYED AFTER MIDNIGHT TONIGHT COMBINED WITH A TIGHTENING SFC PG AS DEEP LOW PRESSURE DEVELOPS OFF DELMARVA LATE TONIGHT... INTENSIFIES AS IT PUSHES SLOWLY TOWARD THE NE DURING THE NEXT FEW DAYS. MODEL TIME HEIGHT DISPLAYS ACROSS THE COASTAL WATERS INDICATE 25 TO 35 KT NW WINDS JUST OFF THE DECK LATE TONIGHT AND WELL INTO THE SHORT TERM PERIOD. EXPECT THE MIXING OF THESE WINDS DOWN TO THE OCEAN SFC AS 25 TO POSSIBLY 30 KT WIND GUSTS FOR EITHER LATE TONIGHT OR INTO THE SHORT TERM PERIOD. SIGNIFICANT SEAS WILL BASICALLY BUILD TO 2 TO 4 FT...WITH 5 FOOTERS APPEARING LATE TONIGHT AND/OR THE ENSUING 1 TO 2 PERIODS. THEIR OCCURRENCE WILL BE OFF CAPE FEAR...AND THE OUTER WATERS OFF THE MOUTH OF WINYAH BAY. LOCALLY PRODUCED WIND DRIVEN WAVES WILL DOMINATE THE SEAS SPECTRUM...WITH VERY LITTLE INPUT IN THE FORM OF A GROUND SWELL. DOMINANT PERIODS WILL RANGE BETWEEN 3 AND 6 SECONDS. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 230 PM TUESDAY...COLD AIR ADVECTION ACROSS RELATIVELY WARM OCEAN TEMPERATURES WILL EQUATE TO GUSTY OFFSHORE FLOW ACROSS THE COASTAL WATERS WEDNESDAY. THE OFFSHORE FLOW WILL PERSIST INTO THURSDAY BUT SPEEDS WILL DIMINISH AS THE COLD AIR ADVECTION WEAKENS ACROSS THE AREA. A RANGE OF SEAS WILL EXIST FROM THE COAST TO THE 20 NM WATERS GIVEN THE OFFSHORE FLOW. SEAS WILL BE HIGHEST WEDNESDAY... THEN SUBSIDE AS THE AFOREMENTIONED OFFSHORE FLOW WEAKENS DURING THURSDAY. WINDS/SEAS SHOULD REMAIN BELOW SMALL CRAFT THRESHOLDS EACH DAY. LONG TERM /FRIDAY THROUGH SUNDAY/... AS OF 230 PM TUESDAY...STRONG LOW PRESSURE DRIFTING SLOWLY AWAY FROM NEW ENGLAND...AND BROAD HIGH PRESSURE RIDGING NORTHEAST FROM THE GULF COAST...KEEPS RATHER UNIFORM FLOW THROUGH THE PERIOD. WINDS BETWEEN THESE TWO FEATURES WILL REMAIN FROM THE NW FRIDAY...SATURDAY...AND MOST OF SUNDAY...BEFORE THE HIGH PRESSURE INCHES OFF THE COAST CAUSING WINDS TO TURN MORE TO THE N/NE. THE GRADIENT REMAINS SLACK HOWEVER...SO SPEEDS WILL BE AROUND 10 KTS EACH DAY. THE COMBINATION OF THE OFFSHORE WIND COMPONENT...LIGHT SPEEDS...AND LACK OF SIGNIFICANT SWELL...WILL KEEP WAVE HEIGHTS AT 1-3 FT THROUGH THE PERIOD...WITH THE 3 FTERS CONFINED TO THE OUTER PORTION OF THE 0-20NM WATERS.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...DCH/SRP NEAR TERM...DCH/RGZ SHORT TERM...SRP LONG TERM...JDW AVIATION...DCH/DL

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