Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 302339 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 739 PM EDT THU OCT 30 2014 .SYNOPSIS...
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HIGH PRESSURE WILL NUDGE INTO THE AREA THROUGH FRIDAY BETWEEN AN APPROACHING COLD FRONT TO THE WEST AND A WEAK AREA OF LOW PRESSURE ALONG A STALLED FRONT OFFSHORE. A POWERFUL COLD FRONT WILL CROSS THE REGION ON SATURDAY AS COLD CANADIAN HIGH PRESSURE BUILDS IN THROUGH THE REST OF THE WEEKEND. THIS AREA OF HIGH PRESSURE WILL THEN BECOME THE DOMINANT WEATHER FEATURE THROUGH THE FIRST HALF OF NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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AS OF 730 PM THURSDAY...LAST NIGHT`S COLD FRONT IS STALLING ABOUT 200 MILES OFF THE COAST. THE FLOW ALOFT STILL HAS A SIGNIFICANT CYCLONIC CURVATURE...AND A SERIES OF SHORTWAVES ARE ANALYZED UPSTREAM OF THE CAROLINAS. ONE DISTURBANCE CURRENTLY OVER COASTAL GEORGIA WILL MOVE NORTHEASTWARD ALONG THE COAST OVERNIGHT...INDUCING SURFACE LOW PRESSURE TO DEVELOP ALONG THE STALLED FRONT OFFSHORE. IN RESPONSE TO THE APPROACHING DISTURBANCE SHALLOW ISENTROPIC LIFT SHOULD DEVELOP ALONG THE COAST BETWEEN THE 295K-300K SURFACES... ROUGHLY BETWEEN 4000-8000 FT AGL...WITH CLOUDS AND SOME PATCHY LIGHT RAIN PROBABLY DEVELOPING AFTER MIDNIGHT. I HAVE INCREASED RAINFALL CHANCES TO 20-30 PERCENT ACROSS COASTAL SE NORTH CAROLINA BUT MAINTAINED A DRY FORECAST ELSEWHERE AS IT APPEARS THE ISENTROPIC LIFT WILL BE WEAKER AND SHOULD INVOLVE MAINLY DRY/UNSATURATED PARCEL MOTION. WITH CLOUDS EXPECTED TO DEVELOP ALONG THE COAST I HAVE NUDGED FORECAST LOWS UP BY A COUPLE OF DEGREES...ESPECIALLY NEAR WILMINGTON...WITH SMALLER OR NO CHANGES MADE ELSEWHERE. LOWS SHOULD REACH THE MID 40S INLAND ALONG I-95...WITH UPPER 40S TO LOWER 50S EXPECTED ALONG THE COAST.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
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AS OF 300 PM THURSDAY...FRIDAY AND FRIDAY NIGHT...FRIDAY WILL MAINLY BE A TRANSITIONAL DAY AHEAD OF THE THE POWERFUL COLD FRONT THAT WILL BEGIN TO PUNCH IN TO THE AREA FROM THE WEST LATE FRIDAY NIGHT. ALOFT...THE UPPER TROUGH AXIS WILL SHIFT EASTWARD AND BEGIN TO AMPLIFY AS A VIGOROUS AND DEEP UPPER LOW DIGS IN AND DIVES SOUTHWARD OUT OF THE GREAT LAKES REGION. BY LATE FRIDAY NIGHT THE UPPER LOW SHOULD BE POSITIONED ALMOST DIRECTLY OVER TOP OF THE SOUTHERN APPALACHIANS. AT THE SURFACE...FRIDAY WILL SEE THE REMNANT FRONT SITTING JUST OFFSHORE WITH A WEAK AREA OF LOW PRESSURE BEGINNING TO DEVELOP ALONG IT. MODELS ARE CONSISTENT IN SHOWING SHOWER ACTIVITY BRUSHING THE COASTAL WATERS AND PERHAPS BRUSHING AREAS NEAR SOUTHPORT AND ALONG BRUNSWICK/NEW HANOVER COUNTIES. OTHERWISE...FRIDAY WILL BE QUIET WITH HIGHS REACHING INTO THE UPPER 60S IN MOST AREAS. OVERNIGHT...THE VERY STRONG COLD FRONT WILL BEGIN APPROACHING THE AREA AND EVEN MOVING THROUGH FAR INLAND AREAS LATE. POPS BEGIN TO INCREASE FROM THE WEST AFTER MIDNIGHT AS THE DEEP FORCING ASSOCIATED WITH THE POWERFUL UPPER LEVEL DYNAMICS INCREASES. HOWEVER...THE BULK OF ANY PRECIPITATION AND ESPECIALLY THE ARRIVAL OF THE COLD AIR WILL BE MORE INTO THE SATURDAY TIME FRAME. SATURDAY THROUGH SUNDAY...OVERALL IT WILL BE A CHILLY AND AT TIMES BLUSTERY WEEKEND AS A STRONG COLD FRONT MOVES THROUGH THE AREA AND COLD CANADIAN HIGH PRESSURE BUILDS IN. ALOFT...A POWERFUL AND DEEP UPPER LOW WILL SWING THROUGH THE BASE OF THE DEEP UPPER TROUGH SATURDAY MORNING AND THEN LIFT AWAY FROM THE AREA THROUGH SUNDAY. AT THE SURFACE...A VERY STRONG COLD FRONT WILL PUSH THROUGH EARLY SATURDAY AND THE STRONG UPPER FORCING ALOFT WILL PROMOTE CYCLOGENESIS OFF THE OUTER BANKS. THE FIRST FORECAST ISSUE REVOLVES AROUND THE PRECIPITATION POTENTIAL ON SATURDAY. VERY IMPRESSIVE DEEP LAYER FORCING WITH THIS SYSTEM WILL SPREAD ACROSS THE AREA INCLUDING STRONG PVA...UPPER LEVEL JET DYNAMICS...EVEN A SLOT OF LOW LEVEL FRONTOGENESIS LATER ON SATURDAY. FURTHERMORE...THE ARRIVAL OF THE IMPRESSIVE COLD POOL ALOFT...500 MB TEMPS AROUND -26C...WILL HELP STEEPEN MID LEVEL LAPSE RATES THROUGH THE DAY. POPS HAVE BEEN INCREASED INTO THE CATEGORICAL RANGE THROUGH THE DAY AS A RESULT. ONE THING TO WATCH FOR IS THE STEEPENING MID LEVEL LAPSE RATES AND FALLING FREEZING LEVELS WILL LIKELY ALLOW FOR SOME PRECIPITATION TO FALL AS GRAUPEL AT TIMES ESPECIALLY LATER ON SATURDAY. THE TOP OF THE MOIST LAYER WILL DEFINITELY REACH INTO THE DENDRITIC CRYSTAL GROWTH ZONE...THEN UNDERGO AT LEAST PARTIAL MELTING AS IT FALLS THROUGH THE ABOVE FREEZING NEAR SURFACE LAYER. GRAUPEL WILL CERTAINLY NOT BE THE PREDOMINANT PRECIPITATION TYPE AND THE WEATHER GRIDS ONLY MENTION LIQUID RAIN...BUT IT IS WORTH MENTIONING NONETHELESS. PRECIPITATION WILL COME TO AN END STARTING SATURDAY EVENING AS THE FORCING BEGINS TO EXIT THE REGION. THE NEXT FORECAST ISSUE IS THE ARRIVAL OF WELL BELOW NORMAL TEMPERATURES AND THE POTENTIAL FOR AN ADVECTIVE FREEZE INLAND SATURDAY NIGHT. 850 MB TEMPS ARE VERY COLD...RUNNING ABOUT 5 STANDARD DEVIATIONS BELOW NORMAL...AND THE LINGERING GRADIENT WILL KEEP WINDS STRONG ENOUGH TO PRECLUDE MUCH IN THE WAY OF FROST CONCERNS. SUNDAY HIGHS WILL BE QUITE COOL WITH MID 50S IN MOST AREAS...AND WILL THREATEN RECORD LOW MAXIMUM TEMPERATURE RECORDS AT THE CLIMATE SITES. SUCH HIGH TEMPERATURES ARE ALMOST 20 DEGREES BELOW FOR EARLY NOVEMBER.
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&& .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
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AS OF 300 PM THURSDAY...SUNDAY NIGHT WILL BE THE COLDEST NIGHT OF THE PERIOD AS THE PRESSURE GRADIENT WEAKENS SUFFICIENTLY TO ALLOW FOR GOOD RADIATIONAL COOLING CONDITIONS. THERE APPEARS TO BE A LINGERING FEW MPH OF NE WINDS THAT MAY SPARE INLAND ZONES FREEZING TEMPS WHEREAS WEAK OCEAN INFLUENCE SHOULD FAVOR UPPER 30S COAST. THE CENTER OF THE HIGH IS HESITANT TO GET EAST OF THE REGION ON TUESDAY PRECLUDING BONA FIDE RETURN FLOW AND SO THE CLIMO TEMPS SEEN IN MOS BULLETINS SEEM TOO OPTIMISTIC...AND HAVE BEEN UNDERCUT BY JUST A FEW DEGREES. THE ACTUAL RETURN FLOW SHOULD GET UNDERWAY TUESDAY NIGHT INTO WEDNESDAY. WILL ADD SOME LOW POPS IN THE RETURN FLOW BUT MOST OF THE MOISTENING MAY STILL BE DEDICATED TO PW RECOVERY FROM THE COLD AIRMASS AS OPPOSED TO ACTUAL RAINFALL.
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&& .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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AS OF 00Z...EXPECT VFR THROUGH THE VALID PERIOD AS HIGH PRESSURE REIGNS OVER THE AREA. VFR PREVAILS THIS EVENING WITH LIGHT NORTHEAST WINDS. EXPECT THIS TREND TO PERSIST THROUGH THE OVERNIGHT HOURS...WITH LINGERING SCT/BKN MID TO HIGH CLOUDS AT TIMES. ON FRIDAY...VFR WILL CONTINUE NORTH-NORTHEAST WINDS INCREASING TO AOB 12 KTS...BECOMING LIGHT TOWARDS THE EVENING HOURS. SCT/BKN MID TO HIGH LEVEL CLOUDS ARE EXPECTED THROUGHOUT THE DAY. EXTENDED OUTLOOK...MVFR/POSSIBLE IFR WITH SHOWERS AND INCREASED WINDS SATURDAY INTO SUNDAY WITH COLD FRONT. VFR ON MONDAY.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 730 PM THURSDAY...A COLD FRONT IS STALLING OUT BEYOND THE GULF STREAM ABOUT 200 MILES OFFSHORE. LOW PRESSURE IS EXPECTED TO DEVELOP ALONG THE FRONT OVERNIGHT...WITH A BACKING TREND IN WIND DIRECTIONS AND INCREASING TREND IN WIND SPEEDS EXPECTED. CURRENTLY WIND SPEEDS RANGE FROM ONLY 5-10 KNOTS ON THE BEACHES TO 15-20 KNOTS OUT AT 20 MILES DISTANCE FROM SHORE...WITH SEAS 2-4 FEET. MODELS HAVE TRENDED A BIT FARTHER WESTWARD WITH THE PRECIPITATION SHIELD ON THE WEST SIDE OF THE UPPER LOW...AND I HAVE THEREFORE ADDED SHOWER CHANCES TO THE FORECAST...MAINLY AFTER MIDNIGHT...WITH THE HIGHEST CHANCES IN THE CAPE FEAR WATERS DUE TO THEIR MORE EASTWARD LOCATION. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 300 PM THURSDAY...FRIDAY THROUGH TUESDAY...THE BULK OF THE SIGNIFICANT MARINE CONDITIONS WILL OCCUR STARTING EARLY SATURDAY AS A VERY STRONG COLD FRONT BEGINS TO IMPACT THE LOCAL WATERS. UP UNTIL THAT POINT...NORTH WINDS MAY SURGE INTO THE 15-20 KT RANGE WITH SEAS UP TO 4-5 FT OUT NEAR 20 NM AT TIMES. BEGINNING SATURDAY MORNING...THE COLD FRONT WILL BEGIN TO SWEEP ACROSS THE WATERS WITH A SIGNIFICANT INCREASE IN WINDS/SEAS THROUGH THE DAY. THE AIRMASS BEHIND THE FRONT IS QUITE COLD AND WITH WATER TEMPERATURES STILL IN THE LOW 70S...IDEAL MIXING CONDITIONS WILL BE IN PLACE ESPECIALLY SATURDAY NIGHT AS THE COLD ADVECTION REACHES IT PEAK. THE DEEPENING MIXING OVER THE WATERS WILL BE HAPPENING COINCIDENT WITH A DEEPENING AREA OF LOW PRESSURE PULLING AWAY TO THE NORTHEAST OFF THE OUTER BANKS. MODEL GUIDANCE SHOWS 1000 MB GEOSTROPHIC WINDS INCREASING TO 70 KT ACROSS MUCH OF THE WATERS SATURDAY EVENING AND EARLY SATURDAY NIGHT. WITH THE EXPECTED MIXING THIS WILL EASILY SUPPORT GALE CONDITIONS ACROSS ALL OF THE WATERS. IN FACT...GIVEN THE MOST RECENT MODEL SOUNDINGS IT IS NOT OUT OF THE QUESTION TO SEE A VERY BRIEF PERIOD OF STORM FORCE GUSTS WITH THE INITIAL PUNCH OF WIND BEHIND THE FRONT IN THE 00-03Z SUNDAY TIME PERIOD. AS SUCH...A GALE WATCH HAS BEEN HOISTED STARTING AT 13Z SATURDAY FOR THE SOUTH CAROLINA WATERS AND 17Z FOR THE NORTH CAROLINA WATERS. GALES WILL CONTINUE THROUGH SATURDAY NIGHT AND THEN BEGIN TO DIMINISH TO JUST SMALL CRAFT ADVISORY WINDS BY SUNDAY MORNING. LONG TERM /SUNDAY THROUGH TUESDAY/... AS OF 300 PM THURSDAY...THE GRADIENT WILL STILL BE QUITE STRONG SUNDAY MORNING ESPECIALLY OVER NORTHERN ZONES. HOWEVER THERE WILL BE A MARKED ABATING TREND AS THE DAY WEARS ON DUE TO THE RAPID NORTHEASTERLY MOVEMENT OF THE STILL DEEPENING LOW THAT AFFECTED US DIRECTLY SATURDAY AND SATURDAY NIGHT. IN FACT AS IT APPEARS NOW THERE MAY BE NO HEADLINES NEEDED BY MIDDAY OR SO. FOR MUCH OF MONDAY HIGH PRESSURE WILL ELONGATE UP AND DOWN THE CAROLINAS WITH A LATE DAY SHIFT TOWARDS THE COASTLINE. N WINDS WILL VEER TO THE NE AND GROW LIGHTER. HIGH PRESSURE WILL BUILD IN EARLY NEXT WEEK AND MUCH QUIETER CONDITIONS ARE EXPECTED.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...NONE. NC...NONE. MARINE...GALE WATCH FROM SATURDAY MORNING THROUGH LATE SATURDAY NIGHT FOR AMZ254-256. GALE WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY MORNING FOR AMZ250-252.
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&& $$ NEAR TERM...TRA SHORT TERM...99/CHS LONG TERM...99/CHS AVIATION...SGL

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