Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 310710 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 310 AM EDT FRI OCT 31 2014 .SYNOPSIS...
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HIGH PRESSURE WILL NUDGE INTO THE AREA TODAY 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 THIS MORNING/... AS OF 1030 PM THURSDAY...RADAR AND SATELLITE IMAGERY IMPLY THAT ISENTROPIC LIFT IS INCREASING 20-40 MILES OFF THE SOUTHERN AND CENTRAL SOUTH CAROLINA COAST. THIS AREA IS MOVING NORTHEAST AND SHOULD MISS THE POINT OF CAPE FEAR BY A COMFORTABLE MARGIN. HOWEVER ADDITIONAL ISENTROPIC LIFT DEVELOPING IN THE 06-12Z TIMEFRAME MAY STILL SPREAD SOME SHOWER ACTIVITY INLAND ALONG THE COAST. BESIDES ADJUSTING FORECAST TEMP/WIND/SKY GRIDS OVER THE NEXT FEW HOURS TO ACCOUNT FOR LATEST OBSERVED TRENDS...NO CHANGES HAVE BEEN MADE TO THE FORECAST. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS... 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. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
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AS OF 3 AM FRIDAY...ALTHOUGH MODEL SOLUTIONS ARE CONGEALING ON SATURDAY THERE ARE STILL SOME MINOR DIFFERENCES. SUCH DIFFERENCES WITH SUCH A STRONG SYSTEM HOWEVER CAN TRANSLATE TO CONSIDERABLE FORECAST UNCERTAINTIES. FOR EXAMPLE, THE GFS HAS SHOWN A BIT OF A WARM SECTOR/TROWAL BRIEFLY GETTING INTO MAINLY COASTAL NC ZONES AT 12Z SATURDAY...LIKELY DICTATING WHAT HIGH TEMPS ARE FOLLOWED BY QUITE A DROP OFF IN THE CAA. AGREEMENT HAS ALSO INCREASED IN THE PORTRAYAL OF DRY SLOT MOVING INTO SRN ZONES TO KEEP HIGHER QPF OVER NRN ZONES. AREAS FURTHER SOUTH SHOULD STILL SEE SOME LIGHT RAIN GIVEN THE STRENGTH OF THE FORCING BUT SHOULD LARGELY MISS OUT ON THE DEEP MOISTURE. TIGHTLY WOUND SYSTEM SO THE WRAP-AROUND MOISTURE ALREADY UNDERWAY BY AFTERNOON AND ONCE AGAIN MORE WIDESPREAD AND W HIGHER AMOUNTS POSSIBLE NC. WINTER-LIKE COLD WITH MOST PLACES STUCK IN THE LOW 50S SAVE FOR POSSIBLE EARLY DAY HIGHS ALONG THE COAST. THERE STILL MAY BE A WINDOW OF OPPORTUNITY FOR SOME GRAUPEL PELLETS TO REACH THE GROUND BUT THEY SHOULD BE THE EXCEPTION AND NOT THE RULE. THE CAA PLUNGES SAT NIGHT LOWS DOWN INTO THE 30S. SOME WIND AND CLOUD COVER PREVENT RAD COOLING. THE UPPER WAVE MOVES OFFSHORE BY 12Z SUNDAY ALLOWING FOR STRONG DRY AIR ADVECTION. NEARLY FULL SUN EXPECTED WITH A DIMINISHING BREEZE AND TEMPS ONCE AGAIN WELL BELOW CLIMO. SUNDAY NIGHT WILL BE A FEW DEGREES COOLER THAN SATURDAY NIGHT ESPECIALLY INLAND WHERE WINDS MAY GO CALM. FOR A PERFECT RAD NIGHT THE CENTER OF THE HIGH WOULD NEED TO HAVE BEEN CLOSER.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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AS OF 3 AM FRIDAY...THE ORIGINAL CHILLY HIGH STILL DIRECTLY OVERHEAD ON MONDAY. HOWEVER BETWEEN WARMING ALOFT AS WELL AS SOLAR INSOLATION MODERATING THE AIRMASS HIGH TEMPERATURES WILL END UP CLOSER TO BUT STILL SHY OF CLIMO. BUILDING UPPER RIDGE TO OUR WEST SPREADS OVERHEAD BY TUESDAY ALLOWING FOR SOME WEAK ONSHORE RETURN FLOW AND HIGHS BACK IN THE 70S. ADDITIONAL MODERATION AND WEAK ADVECTION SHOULD BRING AN EVEN MILDER WEDNESDAY AND MOISTURE RETURN WILL ADD SOME CLOUD COVER. A WEAK UPPER DISTURBANCE MOVES THROUGH WED NIGHT INTO THURSDAY AND TRIES TO TOUCH OFF A FEW SHOWERS.
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&& .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 06Z...EXPECT VFR THROUGH THE VALID PERIOD AS HIGH PRESSURE REIGNS OVER THE AREA. VFR WILL PREVAIL WITH N-NE WINDS LESS THAN 10 KT OVERNIGHT...HIEST ACROSS THE COASTAL TERMS. ALONG WITH LINGERING SCT/BKN MID TO HIGH LEVEL CLOUDS AT TIMES...ESPECIALLY ACROSS THE COASTAL TERMINALS. AFTER DAYBREAK...VFR WILL CONTINUE WITH SLIGHT BACKING OF THE WINDS TO THE NNW-N AOB 12 KTS AS WEAK LOW PRESSURE MOVES BY TRACKING NE ALONG THE STALLED OFFSHORE FRONT. SCT/BKN MID TO HIGH LEVEL CLOUDS ARE EXPECTED THROUGHOUT THE DAY. WINDS TO ONLY DROP TO AROUND 6 KT DURING THE EVENING HOURS. EXTENDED OUTLOOK...MVFR/IFR CONDITIONS WITH SHOWERS THRU SAT. BREEZY TO WINDY CONDITIONS TO DEVELOP ON SATURDAY AND PERSIST INTO SUNDAY AFTER LOW PRESSURE DEVELOPS OFF THE CAROLINA COASTS...BOMBS...AND ACCELERATES TO THE NE. VFR FOR MONDAY AND TUESDAY AS THE CENTER OF STRONG HIGH PRESSURE MOVES OVERHEAD. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1030 PM THURSDAY...NO SIGNIFICANT CHANGES HAVE BEEN MADE TO THE FORECAST. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS... 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 /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 3 AM FRIDAY...GALE WARNING LIKELY IN EFFECT FOR MOST IF NOT ALL OF THE AREA FOR COLD SURGE THAT SHOULD REALIZE GALES BY SAT EVENING OR NIGHT. ITS STILL ABOUT ONE FORECAST CYCLE TOO EARLY TO RAISE THE WARNING ESPECIALLY GIVEN THE SMALL DIFFERENCES IN HOW THE MODELS HANDLE THE OVERALL EVOLUTION OF THE CYCLONE. WINDS WILL BE NW TO W AND THUS STRONGLY OFFSHORE THROUGHOUT WHICH COULD YIELD A CONSIDERABLE WAVE SHADOW ALONG LAND UP AGAINST THE INCREASINGLY LARGE AND STEEP WAVES AS ONE MOVES AWAY FROM THE COAST. LOCALLY GENERATED SWAN DATA APPEARS TO BE HANDLING THIS OK...ALTHOUGH IT WILL BE INTERESTING TO SEE HOW THE POSSIBLE DEEP MIXING OF WIND GUSTS CAUSED BY COOL AIR OVER WARMER SSTS MANAGES TO BOLSTER SEAS. STRONGEST OF THE LOW LEVEL JETTING APPEARS SLATED FOR SATURDAY NIGHT. THEREAFTER THESE WINDS ALONG WITH SURFACE FLOW WILL BEGIN TO ABATE ALBEIT VERY GRADUALLY AT FIRST. THIS TREND WILL BE MORE NOTICEABLE ON SUNDAY AS THE LOW CONTINUES TO BOTH DEEPEN AND ACCELERATE OFF TO THE NORTHEAST. LONG TERM /MONDAY THROUGH TUESDAY/... AS OF 3 AM FRIDAY...NORTHERLY WINDS REALLY RELAX ON MONDAY AS HIGH PRESSURE MOVES OVER THE COAST. WIND DIRECTION MAY VEER SLIGHTLY AS WELL WHILE SEAS SETTLE TO JUST 2 FT OR LESS. THE ACTUAL CENTER OF THE HIGH DOES NOT MOVE MUCH INTO TUESDAY BUT IT DOES TAKE ON AN EAST-WEST ELONGATION THAT WILL FURTHER TURN THE FLOW MOVE ONSHORE. SEAS GENERALLY UNCHANGED AND MINIMAL IN SIZE.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... 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. && $$ SYNOPSIS...MBB NEAR TERM...DCH/TRA SHORT TERM...MBB LONG TERM...MBB AVIATION...DCH/SGL

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