Issued by NWS Wilmington, NC
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --000 FXUS62 KILM 211141 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 636 AM EST SAT NOV 21 2009 .SYNOPSIS... GULF OF MEXICO MOISTURE WILL OVERRUN A WEDGE OF HIGH PRESSURE THROUGH SUNDAY. A BRIEF WARMUP IS EXPECTED TUESDAY AND WEDNESDAY. A STRONG COLD FRONT THURSDAY WILL USHER IN SOME COLDER AIR FOR NEXT WEEKEND. && .NEAR TERM /THROUGH TONIGHT/...-- Changed Discussion --AS OF 3 AM SATURDAY...WEAK WAVE OF LOW PRESSURE WILL MOVE NE THIS MORNING ALONG A STALLED FRONT LOCATED ACROSS THE OFFSHORE WATERS. THIS WILL KEEP THICKEST CLOUD COVER ALONG THE COAST. A BROAD AREA OF HIGH PRESSURE CENTERED ACROSS THE OHIO VALLEY WILL MOVE TO NEW ENGLAND AND QUEBEC PROVINCE. THIS AREA OF HIGH PRESSURE WILL BEGIN TO WEDGE ACROSS THE CAROLINAS THIS PERIOD. THIS WILL SET THE STAGE FOR INCREASING ISENTROPIC UPGLIDE...MAINLY LATE IN THE PERIOD. AT THIS TIME...IT LOOKS LIKE ALTHOUGH CLOUDS WILL BE PLENTIFUL THIS PERIOD...AND THICKEST ALONG THE COAST...RAINFALL WILL BE SLOW TO DEVELOP GIVEN THE DRYNESS OF THE COLUMN BELOW 4 KFT. HOWEVER...WE DO EXPECT LIGHT RAIN TO BEGIN TO MOVE IN FROM THE SW/DEVELOP ACROSS THE AREA BY DAYBREAK ON SUN AS COLUMN SATURATES FROM THE TOP DOWN. WEAK WAVE OF LOW PRESSURE OFFSHORE WILL AID IN REINFORCING COOL NE FLOW ACROSS THE AREA. COUPLE THIS WITH CLOUDS AND WE EXPECT MAXIMUMS THIS PERIOD WILL BE HELD TO THE COOLER SIDE OF MODEL CONSENSUS. COOLEST TEMPS SHOULD BE ACROSS THE CAPE FEAR REGION...BUT STILL ALL AREAS SHOULD BE AT OR JUST A DEGREE OR TWO BELOW NORMAL. TONIGHT... AS WEDGE INTENSIFIES ACROSS THE AREA...AND WITH COOL NE FLOW CONTINUING...TEMPS SHOULD AGAIN BE DOWN IN THE MID 40S TO NEAR 50 DEGREES.-- End Changed Discussion --&& .SHORT TERM/SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 AM SATURDAY... MOISTURE OVERRUNNING NORTHEASTERLY SURFACE FLOW ASSOCIATED WITH WEDGE OF HIGH PRESSURE WILL BRING PLENTY OF CLOUDINESS TO START THE PERIOD. INCREASING ISENTROPIC UPGLIDE WILL ALSO RAMP UP RAIN CHANCES...ENDING UP IN THE CATEGORICAL RANGE BY EVENING. QPF FORECAST IS STILL A LITTLE UNCERTAIN AS GUIDANCE HAS REALLY BACKED OFF WITH RAINFALL WHEN COMPARED TO PREVIOUS DAYS. RAIN CHANCES REMAIN FAIRLY HIGH SUNDAY NIGHT AS THE WEAKENING LOW JUMPS TO THE EASTERN SIDE OF THE WEDGE AND ENDS UP OFFSHORE. SOON THEREAFTER RAIN CHANCES SHOULD TAPER OFF FROM WEST TO EAST EARLY MONDAY. CLOUDS AND POSSIBLY DRIZZLE COULD LINGER INTO THE MORNING HOURS. MIGHT EVEN SEE A TREND TOWARDS OVERALL SLOWER PROGRESSION WHICH COULD MEAN DRIZZLE AND CLOUDS LINGER MOST OF THE DAY. HAVE UNDERCUT GUIDANCE ON MONDAY HIGH TEMPS. && .LONG TERM/TUESDAY THROUGH FRIDAY/... AS OF 3 PM SATURDAY... A WEAK UPPER RIDGE MANAGES TO BUILD ON TUESDAY AND THIS SHOULD BRING A MILD AFTERNOON. WEDNESDAY MAY ALSO BRING HIGHS IN THE LOW 70S AHEAD OF WHAT WILL END UP BEING A PRETTY STRONG COLD FRONT ON THURSDAY. LITTLE TO NO MOISTURE FLOW AHEAD OF THE FRONT SO ITS PASSAGE SHOULD BE DRY. THE ECWMF HAS INDICATED OTHERWISE FOR A FEW RUNS NOW BUT THIS MODEL HAS BEEN DISPLAYING A VERY WET BIAS FOR SOME TIME LOCALLY IN SUCH SETUPS. DRY AND COOL WEATHER FOR THE REST OF THE PD WITH HIGHS STRUGGLING TO LOW 60S BY DAY AND UPPER 30S AT NIGHT. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... WEAK LOW PRESSURE WILL MOVE ALONG A STALLED BOUNDARY JUST OFFSHORE TODAY BRINGING MID LEVEL CLOUD COVER TO THE COASTAL TERMINALS. A MORE SIGNIFICANT SYSTEM DEVELOPING IN THE GULF OF MEXICO WILL CAUSE GRADUALLY THICKENING HIGH CLOUDS AT ALL TERMINALS THROUGH THE PERIOD. 4SM VSBY AT LBT IS ONLY RESTRICTION THIS MORNING...AND THIS WILL BURN OFF QUICKLY AFTER SUNRISE LEAVING VFR ALL TERMINALS. 11U-3.9U MICRON SATELLITE IS BUSY...WITH HIGH LEVEL CI STREAMING ACROSS TO THE NE AND MVFR/VFR STRATUS JUST OFFSHORE. WITH A MODERATE NE WIND TODAY AT AROUND 10 KT...EXPECT SOME OF THIS STRATUS TO OCCASIONALLY MOVE ONSHORE CREATING 5K FOOT CIGS AT ILM/CRE/MYR. DO NOT BELIEVE ANY OF THIS WILL GET TO FLO/LBT...BUT SOME AFTN CU MAY DEVELOP AT THOSE TERMINALS AROUND 4K FEET. THIS CU WILL HAVE VERY LIMITED VERTICAL EXTENT DUE TO THE DRY MID LEVELS OF THE COLUMN. MODEL GUIDANCE HAS SLOWED IN ITS PROGRESSION OF THE GULF OF MEXICO SYSTEM...AND HAVE REMOVED ANY VCSH TO REFLECT THIS MORE DELAYED SOLUTION. VFR WILL BE THE RULE ALL DAY WITH HIGH LEVEL CI LOWERING TO AN AS/AC DECK AROUND 12K FEET BY THE END OF THE TAF PERIOD AS THE COLUMN SATURATES FROM THE TOP DOWN. EXTENDED OUTLOOK...POTENTIAL IFR DUE TO SHOWERS AND LOW CEILINGS SUNDAY AND MONDAY. FOG POSSIBLE TUESDAY MORNING. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 3 AM SATURDAY...WILL HOIST A SMALL CRAFT ADVISORY FOR ALL ZONES EXCEPT AMZ254 WHERE A SMALL CRAFT SHOULD EXERCISE CAUTION HEADLINE WILL REMAIN IN PLACE. PINCHED GRADIENT HAS DEVELOPED ACROSS THE WATERS EARLY THIS MORNING...THE RESULT OF PRESSURE DIFFERENCES BETWEEN WEAK LOW PRESSURE MOVING NE ALONG A STALLED FRONT OFFSHORE OF THE CAROLINAS AND HIGH PRESSURE CENTERED ACROSS THE OHIO VALLEY. THIS PINCHED GRADIENT SHOULD RELAX LATER IN THE DAY AS WEAK WAVE OF LOW PRESSURE MOVES FURTHER AWAY. GRADIENT WILL TIGHTEN UP AGAIN THIS EVE AND ESPECIALLY OVERNIGHT AS WEDGE OF HIGH PRESSURE INTENSIFIES ACROSS THE AREA WHILE LOW PRESSURE REACHES THE NORTHEASTERN GULF COAST. PERSISTENT NE WINDS WILL REACH MARGINAL SMALL CRAFT ADVISORY LEVELS ACROSS THE MAJORITY OF THE AREA. SEAS WILL NOT CHANGE MUCH THROUGH THE PERIOD...AND WILL BE AS HIGH AS 5 TO 7 FT ACROSS THE OUTER WATERS. NEAR SHORE SEAS WILL BE LOWER IN AREAS WHERE FETCH IS GREATLY REDUCED IN NE FLOW. SHORT TERM/SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 AM SATURDAY... SURFACE HIGH PRESSURE WEDGE IN CONTROL ON SUNDAY TO BRING A MODERATE GRADIENT WIND. SMALL CRAFT ADVISORY FROM NEAR TERM HAS BEEN EXTENDED THROUGH SUNDAY FOR NORTHERN TWO ZONES AS 6 FT SEAS AFFECT THE OUTER REACHES ALONG FRYING PAN SHOALS. WAVE SHADOWING WILL PROBABLY PRECLUDE THIS OVER SOUTHERN WATERS. A FLAT WAVE OF LOW PRESSURE WILL RIDE UP THE EAST SIDE OF THE WEDGE SUNDAY NIGHT INTO MONDAY. THIS WILL SLIGHTLY TAPER THE GRADIENT AND COULD LOWER THE SEAS ENOUGH TO DROP ANY ADVISORIES. WEDGE WEAKENS BUT REMAINS IN PLACE FOR THE REMAINDER OF MONDAY AND MONDAY NIGHT KEEPING WINDS WITH A NORTHERLY COMPONENT. && LONG TERM/TUESDAY THROUGH WEDNESDAY/... AS OF 3 PM SATURDAY... LOOKS LIKE A FAIRLY QUIET PATTERN FOR MOST OF THE PERIOD. HIGH PRESSURE REMAINS TO THE NORTH TUESDAY BRINGING A LIGHT NORTHERLY WIND AND SEAS IN THE 2 TO 3 FT RANGE. CHANGES MAY BE UNDERWAY COME WEDNESDAY AS THE HIGH BEGINS TO LIFT OUT AHEAD OF AN APPROACHING COLD FRONT. THE TIMING OF THIS FRONT AND THE EVOLUTION OF SURFACE FEATURES ASSOCIATED WITH IT IS HIGHLY UNCERTAIN. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EST SUNDAY FOR AMZ256. SMALL CRAFT ADVISORY UNTIL 7 PM EST SUNDAY FOR AMZ250-252. && $$ SYNOPSIS...MBB NEAR TERM...RJD SHORT TERM...MBB LONG TERM...MBB AVIATION...JDW
