Issued by NWS Wilmington, NC
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --000 FXUS62 KILM 220820 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 420 AM EDT WED OCT 22 2008 .SYNOPSIS...-- Changed Discussion --HIGH PRESSURE WILL PROVIDE COOL AND DRY CONDITIONS THROUGH THURSDAY. LOW PRESSURE WILL DEVELOP IN THE GULF OF MEXICO AND MOVE NORTHEAST ACROSS THE AREA FRIDAY INTO SATURDAY...BRINGING WITH IT RAINY AND WINDY CONDITIONS. HIGH PRESSURE WILL BUILD BACK IN LATE SATURDAY AND PREVAIL THROUGH THE REMAINDER OF THE PERIOD.-- End Changed Discussion --&& .NEAR TERM /THROUGH TONIGHT/...-- Changed Discussion --AS OF 3 AM WEDNESDAY...A LARGE AND STRONG AREA OF HIGH PRESSURE (1039 MB) WILL BUILD S TODAY AND BEGIN TO TAKE ON A WEDGE SIGNATURE ACROSS THE CAROLINAS TONIGHT. GOOD INFLUX OF CHILLY AND DRY AIR WITH 850 MB TEMPS DROPPING TO 4-6 DEG C THROUGH THE AFTERNOON. BRIGHT SUNSHINE WILL BATTLE THE INCOMING CHILLY AIRMASS...BUT SUNSHINE THIS TIME OF YEAR IS WEAK. DESPITE THE RELATIVELY MILD START TO THE DAY...WILL GIVE THE NOD TO THE CHILLIEST OF THE GUIDANCE. FORECAST WILL CALL FOR ONLY A 10 TO 15 DEG RECOVERY TODAY. THIS COMPARES TO A 28 TO 34 DEG DIURNAL RANGE ON TUE. AIRMASS WILL BE DRY WITH LOW LEVEL INVERSION SHARPENING 4-5 KFT. MODEL MOISTURE PROFILES DO NOT EVEN SUPPORT LOW TOPPED COLD AIR CUMULUS DEVELOPMENT...ALTHOUGH HARD TO BELIEVE THERE WILL NOT BE A FEW AROUND. HOWEVER...THIS WILL NOT DETRACT FROM A CLEAR/MOSTLY CLEAR SKY. DRY ADIABATIC LAPSE RATE THROUGH ABOUT 5 KFT SHOULD ALLOW SOME OF THE HIGHER MOMENTUM AIR TO REACH THE SURFACE...WITH EVEN STRONGER WINDS WELL ATOP THE INVERSION. PRESSURE GRADIENT WILL TIGHTEN UP TONIGHT AND DO NOT EXPECT BOUNDARY LAYER TO FULLY DECOUPLE. CHILLY TEMPS TONIGHT WILL THEREFORE BE A FUNCTION OF COLD AIR ADVECTION RATHER THAN RADIATIONAL COOLING. NORTHEAST BREEZES SHOULD PREVENT THOSE TRADITIONALLY COLD SPOTS FROM DIPPING TO NEAR THE FREEZING MARK. MOST LOCATIONS BETWEEN THE BEACHES AND AREAS WELL INLAND...WILL EXPERIENCE MINIMUM TEMPS WITHIN 5 TO 8 DEG OF ONE ANOTHER AND ABOUT 10 DEG BELOW CLIMATOLOGY.-- End Changed Discussion --&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...-- Changed Discussion --AS OF 3 AM WEDNESDAY...ALL OF THE ACTION WILL BE IN THE SECOND PART OF THE PERIOD...FRIDAY INTO SATURDAY MORNING AS LARGE MID LEVEL CYCLONE AND ATTENDANT UPPER LEVEL JET DYNAMICS INDUCE CYCLOGENESIS IN THE GULF COAST. THIS FEATURE...WITH STILL A LOT OF THE DETAILS TO BE WORKED OUT...WILL MOVE UP THE COAST FRIDAY AND SATURDAY. REALLY WITH THIS SCENARIO SHIFTING INTO THE SHORT TERM FROM THE LONG TERM PERIOD...ATTEMPTED TO ADD MORE DETAIL TO TIMING AND POPS...BUT ESSENTIALLY THERE HAS BEEN LITTLE CHANGE. IF ANYTHING...THE PROGRESSION OF THE SYSTEM IS A LITTLE SLOWER...BUT THIS WILL HAVE IMPLICATIONS IN SATURDAYS WEATHER...IE THE LONG TERM. ISENTROPIC LIFT ON THE 305K SURFACE KICKS INTO HIGH GEAR FRIDAY AFTERNOON AND CONTINUES THROUGH SATURDAY MORNING. RESISTED THE TEMPTATION TO GO CATEGORICAL AT THIS POINT BUT THE DAY SHIFT WILL PROBABLY WANT TO STRONGLY CONSIDER THIS IF THE FORECAST MODELS REMAIN CONSISTENT. DID TAKE THE LIBERTY TO INCREASE LIKELY VALUES ACROSS THE BOARD TO REPRESENT THE TREND. FROM A QPF STANDPOINT...DOESNT APPEAR TO BE SHAPING UP AS ANYTHING OUT OF THE ORDINARY WITH PRECIPITABLE WATERS ON THE SOUNDINGS HOVERING AROUND 1.75 INCHES FOR ABOUT 18 HOURS...FRIDAY AFTERNOON THROUGH SATURDAY MORNING. THE GFS...WHICH IS USUALLY A BIT ON THE HIGH SIDE HAS AN AXIS OF JUST OVER TWO INCHES FOLLOWING THE NC/SC LINE ALMOST ENCOMPASSING THE ENTIRE CWA. ONE INCH WITH ISOLATED AMOUNTS OF 1.5 INCHES SOUNDS MORE REALISTIC. WITH THE GFS BREAKING DOWN THE WEDGE QUICKLY FRIDAY...TEMPERATURE FORECAST IS LESS PROBLEMATIC. LEANED MORE TOWARD THE GFS/MAV NUMBERS ESPECIALLY CONSIDERING THE MET NUMBERS FRIDAY AM ARE A CATEGORY TO ALMOST TWO CATEGORIES IN SOME PLACES COOLER. OH BY THE WAY...NICE DAY THURSDAY UNDER THE INFLUENCE OF HIGH PRESSURE.-- End Changed Discussion --&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...-- Changed Discussion --AS OF 3 AM WEDNESDAY...THE ONLY CHANGES THIS MORNING FORECAST INCLUDED INCREASING POPS FOR THE 1200 TO 1800 UTC HOURS SATURDAY AND ADDING ISOLATED THUNDER AS SOUNDINGS ARE SHOWING SOME CAPE. HIGH PRESSURE DOMINATES FROM LATE SATURDAY ON...NO OTHER CHANGES.-- End Changed Discussion --&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... VFR THROUGH THE PERIOD. COLD FRONT HAS MOVED S OF THE TERMINALS AS OF 06Z. IN ITS WAKE...A FEW ALTO-CUMULUS WILL FILTER ACROSS THE TAF SITES. HIGH PRESSURE WILL BUILD SOLIDLY ACROSS THE AREA FROM THE N THROUGH THE END OF THE FORECAST PERIOD. WINDS WILL BE GUSTY 14-21Z...AS DRIER AND COOLER AIR CONTINUES TO FILTER SOUTHWARD. OUTLOOK THROUGH SUNDAY...VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THU NIGHT. BY FRI...AN AREA OF LOW PRESSURE WILL BEGIN TO DEVELOP TO OUR S. LOW (POTENTIALLY IFR) CEILINGS WILL DEVELOP FRIDAY NIGHT INTO SATURDAY WITH TEMPORARY VISIBILITY RESTRICTIONS IN MODERATE TO HEAVY RAIN. ALL MODEL GUIDANCE SUGGESTS DRIER WEATHER WILL BUILD IN SATURDAY AFTERNOON INTO SUNDAY. && .MARINE...-- Changed Discussion --NEAR TERM /THROUGH TONIGHT/... AS OF 3 AM WEDNESDAY...INITIAL N SURGE WILL WANE THIS MORNING BUT THEN AS HIGH PRESSURE WEDGES ACROSS THE INLAND CAROLINAS TONIGHT... GRADIENT WILL BECOME PINCHED ACROSS THE WATERS WITH THE TIGHTEST GRADIENT PERHAPS SETTING UP ACROSS OUR SOUTHERN WATERS. THEREFORE... HIGHEST WINDS TODAY WILL OCCUR THIS MORNING THROUGH MIDDAY. WINDS WILL DIMINISH THROUGH THE AFTERNOON AND EVE...INCREASING AGAIN LATE TONIGHT INTO THU MORNING. WIND DIRECTION WILL VEER FROM N TO NE THROUGH TONIGHT. SEAS WILL INCREASE THROUGH THE MORNING HOURS AND THEN HOLD STEADY OR PERHAPS FALL SLIGHTLY DURING THE AFTERNOON AND EVE...BUILDING AGAIN AFTER MIDNIGHT IN RESPONSE TO INCREASING WINDS. A SMALL CRAFT ADVISORY (SCA) HAS BEEN ISSUED THROUGH 12Z THU. CONDITIONS SHOULD FALL SHORT OF SCA THRESHOLDS WITH THE SURGE THROUGH MIDDAY...BUT MARGINAL SCA CONDITIONS SHOULD DEVELOP LATE TONIGHT INTO THU MORNING. SHORT TERM /THURSDAY THROUGH FRIDAY/... AS OF 3 AM WEDNESDAY...JUST LIKE THE SHORT TERM PUBLIC...THE ACTION WILL BE IN THE LATTER PART OF THE PERIOD...FRIDAY. UNTIL THEN...NE FLOW COURTESY OF MASSIVE HIGH WILL PREVAIL WITH SEAS OF 2-4 FEET. NOW FRIDAY...THE GFS WHICH IS THE MODEL OF CHOICE...HAS A VERY NOISY LOW LEVEL WIND FIELD WITH SEVERAL MAXIMUMS AT OR IN EXCESS OF 40 KNOTS FRIDAY THROUGH SATURDAY AM. OBVIOUSLY DIFFICULT TO PIN ANY OF THESE DOWN AT THIS POINT. SUFFICE TO SAY SMALL CRAFT CONDITIONS ARE PROBABLY A GIVEN...ALTHOUGH PROBABLY NOT TEASING GALES LIKE THE GFS IS ADVERTISING. WILL BROAD BRUSH RANGES OF 20-25 KNOTS EARLY FRIDAY INCREASING TO 25-30 KNOTS LATER FRIDAY INTO SATURDAY MORNING. FOLLOWED THE SAME STRATEGY WITH SEAS...UNDERCUTTING THE PROLIFIC WAVEWATCH NUMBERS SOMEWHAT. LONG TERM /FRIDAY THROUGH SUNDAY/... AS OF 3 AM WEDNESDAY...-- End Changed Discussion --&& .ILM WATCHES/WARNINGS/ADVISORIES...-- Changed Discussion --SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR AMZ250-252- 254-256.-- End Changed Discussion --&& $$ SYNOPSIS...SHK NEAR TERM...RJD SHORT TERM...SHK LONG TERM...SHK AVIATION...RJD/DL
