Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 242012 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 312 PM EST SAT JAN 24 2015 .SYNOPSIS...
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AN AREA OF LOW PRESSURE OVER THE NORTHERN PLAINS STATES WILL MOVE SOUTHEASTWARD AND ACROSS THE CAROLINAS MONDAY. HIGH PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT THROUGH WEDNESDAY...MOVING OFFSHORE THURSDAY. ANOTHER COLD FRONT WILL PUSH THROUGH THE CAROLINAS FRIDAY...FOLLOWED BY ARCTIC HIGH PRESSURE FOR THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 3 PM SATURDAY...FORCING ASSOCIATED WITH THE PASSING SHORTWAVE HAS LIFTED OFF TO THE NORTHEAST WITH SUBSIDENCE DEVELOPING OVER THE AREA. THIS HAS BROUGHT ABOUT THE END TO THE LIGHT PATCHY SHOWERS THAT HAD DEVELOPED ACROSS WESTERN PORTIONS OF THE FORECAST AREA. SKIES WILL BEGIN TO SLOWLY CLEAR FROM WEST TO EAST THROUGH THE REMAINDER OF THE DAY AS DEEP DRY AIR SPREADS EAST. WINDS WILL REMAIN BREEZY THROUGH SUNSET DUE TO THE COMBINATION OF GRADIENT WIND AND MIXING OF STRONG WINDS ALOFT TO THE SURFACE. SUSTAINED WINDS OF 10 TO 15 MPH WITH POTENTIAL FOR ISOLATED GUSTS UP TO 25 MPH ARE EXPECTED. DEEP DRY AIR CONTINUES TO FILTER IN OVERNIGHT WITH PRECIPITABLE WATER VALUES DROPPING DOWN AROUND 0.25 INCH THIS EVENING. MINIMAL RECOVERY IS EXPECTED OVERNIGHT THANKS TO DEEP WEST TO NORTHWEST FLOW. SUBSIDENCE AND DEEP DRY AIR WILL KEEP SKIES CLEAR DESPITE THE APPROACH OF ANOTHER SHORTWAVE FROM THE WEST...RIGHT AROUND MIDNIGHT. ALTHOUGH THIS WAVE WILL HAVE NO VISIBLE IMPACT ON THE AREA IT SHOULD HELP KICK UP BOUNDARY LAYER WINDS. HAVE BUMPED TEMPS OVERNIGHT A DEGREE OR 2 TO REFLECT THE EFFECT OF ENHANCED BOUNDARY LAYER WINDS. LOWS WILL BE IN THE LOW TO MID 30S.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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AS OF 300 PM SATURDAY...THE FIRST TWO DAYS OF THE NEW WEEK WILL FEATURE A FAST-MOVING WEATHER PATTERN AND LOTS OF CHANGEABILITY. A SURFACE AND LOW-LEVEL (UP THROUGH 850 MB) RIDGE WILL CROSS THE AREA LATE SUNDAY MORNING FOLLOWED BY A BRIEF PERIOD OF WEAK WARM ADVECTION IN THE AFTERNOON. 850 MB TEMPS ONLY HAVE TIME TO MAKE IT UP TO +3C OR +4C BEFORE SUNSET SO EVEN WITH FULL SUNSHINE HIGHS WILL ONLY MAKE IT INTO THE MID TO UPPER 50S...SEVERAL DEGREES COOLER NEAR THE BEACHES WITH A WEAK SEABREEZE. AN ENERGETIC CLIPPER SYSTEM CURRENTLY MOVING SE ACROSS THE DAKOTAS WILL MOVE ACROSS THE CAROLINAS MONDAY AFTERNOON...ROUNDING THE BASE OF THE LONGWAVE TROUGH ALONG THE EAST COAST. DEEP WESTERLY FLOW AHEAD OF THIS SYSTEM WILL MAKE IT STARVED FOR MOISTURE... HOWEVER THE DYNAMIC WIND FIELDS ALOFT WILL INDUCE AT LEAST A COUPLE PERIODS OF IMPRESSIVE LIFT MONDAY...LIKELY LEADING TO CLOUDS AND AREAS OF SHOWERS. FROM A THERMODYNAMIC PERSPECTIVE... 500 MB TEMPS OF -27C AND 850 MB TEMPS AROUND 0C FALL ALONG THE SAME MOIST ADIABAT (THETA E) VALUE MEANING STATIC STABILITY IS AT LEAST NEUTRAL DURING THE UPPER LOW`S PASSAGE. I HAVE INCREASED FORECAST POPS TO 30-40 PERCENT...HIGHEST DURING THE EARLY-MID AFTERNOON MONDAY TO COINCIDE WITH PEAK SOLAR HEATING AND THE COLDEST UPPER LEVEL TEMPS. THIS SHOULD BE AN ALL-LIQUID PRECIP EVENT FOR OUR FORECAST AREA DESPITE 1000-500 MB THICKNESS VALUES OF 535-538 DAM GIVEN THE STEEP LOW-LEVEL LAPSE RATES. IF LAPSE RATES ALOFT WERE TO BECOME STEEPER THAN CURRENT FORECAST (IMPLYING CONVECTIVE INSTABILITY INCREASES TOWARD 300-500 J/KG) THE POTENTIAL FOR SOME SMALL HAIL COULD DEVELOP AS WELL. THE COLD UPPER LOW WILL PRESS OFFSHORE MONDAY EVENING FOLLOWED BY A SHOT OF COLD ADVECTION ON NW WINDS. SKIES WILL ONLY PARTIALLY CLEAR ACROSS SE NORTH CAROLINA WITH DRIER AIR LIKELY ARRIVING ACROSS SOUTH CAROLINA. LOWS SHOULD BOTTOM OUT IN THE MID 30S FOR MOST AREAS.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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AS OF 300 PM SATURDAY...DEEP LOW PRESSURE SYSTEM WILL BE LIFTING OFF TO THE NORTHEAST ON TUESDAY. A DEEP NW FLOW WILL EXIST ON THE BACK END OF THIS SYSTEM TAPPING INTO ARCTIC AIR MASS BRINGING COLD AND RELATIVELY DRY AIR OVER THE CAROLINAS. SOME ENERGY IN THE MID TO UPPER LEVELS WILL RIDE AROUND THIS TROUGH REACHING FAR ENOUGH SOUTH TO PRODUCE SOME CLOUDS AND GUSTY WINDS FOR OUR LOCAL FORECAST AREA. AS SYSTEM LIFTS FARTHER AWAY TUES NIGHT...COLUMN WILL DRY OUT FURTHER IN INCREASED SUBSIDENCE. PCP WATER VALUES DROP OUT FROM NEAR .4 INCHES TO A QUARTER OF AN INCH OR LESS THROUGH WED. TIGHTENED GRADIENT FLOW WILL BEGIN TO RELAX WED MORNING AS HIGH PRESSURE MOVES IN REACHING OVERHEAD BY WED EVE. THE BEST CAA WILL COME IN THE DEEP NW FLOW TUES THROUGH EARLY WED AS 850 TEMPS DROP DOWN CLOSE TO -7 C BUT MORE IDEAL RADIATIONAL COOLING CONDITIONS WILL EXIST WED NIGHT UNDER CLEAR SKIES WITH CALM WINDS AND THEREFORE EXPECT TEMPS WITHIN A FEW DEGREES OF FREEZING BOTH TUES NIGHT AND WED NIGHT WITH HIGH TEMPS BOTH DAYS NEAR 50. FLOW REMAINS QUITE PROGRESSIVE AS HIGH PRESSURE SHIFTS OFF SHORE THROUGH THURS WITH A WARMER RETURN FLOW SETTING UP BRIEFLY THURS AFTN BEFORE NEXT COLD FRONT CROSSES THE CAROLINAS BY FRI MORNING. TEMPS THURS SHOULD SPRING BACK UP TO NORMAL OR ABOVE BUT WILL BE KNOCKED BACK DOWN A FEW DEGREES BY FRI AS FRONT MOVES THROUGH. THERE WILL BE SOME MOISTURE RETURN IN SW RETURN FLOW ON THURS INTO EARLY FRI AHEAD OF NEXT FRONT. INITIALLY LOOKS LIKE IT WILL COME IN THE MID TO UPPER LEVELS SO EXPECT INCREASING CLOUDS THROUGH LATE THURS BUT BEST UPPER LEVEL SUPPORT WILL COME INTO EARLY FRI MORNING. OVERALL MOISTURE WILL BE LACKING BUT WILL ADD LOW END POPS MAINLY TOWARD COAST EARLY FRI MORNING. ANOTHER SHOT OF COLD AND DRY AIR WILL COME ON FRI AS HIGH PRESSURE BUILDS DOWN FROM CANADA. DEEP NW-N FLOW WILL CONTINUE INTO EARLY SATURDAY BEFORE NEXT SYSTEM APPROACHES THE CAROLINAS FOR THE LATTER HALF OF NEXT WEEKEND. SHOULD SQUEEZE OUT A COOL BUT SUNNY FRI AND SAT.
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&& .AVIATION /18Z SATURDAY THROUGH THURSDAY/... AS OF 18Z...THE COLD FRONT AND ASSOCIATED HEAVY CONVECTION HAS MOVED WELL OFFSHORE. A TRAILING UPPER IMPULSE WILL MOVE ACROSS THE TERMINALS EARLY THIS AFTERNOON AND MAY PRODUCE TEMPO MVFR VSBYS IN LIGHT RAIN. CIGS ARE NOW AROUND 1K EXCEPT AT KILM WHERE CIGS ARE STILL IFR. MVFR CIGS MAY DROP TO IFR THROUGH 19Z BUT GENERAL TREND IS UPWARD. CIGS WILL BREAK UP AND SKIES SCATTER AS THE UPPER IMPULSE MOVES THROUGH ABOUT 19-20Z AT KFLO/KLBT AND 20-21Z AT THE COASTAL TERMINALS. WINDS WILL BECOME LIGHT W-NW 23-01Z AND MAY BECOME LIGHT AND VARIABLE BY THE PRE-DAWN HOURS AS A QUICK MOVING SURFACE HIGH SHIFTS EAST AHEAD OF THE NEXT SYSTEM. WINDS BECOME S-SW LATE IN THE TAF VALID PERIOD BUT THIS IS NOT REFLECTED IN TAFS ATTM. EXTENDED OUTLOOK...VFR SUN. SLIGHT CHANCE OF PRECIPITATION/MVFR CIGS MON. VFR AND GUSTY NORTH WINDS TUE-THURS. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 3 PM SATURDAY...SCA REMAINS IN EFFECT FOR ALL ZONES DUE TO STRONG OFFSHORE FLOW. CANNOT RULE OUT ANOTHER HOUR OR TWO OF ISOLATED GALE FORCE GUSTS BUT FOR THE MOST PART GUSTS WILL REMAIN AT OR BELOW 30 KT. OFFSHORE FLOW WILL CONTINUE THROUGH THE DURATION OF THE PERIOD WITH GRADIENT REMAINING PINCHED INTO THE EVENING HOURS. SPEEDS WILL GRADUALLY DECREASE AS GRADIENT RELAXES OVERNIGHT. WINDS OF 20 TO 25 KT WITH GUSTS IN EXCESS OF 30 KT WILL CONTINUE INTO THIS EVENING BEFORE STARTING TO DIMINISH. ALTHOUGH WINDS ARE OFFSHORE THE MAGNITUDE OF THE WIND SPEED IS LIKELY TO KEEP 6 TO 9 FT SEAS WITHIN 20 NM INTO TONIGHT. WIND SPEEDS DROP UNDER 20 KT BY MIDNIGHT AND TO 10 TO 15 KT BY THE END OF THE PERIOD. SEAS WILL RESPOND TO THE REDUCTION IN SPEEDS...FALLING TO 2 TO 4 FT BY THE END OF THE PERIOD. LATEST FORECAST HAS LOW TIDES IN THE -0.50 TO -0.80 RANGE THIS AFTERNOON. DO NOT CURRENTLY HAVE ANY PLANS TO ISSUE ANY STATEMENTS REGARDING THE UPCOMING LOW TIDE BUT WILL CONTINUE TO MONITOR IN CASE A STATEMENT IS NEEDED. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 300 PM SATURDAY...THE FIRST TWO DAYS OF THE NEW WEEK WILL FEATURE A FAST-MOVING WEATHER PATTERN AND LOTS OF CHANGEABILITY. A WEAK HIGH CENTERED OVER THE GULF OF MEXICO WILL SWING A RIDGE AXIS ACROSS THE AREA DURING THE DAY SUNDAY. THIS WILL LEAD TO LIGHT NW WINDS IN THE MORNING...BACKING SW DURING THE AFTERNOON. TEMPERATURES SHOULD RISE ENOUGH INLAND TO INDUCE A WEAK SEABREEZE CIRCULATION TO DEVELOP WITH NEARSHORE WIND DIRECTIONS BECOMING SOLIDLY ONSHORE AT 10 KT OR LESS BY 1 PM. SUNDAY NIGHT THE PRESSURE GRADIENT WILL TIGHTEN SIGNIFICANTLY BEHIND THE DEPARTING RIDGE. SW WINDS WILL INCREASE TO 15-20 KT OUT NEAR 20 MILES FROM SHORE WHERE WATER TEMPERATURES ARE STILL RELATIVELY WARM...BUT NEARSHORE THERE SHOULD BE VERY LITTLE INCREASE IN WIND SPEED DUE TO COOL STABLE AIR REMAINING ENTRENCHED AT THE SURFACE. THIS SHOULD CHANGE MONDAY AS AN AREA OF LOW PRESSURE MOVES ACROSS SOUTHERN NORTH CAROLINA AND OFFSHORE DURING THE AFTERNOON. FAIRLY STRONG WEST WINDS ARE EXPECTED TO DEVELOP BEHIND AND SOUTH OF THIS LOW...PERHAPS REACHING 25 KT MONDAY EVENING AS COLD AIR BLASTS ACROSS THE BEACHES. WE`LL PROBABLY NEED ANOTHER ROUND OF SMALL CRAFT ADVISORIES FOR THIS SYSTEM. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 300 PM SATURDAY...DEEP LOW PRESSURE SYSTEM WILL LIFT OFF TO THE NORTHEAST THROUGH TUES. GUSTY NW WINDS WILL CONTINUE IN TIGHTENED GRADIENT FLOW THROUGH TUES NIGHT. BY WED HIGH PRESSURE WILL BEGIN TO MOVE CLOSER REACHING OVER THE WATERS BY WED NIGHT. THEREFORE NW WINDS UP TO 20 KTS EARLY TUES WILL DIMINISH SLIGHTLY AND BACK THROUGH TUES AFTN BUT AS SHORTWAVE DIGS DOWN TUES NIGHT THE WINDS WILL KICK UP ONCE AGAIN OUT OF THE NW. SEAS WILL SUBSIDE SOME THROUGH TUES BEFORE SPIKING UP AGAIN TUES NIGHT INTO EARLY WED. WINDS WILL DIMINISH THOUGH LATE WED INTO THURS AS HIGH PRESSURE BUILDS OVERHEAD. LIGHT NORTHERLY FLOW WED EVE WILL BECOME MORE VARIABLE BEFORE SHIFTING AROUND TO THE SW AS NEXT SYSTEM APPROACHES THURS EVE. THESE INCREASING SW WINDS WILL PUSH SEAS UP NEAR SCA THRESHOLDS BY THURS EVE.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST SUNDAY FOR AMZ250-252-254- 256. && $$ SYNOPSIS...TRA NEAR TERM...III SHORT TERM...TRA LONG TERM...RGZ AVIATION...III/MRR

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