Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 250530 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1231 AM EST SUN JAN 25 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 /UNTIL 6 AM SUNDAY MORNING/... AS OF 1000 PM SATURDAY...LATEST SFC ANALYSIS ILLUSTRATES THE LOW CONTINUING TO DEEPEN AS IT FURTHER ACCELERATES TO THE NORTHEAST...LIKE A BAT OUT OF HELL. THE LOW IS PROGGED TO DEEPEN FURTHER FROM ITS PROGGED 979MB OFF CAPE COD THIS EVENING...TO 960MB ACROSS THE CANADIAN MARITIMES BY DAYBREAK SUNDAY. WHAT ALL THIS SAYS IS THAT A TIGHTENED SFC PG WILL OCCUR ACROSS THE FA FOR A GOOD PORTION OF THE OVERNIGHT PERIOD...B4 FINALLY RELAXING-SOME AFTER DAYBREAK SUN AND THERE-AFTER. LATEST 11-3.9 MICRON SAT IMAGERY SHOWS A CLOUD-LESS SKY ACROSS THE ILM CWA. EXPECT THIS SCENE TO CONTINUE OVERNIGHT. WITH WINDS STAYING ACTIVE OVERNIGHT...DO NOT SEE RADIATIONAL COOLING AS BEING A PROBLEM TONIGHT. MODELS SIMILAR WITH TONIGHTS MINS...GENERALLY AROUND 32 DEGREES INLAND...AND MID 30S ALONG THE COAST. && .SHORT TERM /6 AM SUNDAY MORNING 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 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. && .LONG TERM /TUESDAY THROUGH SATURDAY/... 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. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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AS OF 06Z...HIGH CONFIDENCE FOR VFR THROUGH THE VALID TAF PERIOD AS HIGH PRESSURE MOVES IN AHEAD OF NEXT APPROACHING WEATHER SYSTEM. CLEAR SKIES AND WEST-SOUTHWEST WINDS AOB 8 KTS WILL PREVAIL THROUGH MUCH OF THE DAY. WINDS WILL THEN SHIFT TO THE SOUTHWEST INLAND... AND MORE SOUTHERLY ALONG THE COAST...WITH SUSTAINED WINDS AOB 10 KT. INTO SUNDAY EVENING...WINDS DECREASE SLIGHTLY AND CLOUDS BEGIN TO INCREASE FROM THE WEST AHEAD OF THE NEXT APPROACHING SYSTEM. EXTENDED OUTLOOK...SLIGHT CHANCE OF PRECIPITATION/MVFR CIGS MON. VFR AND GUSTY NORTH WINDS TUE-THU.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1000 PM SATURDAY...A TIGHTENED SFC PG TO CONTINUE ACROSS THE LOCAL WATERS FOR MUCH OF THE OVERNIGHT PERIOD AS LOW PRESSURE BOMBS OFFSHORE FROM THE NE STATES AS IT CONTINUES TO ACCELERATES NE-WARD. THE SFC PRESSURE PATTERN TO YIELD WNW-NW WIND DIRECTIONS. WIND SPEEDS WILL RUN 15 TO 25 KT THRUOUT THIS EVENING...SHOWING A SLOW SUBSIDING TREND DURING THE PRE-DAWN SUN HRS. SIGNIFICANT SEAS ACROSS THE LOCAL WATERS ARE BASICALLY A FUNCTION OF LOCALLY PRODUCED WIND DRIVEN WAVES...WITH VERY LITTLE INPUT FROM ANY TYPE OF UNDERLYING GROUND SWELL. WITH THAT SAID...SHOULD SEE A QUICK SUBSIDING TREND TO SIGNIFICANT SEAS IN CONJUNCTION WITH THE WINDS DIMINISHING. 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. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST SUNDAY FOR AMZ250-252-254- 256. && $$ NEAR TERM...DCH/III SHORT TERM...TRA LONG TERM...RGZ AVIATION...SGL/RJD

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