Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 260710 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 210 AM EST THU FEB 26 2015 .SYNOPSIS... LOW PRESSURE WILL BRING MOSTLY RAIN TO THE AREA TONIGHT. SNOW WILL FALL MAINLY WEST OF INTERSTATE 95...WITH A COUPLE INCHES POSSIBLE. ARCTIC HIGH PRESSURE WILL BUILD IN THURSDAY INTO THE WEEKEND BRINGING COLD TEMPERATURES AND EVENTUALLY SOME CLEARING SKIES. MOISTURE WILL RETURN FOR THE NEW WEEK WITH TEMPERATURES CONTINUING TO SHOW QUITE A BIT OF DAY TO DAY VARIABILITY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... AS OF 130 AM THURSDAY...NEW UPDATES SENT TO REMOVE ALL MENTION ALL SNOW OR SLEET FROM THE FORECASTS. WILL CONTINUE TO MENTION LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE POSSIBLE FROM ROUGHLY DAYBREAK THU THRU MID-MORNING FOR THE COUNTIES WITHIN THE WINTER WX ADVISORY. TEMPS SHOULD BE ABOVE 32 BY LATE MORNING...ELIMINATING THE THREAT FOR ANY ICING. PREVIOUS DISCUSSION................................... AS OF 820 PM WEDNESDAY...SLEET IS FALLING AS FAR EAST AS WILMINGTON THIS EVENING...WITH A MIX OF SLEET AND SNOW REPORTED AS FAR EAST AS WHITEVILLE. THIS APPEARS TO BE DUE TO A POCKET OF VERY DRY AIR BETWEEN 2,000 AND 10,000 FEET AGL--MUCH DRIER THAN ANY MODEL FORECAST. THE 00Z SOUNDINGS FROM MHX AND GSO SHOWED DEWPOINT DEPRESSIONS ANOTHER 10 DEGREES F WIDER THAN THE 18Z NAM OR GFS THROUGH THAT LAYER. EVAPORATIONAL COOLING WITH THIS INITIAL WAVE OF PRECIPITATION COOLED THE COLUMN SUFFICIENTLY TO MAKE A WRECK OF MY PREVIOUS FORECAST. STRONG WARM ADVECTION IN THE 850-700 MB LAYER SHOULD RAISE AIR TEMPERATURES WELL ABOVE FREEZING IN THE NEXT 1-2 HOURS...ALONG WITH A CONSIDERABLE INFLUX OF GULF AND ATLANTIC MOISTURE WHICH WILL REMOVE ANY REMAINING EVAPORATIONAL COOLING POTENTIAL. BY LATE EVENING I ANTICIPATE FROZEN PRECIPITATION TO BE CONFINED TO WESTERN PORTIONS OF MARLBORO AND DARLINGTON COUNTIES...PERHAPS AFFECTING MAXTON IN WESTERN ROBESON COUNTY AS WELL. I AM GROWING MORE CONCERNED ABOUT THE POTENTIAL FOR WRAP-AROUND COLD AIR AROUND SUNRISE THURSDAY MORNING CHANGING THE LAST OF THE RAIN OVER TO FREEZING RAIN. I HAVE ADDED A CHANCE OF FREEZING RAIN TO THE FORECAST ACROSS NORTHERN FLORENCE...MARION AND COLUMBUS COUNTIES...AND MAY NEED TO CONSIDER RAISING AN ADVISORY FOR FREEZING RAIN IF THIS THREAT GROWS OVERNIGHT. && .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/... AS OF 300 PM WEDNESDAY...ACTIVE WEATHER WILL BE LIMITED TO THE FIRST FEW HOURS OF THE PERIOD AS LOW PRESSURE RACES AWAY FROM THE REGION. THE MAIN FORCING WILL BE LONG GONE LEAVING LOW LEVEL MOISTURE IN THE FORM OF LIGHT RAIN SHOWERS AND MOSTLY DRIZZLE FOR THE MORNING HOURS. I DID LEAVE AN HOUR OR TWO OF FREEZING RAIN FOR THE NORTHERN PARTS OF THE ADVISORY AREA BUT TEMPERATURES SHOULD SLOWLY PLOD TO ABOVE FREEZING IN THESE AREAS BY MID MORNING. BEYOND THIS ARCTIC HIGH PRESSURE BUILDS INTO THE AREA THROUGH THE REMAINDER OF THE PERIOD. CLOUDS WILL BE VERY SLOW TO SCOUR OUT WITH LOW CEILINGS TRAPPED BELOW THE INVERSION. SOME SUNSHINE SHOULD BREAK OUT FOR FRIDAY AFTERNOON. FOR THIS REASON I HAVE OPTED FOR SLIGHTLY COOLER DAYTIME HIGHS AND SLIGHTLY MODERATED OVERNIGHT LOWS VS THE MOS GUIDANCE. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 300 PM WEDNESDAY...NOT SURE WHEN WE`LL SEE SUNSHINE AGAIN. AFTER A RAIN-FREE BUT PROBABLY CLOUDY DAY SATURDAY THE LONG TERM WILL BECOME INCREASINGLY UNSETTLED. SATURDAY THOUGH BRINGS ZONAL MID LEVEL FLOW BUT ALSO LOW LEVEL MOISTURE TRAPPED BENEATH DEEP INVERSION OR PERHAPS NEARLY ISOTHERMAL LAYER AS LARGE SURFACE HIGH PROGRESSES EAST WITH ITS CENTER WELL TO OUR NORTH. SUNDAY THE HIGH TAKES ON MORE OF A WEDGE-LIKE ELONGATION INTO THE CAROLINAS. TROUGHINESS DEVELOPS OFFSHORE AS WELL BUT NOW APPEARS MUCH WEAKER. AS SUCH MODELS HAVE BACKED OFF ON RAIN CHANCES FOR SUNDAY BUT SOME LOW POPS STILL LIKELY WARRANTED FOR COASTAL AREAS. SUNDAY HIGHS HAD TO BE LOWERED CONSIDERABLY AS THE WEDGE WILL LIKELY SPONSOR A DREARY DAY WITH TEMPS MIRED IN THE 40S (MEANWHILE THE NORMAL HIGH CONTINUES TO CREEP UPWARDS...NOW 63 FOR ILM). SPEAKING OF HIGHS IN THE 60S...MONDAY MAY BE OUR BEST CHANCE TO SEE AS SUCH. THE WEDGE BREAKS DOWN ONLY TO GIVE WAY TO A DECELERATING COLD FRONT. HIGHS MAY CLIMB CLOSE TO SEASONABLE DESPITE FAIRLY HIGH RAIN CHANCES. UNSETTLED WEATHER WILL LAST INTO TUESDAY INTO WEDNESDAY BUT THE TEMPERATURES BUST POTENTIAL APPEARS LARGE ESPECIALLY TUESDAY. HIGH PRESSURE WEDGE ON TUESDAY COULD BRING ANOTHER COOL AND RAINY DAY INSTEAD OF THE SEASONABLE WEATHER IN THE CURRENT FORECAST (IN ONE RUN THE MEX FCST WENT FROM 65 TO 52!). FOR WEDNESDAY THE SETUP IS RATHER SIMILAR TO MONDAY WHEREIN THE WEDGE MAY BREAK DOWN FOR A NEAR IMMEDIATE ARRIVAL OF A COLD FRONT, THE END RESULT BEING A RAINY BUT SEASONABLE DAY. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 06Z...MODERATE TO HEAVY PRECIPITATION CONTINUES ACROSS THE TERMINALS EARLY THIS THU AM...WITH ALL TERMINALS FLUCTUATING WITH MVF AND IFR...AND EVEN OCCASIONALLY VFR CONDITIONS. FORECAST THAT! RELATIVELY HIGH CONFIDENCE THAT THE AREA TERMINALS WILL BE TOTALLY DOMINATED BY IFR THROUGH DAYBREAK FROM BOTH CEILINGS AND VSBY...AND MAINLY FROM CEILINGS THERE-AFTER THRU SUNSET THU. HAVE REMOVED ALL MENTION OF -SN AND -PL FROM THE FORECAST AS MODEL SOUNDINGS AND OOZ LOCAL RAOBS AND MODEL DATA INDICATE A DEEP WARM LAYER IN THE LOWER LEVELS. AFTER THE PASSAGE OF THE LOW TO THE EAST OF THE ILM CWA...WINDS BACK TO THE NW-N WITH A RETURN OF SOME COLD AIR AT THE SFC. MAY BE COLD ENOUGH TO INCLUDE A PERIOD OF FZRN OR FZDL TOWARD DAYBREAK...AND UP TO SEVERALS THERE-AFTER. ALL PCPN SHOULD END BY MID TO LATE MORNING...WITH THE LOWER LEVELS REMAINING MOIST DOWN TO THE SFC...RESULTING IN A LOW CLOUD DECK THRUOUT DAYLIGHT THU...AND PARTIALLY INTO THE EVENING BEFORE SOME DRY AIR MIXES IN TO RAISE THE LOW STRATIFORM CEILINGS. WINDS INITIALLY WILL STAY ACTIVE AND GUSTY UP TO 20 KT FROM THE N-NE... THEN SLOWLY BACK TO NW-NNW AND DIMINISH LATER TODAY INTO TONIGHT. EXTENDED OUTLOOK...VFR CONDITIONS FRIDAY THRU SATURDAY...MVFR/IFR POSSIBLE LATE SUNDAY INTO MONDAY. && .MARINE... .NEAR TERM /THROUGH TONIGHT/... AS OF 630 PM WEDNESDAY...THE ONLY CHANGE TO THE FORECAST WAS TO SLOW DOWN THE RATE OF INCREASE IN FORECAST SEA HEIGHTS OVERNIGHT. OUR LOCAL SWAN WAVE MODEL HAS A WELL-KNOWN BIAS OF INCREASING SEAS MUCH TOO QUICKLY IN PERIODS OF STRENGTHENING WIND. NO OTHER SIGNIFICANT CHANGES ARE NECESSARY. DISCUSSION FROM 300 PM FOLLOWS... LOW PRESSURE WILL MOVE OUT OF THE GULF OF MEXICO THIS EVE AND THEN UP THE CAROLINA COAST...INTENSIFYING OFF THE NORTH CAROLINA COAST TOWARD DAYBREAK AND ON THU. THE PRESSURE GRADIENT IS EXPECTED TO BECOME SUFFICIENTLY TIGHT TO SUPPORT 20 TO 25 KT WINDS. THE DIRECTION WILL BE NE THROUGH THE EVE...BACKING TO THE N OVERNIGHT. SEAS WILL RESPOND TO THE INCREASING WINDS...BUILDING UP TO 6 TO 9 FT...10 FT SEAS ARE POSSIBLE AROUND FRYING PAN SHOALS. SEAS WILL BE LOWER ACROSS THE VERY NEAR SHORE WATERS. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 PM WEDNESDAY...ARCTIC HIGH PRESSURE WILL BUILD IN BEHIND DEPARTING LOW PRESSURE AND WILL BE THE MAIN PLAYER DURING THE SHORT TERM FOR THE MARINE COMMUNITY. INITIALLY A NORTHERLY FLOW OF 15-20 KNOTS WILL BE IN PLACE. BY THURSDAY AFTERNOON SPEEDS DROP TO 10-15 KNOTS LEANING HEAVILY TO THE HIGHER SIDE OF THE RANGE. WITH THE SPRAWLING HIGH MOVING SLOWLY...THE COLD AIR ADVECTION ARRIVES IN THE SAME MANNER AND WINDS WILL REMAIN HERE UNTIL BASICALLY THE END OF THE PERIOD. THERE MAY BE A SUBTLE BUT BRIEF LULL EARLY SATURDAY FOLLOWED BY AN INCREASE ONCE AGAIN AS THE EARLY STAGES OF A COASTAL TROUGH FORM. SEAS WILL BE HIGHEST EARLY WITH 5-8 FEET CONTINUING. BY LATER THURSDAY AFTERNOON...A MORE MODERATE RANGE OF 2-4 FEET DEVELOPS. THE EXPIRATION OF THE SMALL CRAFT ADVISORY LATE IN THE DAY LOOKS OK. LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 300 PM WEDNESDAY...LARGE AREA OF EASTBOUND HIGH PRESSURE ON SATURDAY SLIDING ACROSS OHIO VALLEY. THIS LEADS TO A BROAD SWATH OF NORTHEASTERLY FLOW ALONG MUCH OF THE EAST COAST. CONDITIONS MAY GET CLOSE TO SCEC/SCA CUTOFF ESPECIALLY ALONG THE LESS SHELTERED NC WATERS. SUNDAY THIS HIGH MOVES FURTHER EAST BUT LEAVES BEHIND A RIDGE AXIS INTO THE CAROLINAS. AT THE SAME TIME AN OFFSHORE TROUGHINESS SHOULD WEAKEN AND VEER THE FLOW. PRETTY COMPLEX SETUP HEADING INTO MONDAY WITH THE WEDGE BREAKING DOWN LEAVING BEHIND HIGH DUE EAST OF THE REGION AND A COLD FRONT DROPPING INTO THE UPSTATE REGION OF THE CAROLINAS WHILE DECELERATING. SOUTHWESTERLY FLOW AHEAD OF THE FRONT VEERS CONSIDERABLY OVER AT LEAST NORTHERN WATERS DEPENDING ON THE SPEED OF THE BOUNDARY. A NE FLOW RETURNS AREA-WIDE BY MONDAY NIGHT. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR SCZ017-023- 024. NC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ087-096- 105. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR AMZ250- 252-254-256. && $$ SYNOPSIS...SHK NEAR TERM...RJD/TRA SHORT TERM...SHK LONG TERM...MBB AVIATION...DCH

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