Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 170635 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 135 AM EST Sat Feb 17 2018 .SYNOPSIS...
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Cool and damp conditions will exist today as a cold front to the south wavers across the region. High pressure will build down from the northwest tonight giving the front a push southward again, bringing drier and more seasonable weather for Sunday. The front will lift back to the north as a warm front early Monday. Bermuda high pressure will follow bringing very warm temperatures through the middle of next week. Another cold front may reach down into the Carolinas later next week.
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&& .NEAR TERM /THROUGH SATURDAY/... As of 930 PM Friday...The cold front is currently dropping south across the local CWA and is best recognized thru the KLTX 88D as a fine line. Expect this front to be located south of the local area by midnight. In it`s wake, the warm moist air will get lifted over the cool sfc air and produce increasingly cloudy conditions after the FROPA. The nearly saturated air mass in the vertical will extend upwards to 775 mb. This is deep enough for cloudy conditions with the threat for patchy light rain or drizzle. Still up in the air of whether low clouds below 1k ft will become common. Nevertheless, this update will take the latest trends of the 3 main parameters, Temp/Dewpt/Wind, associated with the cold front as it drops south across the FA. Will take these trends and mesh them with the overall fcst which keeps the FA socked in clouds along with patchy stratiform type pcpn during daylight Sat. The RDU airport dropped nearly 15 degrees after the CFP. However that was during the "warmest" part of the day. Do not expect anything like that given temps across the FA prior to the CFP having already dropped into the 690s ahead of the Cold front. Previous................................................... As of 300 PM Friday...unseasonable warmth will come to an end tonight as a cold front sags south across the area. Forcing with the front is limited, mainly in the wake of the front, and moisture is limited. Pattern aloft consists of elongated 5h ridge extending from the Bahamas into the northern Gulf of Mexico. Lack of a Gulf tap prevents moisture return and forecast soundings show most of the moisture below 10k ft with the layer of near saturation ending before 6k ft. Given the weak nature of the forcing, the lack of deep moisture, and the lack of any instability have a hard time believe there will be much measurable rainfall associated with the front. Best chances for rain may end up being from prolonged period of low level saturation with mist/drizzle eventually combining to produce a hundredth or two in some areas. Will carrying slight chance pop for portions of the area overnight. Lows will depend on how quickly the cold air arrives. In these situations guidance is typically too quick to usher in the cooler air and will stay on the warmer side of the guidance for overnight lows. Front stalls south of the area late tonight and Sat as the high builds in from the north. Resulting wedge is not particularly strong and its staying power appears to be limited by the nature of the mid- level pattern over the Mid-Atlantic and Northeast. Front remains stalled south of the area Sat with an abundance of low level moisture and weak isentropic lift. Again, likely not enough lift to produce widespread rain but mist/drizzle on and off all day is possible. Both the GFS and ECMWF depict east and possibly even a little bit of southeast flow developing very late in the period as weak surface wave tracks east-northeast along the stalled front. Best rainfall chances during the period may end up later tomorrow as the wave the approaches. If the east-southeast flow develops late Sat it would still likely be too late to have any impact on Sat highs. Highs end up below climo, ranging from lower 50s inland to around 60 across southern most portions of the forecast area. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...Though a frontal boundary will meander across the area and even see a flat wave or two of low pressure traverse its length rain chances will remain minimal Saturday night. Contributing factors to the area remaining rain-free are the lack of mid level forcing and the fact that the main elevated baroclinic zone stays well to our north (as does all of the rain). High pressure sliding into VA on Sunday shunts the boundary and all of its associated moisture to our south. Even as this occurs models are showing minimal QPF, as the aforementioned reasons still hold. The moisture then returns into the area from the south Sunday night yielding a substantial increase in cloud cover but yet again no appreciable chance for rain. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday...Warm front will lift across the area during Monday, signaling the beginning of a few days of very warm temperatures through the middle of next week. As this warm front lift northwards, it will be accompanied by increasing moisture noted by PWATs climbing towards 1.5 inches and some weak mid-level forcing as impulses move up to the NW. Moisture in the column is mostly confined to the lower half, so while a few showers are possible during Monday, QPF will be minimal and many places will likely remain dry. The best chance for rain Monday will be NW zones. This front blasts through and will be well north of the area Monday night. This is in response to rapidly blossoming mid-level ridging and the development of a Bermuda ridge. Highs Monday will rise into the low 70s, with further warming to around 80 away from the beaches Tue/Wed along with drier conditions and more sunshine, although cirrus within the subtropical jet may plague the area each day. On Thursday a shortwave rotating around the ridge will try to suppress the expansive ridge and push a weak cold front into the area. Guidance has backed off on the southern progress of this feature, which seems likely based off the strength of the aforementioned ridge. Still, this feature impinging on the local area will bring more clouds with better shower chances and slightly cooler temperatures. However, this front will wash out quickly by the end of the week bringing drier weather once again for Friday, and temps will remain above climo even during this more unsettled period late in the week. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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As of 06Z...Winds have shifted to the N-NE remaining around 5 to 10 kts behind a cold front sagging south into SC. Cloudy and damp conditions will exist through today as this front wavers across the area. Warm SW winds above the surface will ride over the shallow cool air mass producing low clouds and drizzle or light rain through today. Steep frontal inversion will keep this moisture locked in with VFR/MVFR ceilings dropping to IFR this afternoon. Potential for LIFR ceilings will exist later this afternoon with potential for fog this evening. Winds will continue to veer around to the E and then S by later today as the front lifts northward. Extended Outlook...MVFR/tempo IFR Sun morning becoming VFR. Tempo MVFR/IFR/SHRA cig/vsby Sun night/Mon. Becoming VFR Tue. VFR/SHRA Wed.
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&& .MARINE... NEAR TERM /THROUGH SATURDAY... As of 915 PM Friday...SCA and SCEC conditions ahead of the cold front due to gusty SW winds. After the CFP later this evening, winds will veer to the NE and to the ENE during Sat. The best sfc pg and CAA will occur over the NC Waters and will extend the SCA til noon Sat. The same holds for the ILM SC Waters, except the SCEC will extend to noon Sat. Peak winds and seas will occur thru midday Sat then quickly abate and subside respectively as the sfc pg relaxes and the high`s center progresses out to sea from the Mid-Atlantic States. Significant seas will peak in the 3 to 6+ ft range with the 6+ footers primarily across the outer waters of the ILM NC Waters. Dominating periods will come from wind driven waves at 4 to 6 seconds. Previous................................................. As of 300 PM Friday...SCA continues for NC zones this afternoon. Strong west-southwest flow will begin weakening this evening as a cold front drops in from the north. Flow direction is not very favorable for sea fog and have removed it from the forecast as fog has yet to materialize. The front slowly moves south across the waters tonight with north-northeast winds developing after midnight. Pinched gradient as the high noses down the coast will increase winds to a solid 20 kt at times after midnight. Speeds approaching 25 kt will be possible across NC zones around daybreak. Based on these speeds, and the high probability of the winds pushing seas to 6 ft, have decided to extend SCA for NC zones through 12Z. Did not alter the SCEC end time of 00Z for SC zones. Front stalled south of the area tomorrow will try to lift back north later Sat, weakening the gradient. Winds drop under 10 kt during the mid to late afternoon hours and remain light and variable through the end of the period. Seas will be a mix of a southerly swell and a northeast wind wave once the front passes. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...Pretty light and variable winds Saturday night due to a front stalled in the area and a few flat waves of low pressure moving by. NE winds then take over on Sunday as high pressure pushes the boundary off to the south. This will also open wind speeds up a bit. As the front weakens Sunday night winds may fall back to 10kt late as they remain out of the northeast. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Warm front will lift across the waters Monday, turning winds from east early, to south late. This will be followed by a Bermuda type high pressure setting up offshore for the remainder of the period through Wednesday. As this develops, winds will slowly veer from south to southwest, but speeds will be only around 10 kts regardless of direction. With light winds and a prolonged period of S/SW winds, seas will be primarily driven by a SE swell but remain low amplitude. Highest seas are forecast Wednesday when wave heights will reach around 3 ft, 2 ft otherwise Monday and Tuesday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until noon EST Saturday for AMZ250-252. && $$ NEAR TERM...DCH/III SHORT TERM...MBB LONG TERM...JDW AVIATION...RGZ is the U.S. government's official web portal to all federal, state and local government web resources and services.