Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201925 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 325 PM EDT Fri Oct 20 2017 .SYNOPSIS... Dry and warm conditions are expected through the weekend, as an upper ridge over the Gulf states moves east, and off the Carolina coasts. An approaching storm system will bring increasing rain and thunderstorm chances late Monday through next Tuesday, followed by much cooler air through mid week. && .NEAR TERM /THROUGH SATURDAY/...
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As of 3 PM Saturday...high pressure aloft will be centered just south of the area on Saturday morning, and at the surface, high pressure will ridge down the eastern seaboard. This will bring another sunny day for the coastal Carolinas. Models are showing the the precipitable waters remaining between 0.50 and .75" and the time heights are not showing distinct layers of clouds developing on Saturday. With the moisture at the surface limited will put in some patchy fog but it will be limited. Lows overnight will again be around 50 inland and the middle 50s at the coast. Highs on Saturday will range from the upper 70s at the immediate beaches to the lower 80s inland.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
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As of 3 PM Friday...Ridging sfc and aloft will dominate the FA weather Sat night thru Sunday. Skies will mainly be clear with mainly thin Cirrus overhead. Some increase in the low level moisture, below 850mb, from onshore flow will likely be enough for diurnal Cu with possible onshore movement of Stratocu especially across the southern portions of the ILM CWA. For Sun night, the upper ridge axis slides further off the Southeast U.S. coast allowing more opaque cirrus to move overhead. The center of the sfc high just off the Mid-Atlantic States Sat night will slide well offshore Sun thru Sun night but will continue to ridge back across the FA. Flow thruout this period will be onshore with a slow veering trend from ENE at the start of the period to ESE at the end of this period. This will further increase the low level moisture in the form of low level clouds. A weak low-mid level impulse riding up the backside of the upper ridge across SC during Sun may interact with just enough low level moisture for possible low topped showers to occur. However, have kept a dry fcst across the FA, keeping the chance of rain just south and west of the SC portions of the ILM CWA. Onshore flow will limit max temps but nevertheless, low 80s for Sun highs and widespread 50s for Sat night lows and widespread 60s for Sun night lows due to the deeper onshore flow across SSTS that are in the 70s.
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&& .LONG TERM /MONDAY THROUGH FRIDAY/...
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As of 3 PM Friday...Week begins with highly amplified pattern over the eastern CONUS. Deep 5h trough, which may or may not become briefly cutoff, will be over the Mississippi Valley Mon morning and steadily moving east, pushing a cold front with it. Mid-level ridging along the Southeast will also shift east, but the rate at which these features move ultimately determines when showers and thunderstorms ahead of and along the front reach the area. Strong warm advection ahead of the front will push temps close to 10 degrees above normal Mon while ensuring abundant moisture. Still to early to say if strong or severe storms are a threat but low level jet Mon night and Tue will be 40-50 kt so at least some potential exists. Front crosses the area during Tue but cold advection will be delayed and temps will be near to slightly above climo. A shortwave dropping southeast across the western Great Lakes and into the OH/KY Valleys Tue night drives a cold surge into the southeast Wed. Cold advection will drop 850 temps from low teens late Tue to near zero Wed night, ushering in a 36 to 48 hour period of temperatures 5 to 10 degrees below climo. Mid-level trough axis shifts off the coast Thu morning and lifts northeast during the day. Warm advection will already be under way at this point but cold air will linger at the surface through Thu. Thu night or Fri will see temperatures return to levels typical of late October in the southeast.
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&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... As of 18Z...High confidence of VFR at all sites through 21/00Z, and after 21/12-13Z. Except for a few cirrus skies will be mostly clear through the overnight hours. Winds will be light and variable this afternoon except E-SE at KCRE/KMYR 5-10 kts until 00Z. Winds become calm this evening with good setup for BR with excellent radiational cooling. Still fairly dry so think MVFR worse case. Except IFR could occur at times at KCRE due to more available moisture from this afternoons onshore flow, and at KLBT due to proximity to river. Extended Outlook...Showers and thunderstorms may result in flight restrictions Mon-Tue. && .MARINE...
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NEAR TERM /THROUGH SATURDAY/... As of 3 PM Friday...high pressure will continue to control the near- shore waters through Saturday. Winds are expected to be light and variable with the weak afternoon sea-breeze dissipating. Winds will become north at 10 knots and veer to the east by Saturday afternoon. Sea are expected to run 2 to 3 feet this evening and settle out at 2 feet on Saturday. A southeast, 2 foot, swell every 9 seconds is forecast by WaveWatch to begin this evening and continue through the tomorrow. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 3 PM Friday...This period will continue to be favorable for Mariners navigating across the local waters. Onshore flow will highlight this period, starting from the NE-ENE Sat night veering slightly thru the period to ESE-SE by Monday morning. This in response to the sfc high`s center migrating from the Mid- Atlantic Coast Sat night to well offshore by Mon morning. The sfc ridging from the high will extend inland from the coast resulting in the onshore flow. The sfc pg will remain relaxed at the start of this period with around 10 kt for speeds. The sfc pg will begin to tighten-some Sun thru Sun night resulting in 10 to 15 kt speeds, except closer to around 15 kt for the southernmost waters. Significant seas will run 2 to 3 ft Sat night followed by a slow 1 foot building trend thru Mon morning when seas will run 3 to 4 ft except around 4 ft southernmost waters. Dominant periods thruout this time-line will run 8 to 9 seconds due to a persistent ESE ground swell. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 3 PM Friday...Cold front approaching from the west will lead to increasing southerly flow on Mon. Winds start out east- southeast 10 to 15 kt but turn more southerly during the day, increasing to a solid 15 kt later in the day. Winds peak at 20 to 25 kt late Mon night and continue in the 20 to 25 kt range into Tue evening before dropping under 20 kt Tue evening/night and shifting to offshore as the front passes. Seas ahead of the front will build to 5 to 7 ft Mon night and exceed 8 ft in places on Tue. Headlines will likely be raised early Mon night and continue through Tue and into the first part of Tue night. Combination of offshore flow and decreased speeds late Tue night and Wed should allow conditions to drop below headline thresholds. Cold advection following the front is delayed so offshore flow will not be strong right behind the front. However cold air is expected to arrive near the end of the period and offshore winds approach 20 kt Wed night.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...DRH SHORT TERM...DCH LONG TERM...III AVIATION...MRR

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