Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 240240 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1040 PM EDT Fri Jun 23 2017 .SYNOPSIS... Deep moisture will become increasingly squeezed by an approaching cold front through Sunday morning. Some drier air should move in later Sunday. More seasonable weather will return next week with isolated mainly afternoon thunderstorms. && .NEAR TERM /THROUGH SATURDAY/...
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As of 1000 PM Friday...The few showers that were around earlier in the day have long since dissipated. Some of the convective debris cloudiness continues to feed across the area from the SW. The leading edge of the widespread clouds was aligned along the Appalachians in association with a cold front. These clouds will continue to head in our direction overnight. Nocturnal jetting on the order of 35 to 40 kt will keep the environment well mixed tonight and this will serve to keep winds elevated. Wind speeds will be sustained in the 10 to 20 mph with higher gusts. The beaches are expected to gust to 20 to 25 mph right through the night as the pressure gradient ahead of the cold front continues to tighten. Model soundings show an elevated inversion between 1-2kft. The soundings do not show saturation in this layer, but do show a moist enough environment for stratus to develop during the late night and early morning hours of Sat and this is similar to the early morning hours of Fri. Our forecast is for skies to become mostly cloudy during this time. Showers well west will make a run for portions of the I-95 corridor, but are expected to eventually dissipate near our westernmost CWA toward morning. This is in line with the higher resolution models. However, showers and thunderstorms are expected to become numerous if not widespread on Sat, especially later in the afternoon and Sat night. The main risk with these thunderstorms will be torrential downpours as precipitable water values surge well up over 2 inches as we come under the influence of a tropical-like airmass. This may very well lead to significant ponding with urban areas most susceptible to flooding. If enough precipitation loading occurs, then wet microbursts may become possible. A muggy night with lows in the mid and upper 70s. Highs on Sat will be near 90, except mid and upper 80s at the immediate shore. A few locations on Sat may again see the afternoon heat index pop up to near 100 degrees before the arrival of thunderstorms.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...Slow moving cold front will move into the region as the period begins with showers and thunderstorms likely ongoing. There will be an abundance of deep moisture for much of the period. Precipitable water values rise to almost 2.25 inches Sat night into Sun. Surface based instability will be lacking Sat night but convergence along the weak surface boundary as well as the presence of outflows in a moist, conditionally unstable environment should maintain at least some nocturnal convection. In addition there will be a little bit of shortwave energy approaching from the southwest which should lead to an increase in PVA after midnight. Storm coverage will be highest along the coast but everywhere will have at least a chance of showers and thunderstorms overnight. Front and deep moisture remain in the area Sun, although the 5h trough and drier air to the northwest start moving into northwestern portions of the forecast area later in the day. This will likely curtail convection in these areas but closer to the coast coverage will be higher. There will be another in a stream of shortwaves within the vorticity channel that spreads some PVA into the area on Sun. Combined with surface heating this should light off another round of convection. Storm motion will be around 15 kt which should prevent any 1 storm from posing a flooding risk however, training storms could pose a problem. Storms that develop will be very efficient at producing rainfall having warm cloud layers on the order of 13k-14k ft deep. While severe weather is unlikely given vertical profiles/limited shear a wet microburst from a storm cannot be ruled out. Still the main concern Sun will be flooding and not strong to severe storms. Dry air spreads in from the northwest late Sun and Sun night with most if not all convection shifting off the coast by midnight. Push of dry air is significant with pwats forecast to drop over an inch from 18Z Sun to 06Z Sun night. Some convection just off the coast cannot be ruled out late Sun night but wind direction/storm motion would tend to push any activity off the coast and thus pop after midnight is unlikely. Temperatures Sat night will run well above climo while temps Sun and Sun night will be near climo. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday...Mid level troughiness Monday sharpens through Tuesday or Wednesday. Initially this will be a dry westerly flow Monday but a slightly more moisture-laden WSW flow Tuesday. Daytime temperatures will be held a bit below climatology through this time frame. The trough axis appears to swing through on Wednesday bringing a more decided drying. The rest of the period will be characterized by a building upper ridge over the Southeast and Bahamas. This will mark a transition back towards seasonable temperatures and isolated convection mainly during the diurnal maximum. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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As of 00Z...A few spot showers from earlier in the day have dissipated. Convective cloud debris continues to work across the area from the SW while more clouds well upstream continue to work in our direction. We expect VFR through the first part of the overnight. A stiff nocturnal jet will keep things well mixed overnight and we expect gusts around 20 kt to continue for the coastal terminals with winds backing down to 10 to 15 kt at KFLO and KFLO this eve. The direction will be SW. Expect winds of 15 to 25 kt on Sat, again from the SW. Model profiles continue to show an inversion 1-2 kft above the surface developing overnight and given what transpired last night, went ahead to include stratus near 1kft with ceilings at all the terminals in the 08-09z through about 13z. Sat is expected to be an unsettled day with numerous thunderstorms developing during the afternoon and then persisting into the nighttime hours. These thunderstorms will have the potential for significant flight restrictions. At this time included a prevailing group for thunderstorms after 20-22z at all the terminals. Extended Outlook...MVFR/IFR conditions are possible in thunderstorms Saturday night and into Sunday. Thunderstorms are expected to be most numerous Saturday evening and overnight.
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&& .MARINE...
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NEAR TERM /THROUGH Saturday/... As of 1000 PM Friday...A Small Craft Advisory is in effect. A tightening pressure gradient ahead of a cold front will result in winds increasing to 20 to 25 kt overnight and then continuing in this range through much of Sat. The direction will be SW. Seas will build to 4 to 6 ft overnight and persist through Sat. Developing showers and thunderstorms Sat afternoon will become numerous to widespread Sat eve. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...Will continue to carry small craft advisory headline Sat night but hazard will be marginal at best. Front moving into the area combined with Bermuda High will tighten the gradient and speeds will increase to a solid 20 kt. Sustained 25 kt may be hard to come by and highest seas may end up closer to 5 ft than 6 ft but given at least some uncertainty with respect to the strength of the surface features will maintain the headline unchanged. Bermuda High remains in control Sun with southwest winds continuing, though in a weaker state as the front slowly moves closer and the high retreats east. Winds and seas will gradually decrease Sun into Sun night with flow becoming offshore late in the period as the surface boundary slips east of the waters. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Not a typical summertime pattern in place for most of the period. A sharpening mid level trough will be in place. A series of weak surface boundaries may come through but with only very minor fluctuations of wind direction, though a northerly component will dominate. Wind speeds never really look to exceed 10kt by much though a few higher gusts will be possible. Seas will average 2 to occasionally 3 ft with near shore wave shadowing much more pronounced than usual this time of year where SW winds much more common.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...Beach Hazards Statement through Saturday evening for SCZ054- 056. NC...Beach Hazards Statement through Saturday evening for NCZ106- 108. Coastal Flood Advisory until 11 PM EDT this evening for NCZ107. MARINE...Small Craft Advisory until 6 AM EDT Sunday for AMZ250-252-254- 256.
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&& $$ NEAR TERM...RJD SHORT TERM...MBB LONG TERM...III AVIATION...RJD

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