Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 240623 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 223 AM EDT Wed May 24 2017 .SYNOPSIS...
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Waves of low pressure will continue to move along a slow-moving cold front, producing a good chance for showers and thunderstorms today and tonight. Another cold front trailing from a deep low pressure system over the Ohio Valley on Thursday will cross the area, bringing the final round of showers to the area. High pressure will build in late Thursday into Friday maintaining quieter weather for much of the weekend. Low pressure may affect the area early next week producing more unsettled weather.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 3 AM Tuesday...Post wave subsidence has helped dry out the mid levels overnight, leading to a lull in rainfall. Sizable area of dry air, evident in water vapor imagery, will work its way northeast through the morning hours. Not only do forecast soundings show the increasing mid level dry air but they also depict weakening of the 850 to 500 mb lapse rates, another sign of increasing subsidence. There is a weak shortwave currently moving across GA, heading northeast that could generate some isolated elevated convection in the area a few hours either side of daybreak. Front continues to linger in or just northwest of the area and will gradually weaken today. Mid level dry air and subsidence will linger in the area through much of this morning before next slug of deep moisture, with precipitable water values exceeding 1.9 inch, starts moving into the region. Increase is not instant but will be steady from late morning, peaking in the evening. Heights start to fall in the afternoon, just as surface based instability peaks. Although the GFS is riddled with feedback this afternoon it is possible to discern a shortwave moving northeast from the Gulf coast later this morning. PVA ahead of the wave arrives coincident with the other favorable factors. While there is a 110 kt+ 300 mb jet the wind max ends up passing northwest of the area. Although limited by less than favorable jet location there will still be some divergence aloft. Deep warm cloud layer continues to be a theme in this environment, forecast soundings suggest a depth around 11k ft, which will aid precipitation efficiency and keep flooding a concern, especially in areas that have received 3+ inches of rain in the last day or so. Storm motions will be high enough that a single storm is unlikely to be a concern but training storms will pose a significant flood risk and so the flash flood watch will remain in effect. Temperatures today will be in the upper 70s to lower 80s but with potential for localized areas where highs run several degrees warmer if the late May sun is able to break out for a brief period of time. Widespread convection continues into the evening and first part of the overnight. Low level jet strengthens to a solid 45 kt this evening, although shear is somewhat limited. Still a strong or severe storm cannot be ruled out and SPC has marginal risk for the region. Dry slot wrapping around the 5h trough spreads over the area around midnight, bringing an end to significant rainfall. The cold front will still be west of the area at this point, likely just entering the western Carolinas. The 5h trough axis continues to be slow moving and it is the strong shortwave rounding the base of the trough the ultimately pushes the cold front into the forecast area as the period ends. Although the mid levels dry out rapidly and the forcing exits to the northeast by midnight, lingering low level moisture will keep skies cloudy. Temperatures will range from mid 60s west to around 70 along the coast.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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As of 3 AM Tuesday...Cold front will be in process of moving offshore Thursday morning, and along with it, much of the deep moisture associated with our recent wet period. However, a potent upper disturbance will swing through on Thursday afternoon behind FROPA, and this combined with residual moisture should be enough to kick off a scattered round of daytime convection. Rapid improvement will follow as the short wave lifts northeast of the area and weak surface ridging builds in from the west. Expect dry weather and clearing skies for Thursday night through Friday. Relatively cool temperatures following FROPA on Thursday will give way to seasonal readings on Friday.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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As of 3 PM Tuesday...Plenty of dry air will move in with deep westerly flow on the back end of exiting low pressure system on Fri. Pcp water values drop down to .75 inches or below early Fri but do creep back up over an inch by late Friday. Overall expect a sunny dry day on Friday with temps reaching into the mid 80s. High pressure ridge to the south will reach up into the Carolinas maintaining pleasant weather through much of the weekend. A shortwave rides across the top of the ridge over the weekend mainly remaining north of the forecast area. This could produce some clouds or a spotty shower late Sat into Sat night, mainly over NC. The GFS builds the ridge a little farther north and therefore holds any weather farther to the north with a deep warm southerly flow and sunnier weather overall all weekend. A deeper mid to upper trough digs down late in the weekend and could produce an increase of clouds and showers Sun through Tues timeframe. Will have to see how the models evolve. For now, will keep chc of shwrs north of area through Sat night but will include Pops for Sun through Tues. The building ridge and westerly downslope flow through the mid levels will produce above normal temps through much of the period with temps reaching above 90 in spots especially over the weekend.
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&& .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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As of 06Z Wednesday...Low level moisture and stability inland, in close proximity to the stalled front are keeping low ceilings inland and continue to maintain IFR ceilings. Along the coast slightly warmer temperatures are thus far limiting surface based stability, keeping ceilings in the MVFR range. Do not think IFR ceilings will reach the coast, if forecast soundings and moisture profiles are to be believed. Better chances for IFR at coastal sites (as well as inland sites) will be with convection later today when both ceiling and vis could drop into the IFR realm. IFR will remain a possibility through the end of the valid TAF period, although after 00Z-04Z window (west-east) the probability of MVFR increases. Extended Outlook...VFR anticipated through Sunday.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 3 AM Tuesday...Small craft advisory remains in effect for all zones through tonight. Southwest winds around 15 kt this morning will increase to 20 to 25 kt today and 25 to 30 kt tonight as gradient becomes pinched ahead of advancing cold front. Front will remain west of the waters through the period, keeping wind direction southwest. Exception would be thunderstorm outflow which would be capable of producing winds in excess of 34 kt from any direction. Seas will build from 4 to 6 ft this morning to 5 to 7 ft this afternoon and evening with potential for 10 ft tonight. SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 3 AM Tuesday...Expect Small Craft Advisory criteria to be breached Thursday and Thursday night as a cold front passes across and then moves east of the waters. Have extended the SCA into Thursday as a result. Gradually improving conditions on Friday as high pressure builds in from the west means we will likely be advisory-free for the end of the work week. LONG TERM /SATURDAY THROUGH SUNDAY/... As of 3 PM Tuesday...A stronger off shore westerly flow on Friday will diminish and back around to the W-SW through the day as low pressure system exits farther off to the east and high pressure builds up from the south. Seas of 3 to 5 ft will diminish to 2 to 4 ft through Friday and down below 3 ft by Fri night in weakening offshore flow. High pressure south of the area waters will shift east through the weekend into early next week producing a persistent SW return flow. Initially winds will only be 10 kts or so but low pressure moving by to the north Sat night into Sun and an approaching cold front late in the weekend into early next week may produce an increase in SW winds. Seas less than 3 ft Saturday in lighter winds will rise up to 3 to 5 ft in increasing SW winds Sat night into Sun.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...Flash Flood Watch through this evening for SCZ017-023-024-032- 033-039-053>056. Beach Hazards Statement through this evening for SCZ054-056. NC...Flash Flood Watch through this evening for NCZ087-096-099- 105>110. Beach Hazards Statement through this evening for NCZ106-108. MARINE...Small Craft Advisory until 6 PM EDT Thursday for AMZ250-252- 254-256.
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&& $$ SYNOPSIS...REK NEAR TERM...III SHORT TERM...REK LONG TERM...RGZ AVIATION...III MARINE...REK/III/RGZ

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