Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 200605 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 204 AM EDT Tue Jun 20 2017 .SYNOPSIS... Bermuda high pressure will remain centered offshore this week, but will continue to ridge back to the west, and onshore and inland in the vicinity of Cape Romain. A cold front will drop southward tonight and stall just inland from the coast on Tue before dissipating altogether by Wednesday. Tropical moisture will funnel northward from the Gulf of Mexico for much of this week, further enhancing the convection across the area thruout this week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... As of 900 PM Monday...Much of the ILM CWA has been worked over by the earlier convection. As a result, will see a brief reprieve in the convection for the remainder of this evening and thru the pre-dawn Tue hrs. The exception will be the coastal counties within the ILM CWA where convective activity will develop over the adjacent Atl Waters and then push north by northeast and likely either push onshore or side-swipe the ILM Coasts. Have upped POPs to a solid 50 for the immediate coast. Near term models ie. HRRR and HIRESW indicate the cold front to drop SSE closer to the ILM CWA overnight with convection still firing along it. Thus activity from the south and from the north will come together over the ILM CWA during daylight Tuesday with POPS either good chance or likely. Mid- level vorticies ie. sheared vort, sfc cold front, resultant wind bndry aka sea breeze and outflow boundaries, will all become players in keeping convection ignited across the ILM CWA. PWS are progged to run greater than 2 inches. Thus looking at heavy rains producing localized flooding. Will have to look at 00Z model runs and see if the potential is there for precip loading to occur with an end result in a wet microburst. Will update the HWO and indicate the local flood potential. Previous...................................................... As of 245 PM Monday...Sea breeze and Bermuda High convergence is shifting the storm focus farther inland this afternoon. GOES-16 low- level water vapor shows the mid-level cap well inland is beginning to erode from WSW to ENE this afternoon and may allow for storms to become more numerous along the I-95 corridor into mid/late afternoon. Untapped air and larger downdraft CAPES in this area could lead to stronger storms in the hours ahead. Active period through Tuesday, as an upper trough trough slowly translates east toward the area coupled with a feed of tropical moisture. PW values will climb a bit more and exceed 2 inches. Low-levels winds not very strong Tuesday so the primary threat looks to be localized flooding, as storms drop tropical moisture while exhibiting sluggish storm motion. As buoyancy increases tonight over the waters, scattered deep convection should develop late tonight into very early Tuesday, and a portion of this may get directed onshore into the coast. Meanwhile, upper support will increase well inland as the trough aloft nears, so most places will have a shot at rain overnight. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... As of 3 PM Monday...Front stalled west of the area at the start of the period will gradually dissipate Tue night and Wed. Although the surface boundary will be ill defined there will be an abundance of deep moisture moving into the area as the 5h trough taps into moisture plume associated with the Gulf of Mexico system. Currently it appears that the system will not have a direct impact on the region during the period. However, there is some uncertainty with respect to how much moisture spreads over the Southeast and how long the moisture lingers. The GFS has a huge plume of moisture spreading over the area Tue night and lingering through the end of the period. The Canadian and ECMWF has a toned down version of the tropical plume and have the moisture shifting east during Wed with decreasing precip chances late Wed and Wed night. Precipitable water values climb above 2 inches Tue night as the plume arrives but forcing may be limited, outside of already ongoing diurnal convection from Tue afternoon and evening. The odd shortwave rotating around the base of the 5h trough could help light off convection but the best shot may be with diurnal heating Wed, provided the tropical moisture hangs around into peak heating. Low temperatures will run well above climo while highs on Wed will be held below climo by cloud cover and rainfall. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 300 PM Monday...Unsettled weather with a chance for showers and thunderstorms is expected through the extended period though chances for showers and thunderstorms will diminish a little Friday and Saturday as upper ridge builds west into the area. Upper troughing will return for Sunday and Monday resulting in increasing chances for showers and thunderstorms again. High temperatures will increase from the mid to upper 80s thursday to the upper 80s to lower 90s for the weekend before moderating slightly to the mid to upper 80s for Monday. Lows should be in the low to mid 70s through the period. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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As of 06Z...Deep moisture will stream across the TAF area in S-SW winds through the period. Light SW winds should keep fog out of forecast but low stratus will plague the TAFs through early morning. A cold front will ease its way toward the area remaining west of TAF sites, but convection will continue ahead of the front up to 30 miles to the west overnight but nearing the TAF sites through the morning hours and then expect SHRA/TSRA through much of the afternoon into the early evening hours. As for coastal terminals, moisture will continue to stream northward with low clouds and then SHRA/TSRA through mid to late morning into the afternoon. Winds will back slightly from SW to S into this afternoon as sea breeze kicks in and pushes inland. With very deep moisture present, heavy rain will dominate the convection, enough to briefly lower vsby to 2sm or less at times. Extended Outlook...The risk for flight restrictions due to thunderstorms will continue through the period. The probability for reduced ceilings and visibility in thunderstorms with heavy rain should be highest tonight through Wed and possibly again on Fri.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 900 PM Monday...SCEC to continue across the local waters. Ridging from the center of high pressure well offshore and east of Cape Hatters will extend westward and inland just south of Cape Romain tonight thru Tue. The sfc pg will be at its tightest tonight then slightly relax during Tue as a result of the cold front having dropped south and becoming stalled just inland and north of the local waters. As a result, the SW wind direction will persist. Wind speeds in the 15 to 20 kt range will diminish to around 15 kt or 10-15 kt during Tue. Significant seas will initially run 3 to 5 ft and only lower to 2 to 4 ft during Tue. Wind driven waves at 6 second periods will dominate the seas spectrum. A 1 to 2 foot SE-SSE ground swell at 13 to 15 second periods will remain in the background. Previous........................................................ As of 245 PM Monday...An `Exercise Caution` headline was needed to account for seas up to 5 feet offshore and widespread 20 KT SW winds remainder of this afternoon and overnight. TSTMS will also increase overnight, leading to localized strong winds in and near convection. Spectral data indicates see energy is dominated by SSW waves in 5-6 second wave periods, with fading long period east swell. Mariners are encouraged to obtain a radar update before heading out this evening and overnight as a few robust storms are expected to move onshore late tonight. Seas 3-4 feet near shore will remain bumpy through tonight as winds remain elevated. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 3 PM Monday...Bermuda High will maintain southwest flow through the period with speeds peaking on the high end of the 10 to 15 kt range late Wed afternoon and evening. Seas will run around 3 ft through the period with an occasional 4 ft creeping in late in the period. LONG TERM /THURSDAY THROUGH SATURDAY/... As of 300 PM Monday...South to southwest winds of 10 to 15 kt are expected through the period with seas of 2 to 4 ft. Winds and seas may run higher in scattered thunderstorms. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...DCH NEAR TERM...DCH/MJC SHORT TERM...III LONG TERM...RAN AVIATION...RGZ

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