Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 181932 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 332 PM EDT Sun Jun 18 2017 .SYNOPSIS...
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Isolated to scattered thunderstorms this afternoon and Monday will become more widespread Tuesday as a cold front approaches from the northwest. The cold front is expected to stall and slowly dissipate Wednesday. Bermuda High pressure should reestablish itself late in the week. Tropical moisture will spread northward from the Gulf Coast states, increasing the risk for showers and thunderstorms Friday and Saturday.
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&& .NEAR TERM /THROUGH MONDAY/...
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As of 3 PM Sunday...The drier mid-level air has greatly diminished the number of showers and thunderstorms across the area this afternoon as expected. The convection developed along the seabreeze and ahead of the Piedmont trough. This should keep thunderstorms out of the forecast for the more immediate coast through the early eve. The corridor of greatest convective coverage is expected from about HYW to MAO to around EYF, as the seabreeze boundary nudges westward. Isolated showers and possibly a thunderstorm are possible across the remainder of our inland communities. The lack of deep moisture is expected to keep the convection on the shallow side which will decrease the potential for heavy rain, frequent lighting and strong wind gusts. Showers and thunderstorms should dissipate quickly late day through early eve. Showers and thunderstorms associated with Atlantic plume of deeper moisture should largely stay offshore overnight, although prevailing flow is more SSW than SW, so some of the convection may skirt some of the beaches. Will increase POPS to slight chance and chance around sunrise, mainly across the Cape Fear coast, although morning through midday seabreeze activity could develop anywhere along the coast. On Mon, Forecast Area will be in between Western Atlantic ridge and upstream progressive trough. This trough will help drive a surface cold front as far east as the Appalachians by Mon eve. A mid-level shortwave trough embedded in SW flow is expected to skirt the area to the W as we approach peak heating and then exit during the eve. Precipitable water values do increase to near 2 inches, as the depth of moisture increases through the day. These factors should promote at least scattered afternoon and eve thunderstorms, favoring inland areas, west of the seabreeze as it pushes inland.
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&& .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 AM Sunday...Deep layer moisture advection increases P/W content from 1.75 inches Monday morning to around 2.00 inches Monday afternoon and into Tuesday. At the surface the Bermuda ridge will persist through the short term as a weak and slow-moving cold front drifts SE and stalls along the Appalachians. Expecting scattered convection Monday becoming more widespread on Tuesday as an H/5 L/W trough deepens over eastern CONUS and the column continues to moisten. Very seasonal temperatures on Monday will drop a few degrees on Tuesday due to extensive cloud cover and bouts of precipiation. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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As of 3 PM Sunday...Stalled front across the southeast Wed, likely just west of the local area, will gradually dissipate as 5h trough starts to de-amplify. Little of the front will remain in the vicinity Thu as Bermuda High and and 5h ridge expand over the region from the east. Despite the expanding/strengthening mid level ridge late in the week diurnal convection will remain a fixture through the period. Best chances on Wed may end up being earlier in the day with the stalled boundary and deeper moisture in place. Moisture shifts east later in the day which may lead to decreasing coverage. It is worth noting the Canadian/ECMWF solutions are being favored midweek with the handling of the low in the Gulf of Mexico. The GFS has been insistent on the low tracking quickly north to the FL panhandle which then leads to an abundance of tropical moisture moving into the region early Wed and lingering well into Thu. The favored solutions eventually spread tropical moisture associated with this system into the region, but not until late in the week. This leads to increased coverage of diurnal convection Fri and Sat despite the aforementioned expansion of the 5h ridge late week. Deeper moisture exits on Sun as the 5h ridge retreats east and 5h trough approaches from the west. Enough moisture lingers Sun afternoon to support convective coverage more typical of summer in the Carolinas. Although a fair amount of cloud cover and convection is expected for much of the period temperatures will run slightly above climo during the day, a combination of starting out warmer due to morning temps well above climo, and warming under the mid level ridge.
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&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/... As of 18Z...Thunderstorms that do develop today will be fewer than in recent days and should be located mainly in between our coastal terminals and our inland terminals. However, a thunderstorm can`t be ruled out at least near KFLO and KLBT this afternoon and so will watch trends and issue amendments should a shower or thunderstorm get within 5 miles of a terminal. The convection will dissipate quickly late day/early eve. The convection overnight is expected to stay just E of the coastal terminals. Given this, I plan on leaving convection out of the valid TAF period for all terminals. Will forecast VFR throughout until overnight when stratus development may bring bases/ ceilings down to around 1kft after 06z. These lows clouds will gradually lift after sunrise, but MVFR conditions may linger through a good portion of Mon morning. 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 Tue and Wed. && .MARINE...
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NEAR TERM /THROUGH MONDAY/... As of 3 PM Sunday...The combination of the seabreeze circulation and nocturnal jetting will keep wind speeds near 15 kt through the period. Gusts to around 20 kt will be most common through mid or late eve. The Wind direction will be S, veering to SSW later tonight. Seas will be 3 to 4 ft. On Mon, the seabreeze circulation will again become well established during the afternoon. The pressure gradient will begin to tighten late in the period as a trough approaches from the W. These factors will increase SSW winds to 15 to 20 kt Mon afternoon. These increasing winds will add about a foot to the overall sea heights, up to 5 ft. Weak SE swell on the order of 15 to 17 seconds will persist. SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 3 PM Sunday...Southwest winds will persist through the period ahead of a slowly approaching cool front. Sustained winds Monday night into Tuesday will remain around 15 kts, with gusts around 20 kts on Monday as pressure gradient is temporarily tightened. Into Tuesday night, expect winds to become west- southwest around 10 kts. Up to 4 ft seas will continue Monday night into Tuesday, retreating back to 2 to 3 ft Tuesday afternoon/evening. LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 3 PM Sunday...Front will remain stalled west of the waters Wed with the boundary expected to dissipate by Thu. Bermuda High will remain the dominate surface feature through the period with southwest winds 10 to 15 kt. Afternoon and evening winds could exceed 15 kt for a few hours, especially later in the period as heating leads to a slight increase in gradient. Seas 2 to 3 ft Wed will build to 2 to 4 ft during Thu, eventually reaching 3 to 4 ft Fri.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...RJD SHORT TERM...SGL LONG TERM...III AVIATION...RJD

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