Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 151436 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1035 AM EDT Tue Aug 15 2017 .SYNOPSIS... Summertime heat and humidity will build and should peak Wednesday through Friday as showers and thunderstorms gradually become fewer in number. Showers and thunderstorms will be on the increase during the weekend as a cold front approaches from the north. This front may actually push to our south early next week as cooler high pressure builds from the north. && .NEAR TERM /THROUGH TONIGHT/... As of 1030 AM Tuesday...Areas of stratus and strato-cumulus are decreasing in coverage and becoming increasingly cumuliform with the day`s heating. A few showers have already developed in the vicinity of Cape Fear and expect widely scattered to scattered convection to initiate along the sea breeze as the primary focus today in a high precipitable water environment. Will need to re-asses with new model data however could see a new round of convection tonight as an impulse in the westerly flow moves primarily across NC. Otherwise heat and humidity will become the main issue with heat indices of 100 to 104 this afternoon (along with a few pockets of 105 possible). Warm low temperatures expected again tonight with the heat issues persisting into the short term period. Otherwise, Gert`s swells are moving into the beaches. WaveWatch appears to be 1-2 ft too high with this swell, however enough swell to support enhanced rip current risks at all beaches (especially the E and SE facing beaches). && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday...The period will be dominated by high heat and humidity. A Heat Advisory may be required both days for heat index values near or in excess of 105 deg. High temps will be mainly in the lower to mid 90s with near 90 at the beaches where the seabreeze should have a difficult time pushing inland given the deep WNW to NW flow just off the surface. Lows will be in the muggy mid and upper 70s. A very warm ridge of high pressure will be centered across FL and portions of the Southeast states during this period. Subsidence and warmer temps aloft should help to decrease, but not eliminate the number of showers and thunderstorms. A weak front should be all but washed out and the seabreeze looks like it will be the primary impetus for convection, especially on Wed when subsidence and warmer temps aloft will be building, but not quite as strong as on Thu. The Piedmont Trough may also act to focus showers and thunderstorms as it will be displaced further east given the flow aloft. A NW flow will become established across the area and this flow is often tricky for the Carolinas and will continue to monitor for any upstream impulses aloft which would warrant higher POPS. However, at this time, will show higher POPs Wed than on Thu, mainly scattered. Eve convection should tend to dissipate quickly with loss of heating. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 300 PM Monday...Ridge building across the Southeast late in the week will bring increasing heat and humidity before a cold front drops into the region for the wknd. Highs Friday will likely climb well into the 90s away from the beaches as 850mb temps climb above 20C, and this will combine with continued high dewpoints and humidity to produce heat index values above 100 degrees. This environment is supportive of typical aftn thunderstorms, but coverage is not forecast to be too widespread as the ridge aloft helps to minimize total convective development. Still, will carry CHC POP, focused along the typical boundaries, and any storm could produce torrential rainfall. The cold front drops into the area Saturday as a 500mb shortwave digs into the OH VLY and then shifts east through Sunday. This will push the front through the area before stalling and beginning to dissipate on Monday thanks to increasing mid-level heights again behind the departing shortwave. Showers and thunderstorms will become widespread Saturday and possibly again on Sunday before W/NW flow behind the aforementioned shortwave begins to dry the column. Temperatures and humidity will remain elevated although cooler than late week. First glance at the all-important Monday forecast is looking promising right now for the solar eclipse watchers out there. If the front can sag far enough south as currently shown by long-range guidance, the combination of surface high ridging from the OH VLY and increasingly dry W/NW flow aloft could support good viewing locally. Of course, if that front stalls overhead or begins to lift back to the north during Monday, it would create much more unsettled weather across the area. For what its worth, the 12Z/14 GFS average sky cover currently shows mostly clear sky conditions for the area Monday afternoon. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... As of 12Z...May be a brief period of lingering IFR at KLBT initially, but otherwise VFR to start the TAF period. Thunderstorms this afternoon will have the potential to produce MVFR or lower conditions. A trough approaching from the N and NW late day and this eve may help to initiate a round of showers and thunderstorms as well, otherwise we expect VFR condtions to redevelop this eve. Model profiles support at least the mention of some low stratus after 08z and did add MVFR BR at KLBT and KFLO as well. Confidence was too low to introduce an IFR ceiling late in the valid TAF period. Extended Outlook...A brief period of MVFR or lower conditions can not be ruled out in isolated to scattered showers and thunderstorms Wed through Fri. The risk for flight restrictions due to showers and thunderstorms will increase on Sat. Low stratus and some fog during the overnight and early morning hours may result in flight restrictions as well. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1030 AM Tuesday...Swells from Gert have moved into the coastal waters but are coming up 1-2 ft lower than previous Wave Watch guidance indicated. Still expect steep conditions at inlet entrances, especially when combined with the current during the falling tide. The local wind wave will add some chop during the day. Once the sea breeze weakens this evening the flow will veer to a westerly direction overnight also supported by the eastward shift of a weak trough. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday...Winds Wed morning may be light from the NW as trough pushes out across the waters. SW winds will return Wed afternoon, but still less than 10 kt, as a pinned seabreeze develops. Light and variable winds Wed night and Thu morning should settle on a SSE to S direction Thu afternoon, still less than 10 kt, as the seabreeze redevelops and a trough briefly tries to amplify offshore. Seas will be highest Wed morning, 2 to 3 ft with some residual 4 ft seas across portions of the outermost waters as Hurricane Gert swell decays. Seas will be 2 ft Wed night through Thu night. LONG TERM /FRIDAY THROUGH SATURDAY/... As of 300 PM Monday...A messy wave spectrum expected late week as a weak gradient exists in the vicinity of offshore high pressure. This gradient will gradually tighten beginning late Friday and on Saturday as a cold front drops into the area from the NW. Although no wind shift is expected during this period, speeds will increase, becoming SW at 10-15 kt late Friday and Saturday, after being SW less than 10 kt. Wave heights will be 2-3 ft Friday with a variety of low-amplitude wave groups comprising the spectrum. On Saturday seas will build to 3-4 ft as a SW wind wave becomes more significant. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...High Rip Current Risk through this evening for SCZ054-056. NC...High Rip Current Risk through this evening for NCZ106-108-110. MARINE...None. && $$ NEAR TERM...SRP SHORT TERM...RJD LONG TERM...JDW AVIATION...RJD

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