Area Forecast Discussion
Issued by NWS Wilmington, NC

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989 FXUS62 KILM 231440 AFDILM Area Forecast Discussion National Weather Service Wilmington NC Issued by National Weather Service CHARLESTON SC 1040 AM EDT Wed Aug 23 2017 .SYNOPSIS... An approaching cold front will bring increasing storms over the area late today into Thursday. Canadian high pressure will bring an early fall feel Friday and into the weekend. Breezy conditions may develop late Sunday into Monday, as a possible tropical low passes offshore and interacts with the Canadian high. && .NEAR TERM /THROUGH TONIGHT/...
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A weak upper vort moved off the coast around daybreak, taking along with it scattered showers and tstms. 500 mb analysis indicates fairly widespread negative vorticity advection today in the wake of the shortwave. The resulting subsidence should result in mostly dry weather through mid afternoon, aside from an isolated sea breeze shower or tstm. Late this afternoon a strong shortwave approaches from the northwest and a cold front moves toward the area. Latest high-res model data brings the leading edge of the showers and tstms into the western zones late this afternoon or early evening. Shear will be increasing to around 20 kt by late today which is not terribly impressive but could assist with some quasi-linear organization of convection along the front. CAPE values will be at a relative maximum late this afternoon around 2,000 J/kg. Severe thunderstorm potential will depend on the exact timing of the frontal convection, though it still appears that isolated severe thunderstorms will be possible between about 5 PM and 11 PM. The front will stall across the area tonight even as convection pushes offshore by Thursday morning. Cool advection lags, so mins will remain elevated tonight, mid 70s at the coast to low 70s far NW zones.
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&& .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... As of 300 AM Wednesday...A cold front will move through the area Thursday and off the coast Thursday night accompanied by scattered showers and storms. The greatest chances for rain during this period will be over the south and east. Small pops will longer along the coast Friday and south coast Friday night in NE flow as low level moisture is slow to be driven out of the area. Max temperatures will be in the mid to upper 80s both days with mins in the upper 60s to lower 70s with mid 70s at the beaches. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 300 AM Wednesday...At the surface a cold will push into the Bahamas by early Saturday with high pressure building down into the Carolinas. Saturday should be cooler and mostly dry although the easterly flow may keeps some low clouds and perhaps a light shower or two offshore around. The forecast gets interesting later in the period when the global guidance spins up what could be a tropical system along the residual front and moves it up off the southeast coast. The guidance has been showing this for a few cycles but the disclaimer of its pretty far out in time still holds. I did keep a partly to mostly cloudy forecast intact with some pops increasing especially along the coast. Temperatures will be on the cool side especially for highs more near normal for overnight lows. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... As of 11Z...Isolated showers and thunderstorms are possible coastal areas this am and along the sea breeze this aftn. More numerous showers and thunderstorms are expected to develop ahead of a cold front and affect all the terminals. Have continued VCTS with -SHRA at all terminals late this afternoon into tonight. Generally expect MVFR with SHRA but brief IFR is possible. Extended Outlook...Showers and t-storms Thursday associated with a cold front could produce localized IFR conditions. Most showers and storms will push offshore Thursday night into Friday. MVFR ceilings could linger, especially near the coast Friday. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 300 AM Wednesday...High pressure offshore and a cold front approaching from the NW will pinch the gradient today causing SW winds to increase across the waters. SW winds of 10-15 kts will slowly increase to 15-20 kts this evening and tonight, while subtly veering more to the W/SW. This increase in wind speed will allow the wind wave contribution to the wave spectrum to increase, with a 3-4 ft/4 sec SW wave topping a persistent 2-3ft/9sec SE swell. These two groups combined will produce significant seas building from 2-3 ft early, to 3-4 ft late, and at this time no cautionary statements are expected. Showers and tstms are expected across the waters late tonight as well, moving from west to east mostly after midnight, with gusty winds, lightning, and heavy rainfall. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 AM Wednesday...Westerly flow of 10 to 15 KT Thursday will shift to the NE Thursday night and increase 15 to 20 kt by Friday night. Seas will build from 2 to 3 FT Thursday to 3 to 5 feet Friday night. LONG TERM /SATURDAY THROUGH SUNDAY/... As of 300 AM Wednesday...Not the best of weekend`s coming up for the marine community as high pressure will be building down into the area from the north. At the same time a front will become stationary to the south and keep the gradient elevated. For basically the entire period expect northeast winds of 15-20 knots. Seas will be elevated as well with values from 3-6 feet. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...JRL SHORT TERM...JMC LONG TERM...JMC AVIATION... MARINE...

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