Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 260605 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 830 PM EDT Tue Jul 25 2017 .SYNOPSIS... Drier weather will make its way south behind a cold front as it drifts slowly south into South Carolina today and then dissipates. Isolated to scattered storms will become more numerous Friday and Saturday, as a moderately strong frontal system arrives at the coast. A slight cooling and drying trend may occur Sunday into early next week, as this system is kicked offshore. && .NEAR TERM /THROUGH WEDNESDAY/... As of 830 PM Tuesday...Multiple boundary interactions and an unstable airmass fueled isolated strong convection this evening, but with the sunset activity is now on the decline. Will knock pops back with the next update. Otherwise forecast is good to go. Previous discussion follows: Potential for widely scattered showers and a few thunderstorms with the sea breeze through the afternoon. Additional storms are possible tonight as a cold front drops southward across the forecast area. The front is expected to drift south of the forecast area during Wednesday and become increasingly diffuse. Dewpoints will lower across the northern zones while the best chance for showers/thunderstorms will be across the southern zones during the day. Northeast to easterly wind in the wake of the front will help hold temperatures to the mid 80s at the beaches on Wednesday. Followed a blend of MAV/MET numbers through the period. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 215 PM Tuesday...Very interesting synoptic setup through mid- week despite very weak surface features and gradients. The interesting aspect is focused mostly at and above 500mb as a nearly stationary shortwave spins across N FL in response to a persistent ridge in the west, and jet level winds increase and dive SW between the ridge and the trough. This drives a strong deformation axis across the Carolinas where NE 250mb winds converge with more typical westerly 250mb winds along a jet axis off the coast. As is typical with deformation axes, most of the precip occurs SE of this feature, as drier air advects behind it. This is clearly evident on forecast profiles with exceedingly dry air developing above 600mb, which should limit convective coverage considerably on Thursday. This dry air, combined with weak confluence into the deformation axis, and a weakening surface front to the south will preclude much in the way of convection Thursday, and have opted to remove any mention even along the sea breeze despite temperatures around 90. Wednesday night will be dry as well, minus a few isolated showers well south, with mins in the low 70s, while subtly increasing column moisture ahead of an approaching front and developing S/SW winds will keep mins several degrees warmer Thursday night, falling only into the mid to upper 70s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 215 PM Tuesday...An unseasonably amplified upper trough becomes the primary feature and key player for late week and weekend sensible weather. This will translate to elevated rain chances late Friday and Saturday as this system ushers a fairly strong surface trough across the coast. ECMWF and GFS clear this boundary off the coast into early Sunday, the GFS much stronger. Both suggest therefore some drying and cooling, but of differing magnitude. A blend still brings surface dewpoints into the 60s early next week, helping to take off the bite of high absolute humidity values. A dry mid-level air intrusion will curtail deep convection Sunday through early next week. A few showers could linger and remain favored closer the coast in proximity to higher moisture and the oceanic front, but the overall coverage should trend down Sunday onward. Temperatures slightly above normal Friday at the start of the period, may dip below normal from Sunday forward, as cool air advection pushes into the balmy sea air. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... As of 06Z...Cold front draped from W-SW to E-NE across the area has reached a line between FLO to ILM and will continue to drift slowly south through today. This boundary will remain the focus for convection, as well as, convergence along sea breeze front. North of the front, have included some stratus and may see some patchy lower clouds over coastal terminals around daybreak. As drier air makes its way in from the north today, expect mainly VFR by later this aftn into tonight across most terminals. Light NE flow will veer to the E-NE through this afternoon and slightly E-SE in sea breeze this aftn. Extended Outlook...Possible MVFR conditions with some flight restrictions with convection Friday through Saturday as cold front sweeps through. && .MARINE... NEAR TERM /THROUGH WEDNESDAY/... As of 830 PM Tuesday...Latest obs show seas of around 3 ft with SW winds of around 10 kts. No changes needed with the latest update. Previous discussion follows: A cold front will drop south across the waters during tonight. Southerly winds ahead of the front will become variable for a brief period tonight prior to shifting to a northeast-easterly direction overnight into Wednesday morning. Easterly flow will prevail through Wednesday afternoon with speeds of 10-15 knots. Seas are expected to be 3 ft or less through the near term period. SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 215 PM Tuesday...A cold front will be dropping across the southern waters Wednesday night before stalling south of the area on Thursday. This leaves E/NE winds less than 10 kts Wednesday night, gradually shifting to E/SE and eventually coming around to the SW Thursday night as the front dissipates and high pressure becomes dominant once again. Speeds through the period will be 10 kts or less, with the exception being within the near shore sea breeze Thursday when gusts to 15 kts are possible, and again very late Thursday night when 10-15 kt winds will overspread the waters. These light winds will allow the SE swell to be dominant until the wind wave amplifies Thursday night. Seas will be 2-3 ft through the period but the average period will begin to shorten late. LONG TERM /FRIDAY THROUGH SUNDAY/... As of 215 PM Tuesday...Wind direction will become changeable this period, but the good news is that wind-speeds will decrease into the weekend, as a front lays up along the coast then offshore. TSTMS will become more numerous along the front however Friday night and Saturday, so a radar update should be on the checklist first part of the weekend. Gusts to 20 KT from SW likely Friday out ahead of the front, and could be stronger so an SCA is not out of the question yet for Friday. Seas 2-4 feet this period because of initially gusty winds, then because of swell over the weekend. TSTMS will decrease in coverage Sunday, although the Gulf Stream and outer waters may remain unsettled due to the offshore front. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...REK/SRP SHORT TERM...JDW LONG TERM...MJC AVIATION...RGZ

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