Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 202218 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 618 PM EDT Tue Sep 20 2016 .SYNOPSIS... The remnants of Julia will remain across eastern North Carolina through much of the week and this will keep the weather rather unsettled. High pressure will build into the area by the weekend finally bringing drier conditions. A cold front will move across the area during Sunday bringing the first hint of Autumn early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of 300 PM Tuesday...An upper low spinning around in the Carolinas will continue to provide unsettled weather across the area through tonight. Low clouds and spotty light showers or drizzle were covering much of the area into this afternoon. A moist northerly flow was wrapping around the remnant low from Julia as some drier air aloft wraps around the back of the upper low. Sounding data and time height sections show drier air aloft from h70 and above which looks like it may mix down enough to produce a few breaks in the clouds especially across inland. This all makes for a tricky forecast as the clouds will hamper heating and therefore instability while areas that see any sunshine will become more unstable and should see some convective development this aftn. The cool pool aloft will drift south over the area helping to sharpen lapse rates and promote some convection associated with differential heating or low level convergence. It looks like the best upper level energy and support will ride around the upper low and combine with best convergence associated with sfc low to produce best chc of shwrs from N-NE to S-SW across the area through tonight. HRRR shows pcp mainly aligned along I-95 corridor and west with only spottier shwrs to the east closer to the coast. With such a cool pool aloft, you can not rule out isolated thunderstorms, but temps were struggling to make it much past the mid 70s limiting the sfc heating needed to steepen lapse rates. Temps will hold in the mid 70s in most places and will not drop too much tonight under a very moist air mass with plenty of cloud cover. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...The remnants of Julia or a broad area of low pressure/trough will remain up the Carolina coast through mid week. Initially the circulation will drift southwest as it continues to be pulled by upper low. This will leave a moist northerly flow across much of the area through Wed into Thurs. The models are not in total agreement with evolution of this low/trough but it looks like it will be pulled back westward briefly on Wed which may produce a period of on shore flow and possibly enhance low level convergence but also may enhance thunderstorm activity along the coast. It will depend on the exact location of the low, both at the surface and aloft, to determine where the best convergence, lift and upper level support will be, but the potential will exist with a decent cool pool aloft. Overall, expect a good deal of clouds and showery weather through much of the period with isolated thunderstorms possible. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 300 PM Tuesday...Remnant mid-level circulation of Julia will still be overhead by Friday, before finally lifting off to the NE as high pressure builds across the area on Saturday. Friday will be near seasonable temperatures with periods of clouds of showers, but as subsidence develops behind the departing upper impulse, Saturday will likely rise to above climo again with much more sunshine. This warmth will be short-lived however, as a deep trough then digs into the northeast driving a back door type cold front into the Carolinas Sunday, with much cooler temperatures lasting into the beginning of next week. Increased clouds and showers are possible Sunday into Monday with the FROPA, but the forcing is weak and moisture is limited to the lowest part of the column. This suggests more clouds/drizzle into Monday than true showers, but will carry low-end POP before drying out by Tuesday. Temps Sun-Tue will drop to more seasonable levels, and our first taste of fall-like temperatures may occur early next week. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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As of 00Z...Pretty ugly aviation conditions tonight through the overnight hours with IFR conditions becoming widespread due to stratus. Likewise visibilities will lower below two miles at times due to drizzle. Conditions will be at their worst from 06Z-13Z, with slowly improving conditions after 15Z. North northwest flow is expected through Wednesday morning, becoming more easterly in the afternoon. If we get any sun on Wednesday (which is pretty unlikely), we could see some heavier convection in the afternoon. EXTENDED OUTLOOK...Isolated to scattered afternoon and early evening convection possible underneath the cutoff upper low through Friday. MVFR/IFR morning stratus/fog possible each day thru Sunday.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 300 PM Tuesday...Northerly winds will back a little overnight as low pressure gets pulled southward, but overall expect N-NW 10 to 15 kts. Winds will diminish a bit and become more variable overnight. Seas will remain less than 3 ft. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...Northerly winds may become quite variable as remnant low of Julia gets pulled southward and possibly inland late Wed. This should produce a more on shore flow on Wed. Overall winds and seas will be determined by the exact fate of this remnant low/trough through mid week. A longer period up to 12 second SE swell will mix in by Wed night into Thurs. LONG TERM /FRIDAY THROUGH SUNDAY/... As of 300 PM Tuesday...A mostly weak gradient with N/NW winds will persist Friday and Saturday ahead of a back door type cold front which will sag across the waters during Sunday. Wind speeds Fri/Sat will be light, 5-10 kts or less, before steadily increasing behind the front to 10-15 kts from the NE during Sunday. WHile the wind will provide little contribution to the sea spectrum, a 3-4 sec/11 sec SE swell from Tropical Cyclone Karl will exist both Friday and Saturday, producing seas of 2-4 ft. On Sunday, this swell will slowly wane but a NE 5-6 sec wave will quickly amplify, producing wave heights of 3-5 ft the latter portion of the extended. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...RGZ SHORT TERM...RGZ LONG TERM...JDW AVIATION...43 MARINE...JDW/RGZ

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