Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 251050 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 650 AM EDT Sun Sep 25 2016 .SYNOPSIS... A backdoor cold front will stall in close proximity later today or this evening before moving back to the north overnight and Monday. A stronger cold front will move across the Carolinas Tuesday night and Wednesday. Unsettled weather will return today and remain until the passage of the mid week cold front. Then in the wake of this front, drier and cooler weather will arrive on northerly winds. && .NEAR TERM /THROUGH TONIGHT/... As of 600 AM Sunday...A backdoor cold front was moving across Wilmington as well as across Lumberton and Elizabethtown at daybreak. The front will continue to slip S, but at a slow pace. Lower clouds will fill the sky in the wake of the front. Further S across the Santee River area, patchy to areas of fog were restricting visibility to a half mile or less. The front is currently being nudged to the south by high pressure across the Great Lakes and northeast states. The center of the high is expected to move across New England tonight. The front will likely get hung up as it tries to push through the the forecast area today and should stall in close proximity tonight before drifting back to the N late tonight and Mon. Low clouds across northeast NC will continue to push south behind the front and we expect clouds to be on the increase today, especially across NC. Still a fair amount of dry air in the mid- levels today. Moisture will be increasing below 25 kft or so. Instability will be increasing with mixed layer CAPE values peaking this afternoon in the 800 to 1200 J/kg range, highest across SC. There is no appreciable upper level support and the high resolution HRRR is not showing any convection developing until mid afternoon. Will show POPs increasing above threshold early to mid afternoon and include isolated thunderstorms by mid afternoon and into early this eve. Depth of moisture should largely preclude heavy rainfall amounts despite the slow storm motions. Given the proximity of the front, will keep a mention of showers in the forecast through the eve and overnight, but the moisture depth will be restricted to about the lowest 15 kft of the column and so will pull any mention of late night thunderstorms. Highs today will be in the lower to mid 80s, warmest across the Pee Dee. Lows tonight, mid 60s to lower 70s. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 300 AM Sunday...High pressure across New England will drift offshore and this will allow the cold front to push back N of the area during the day with surface winds turning onshore and eventually to the SE Mon afternoon and eve. A subtle mid-level shortwave will sneak up the coast late in the day Mon and Mon night. A vigorous trough carving out across middle America is expected to drive a cold front into and eventually through the eastern Carolinas Tue night or Wed. Moisture will increase steadily during Tue and Tue eve and then begin to drop off sharply with frontal passage overnight, lastly along the coast Wed. Will show convection through the period, but include the highest probability Tue afternoon and night. Highs will be about normal, lower 80s. Lows will be in the upper 60s to lower 70s Mon night and then cooling in the wake of the cold front to mid and upper 60s. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 300 AM Sunday...Deep upper low will evolve across the Great Lakes and then sink slowly SE through late week before ejecting into Canada during the wknd. This will drive a cold front across the Carolinas on Wednesday, but its overall progression is a low confidence forecast due to model uncertainties into the evolution of the aforementioned upper low. ECM is deeper and stronger with this upper low, cutting it off entirely from the mean flow into next wknd. The CMC is the fast solution with short cutoff followed by rapid progression into the westerlies by late week. The GFS is a decent compromise, although its ensembles show a very large spread by D6. The biggest difference to the sensible weather from these solutions revolves around precip potential, as temperatures will likely be seasonable or slightly below regardless of which outcome is correct. Will favor the GFS attm which is supported by WPC, which suggests the front will push offshore as the upper low begins to move NE Thursday, with cool high pressure building down the coast thereafter. Temperatures Wed/Thu will likely be around seasonable norms or slightly above, but clouds and showers will be likely as the front drifts towards, and then off, the SE coast. As the high builds south late week and into Saturday, temps will cool to below normal with mins potentially dropping to 60 or below, especially inland, by the end of the period. If the ECM solution ends up being correct, temperatures will still follow this trend, but both Friday and Saturday could also feature periods of showers instead of the drier forecast currently being shown. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... As of 12Z...A cold front is passing through our northern CWA at this time. Predominately northeast flow and MVFR conditions are expected with brief IFR ceilings possible early on. There will probably be a shower or two around, however they will be very weak as things should remain quite stable with low CAPE expected. The front will stall over our southern counties with light northeast flow overnight. EXTENDED OUTLOOK...Chance for SHRA/TSRA each day through Wed. Otherwise expect VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 600 AM Sunday...A backdoor cold front was moving through the northern waters this morning and will likely stall across the southern waters this afternoon and eve before moving back to the N late tonight and Mon. High pressure will be moving into and through the northeast states today and tonight and then offshore Mon. Winds across our coastal waters will be from the NE through the period at speeds of up to 15 to 20 kt. Seas will be mainly 3 to 4 ft, but up to 5 ft around Frying Pan Shoals in part due to a robust 9 to 11 second easterly swell. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 300 AM Sunday...High pressure across New England will move offshore and this will allow winds to shift from NE and ENE Mon morning to E Mon afternoon and to SE Mon night. As a cold front approaches the waters, SE winds Tue will become S and SW Tue night. If the front does not slow down, winds may shift to the N as early as the wee hours of Wed morning. The highest winds this period will be Mon and Mon eve, up to 10 to 15 kt. Seas of 3 to 4 ft Mon and Mon night will subside to 2 to 3 ft Tue and Tue night. LONG TERM/WEDNESDAY THROUGH THURSDAY/... As of 300 AM Sunday...Some uncertainty exists in the extended with respect to the timing of a cold front moving across the waters, but attm it appears the front will stall over the waters Wednesday and then shift well offshore during Thursday. This leaves a period of highly variable winds on Wednesday with speeds of 5-10 kts, before the front moves away Thursday followed by N to NE winds of 10-15 kts. Seas Wed and most of Thu will be 2-3 ft with residual 11-12 sec swell remaining in the spectrum combined with low-amplitude wind waves. Late in the period a northerly 4-5 sec wave will amplify, and seas may build towards 3-4 ft late Thursday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...RJD SHORT TERM...RJD LONG TERM...JDW AVIATION...DL

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