Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 260724 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 324 AM EDT Mon Sep 26 2016 .SYNOPSIS... A stalled front will waver across the area today. A stronger cold front will approach Wednesday before slowly crossing the area through late in the week although timing of this front is highly uncertain. Cooler and drier weather is expected by the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1025 PM Sunday...Have dropped pops for the overnight period with the latest update as showers have faded with loss of diurnal heating. Relevant portion of previous discussion from this afternoon follows: This morning`s cold front has nearly stopped moving southward and is stalled over eastern South Carolina in the vicinity of Georgetown, Florence, and Hartsville. With northeast winds on both sides of the boundary it`s a bit nebulous exactly where the front is. Dense low clouds never burned off across northern and central North Carolina, but fortunately the post- frontal airmass never became that well established here before the sun rose this morning. Northeasterly low-level flow should push these lower clouds southwestward after sunset. Weak cool advection should be felt most strongly across coastal SE North Carolina tonight as the high over New England points its ridge axis down in that direction. Broken low clouds will help to hold heat in overnight and my forecast lows are close to the warmer NAM MOS guidance, except at ILM where a slug of dry air after midnight associated with the ridge may allow better radiational cooling to occur. Lows mainly upper 60s with some lower 70s on the beaches. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 300 PM Sunday...The 500 mb ridge over the Southeastern U.S. will get beaten down over the next two days as an upper level trough begins to dig southward across the Great Lakes. The surface high will move off the New England coast Monday; return flow behind this high should lift today`s cold front back to the north again, with the boundary moving back into Virginia by Monday evening. A weak low in the northern Bahamas will get lifted northward by the same low and mid-level flow. While this feature should remain 50-75 miles off the coast as it moves northward Monday into Tuesday, its closest approach late Monday night into Tuesday morning could enhance rainfall potential, at least along the coast. By Tuesday, attention will shift to a cold front entering the western Carolinas, preceding the upper level trough over the Great Lakes. This front should stall as the upper trough deepens and cuts off. With a humid tropical airmass in place Tuesday ahead of this stalled front, scattered showers and t-storms appear quite possible, especially inland. Assuming there are no unresolved upper level disturbances present, precipitation should diminish Tuesday evening with the loss of daytime heating. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 300 AM Monday...Big differences in the extended continue to cause lowered confidence for late this week. While the guidance all shows a deep trough closing off across the OH VLY, the evolution thereafter becomes quite muddled. The ECM continues to be a strong/slow/west outlier with this feature as it digs into the lower Appalachians and then actually retrogrades to the NW through Saturday before finally ejecting late in the wknd. The GFS/CMC are more in line with a sharp digging through Thursday and then lifting off to the NE through New England Friday and into the wknd. Although the ECM has been consistent the last few days, the GFS solution is still preferred as a retrograde west of the upper low into a +3 SD ridge seems unlikely. WPC cannot rule out any solution at this time however, so a blended forecast is preferred with highest weight on the GFS. This upper low will determine the passage of a surface cold front which continues to slow in forecast guidance. Favoring the GFS, FROPA is now expected early Thursday, with cool and dry weather expected Fri-Sun. In fact, temps Fri-Sun may fall slightly below climo for both highs and lows as the first fall-like airmass of the season advects into the Carolinas beneath Canadian high pressure. Will note that if the ECM solution verifies, the front won`t cross until Saturday, leaving much more unsettled weather through the week, along with continued above normal temperatures. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... As of 06Z...Stalled cold front is draped across NE SC this morning, with high pressure building down the coast from the NE. Moisture is pooling along the leading edge of this ridge of high pressure and behind the front, creating increasing stratus across the area. This stratus will likely become more widespread overnight, but should remain at MVFR levels, and no IFR is forecast. Best chance for persistent stratus will be at the inland terminals, and while confidence is lower at the coast, have included MVFR at all sites through dawn. Winds will remain 5-10 kts overnight, highest near the coast, so no visibility restrictions are expected. The front will waver across the area again during Monday, with showers and isolated tstms possible at all terminals. Have not included any mention of TS in the TAFs attm, but VCSH has been introduced to all terminals. Winds are expected to rise to around 10 kts, while veering to the SE through the aftn/eve. Any showers will wane after dark Monday night, with more stratus possible at the end of this valid period. EXTENDED OUTLOOK...Chance for SHRA/TSRA each day through Wednesday, with morning fog/stratus also possible. VFR Thursday and Friday. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1025 PM Sunday...Latest obs continue to show E to NE winds of around 15 kts in the wake of the recent cold front, with seas of 3 to 4 ft. This fits in well with the latest forecast, of which there is no change. Previous discussion from this afternoon follows: This morning`s cold front has made it only a short distance down the South Carolina coast this afternoon. The boundary will settle somewhere near the Santee River tonight where it should remain stalled through Monday. A healthy northeast breeze around 15 knots with gusts to 20 knots should continue most of the night as high pressure builds south across New England. Seas 3-5 ft across the NC waters and 3-4 feet across the SC waters consist of a mix of 11-second easterly swell from former Tropical Storm Karl and 4-5 second wind waves. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...As high pressure moves off the New England coast Monday and out to sea Tuesday, our synoptic wind direction will veer from northeasterly Monday morning to southeasterly by Monday night. Normally it would hold this direction, however it appears that a weak area of low pressure in the Bahamas will move north along the Gulf Stream Monday, approaching to within 50-75 miles of Cape Fear Tuesday. Circulation around this feature may turn our winds back to the northeast for at least the first half of Tuesday before the southeasterly winds redevelop Tuesday afternoon or evening. Wind speeds should average 10-15 kt Monday, but lighter through Tuesday and Tuesday night. LONG TERM/THURSDAY THROUGH FRIDAY/... As of 300 AM Monday...Still some uncertainty in the extended with respect to a frontal passage, but attm expect FROPA to occur Thursday with W/SW winds around 10 kts becoming NW late. High pressure will build in behind this front creating a very weak pressure gradient, so winds across the waters on Friday will feature highly variable direction with speeds of 5-10 kts. Seas of 2-3 ft Thursday will fall to around 2 ft on Friday thanks to the weaker winds, and a continuing 2ft/9-10 sec SE swell. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...DCH SHORT TERM...DCH LONG TERM...JDW AVIATION...JDW MARINE...

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