Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 251905 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 300 PM EDT Sun Sep 25 2016 .SYNOPSIS...
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A cold front will stall across South Carolina tonight before returning north Monday. A stronger cold front will move across the Carolinas late in the week though its timing is highly uncertain.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 300 PM Sunday...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. So far we`ve seen virtually nothing on radar. The HRRR appears to have been right all along and I`ve trimmed PoPs back to just a small 20 percent chance through this evening from west of Wilmington to around Conway and Marion. 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.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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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.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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As of 3 PM Sunday...Interesting weather early in the period with a very large trough on Wednesday turning into a major cutoff low well into the weekend. Trouble is, models are not in agreement regarding the longitude of the cutoff. As a result it is difficult to determine whether we see a FROPA locally or spend most of the long term in the warm sector of the deeply occluded surface low. Even FROPA model solutions do not push the boundary very far offshore so either way the weather appears to be unsettled. The main ramifications of the aforementioned uncertainties then will likely affect temperature/dewpoint forecast. The ECWMF has been seemingly leading the way in figuring out how this system will evolve and it has been showing the least progression. It now delays the front until about Saturday morning and it is not indicative of any significant airmass change. The GFS looks like it is trending in the direction of the EC so the forecast will be hedged in that direction.
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/... As of 17Z...Favored a blend of the models for this period with more confidence in the NAM and GFS then the ECMWF due to the handling of the H5 low across the nrn portion of the country during the next few days. Cold front south of KILM and KLBT at this time and right near KCRE/KMYR/KFLO. Predominately northeast flow and MVFR conditions are expected with mention of vcsh along the coastal terminals but will leave out mention inland. HRRR a bit overdone with the pcpn potential across the region but as mentioned in the near term forecast best chances for pops are just behind the front so that is enough reason for the vcsh. BUFKIT seems to agree with this scenario as well with pcpn ending around 00z across the coastal terminals. Moderate confidence in MVFR due to ceilings during the overnight period with improvement to vfr after daybreak. Winds will stay up along the coast but I will lower across KLBT and KFLO overnight. EXTENDED OUTLOOK...Chance for SHRA/TSRA each day through Wed. Otherwise expect VFR. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 300 PM Sunday...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/WEDNESDAY THROUGH FRIDAY/... As of 3 PM Sunday...Confidence is very low for the long term. A cold front driven southward by a cutoff upper low is being handled very poorly by various models. Solutions range from a somewhat clean FROPA on Thursday to the front lingering to our west until Saturday morning. Have trended the forecast towards the slower timing since models do tend to be gravitating in that direction. While the current wind direction forecast may be way off given the uncertainties at least that is some confidence that both wind speeds and seas will remain quite manageable for most mariners.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...TRA SHORT TERM...TRA LONG TERM...MBB AVIATION...MAC

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