Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 241624 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1224 PM EDT Sat Sep 24 2016 .SYNOPSIS... High pressure today will bring dry weather and above normal temperatures. A back door cold front will be accompanied by slightly cooler temperatures and increasing shower chances late this weekend and into the early week. A more robust cold front will cross Tuesday into Wednesday with continued rain chances. Drier and potentially much cooler air will build southward for late in the week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1230 PM Saturday...Fog burned off on schedule, and the subsequent cumulus are dissipating into drier air aloft. Clouds will be most prevalent along the SC coast where deeper moisture and some seabreeze convergence will occur. 700 mb temps too warm for showers. Discussion from 930 AM follows... Very few tweaks were needed to the forecast this morning. A persistent area of fog is finally burning off in the Burgaw to Wilmington corridor. The 12z MHX sounding was very similar in surface-to-850 mb temps to the 06z runs of the GFS and NAM. Compared to the past few days, today`s gonna be great. Enjoy the weather! Discussion from 600 AM follows... Not much in the way of stratus as compared to the last several mornings, so the day will dawn on the sunny side in many locations. We will finally experience drying today as weak ridging develops ahead of a backdoor cold front which will be approaching the area tonight. Offshore showers are generally not expected to reach the beaches this morning. A resultant boundary should become rather pronounced, but given the lack of moisture depth to support convection, will keep POPs below threshold. A good deal of sunshine is expected and this will make for summer like highs today, upper 80s to around 90. Lows tonight will be in the upper 60s to around 70. Model soundings are showing considerable saturation near ground level overnight and with cloud cover not expected to increase until late, from N to S, will include at least patchy fog at this time.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...A backdoor cold front will move slowly across the area on Sun. Moisture convergence along this front will allow columnar moisture to increase both in magnitude and depth as onshore flow deepens. Mixed layer CAPE values also project increasing instability. However, there will be no appreciable upper level support with ridging aloft. Thus, will only include isolated to scattered showers and thunderstorms in the forecast favoring the afternoon and eve hours for the best coverage. High pressure centered across New England Mon morning will shift offshore through the remainder of Mon and Mon night. This will veer the low level flow across the eastern Carolinas from E to SE. Weak shortwave energy will lift N toward the forecast area Mon and Mon night coincident with an inverted trough along the coast. Depth of moisture looks rather shallow. Still, POPs are warranted and will include isolated to mainly scattered during this time. Highs will be slightly cooler on Sun, mainly mid 80s with lower 80s more common on Mon. Lows will be in the upper 60s to around 70. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 300 AM Saturday...Deep early fall trough will dig across New England mid-week pushing a slow moving cold front through the Carolinas. This front will drag slowly southward Tuesday into Wednesday, and while total forcing is not very strong thanks to the primary vorticity center moving east, increasing moisture and instability combined with at least weak PVA within the stretching lobe of vorticity will drive showers with isolated tstms the first 48 hours of the extended. This front looks to provide a true air mass change for the latter half of the week, as 850mb temps drop to 10-12C, and much drier air advects down the coast within large high pressure expanding from the northeast. Must note that the 00z/24 ECM guidance has changed drastically - stalling the upper low across the OH VLY - with height falls and a pressure trough locally continuing rain chances right into the wknd. While this is new to the ECM, it mimics at least somewhat previous runs of the GFS from 24-48 hours ago, which begs the question whether this will be a trend towards that more amplified solution. At this time will favor the faster solution of the GFS and preferred by WPC which would bring cooler and drier weather in here by week`s end. After above climo temps on Tuesday, MOS numbers suggest slightly below normal temps for both max and min by the end of the week, with lows possibly dropping into the 50s for the first time since the end of May. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... As of 12Z...Shallow fog in spots will mix out by 13Z at the latest. High pressure will be in control today, with little in the way of cloud cover. Predominately northeast flow is expected. Some isolated convection is possible this afternoon along the sea breeze resultant, but most will be inland from the coastal terminals. Fog is again possible at the end of the forecast period. EXTENDED OUTLOOK...Chance for SHRA/TEMPO MVFR Sunday. Chance for SHRA/TSRA Tue through Wed. Otherwise expect VFR. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 1230 PM Saturday...NE winds are in the 10-15 kt range near/north of Cape Fear, but 10 kt or less to the south. Except for adding the development of a weak seabreeze this afternoon, no significant changes were made to the wind forecast. Seas are coming in about 1 foot lower than forecast across the board. The 11 second swell from Tropical Storm Karl may be a little smaller than models indicated. I have adjusted sea heights down a little through tonight. The last of the showers are ending now and dry weather is expected through tonight. Discussion from 600 AM follows... Weak ridging will develop today ahead of an approaching backdoor cold front which is expected to move slowly through the area on Sun. Isolated to scattered showers are expected to dwindle and come to an end this morning. Winds will be from the NNE or NE at 10 to 15 kt. Seas will remain 2 to 4 ft with most of the 4 ft seas near Frying Pan Shoals. A robust 10 to 12 second easterly swell will be present. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...A backdoor cold front will move slowly across the waters on Sun. NE to ENE winds Sun and Sun night will be up to 15 to 20 kt. Seas will be mainly 3 to 4 ft with some 5 ft seas across the outermost northern waters. High pressure ridging across the waters from the N is expected to push eastward and with that, winds should veer from E Mon morning to ESE or SE. Wind speeds should be no higher than 10 to 15 kt. Swell energy is expected to weaken Mon and Mon night and seas should drop about a foot. LONG TERM /TUESDAY THROUGH WEDNESDAY/... As of 300 AM Saturday...Slow moving cold front will be the primary weather concern through mid-week as it drags NW to SE across the area. Ahead of this boundary, broad high pressure will create light E/SE winds over the waters, with the direction slowly veering to the SW and eventually N as FROPA is slated by Wednesday morning. Speeds will remain light much of Wednesday before a NE surge develops late in the period, increasing winds to 10-15 kts. Although wind speeds will create only limited amplitude in any wind-wave groups until a NE 4 sec wave develops late, continuing 10-12 sec swell from distant tropical systems will allow seas to persist at 2-4 ft through the period.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...RJD/TRA SHORT TERM...RJD LONG TERM...JDW AVIATION...DL

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