Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 232345 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 745 PM EDT Wed Aug 23 2017 .SYNOPSIS...
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An approaching cold front will bring thunderstorms tonight through Thursday, some of which may be strong. Canadian high pressure will bring an early fall feel Friday and through the weekend. We will be watching the tropics for possible development of low pressure off the Southeast coast early next week.
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&& .NEAR TERM /THROUGH THURSDAY/...
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As of 730 PM Wednesday...A synoptic cold front across central North Carolina extends from Greenville, NC to Fayetteville to near Charlotte and is dropping southward. A large cluster of thunderstorms has developed just ahead of the boundary, taking advantage of uncapped surface-based CAPE of 2500 J/kg. Precipitable water values near 2.0 inches normally doesn`t coexist with large DCAPE values, but in this case just large enough temp-dewpoint spreads exist above the boundary layer to support DCAPE as large as 1300 J/kg -- leading to the gusty winds we have seen in today`s storms. A gust to 55 mph was measured at the ASOS in Lumberton, NC, and trees were blown down in Dillon, SC. Evolution of this event through the evening is shown very well on the last few HRRR runs as well as the 18Z NAM. A massed-line of storms should work down into Wilmington and the Cape Fear region by late evening, joined by scattered showers and storms across the Myrtle Beach area. One weak upper level vort max is supporting our current storms, but a second vort digging across eastern Tennessee and western North Carolina later tonight may begin to back the mean flow just enough late tonight to cause activity to cease its eastward progress and hang up across the coastal waters and perhaps the coastal counties as well. On this latest update PoPs were increased to 70-100 percent for SE North Carolina, with QPF raised to 1+ inches in spots.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...Some cooler and drier air will be filtering in Thursday night from the northwest behind slow moving cold frontal boundary. A little rain may linger along the coast due to the later arrival of the drying. By Friday the front will stall just far enough south for a rain-free day as a sprawling, cool season-like 1025mb high is centered over the Great Lakes. This high will show little to no movement Friday night. The movement of the front, if any will thus be determined by any potential low pressure development off of JAX. This could also lead to a coastal increase in moisture. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 300 PM Wednesday...A stationary front will be located well offshore and S of the area Sat with an area of low pressure positioned on the front, but well offshore. High pressure will be ridging across the Carolinas from New England. The pressure gradient between these two features will keep a fairly brisk NE wind in place across the Forecast Area through the weekend. This will ensure the cool air is continually reinforced and highs during the weekend should only be in the lower to mid 80s and this will be coupled with comfortable humidity levels. Model profiles continue to be quite dry with precipitable water values below climatological normals and thus will not include any mention of a shower or thunderstorm during the weekend. This pattern looks to hold through Sun. The flow becomes more onshore and the column begins to moisten Mon and Tue. There may also be some mid- level shortwave energy impinging on the area from the SW. Will paint more in the way of cloudiness as a wedge likely sets up and introduce the potential for some showers and perhaps a thunderstorm. The probabilities for precipitation will be highest at the coast. The heat is not to be found, even early to the middle of next week with highs only in the lower to mid 80s. Lows will be in the mid 60s to near 70 through the period. As a caveat, we will be watching the tropics early next week to see if a weak disturbance is able to develop somewhere off the SE coast. Confidence in any development is very low as is its eventual track. && .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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As of 00Z...A large cluster of thunderstorms across the Coastal Plain will move east-southeast toward the coast this evening. Storms should reach the ILM and CRE airports between 02-03Z, and perhaps MYR around 04Z. Gusty winds and visibility falling to MVFR (or even briefly IFR) in heavy rainfall are expected. Current thunderstorms should move away from the FLO and LBT airports, but we are watching for showers and weaker embedded thunderstorms to redevelop and affect the interior Coastal Plain through 04Z. All this convection is the result of a cold front plowing southeastward into a hot and unstable airmass across the eastern Carolinas. The front should reach the South Carolina border early Thursday morning between 09-13Z, with winds shifting more northwesterly at the LBT, ILM, and possibly FLO airports. This could also allow IFR stratus to develop just before daybreak. Thursday afternoon`s seabreeze should turn winds back onshore, with converging low- level winds leading to another round of showers and t-storms Thursday afternoon, particularly near the coast. Extended Outlook...Showers and t-storms Thursday associated with a cold front could produce localized IFR conditions. Most showers and storms will push offshore Thursday night into Friday. MVFR ceilings could linger, especially near the coast Friday.
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&& .MARINE...
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NEAR TERM /THROUGH THURSDAY/... As of 730 PM Wednesday...A cold front currently across central North Carolina is moving southeastward and should reach Cape Fear by daybreak Thursday. Steady southwesterly winds around 15 knots ahead of the front should become disturbed by late evening as a large line of thunderstorms across the interior Coastal Plain moves out across the waters. Variable wind gusts in and near these storms should settle down to a weaker, more westerly average wind after midnight. Mariners planning to be out on the waters, especially north of Myrtle Beach, should closely watch these storms now through midnight. SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...Cold front comes through early Thursday night turning winds to the NE by midnight. The NE to E winds will last for the remainder of the period as a large area of high pressure sits centered over the Great Lakes and the front remains stalled to our south. Low pressure developing on the boundary off NE FL coast gradually should pinch the gradient and allow for a slow building of wind and seas. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Wednesday...Persistent and brisk NE winds will likely require a Small Craft Advisory for much of the period. The tightening pressure gradient will be the result of high pressure ridging down into the Carolinas from the N and an offshore front and area of low pressure. NE winds will be around 25 kt for much of the period. Seas will be 5 to 7 ft and perhaps up to 8 ft by Mon.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...TRA SHORT TERM...MBB LONG TERM...RJD AVIATION...TRA MARINE...

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