Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 250818 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 418 AM EDT Tue Apr 25 2017 .SYNOPSIS...
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A complex and slow moving storm system, nearly overhead this morning, will finally and slowly lift NE, away from the forecast area this afternoon and continuing thru the mid-week period. Look for improving conditions, albeit slow today, but by Wednesday thru Thursday sunshine and summerlike temperatures will become the norm. A weak cold front will dissipate as it moves across the area Thu night with an isolated shower possible. This will be followed with expanding high pressure aloft and at the surface, that will continue the summer-like warm and dry conditions for Friday thru the upcoming weekend. A few locations away from the immediate coast, may break the 90 degree barrier.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 330 AM Tuesday...Upper low and its surface reflection will continue to drift slowly but inexorably to the NE, and while today will be much drier than Monday, low clouds and showers will hang on much of the day. Upper low clearly evident on IR this morning is directly overhead the Grand Strand of SC, while the surface low is demarcated by a triple point just east of Little River Inlet. This vertically stacked system will move NE to be near the Outer Banks tonight before finally lifting towards New England late. Best moisture will remain offshore the local area, with moisture tap confined to the Crystal Coast and Outer Banks after sunrise. However, column moisture will remain high, and with a cold pool of around -17C overhead this aftn, steep lapse rates will drive showers with isolated tstms across the region. Widespread low cloudiness will take a long time to erode, so temps will only rise into the upper 60s to low 70s, warmest S and E portions, but this will be enough to create instability this aftn. Typically with a setup such as this, brief small hail is possible, but forecast soundings suggest simply moist adiabatic LR`s up through about 600mb with rapidly drying air above the FZL, not conducive to anything other than rain. Cannot rule out some small hail this aftn, but that will be the exception rather than the rule. As the stacked system moves NE tonight, drier air will finally advect from SW to NE through the CWA. Do not anticipate this will occur much before dark, but we may see stars tonight, especially inland. The ground remains moist however, so as temps fall towards mins in the upper 50s, fog may develop late.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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As of 330 AM Tuesday...At the start of this period, the nemesis closed low aloft, off the DELMARVA Coast, will continue to fill in as it tracks to the northeast, further away from the forecast area. It`s corresponding, captured sfc low, will also be weakening during this time-frame. Overall, in their wake, the ILM CWA will commence an extended "drying out out" period. Weak s/w ridging aloft will affect the FA thru Thu night. It`s upper ridge axis will lie overhead Thu morning, moving off the Carolina coasts by Fri daybreak. A rather expansive upper trof will have taken shape across the central U.S. by Fri morning. At the sfc, weak cyclonic NW flow will dominate the FA early Wed until the upper/sfc lows move far enough away. By late Wed thru daybreak Fri, sfc ridging from Bermuda High pressure centered well east of Florida, will extend WNW and onshore in the vicinity or south of Cape Romain, SC. Enough moisture in the low levels will be avbl for diurnally driven cu fields each day. Enough subsidence aloft will prevent the cu from growing too much in the vertical, resulting in no POPs being advertised Wed thru sunset Thu. A fading cold front will push across the FA from the west late Thu night. The front will be displaced a good distance from it`s parent low as it traverses the ILM CWA. Other than frontal dynamics, not much forcing is left for pcpn development. As a result, will include low chance pops for showers and possibly an isolated tstorm Thu night if enough instability becomes avbl. A low level SW jet will develop during Thu night into early Fri. This will keep winds active enough at the sfc to prevent widespread fog but also keep min temps on the high side. Summer time temperatures will be back across the FA with widespread max temps in the low to mid 80s Wed and mid to upper 80s Thu. Min temps will follow the general trend and run in the low 60s Wed night and the mid to upper 60s Thu night. This a consensus amongst the avbl model mos guidance. This fcst has temps that will run 10 to 15 degrees above normal by the end of this period. Normal lows/highs are in the low to mid 50s and the upper 70s respectively.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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As of 3 PM Monday...Medium range guidance is fairly consistent with regards to the extended forecast. Longwave troughing will be in place out west with a cutoff low eventually developing with a southwest flow and strong ridging developing just off the southeast coast. At the surface it will be primarily high pressure anchored offshore. A weak front will fade away as it moves across the FA early Fri leaving a continued dry forecast. Temperature trends remain mostly intact well above normal throughout the period but moreso first half as heights fall slightly late in the period.
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&& .AVIATION /07Z TUESDAY THROUGH SATURDAY/...
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As of 06Z...Low confidence forecast as a weak low pressure moving across the coast will create varying cigs and IFR along with periods of showers. Weak low nearly due east of CRE will meander to the NE through the overnight before lifting away slowly during Tuesday. On the north side of this surface low, a warm front is pushing NW and inland from the coast, while a cold front moves offshore and a secondary surface trough pushes SE off the SC coast. The inland terminals are locked into IFR cigs and expect IFR/LIFR to persist into Tuesday morning. The forecast is trickier at the coast where breaks in cigs are expected until the low pulls away and the IFR can flood back towards ILM/CRE/MYR. However, as cigs break, fog is likely to quickly develop, so periods of IFR are also expected at the coastal terminals, with LIFR/VLIFR possible due to the very saturated surface. Additionally, periods of showers, some of which may be briefly heavy, are expected overnight at all terminals. Winds will remain northerly most of the night at speeds 10 kts or less. After daybreak, surface low will slowly pull away but cool northerly flow will keep stratus entrenched with only a slow lift to MVFR Tuesday night. Still quite a bit of uncertainty into how quickly cigs will lift as dry air tries to advect into the region, and have been pessimistic with the ceiling forecast. Showers and isolated tstms are also possible during the aftn/eve creating periods of MVFR or IFR vsbys. Late in this valid period VFR is expected to develop at all terminals as cigs finally erode, with any fog development likely after 06Z on Wednesday. Extended outlook...IFR or lower conditions possible in fog and stratus Tue night and early Wed. VFR Thursday through Saturday.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 330 AM Tuesday...Low pressure just off the Grand Strand will spin slowly off to the NE today. As this surface feature pulls away, winds will become predominantly S/SW and increase back towards 15-20 kts before slowly veering to the West, and then NW tonight, while easing to around 10 kts. Seas remain high this morning thanks to a variety of wave groups, and the SCA has been extended for the NC waters through late this aftn, while expiring in the next few hours across the SC waters. Seas recently at 41013 were still near 9 ft, and 7 ft at 41004. Expect these to gradually ease through today, becoming a more uniform 3-5 ft this evening, and 2-4 ft tonight, as both the SE swell and SW wind wave begin to decay in amplitude. SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 330 AM Tuesday...Improving seas and winds will continue from where the near term left off as the last affects from the departing upper and sfc lows occur early Wed with diminishing NW flow and a transition to light SSE to SSW flow by late Wed and continuing thru Thu night. This a result of sfc ridging, from Bermuda high pressure located well offshore and east of Florida, extending WNW and onshore in the vicinity of Cape Romain by and thru Thu. Wind speeds around 10 kt Wed, with 10 to 15 kt near shore Wed aftn/evening due to a weak sea breeze. Wind speeds Thu will run 10 to 15 kt, except 10-20 kt near shore Thu aftn/evening due to a moderate sea breeze. The ESE ground swell at 8 to 9 second periods, will dominate the seas spectrum Wed and for much of Thu. A low level SW jet Thu night will keep winds active thru the night resulting in 3 to 5 second period wind waves becoming more dominate. LONG TERM /FRIDAY THROUGH SATURDAY/... As of 3 PM Monday...Essentially a summertime pattern for the coastal waters as ridging from Bermuda High pressure affects the area waters thruout this time frame. South to southeast winds of 10-15 knots will prevail Friday through Saturday. Significant seas will be 2-4 feet.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...None. NC...None. MARINE...Small Craft Advisory until 8 AM EDT this morning for AMZ250- 252-254-256.
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&& $$ SYNOPSIS...DCH NEAR TERM...JDW SHORT TERM...DCH LONG TERM...MBB AVIATION...JDW

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