Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201958 CCA AFDILM Area Forecast Discussion...CORRECTED National Weather Service Wilmington NC 358 PM EDT Sat May 20 2017 .SYNOPSIS...
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Influence of Bermuda High will start to weaken as a cold front approaches from the west. Showers and thunderstorms will begin to increase Sunday ahead of a cold front that will move in from the west on Monday. Showers and thunderstorms will continue through the middle of the week as the front lingers in the region before a second cold front moves into the area later Thursday. High pressure will bring a drying trend for the end of the week.
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&& .NEAR TERM /THROUGH SUNDAY/... As of 3 PM Saturday...Convergence along a surface boundary was becoming evident in visible data as cumulus begins to congest along it. Showers and few storms may fire along this feature later this afternoon and if so, will drop south and approach Pender and Bladen counties. Diurnal cooling and the dry air aloft into which they are moving will likely kill or weaken any convection by 7pm however and only slight chances were painted in along the northern tier of SE NC. The actual frontal boundary will surge southward over the area late tonight and bring winds from NE-E across the forecast area. As this occurs the dry air aloft maintains its hold and only isolated rain chances are being advertised and this may even be a stretch. Slightly better rain chances occur late Sunday as a cold front richer in column moisture approaches from the west. As it nears late Sunday, it will pull the old weak boundary northward and this may serve as a focus mechanism potentially intersecting the sea breeze boundary. Although the highest POP values approach from west to east late Sunday, a mentionable value was place across much of the area by Sunday mid-afternoon. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 3 PM Saturday...Stalled front will be lingering just north of the area as the period begins. Expect there will be some waning sea breeze/diurnal convection Sun evening with more robust storms west of the forecast area, along the slowly advancing cold front. Some of the activity associated with the front may spread over western areas late Sun night, however there are a few negating factors. Low level stability and dry air below 12k ft being the biggest. Also the front`s movement is rather slow with low level convergence being weak and strongest forcing aloft is still west of the area at this time. Will carry low chc pop for western areas with slight chance farther east. Front moves into the region Mon, accompanied by deep moisture and forcing. Forecast precipitable water values exceed 2 inches as deep southwest flow spreads abundant moisture over the region Mon afternoon. All traces of mid level ridging will be gone as broad 5h troughing moves over the region. Surface front ends up laying parallel to flow aloft later Mon and the front ends up stalled in the region Mon night. Weak surface wave develops in GA along the front late Mon. This wave lifts northeast Mon night, resulting in an increase in precip chances late in the period. Best rainfall chances will be Mon afternoon when diurnal heating, surface/frontal convergence and support aloft are present. There is some potential for very heavy rain with the deepest convection. Warm cloud layer depth approaches 12k ft and storm motions of 10 to 13 kt suggest there could be some urban rainfall issues if the heaviest, slow moving storms pass over more urbanized areas. High temps on Mon will be near climo given the abundance of cloud cover and the anticipation of widespread rainfall. Lows will run well above climo mostly due to increased low level moisture and cloud cover. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 3 PM Saturday...Southwesterly vorticity-laden flow in place on Tuesday while a weak surface boundary drops into the region. Showers and thunderstorms should spread west to east across the area, becoming more numerous than previously anticipated. Low level wind fields are also stronger than previously progged but this may be related to some apparent convective feedback in guidance, especially the GFS. Assuming this is correct the severe weather threat appears minimal. The next batch of shortwave energy crosses on Wednesday, which should also shape up to be an active day of showers and thunderstorms. The previously anticipated minor severe threat is complicated by the GFS pushing the surface front south of the area. Should the area remain in the warm sector as anticipated then storms could approach severe criteria with damaging winds likely the main threat. The main trough axis swings through either Thursday or Thursday night and this should herald the trend towards dry weather with lower humidity and cooler temperatures especially at night. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... As of 18Z Saturday...VFR initially with FEW-SCT040 til 00z then mainly SKC through evening. Late tonight a weak cold front will drop southward over SE NC. AFT 04z winds become E-NE 9 KT or less as weak front drops south. Air aloft still dry so little to no PCPN expected. Weak isentropic lift and thin low level saturation will result in IFR cigs into pre-dawn hours. AFT 14-15Z CIGS rising to MVFR with VCSH. Extended Outlook...Reduced flight categories will be possible in periodic showers and thunderstorms Sunday afternoon through Monday, and again on Wednesday. && .MARINE... NEAR TERM /THROUGH SUNDAY/... As of 3 PM Saturday...A weak front will drop south late tonight into early Sunday...bringing a light wind-shift to N-NE over night and mainly E on Sunday becoming SE. The front and pressure fields are weak with the front and winds will remain well below advisory speeds. Sea heights overall will not change a great deal either, mainly just the direction of the chop and the fresh wind waves. It is possible a few showers may move off land and across the inshore waters of Pender county late today or this evening but coverage if any should remain minimal, but a radar check before heading out would not be a bad idea. Sunday an E wind 15 KT or less will become SE 10-15 KT as a weak boundary lifts north and a stronger front approaches from the west. Seas will not change much, holding essentially in a 2-3 foot range. SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 3 PM Saturday...Bermuda High will start retreating east as cold front to the west slowly moves east. This will maintain southerly flow through the period, with the front expected to stall along the coast late Mon or Mon night. Increased gradient will lead to a steady increase in south to southwest flow Sun night and Mon. Surface boundary moves into the area late Mon before stalling along or just off the coast. This helps weaken the gradient late in the period with speeds dropping from a solid 15 kt Mon evening to under 10 kt late Mon night. Seas 2 to 3 ft Sun night build to 3 ft Mon and 3 to 4 ft Mon night. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 3 PM Saturday...Cold front slated to approach Tuesday while a large area of high pressure remains off the coast. Previously there was not to be an area of low pressure along the boundary to strengthen the wind fields and this is still likely though some guidance supports otherwise. The absence of the low should stave off advisory level winds/seas until Wednesday as previously anticipated but Tuesday deterioration not impossible at this point. Cold front approaches Thursday veering the flow and perhaps knocking about 5kt off the wind speeds. These two factors will allow for advisory to be dropped though SCEC may be needed. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...MJC SHORT TERM...III LONG TERM...MBB AVIATION...MJC is the U.S. government's official web portal to all federal, state and local government web resources and services.