Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201947 AFDILM Area Forecast Discussion...COR National Weather Service Wilmington NC 333 PM EDT FRI MAY 20 2016 .SYNOPSIS... A weak storm system will bring showers and isolated thunderstorms tonight. More thunderstorms are possible ahead of a cold front Saturday afternoon and evening. An upper low will keep conditions cool with a slight chance for showers through Monday. More summer like weather develops by the middle of next week with above normal temperatures and drier conditions. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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As of 300 PM Friday...Penny and nickel rain amounts will transition to dimes and quarters overnight...as a stationary frontal boundary straddled east to west across southern SC and central GA lifts north as a warm front overnight and early SAT. Satellite derived precipitable water sensors reveal 1.7 - 1.9" along and in proximity of the boundary presently. The bulk of rainfall associated with the offshore coastal trough will fall into the ocean but coastal zones should receive some contribution bleeding off this feature given the stout low-LVL easterly flow per recent KLTX VWP scans and time height plot forecasts into this evening...and weak upglide. Overall it appears 0.50 - 0.75" of rainfall on average will descend on NE SC and SE NC now through Saturday morning...equally distributed for the most part as 2 features (upper disturbance to the W and coastal trough E) impact our eastern and western halves...and a broader encompassing warm frontal passage as the 3rd trigger. While a rumble of thunder may grumble overnight no severe threats are expected since column winds and shear parameters are weak through the near term period. Surface dewpoints are on their way up and this will maintain elevated minimum temperatures overnight...63-69 mildest near the sea.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... As of 300 PM Friday...Primary headline here is a marginal risk of severe TSTMS Saturday afternoon ahead of the cold front. Fruition hinges on the degree of low-level heating/destablization from late morning through afternoon...which is contingent upon getting cloud breaks and warming up the ground. Plenty low-level moisture will still be in place so this may not be an easy task and much if not all of the morning should feature considerable cloudiness. Because of the timing of the frontal passage Saturday night...the zone of frontal convergence may not be a player except possibly west of I- 95. If the warm sector can reload however then the coupling of DCAPE and modest Bulk Shear values could lead to a few severes. The continued drying trend will take its toll on convective coverage and strength into Saturday night and dwindling POP values played. Sunday a cold pool aloft will slip off the mid- atlantic coast. Lapse rates are highest north of us but enough instability should trip off showers in scattered to isolated fashion Sunday under a partly sunny dome. The coolest portion of the period is Monday morning in the 50s...the mildest Saturday afternoon reaching around 80. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday...Yet another closed upper low will plague the east coast early next week...but fortunately will get kicked out to the northeast by Tuesday. Residual lowered heights will exist Tuesday...but late Tuesday and Wednesday ridging blossoms across the southeast bringing a return to more typical summertime weather through mid-week. After a chance for showers and storms beneath the upper low Monday...Tue/Wed should be dry with more seasonable temperatures. A brief return to increased POP is forecast Thursday as a shortwave races across the mid-atlantic bringing some mid-level forcing and slightly lower heights in an otherwise warm and increasingly humid airmass. Thunderstorms will be possible Thursday before ridging increases even more significantly late in the period. This will bring a return to drier and potentially above normal temps leading into the Memorial Day weekend. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... As of 18Z...High pressure extends down through the Carolinas from the north as coastal trough remains off the coast. Coastal trough/warm front will lift north through tonight as low pressure moves north. This will produce a shift in winds from E-NE to E-SE through this evening and eventually more SW behind warm front through early tomorrow morning. Overrunning type precip is expected through much of the day as warm air out of the south overruns the cooler NE-E flow. Periods of heavier rain and some fog overnight will will reduce visibilities and lower ceilings to IFR levels. As low pressure lifts off to the northeast Sat morning, IFR will transition to MVFR conditions. Expect MVFR/VFR by Sat aftn. Extended Outlook...Expect MVFR/VFR Sat aftn with periods of IFR in any isolated thunderstorms. Shwrs/tstms on Sat decrease with improvement to VFR on Sunday through the end of the extended period. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 300 PM Friday...An exercise caution headline will need to remain posted for 15-20 kt winds and 4-5 foot seas. This headline will likely be removed tonight sometime as winds ease...either prior to warm frontal passage or into daybreak...because even the S-SSW windspeeds behind the warm front could remain frisky and extend the SCEC. Spectrum analysis shows the dominant energy will be SE waves 3 to 5 feet every 7 seconds co-mingled with a NE wave 1-2 feet every 5 to 6 seconds. Showers and isolated TSTMS will reduce VSBYs at times tonight below 2 NM. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 300 PM Friday...Although no advisories are expected sea heights will run 3-4 feet Saturday with visibility restricting rain in the morning. Dominant wave periods will run between 7-9 seconds so the wave faces will not be extraordinarily steep. During the afternoon a few TSTMS could move off land over the 0-20 NM waters...and some could be strong to severe. A wind shift to W and NW will occur late Saturday night as cold front crosses the waters. An improved marine environment Sunday as winds become offshore W-NW and knock down near shore chop. Gusts to 20 KT from the NW can be expected Sunday...and sea heights will be 3-4 feet offshore and 1-2 feet inshore. Isolated showers or a TSTM will be in the mix but they will remain widely separated and favored mostly over the NC waters. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...High pressure expanding towards the waters will create W/NW winds Monday...of 10-15 kts early and just 5-10 kts late thanks to the diffuse pressure gradient. On Tuesday...this high will move offshore and then expand off the coast creating persistent SW winds around 10 kts Tuesday...and 10-15 kts Wednesday. Seas will be 1-3 ft Monday...with the offshore flow producing 0-1 ft near shore. Sea heights will become more uniform Tue/Wed as a SE swell and southerly wind wave drive the spectrum. Wave heights will be around 2 ft Tuesday...and 2-3 ft on Wednesday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...MJC SHORT TERM...MJC LONG TERM...JDW AVIATION...RGZ MARINE...MJC/JDW

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