Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 231803 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 203 PM EDT Fri Jun 23 2017 .SYNOPSIS... Bermuda High pressure will build westward over the Eastern Carolinas through today. The remnants of Cindy moving up from the Gulf coast will get absorbed into a cold front marching east reaching the Carolinas Saturday with an increasing chance of showers and thunderstorms heading through the weekend. This cold front will reach the coast by Sunday but will not get pushed completely out of the area until a second front sweeps through by Tuesday. Dry High pressure will build in through the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... As of 945 AM Friday...At the moment, the KLTX 88D is echo free across the ILM CWA. It will likely be short-lived, current insolation is reaching the sfc allowing instability to quickly increase. PWs are 2 inches and hier across the FA complements of the Tropical/Subtropical ridging extending NW from off the Southeast U.S. Coast but will have some mid-level drying that pivots across the FA later today and tonight. Widespread synoptic forcing will be lacking for convection to either get started or to steadily/continually develop. Will have to rely on the mesoscale induced resultant wind bndry, aka the sea breeze, with SW-WSW winds backing to the SSW. The sea breeze will likely remain pinned close to the immediate coast given the winds within the lower atm column, from sfc-700mb, remaining quite active SW-WSW at 20-30 kt. Not looking at widespread convection but pcpn that does occur will primarily be quick heavy rain producers with storm motions progged at NE at 20-25 mph. Previous.................................................... As of 300 AM Friday...An area of pcp will just miss our local forecast area to the west early this morning but plenty of deep layer moisture continues. A southwest flow around 5 mph or so should keep fog out of the forecast but expect some low clouds around especially inland through daybreak. The Atlantic ridge extending back westward over the Southeast coast will provide a drier upstream flow as compared to the plentiful moisture we saw from Cindy the last several days. Water Vapor imagery shows drier air in the mid to upper levels working its way northward toward the Carolinas. Therefore expect the overcast mid to high level deck of clouds to break up today leaving increasing sunshine through this afternoon. The gradient will tighten as the remnant low of Cindy moves up ahead of a cold front which will be approaching the Carolinas from the west tonight. This will produce gusty S-SW winds through today, especially along the coast in the afternoon sea breeze. Expect some cu development along the sea breeze front as it pushes inland and have included mainly isolated shwrs along this boundary this afternoon. HRRR once again shows best chc along or just inland of SC coast this afternoon, but overall more isolated in coverage. A warm start to the day, with temps in the mid 70s, combined with sunshine will push temps up near 90 most places in a continued moist tropical air mass. Heat index values will reach over 100 degrees in many spots inland this afternoon. This diurnal convection will come to an end this evening with gusty winds continuing across the area. Temps will remain warm once again with lows in the mid 70s. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 300 am Friday...The upper pattern will support unsettled weather across the Carolinas this weekend as a series of shortwaves dig out a longwave trough from the Great Lakes down through the Mississippi Valley. The 500 mb subtropical ridge that has been centered off the Florida east coast for much of the week will relocate out near Bermuda Sunday as upper level heights steadily fall along the Southeast coast. Tropical Storm Cindy`s remnants will not directly affect our area, however the airmass advected in with Cindy and covering the Carolinas Saturday into Sunday should be exceptionally humid with precipitable water values expected to reach 2.1 to 2.6 inches. That will potentially reach the top 5 June PW values recorded since 1948 using the MHX/HAT data from the SPC sounding climatology webpage. At the surface, the remnant circulation of Cindy should race off the Mid-Atlantic coast around daybreak Saturday. A cold front extending from the Appalachians into central Texas will slowly move into the eastern Carolinas late Saturday night, stalling Sunday before reaching the beaches. Saturday should begin dry with some sunshine, but deeper moisture arriving during the afternoon will intercept an unstable atmosphere with CAPE 1500-2500 J/kg. Scattered showers and storms should develop along and west of the seabreeze front. Along with plenty of lightning due to large CAPE up in the -10C to -30C region aloft, the strongest of these storms could also produce wet microbursts. Storms should remain only loosely organized due to weak environmental shear. The most serious weather might occur Saturday night as what`s left of Cindy`s gulf inflow jet moves across the eastern Carolinas. This is when the GFS and NAM both show excessive precipitable water values present, and indicate a larger proportion of environmental CAPE moving down below the freezing level which favors efficient coalescence raindrop growth processes that can produce excessive rainfall rates. I`ve beefed up wording in the forecast to mention "heavy rain" possible Saturday night. Still too much uncertainty with coverage and duration to issue any flood watch products. With the front stalled near the coast Sunday another round of scattered showers and storms should develop during the day. Precipitable water values should return to "normal" wet-summer conditions around 2.0 inches. As the longwave trough takes shape to our west Sunday night, increasingly westerly wind directions should begin to advect drier air into the Carolinas, leading to a reduction in precipitable water values and eventually pushing the stalled cold front off the coast late Sunday night. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 300 PM Thursday...Cold front will be stalled along the coast Monday before being pushed offshore and out of the area by Tuesday. The stalled boundary combined with deep SW flow aloft and residual moisture from the departing remnants of TS Cindy will create a good chance for showers and thunderstorms the into Monday. The GFS has been consistent with widespread activity mainly near or along the coast on Monday, and now the latest ECM/CMC have trended in that direction as well. PWATs fall on Monday from west to east, so the highest POP will be at the coast on Monday, but an unsettled period is expected until a secondary front beneath an anomalously deep trough clears everything out by Tuesday. This secondary front will usher in much cooler air for the remainder of the period. 850mb temps crash towards +10C, near the bottom 10th percentile for late June, and highs will likely remain at least 5 degrees below climo Tue/Wed with dewpoints potentially falling into the 50s! This will feel quite refreshing, especially after the high humidity of Sunday. By Thursday the surface high shifts offshore and height rises begin again, so temps and humidity will increase, but remain below seasonable norms into late week. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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As of 18Z...For the remainder of this aftn and evening, NVA and Subsidence aloft will keep convection from firing and/or developing. The pinned sea breeze may have enough forcing to overcome the subsidence aloft and result in isolated convection. Once the days insolation ceases, so will the threat for any tstrm formation. Have indicated thunderstorm threat by midday Sat as upper levels become more conducive for convection chances ie. no longer debilitating NVA present overhead. The sfc pg will remain tightened this aftn thru tonight and well into daytime Sat. The inland terminals will see SW-WSW 10g15 kt thru this period with the exception of possibly going SSW 10g15kt this evening. The coastal terminals will run SSW-SW 10-15g20+ kt this aftn thru tonight and likely continuing thru midday Sat. Extended Outlook...Local MVFR/IFR conditions are possible in thunderstorms Saturday afternoon through Sunday afternoon. Thunderstorms are anticipated to be most widespread Saturday evening thru the overnight.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 945 AM Friday...Marine conditions will slowly erode today, reaching SCEC conditions during this evening, and further erode to SCA conditions after midnight tonight. This a result of the sfc pg, having already tightened, is progged to further tighten ahead of a cold front that will drop southeast to the western Carolinas late tonight. At the same time, the Cindy remnants, will move along this cold front, reaching the DELMARVA coast Sat morning. Wind directions will run SSW-SW at 10 to 20 kt speeds thru this evening and veer slightly to SW-WSW at 15 to 25 kt speeds by and/or after midnight tonight. Wind driven waves at 3 to 5 second periods will dominate the significant seas. Moderate to strong longshore currents will become apparent, especially south of Cape Fear to Murrells Inlet. Previous...................................................... As of 300 AM Friday...Atlantic ridge reaching back westward into the Southeast coastal waters will maintain a S to SW flow over the local waters through tonight. The remnant low from Cindy moving up from the western Gulf coast will combine with a cold front marching east toward the Carolinas, tightening the gradient flow through today. Therefore expect increasing southerly flow from 10 to 15 kts up to 15 to 20 kts through this afternoon into tonight. Expect especially gusty winds near the coast in afternoon sea breeze. This persistent southerly flow will push seas up from 2 to 4 ft early to 3 to 5 ft by midnight and increasing further to 4 to 6 ft overnight into early Saturday. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 300 AM Friday...The remnants of former Tropical Storm Cindy will race off the Mid-Atlantic coast Saturday morning just ahead of a cold front advancing toward the East Coast. This front will slow as it moves into the Carolinas Saturday night, stalling just inland from the beaches Sunday. Several waves of thunderstorms are expected to develop across the area, especially Saturday Night and again Sunday afternoon. The front should finally begin to move out across the coastal waters very late Sunday night with winds shifting to the north. Breezy conditions are expected Saturday into Saturday evening as the pressure gradient should tighten between Bermuda High pressure offshore and the cold front approaching from the west. Add the seabreeze in and wind gusts could easily exceed 25 knots Saturday afternoon. A Small Craft Advisory will remain in effect through Saturday night for these winds and seas in the 4-6 foot range. LONG TERM /MONDAY THROUGH TUESDAY/... As of 300 PM Thursday...Stalled cold front along coast will waver in the vicinity Monday before a secondary front pushes everything out to sea and clears the waters on Tuesday. Winds will fluctuate between S to the east of front and W behind it on Monday, but the weak gradient immediately near the front will keep winds at 10 kts or less regardless of direction. As the second front kicks everything off to the east on Tuesday, winds will become northerly, with speeds around 10 kts. A 2 ft/8sec SE swell will exist in the spectrum each day, and thanks to light winds on Mon, it will likely be the predominant wave group despite a present S/SW wind-wave. Seas will be 2-3 ft most of Mon, and then fall further to 1-2 ft Tuesday as the winds turn offshore. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Beach Hazards Statement until 8 PM EDT this evening for SCZ054- 056. NC...Beach Hazards Statement until 8 PM EDT this evening for NCZ106- 108. MARINE...Small Craft Advisory from midnight tonight to 6 AM EDT Sunday for AMZ250-252-254-256. && $$ SYNOPSIS...RGZ NEAR TERM...DCH/RGZ SHORT TERM...TRA LONG TERM...JDW AVIATION...DCH is the U.S. government's official web portal to all federal, state and local government web resources and services.