Area Forecast Discussion
Issued by NWS Wilmington, NC

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948 FXUS62 KILM 220258 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1058 PM EDT Wed Jun 21 2017 .SYNOPSIS... Tropical moisture will lessen across the area which will result in fewer showers and thunderstorms through Friday. The remnants of Tropical Storm Cindy should reach the southern Appalachians Friday night with its associated moisture increasing the risk for showers and thunderstorms Saturday. A cold front will stall in close proximity Sunday and Monday. Finally, the cold front will move offshore, bringing cooler and much drier air into the area Tuesday and Wednesday. && .NEAR TERM /THROUGH THURSDAY/...
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As of 10 PM Wednesday...Some tweaking applied to the current fcsts. Lowered POPs along the northern periphery of the ILM CWA for the remainder of the overnight but continued with a low chance across southern portions of the ILM CWA. Applied some hourly tweaks to the temps/dewpoints based on current trends and 1st look of 00Z Data. Previous........................................................ As of 3 PM Wednesday...Transition to a weak zonal flow aloft with little to no upper support appears in the cards overnight. There may be developing convection tonight over the waters as the nocturnal buoyancy ramps up, or as a weak land breeze forms, but the steering flow will prevent them from reaching onshore. As a result am debating scaling back POP values below mentionable values overnight, at best isolated. Another observations is the precipitable water decrease overnight. Thursday appears quiet overall, plentiful high clouds may dampen surface heating, limiting convective generated rain. Saturation aloft may lead to a few drops from mid-level clouds, but chance of measurable rainfall Thursday appears to remain low-end. H6-H4 omega however warrants a slight chance of rain and this may be stratiform in nature. Very low QPF numbers this time period.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...High pressure aloft, centered offshore of the east coast of FL at the start of the period will help guide Tropical Storm Cindy northward and eventually into the stronger westerlies where it will weaken. Cindy will get intermingled with a frontal boundary with the remnants of Cindy expected to move into the southern Appalachians Fri night. The circulation associated with Cindy is expected to mop up much of the deep moisture that has been streaming across the Carolinas from the Gulf of Mexico in the last several days. Precipitable water values are finally expected to be on a downward path from near 2 inches Thu eve to near 1.5 inches on Fri and Fri night. Some ridging will also help to suppress convection during this time and will carry slight chance/small chance for showers and thunderstorms Thu night and Fri and then keep POPs below threshold Fri night, although organized convection should be just upstream of I-95 by daybreak Sat. Nocturnal jetting is evident both nights, strongest Fri night as the pressure gradient tightens up ahead of the remnants of Cindy and the approaching trough. Wind speeds about 1500 ft up will be up to 25 to 35 kt Fri night. Model profiles show a distinct subsidence inversion and would not be surprised to see a good amount of nighttime stratus develop and this is something the models are hinting at. Nighttime winds should be elevated, especially Fri night and lows during this time will be above normal, low and mid 70s Thu night and mid and upper 70s Fri night. A warm and humid day is expected Fri with highs in the upper 80s and lower 90s. It will be breezy on Fri, especially at the coast where the seabreeze circulation will push wind speeds up to 20 to 25 mph during the afternoon. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 300 PM Wednesday...Potentially very unsettled through the period but lots of uncertainty exists even in the first part of the extended. Remnant mid-level vorticity from TS Cindy will be ejecting east across the Carolinas during Saturday. This feature will be accompanied by a weak surface low, likely moving near the NC/VA border, and will bring a surge in PWAT due to the tropical origin of the remnants. This will likely bring showers and tstms with periods of heavy rainfall through Saturday before the trailing cold front moves offshore. The caveat to this is that while the front tries to push east, the mid-level pattern features an amplification of the ridge across the east, thus slowing and stalling the front. Where this front stalls will be key to the Sun/Mon forecast. The GFS stalls this front along the coast with continued showers and storms due to deep SW flow and overrunning, and potentially secondary low development. The ECM/CMC push the front far enough offshore to create dry weather the latter half of the wknd. Climatologically the stalled boundary makes sense, and is supported by WPC progs, so will maintain the inherited unsettled forecast into early next week with temps cooling to below climo after a very warm Saturday. Anomalously deep longwave trough then digs into the east clearing the front and bringing much cooler temperatures to the region. 850mb temps may drop towards 10C by the middle of next week, which is below the 10th percentile for late June, suggesting highs and lows several degrees below climo along with a much drier and refreshing airmass. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... As of 00Z...Insolation reaching the sfc has been kept at bay from the blanket of mid and upper level clouds. As a result, only expect vcnty shra early this evening. Otherwise, the next shot of MVFR/IFR will occur between 08Z and 14Z from low ceilings. Model MOS Guidance continues to show sub 1k foot ceilings during this time-line and see no reason to detour from it`s prognosis. Winds will drop off to calm conditions at times which brings up the possibility of fog and how much of it. For now, will stick with the low stratus or stratus fractus ceilings. For daytime Thu, the area terminals will be under the veil of mid and upper level clouds basically the exhaust clouds from Cindy. Any insolation that makes it to the sfc, will be enough for a SCT/BKN Cu deck in the 2.5k to 5.0k foot range during Thu aftn/eve. Will also indicate VCSH after 1900Z for all terminals. Forcing mechanisms will remain lackluster for convection initiation but enough to atleast have vcnty shra. Extended Outlook...MVFR ceilings/vsbys Saturday as tropical moisture associated with Cindy remnants traverse the region. Patchy fog and low ceilings possible 08z-13z Friday. && .MARINE...
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NEAR TERM /THROUGH THURSDAY/... As of 10 PM Wednesday...Stalled sfc boundary still evident across the southern ILM Waters. This should eventually dissipate altogether overnight. Wind speeds generally 10 kt or less for the overnight. Will indicate wind directions SSW-SW or becoming SSW-SW as sfc ridging from the well offshore centered Bermuda high becomes dominant. Significant seas will run 2 to 3 ft overnight thru Thu. A SSE pseudo-swell at periods of 6 to 7 seconds will dominate. Previous................................................ As of 3 PM Wednesday...A manageable marine environment tonight and Thursday, essentially SW winds 10-15 KT and seas around 3 feet. The wave energy will be primarily from the S every 6-7 seconds mixed with very weak ESE swell of a foot or less. Isolated to scattered showers are possible overnight, with only a slight chance of a TSTM, mainly favored near or over the Gulf Stream. A changing steering flow aloft will guide any showers or storms developing over the waters farther offshore versus onshore. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...Winds will strengthen as we progress from Thu night into Fri night as the pressure gradient tightens between the approaching remnants of Cindy, crossing the southern Appalachians Fri night, and the Bermuda High centered offshore. Nocturnal jetting is evident both nights. We will likely reach Small Craft Advisory thresholds late in the day Fri and Fri night. Wind speeds will be increasing to 10 to 15 kt Thu night, 15 to 20 kt Fri and up to 20 to 25 kt Fri night. The direction will be SW. Seas will build to 3 to 4 ft Thu night, 4 to 5 kt Fri and 4 to 6 ft Fri night. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Tuesday...High pressure offshore will gradually retreat as a cold front approaches from the west. Ahead of this front, a weak wave of low pressure, the remnants of TS Cindy, will move near the area bringing showers and storms to the waters Saturday. Additionally, as the gradient pinches ahead of the front, SW winds will increase to 15-25 kts, building seas to 4-6 ft, and an SCA will likely be needed much of Saturday. Thereafter, the front will waver in the vicinity Sunday and Monday before finally pushing offshore late in the period. This will create a weaker gradient and wind speeds around 10 kts, with direction varying from S to W at times. After the seas fall below SCA thresholds Saturday night, they will continue to drop to just 2-3 ft late Sunday and remain at these amplitudes on Monday.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...DCH/MJC SHORT TERM...RJD LONG TERM...JDW AVIATION...DCH

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