Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 190547 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 147 AM EDT Wed Jul 19 2017 .SYNOPSIS... A strong ridge of high pressure will bring the hottest temperatures of the summer season and Heat Advisories or Excessive Heat Warnings may be required late week or during the weekend. The risk for thunderstorms will be low for much of the rest of the week and this weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1000 PM Tuesday...Cold pool generated ahead of large cluster of thunderstorms has allowed organized thunderstorms to push south across most of the I-95 corridor and as far E as Marion County. The axis of the thunderstorms is aligned along a moisture gradient. The high resolution models are showing the thunderstorms will gradually weaken as they slip further south and into Williamsburg and possibly portions of Georgetown County. Wind gusts of up to 30 mph and rainfall rates of 1 to 2 inches an hour are occurring with these thunderstorms. Any thunderstorms still around late eve should dissipate shortly after midnight. The rain cooled air has forced temps into the upper 60s to near 70 across the majority of our western zones and these will be the lows for the night. Temps across the eastern third of the forecast area were still in the mid and upper 70s at mid eve, but will cool to the lower 70s overnight. Stratus and fog should develop in the wake of the heavy rain. The greatest coverage of fog and stratus should occur where the heavy rain is falling tonight, along and a line from LBT to MAO and westward. A mid/upper low will slowly meander across eastern NC over the next 24 hours and bring a drier column to the forecast area. Still enough instability and lingering moisture warrants mainly diurnal isolated to widely scattered convection during Wednesday. Wednesday`s max temperatures will rebound from the cloud limited and rain-cooled high temperatures observed today across a large part of the forecast area. However, even warmer temperatures are expected beyond the near term period as the focus shifts from heavy rain producing convection to heat index concerns. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...Unusual summertime cutoff upper low will drift right overhead at around 06Z Thursday as it sinks southward. Thursday afternoon and night it then turns west and retrogrades into Savannah, feeling the influence of a large anticyclone covering most of the south-central U.S. Unsettled weather had preceded this feature while we were on its eastern side but we now spend the short term forecast period under the subsidence associated with its exit, which will lead to negative differential vorticity advection and height rises. Most of the period thus appears rain-free save for the possibility of very isolated thunderstorm activity along the seabreeze during peak heating Thursday afternoon. This is suggested by the GFS and SREF but not the WRF. The current forecast of 20 POPS along the coast looks reasonable. Thursday highs will be a few degrees above climatology while lows will remain slightly elevated both nights. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 300 PM Tuesday...Initially mid level low pressure will be wobbling westward along the Gulf Coast undercutting a potent ridge centered along the Mississippi Valley. This area or Col in meteorological parlance will keep convection to a minimum via mid level capping although this time of year it can never be ruled out. I suspect as we move forward in time small pertubations may show up in the weak circulation thus increasing pops albeit slightly. The pattern becomes more conducive for convection in time and this is reflected in the later parts of the forecast. Guidance has trended a little lower on overall temperatures especially the ECMWF but still expect most of the period to see temperatures somewhat above normal. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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As of 06Z...Upper low responsible for showers and tstms early this evening will continue to spin overhead through the valid period. Although convection has waned this evening, a very moist environment remains, and debris cloudiness is expected to dissipate in the next few hours. This leaves an environment ripe for fog and stratus, and IFR is expected inland where heavy rainfall fell earlier. A moist ground combined with weak WAA is usually a good setup for IFR, and guidance is in good agreement developing stratus at LBT/FLO overnight. Some uncertainty remains into how low the stratus will go, and LIFR is possible, but confidence in this is not high enough for a TAF mention. At the coast, rain did not occur this evening, and WV imagery shows much drier air aloft. This may allow for some MVFR fog at the coast with 20 kts of wind at 2kft preventing more significant vsby reduction. Any restrictions will erode shortly after daybreak with VFR developing by late morning. Much drier air aloft will preclude much more than isolated convection this aftn/eve, despite the upper trough persisting. It is possible a terminal will receive a shower or tstm today, but this will need to be handled with short duration AMDs, and coverage is expected to be isolated enough that even VCTS has not been added. Winds will be light through the period, from the W early and backing to the S this evening, with speeds 10 kts or less, highest at the coast. More fog/stratus is possible Thursday morning, but just beyond the current valid period. Extended Outlook...Fog and stratus possible Thursday morning. VFR thereafter.
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&& .MARINE... NEAR TERM /THROUGH WEDNESDAY/... As of 1000 PM Tuesday...Light and variable winds will become W and NW as a landbreeze/thunderstorm outflow moves across the waters toward morning. Wind speeds will be no higher than 10 kt. Seas will be 2 to 3 ft and mainly the result of an 8 to 9 second ESE swell. A sea breeze circulation will turn the flow back around to a southerly direction during Wednesday with speeds around 10 knots. Seas will average 2 to 3 ft. SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...Very light SW winds and just 2 ft seas through most of the period. An upper low will somewhat disrupt the normal 10-15kt/2-3 ft forecast usually borne of the Bermuda high this time of year. 15kt winds may represent a few gusts but will generally not make it into the forecast and seas will remain capped at 2 ft. A minor uptick in winds/seas may be noted Thursday night as the upper feature retrogrades south and west. LONG TERM /FRIDAY THROUGH SUNDAY/... As of 300 PM Tuesday...Expect southwest winds of 10-15 knots for the duration. There will inevitably be some nocturnal acceleration from time to time but this amount of detail is all but impossible to put into the extended. Significant seas will be 2-4 feet. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...RJD/JDW SHORT TERM...MBB LONG TERM...SHK AVIATION...JDW MARINE... is the U.S. government's official web portal to all federal, state and local government web resources and services.