Area Forecast Discussion
Issued by NWS Wilmington, NC

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508 FXUS62 KILM 240525 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 125 AM EDT Thu May 24 2018 .SYNOPSIS... A weak cold front approaching from the north will produce a continued low chance for showers and thunderstorms late this evening and overnight. The front across or just south of the local area will dissipate during Friday. Low pressure developing across the Gulf of Mexico will bring tropical moisture northward and help fuel a higher probability of showers and thunderstorms with heavy rain across the eastern Carolinas Sunday and into early next week. && .NEAR TERM /THROUGH TODAY/... As of 845 PM Wednesday...The diurnally induced convection across the FA is waning fast at the moment and is nearly gone. Have lowered POPs to chance or slight chance for the remainder of this evening as a result. However, HRRR model runs indicate that as the sfc cold front drops further south and across the FA toward daybreak, showers and or tstorms could re-develop given a better convergence zone for initiation. As a result, have kept the 20-30 POPs going thruout the night. Some tweaks to overnight mins and Hrly temps and dewpts based on trends with no categorical changes. Previous....................................................... As of 300 PM Wednesday...A mid-level disturbance along the Savannah River surrounded by very light steering flow should move very little over the next 24 hours. Surface high pressure moving across the Great Lakes will nudge a surface cold front southward across North Carolina tonight, stalling out across eastern South Carolina on Thursday. This should be the focus for another day of showers and thunderstorms. Today`s thunderstorm activity is developing along multiple east-west oriented convergence boundaries where the airmass is uncapped with CAPE of 1500-2500 J/kg. Convective organization has remained minimal due to very weak wind shear: bulk shear across the 0-6 km layer is only 10-20 kt. SPC`s marginal severe weather threat across northeastern NC and southeastern VA is keyed to the stronger shear and potential for more significant storm cell organization that exists there. Convective activity should diminish this evening, however most recent runs of the synoptic and rapid update models show convection lingering through the night along the south end of the higher shear zone across North Carolina, particularly as the cold front eases its way south overnight and increases low- level convergence. A relative minimum in convection should occur Thursday morning, with showers and storms reblossoming Thursday afternoon mainly across South Carolina near the stalled front and pooled low-level moisture. Forecast PoPs are as high as 70 percent in the Florence vicinity Thursday afternoon. Lows tonight should range from 68-71. Highs Thursday are forecast to reach 80 on the beaches to around 84 inland. && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... As of 3 PM Wednesday...Weak upper low across GA Thursday night will drift northward and weaken further across the far western Carolinas during Friday. In addition, the H5 ridge situated off the coast will help direct moisture plume back into the Carolinas and precipitable water will increase during the day in response. Expect the best convective coverage to be across the SC zones initially during Friday, then in the LBT zone group later in the day. During Friday the residual foot print of the old front will drift northward and finally become absorbed in the broader scale flow and awash in the sea breeze circulation. Favor a blend of MAV/MET numbers through the period which suggests near climatology high temperatures Friday and warmer than normal low temperatures each night. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 3 PM Wednesday...A return to a very wet period appears to be in order for the extended time frame. A ridge of high pressure will weaken and the trough will open up across the eastern half of the United States. The models continue to show a low developing over the Gulf either as a subtropical or tropical system. For our area this means we should expect to see increased moisture and the chance of heavy rain. The models continue to show a surface low developing over the Gulf of Mexico, the 12Z ECMWF shows the low moving northward to Louisiana and slowing off the coast on Tuesday. The GFS is near the Florida peninsula and the Canadian is in middle. With the recent rains flood watches may be required Sunday into early next week. With cloud cover and rain chances high temperatures are expected to remain in the middle 80s and lows should be range from 68 to 73 through the period. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... As of 23Z...Overall expect VFR conditions through the period outside of convection. There could be some activity across the northern sites this morning and for later today convection is expected to focus more to the south. Plenty of debris cloudiness should keep BR limited this morning. Extended Outlook...Brief/local IFR visibility is possible in thunderstorms Thursday afternoon. Tropical moisture returning to the area Sunday and Monday could bring more widespread thunderstorms with periods of IFR ceilings/visibility possible. && .MARINE... NEAR TERM /THROUGH THURSDAY/... As of 845 PM Wednesday...Winds ahead of sfc cold front dropping southward, will drop to 5 to 10 kt with the sfc pg ahead of it becoming quite relaxed. By daybreak, the cold front`s position will be near Cape Fear. This front will continue to push southward and by midday will likely stall just out of the ILM waters. Have continued the brief veering trend with winds until it`s final direction of NE-ENE is established. Could see isolated convection along and ahead of the cold front dropping southward during this overnight period. Significant seas will run 2 to 3 ft, with only a few 4 footers possible from Cape Fear northward. The 8 to 9 second period SE Ground swell will continue to dominate the overall seas with the higher producing wave energy via spectral density plots from NDBC. Previous......................................................... As of 300 PM Wednesday...High pressure pushing east across the Great Lakes will ease a cold front southward through North Carolina tonight. The front should reach the Cape Fear area shortly after sunrise Thursday, with the boundary slipping south along the Grand Strand between 8-11 AM. Southwesterly winds ahead of the front should turn northeasterly behind the front, but with no significant increase in wind speed expected. Scattered showers and thunderstorms should end early this evening south of Cape Fear but may continue overnight north of Cape Fear. Showers/storms should develop again Thursday afternoon, mainly south of Cape Fear. Seas currently around 3 feet should diminish by about a foot with lighter wind speeds on Thursday. SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 3 PM Wednesday...Onshore flow around 10 knots expected Thursday night with seas less than 3 ft. As high pressure off the Southeast U.S. becomes better established the flow will veer to a southerly wind by Friday night. Chance of showers and thunderstorms across the waters, more-so during Friday and Friday night. Seas 3 ft or less expected Friday and Friday night. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Wednesday...As high pressure off the coast shifts eastward and a trough of low pressure exists over the east half of the United States, the winds will be from the south- southeast to south-southwest at 10 to 15 knots. This extended period of fetch will see the seas rising from around 2 to 3 feet on Saturday to 4 to 6 feet by late in the day on Monday, when a small craft advisory may be needed. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...DCH NEAR TERM...DCH/TRA SHORT TERM...SRP LONG TERM...DRH AVIATION...SHK MARINE...

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