Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 290529 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 129 AM EDT Thu Jun 29 2017 .SYNOPSIS...
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Dry high pressure will move off the Mid-Atlantic coast through Thursday. A warm front will lift northward across the Carolinas Friday, accompanied by increasing chances of showers and thunderstorms. Bermuda High Pressure offshore this weekend and much of next week will bring warm and humid conditions along with scattered thunderstorms each day.
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&& .NEAR TERM /THROUGH TODAY/... As of 900 PM Wednesday...No major changes needed. Just applied hourly tweaks to basic parameters; temps/dewpts/winds based on latest obs and trends for the remainder of the evening and overnight period. Only clouds to contend with will be scattered thin cirrus. Previous.................................................... As of 300 PM Wednesday...Almost perfect weather this afternoon with a a few cumulus developing northwest of a line from Darlington to Lumberton. The high pressure center that is controlling our area is over the DelMarVa this afternoon and will continue to slide to the east. This will allow for a return of moisture and the warm up will begin for the area. The statistical guidance continues to show a dry Thursday but the GFS20 model indicates possible convective activity along the sea breeze on Thursday afternoon. At this time will keep just below 20% for the afternoon thunderstorms. Lows overnight will range from 62 degrees inland to the upper 60s at the beaches. Thursday`s highs will reach the upper 80s inland to the middle 80s at the coast. && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...High pressure off the Mid-Atlantic coast will spin in place through the end of the week as mid-level ridging amplifies offshore. The increasing 1000-500mb thicknesses will back into the Carolinas this period, so temperatures will slowly begin to warm, most notably by increasing overnight mins vs higher aftn maxes thanks to onshore flow. Highs Friday will rise into the mid and upr 80s, with mins Thursday night hovering around 70, and only cooling into the low 70s Friday night. As the ridge amplifies offshore, mid-level moisture gets funneled into the Carolinas from the Gulf Coast and PWATs approach 2 inches during Friday. This occurs in tandem with a slow moving shortwave lifting SW to NE across the Southeast, and Friday should feature quite a bit of thunderstorm coverage. The peak of this activity will be diurnally forced as MLCape rises over 1500 J/kg, but will be mainly of the pulse variety thanks to 0-6km shear less than 20 kts. However, as thicknesses climb and moisture increases, the warm cloud depth will climb to near 14 kft, so torrential rain will be possible in any stronger storms. Most activity will wane diurnally, but the presence of the upper vort necessitates at least SCHC POP through at least the first part Friday night, although the best axis will likely shift offshore. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 300 PM Wednesday...After the cool weather of the last couple of days, summer heat and humidity should come roaring back next week. Persistent upper level ridging across Florida and the Gulf Coast and the Bermuda High offshore will allow heat and humidity to build through the period. A time-series plot of forecast 850 mb temps shows +17C Saturday, +17.5C Sunday, and +18C Monday through Wednesday. The ECMWF actually has some forecast 850 mb temps near +20C by next Wednesday, however we`ve noticed over the past several years there is a summer warm bias in the ECMWF at the extended range. The airmass should be moderately to strongly unstable through the period with CAPE values rising to 2000-3000 J/kg each afternoon. West to northwest flow aloft, a pinned seabreeze near the coast, and a well-defined Piedmont trough (perhaps evolving into an inland thermal low for a few days next week) should set the stage for scattered diurnally-driven storms each day. Precipitable water values are highest Saturday (2.0 to 2.2 inches) falling to around 1.8 inches Monday and Tuesday. With afternoon in the 90s inland with dewpoints in the lower 70s, heat indices should reach 100 to 103 degrees in most locations away from the beaches each day next week. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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As of 06Z...Period of VFR will continue today into tonight with surface high to the northeast providing onshore flow. Sea breeze will make its way inland with some low topped cumulus clouds developing along it. No rainfall is expected but marginal increase in low level moisture will lead to some potential for MVFR or even IFR ceilings as the forecast period comes to an end Fri morning, especially at SC terminals. Extended Outlook...Brief MVFR/IFR possible in and near diurnal driven convection starting Friday. Brief morning MVFR/IFR possible from fog or low stratus between 08-12Z starting Sat.
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&& .MARINE... NEAR TERM /THROUGH THURSDAY/... As of 900 PM Wednesday...No major changes needed. Applied hourly winds update based on latest obs and trends for the remainder of this evening and overnight. Basically looking at ENE-ESE winds around 10 kt north of Cape Fear and 10-15 kt south of Cape Fear to South Santee River. Significant seas in the 2 to 3 foot range, with the more solid 3 footers south of Murrells Inlet. Dominating periods will run from 5 to 7 seconds. Previous.................................................. As of 300 PM Wednesday...Northeast to east winds of 10 knots over the waters will continue to veer slightly overnight and will be from the east over all the waters by daybreak. Seas are running 2.5 feet at Frying Pan Shoals and 2.0 feet at 41110 and the seas of 2 to 3 feet are expected to continue throughout the overnight. SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...Surface high pressure off the Mid-Atlantic coast will gradually retreat to the east through Friday night allowing winds to shift from E/SE to S/SW through the period. The gradient remains relaxed in the vicinity of this high pressure, so wind speeds will be 10 kts or less regardless of direction. This will keep seas at relatively low amplitude, 2-3 ft, with a 2 ft SE swell and 2 ft S wind wave comprising the spectrum. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Wednesday...Bermuda high pressure well offshore will extend its ridge axis westward across Florida and into the northern Gulf of Mexico this weekend into early next week. With the ridge remaining south of the ridge, mainly southwesterly winds are expected through the period with the typical afternoon seabreeze backing wind directions more southerly with an increase in wind speeds. With inland highs in the 90s and westerly winds aloft, there should be scattered thunderstorms making their way down to the beaches and offshore virtually every afternoon. The best potential appears to be Saturday, however no day will be immune to this potential. Average sea heights of 2-3 feet are expected. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...TRA NEAR TERM...DCH/DRH SHORT TERM...JDW LONG TERM...TRA AVIATION...III

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