Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 182302 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 702 PM EDT Fri Aug 18 2017 .SYNOPSIS... High heat and humidity will continue into Saturday with scattered showers and thunderstorms ahead of a cold front. This front will stall in close proximity to the coast during the weekend before dissipating Monday. High pressure will build across the area Tuesday and Wednesday. Another cold front will approach from the northwest Thursday. && .NEAR TERM /THROUGH SATURDAY/...
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As of 7 PM Friday...Forecast area is convection-free this evening and high-res guidance indicates this will be true through the overnight period. Have allowed the Heat Advisory to expire on time at 6 PM as heat index values have dropped below criteria except in a few isolated locations. Forecast requires no major adjustments. Previous discussion follows: The HRRR continues to show almost no convection over the forecast area. When the HRRR does not want to produce convection you know it will be hard for it to develop. A few showers and thunderstorms are still possible along the coast mainly north of Little River. The heat continues to be a factor for this afternoon with heat indices in the 105 to 108 range. Models continue to show a cold front moving into the eastern Carolinas on Saturday and stalling along the I95 corridor. Models have backed off on the rain percentages slightly and will go with a 30 to 50% chance of showers and thunderstorms. The coverage is expected during Saturday afternoon. High temperatures are expected to be a few degrees cooler and the heat indices overall will range just below heat advisory criteria. With the new moon on Monday the tides are becoming a little higher and there is a threat of minor coastal flooding downtown tonight between 7 and 9 PM.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...A cold front makes a run for the coast but comes against the sea breeze and should keep a few lingering showers into Sat evening close to the coast. The steering flow is W-SW up to 15 kts or so and therefore any storms will move off to the E-NE through the evening, basically off shore. Expect diurnal heating to cut off and any convection to dissipate into Sat night. The dynamics associated with mid to upper trough helping to give the front a push will lift off to the northeast through the latter half of the weekend. Ridging tries to build in aloft with enough subsidence and dry air to keep pcp mainly along the coast or offshore on Sun. Looks like best moisture will be off the coast with pcp water values dropping from 2 inches in isolated spots along the coast in late day convection on Saturday, down to 1.5 inches or less Sat night into Sun. The NAM is a little more bullish bringing moisture back on shore as Bermuda High builds westward. Overall looks like iso to sct convection is possible along sea breeze as it pushes inland on Sunday. Will keep lower end PoPs for Sunday then dissipating into the evening and increasing again toward Mon morning as boundary and moisture get a nudge back on shore. Heat indices will be much lower on Sunday inland and probably will only reach near 100 along the coast with dewpoint temps down near or below 70 west of I-95 and closer to 75 Sun aftn. It will still be very warm on Sunday with plenty of sunshine especially inland with temps reaching into the 90s. Lows will be in the 70s Sun night, but about 5 degrees lower than previous nights. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday...A flat mid-level ridge will extend from the Atlantic across the Carolinas Monday-Tuesday, then get suppressed south as a trough carves out across the Eastern seaboard for the latter half of the week. With no real airmass change evident in guidance until perhaps Thursday, precipitable water values will hover around 2 inches until then. Scattered pulse showers and thunderstorms are expected each afternoon and evening Monday through Wednesday, with the highest chances Wednesday night through Thursday when convection becomes organized along and ahead of a frontal boundary. As usual in the extended period, and especially in August, there is a great deal of uncertainty with timing the front and determining how far south it will push. Will hang on to higher PoPs across the southern CWA on Friday to account for that. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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As of 00Z...Good confidence VFR all terminals through the overnight period. Limited convection in evidence this afternoon has faded for the evening. Possibility that scattered showers/thunderstorms will re-develop by late morning along the sea breeze front on Saturday, affecting our coastal terminals. Extended Outlook...Scattered TSTMs Sun through Wed. Flight restrictions will be possible in early morning stratus/fog Sun-Wed.
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&& .MARINE...
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NEAR TERM /THROUGH SATURDAY/... As of 7 PM Friday...Latest obs show SW winds in the 15 kt range with seas of around 3 ft. Forecast good to go with no changes needed. Previous discussion follows: At this time there are south winds along the beaches due to a mature sea breeze circulations. Farther off the coast outside the circulation, winds will be from the southwest. Currently, wind speeds are running between 15 and 18 knots and seas on average are around 3 feet. With a cold front approaching and stalling inland, winds speeds over the waters will be 14 to 18 knots overnight and will slowly weaken on Saturday with the front stalling. Seas are expected to run 3 to 4 feet tonight and fall off to 3 feet late Saturday afternoon. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...A front will make a run for the waters but should stall upstream of the waters Sat and then slowly begin to dissipate late in the weekend. Winds will diminish Sat night down to 10 kts or so by Sun morning. Expect lighter more westerly winds on Sunday as front remains nearby. Looks like convection could be focused moreso off the coast then inland. Seas will subside down to 3 ft Sun, diminishing further, to around 2 ft or less by Mon morning. Higher winds and seas will be possible in and near thunderstorms. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...A benign pressure field across the waters will keep winds 10 knots or less Monday and Tuesday, as a weak Bermuda high pressure remains in place off the coast. Winds will begin to pick up out of the southwest by Tuesday afternoon as a surface trough takes shape across the Carolina piedmont. Shower and thunderstorm activity is expected to remain isolated to widely scattered over the waters in a general southerly flow through the period.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...None. NC...Coastal Flood Advisory until 9 PM EDT this evening for NCZ107. MARINE...None.
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&& $$ SYNOPSIS...99 NEAR TERM...REK/DRH SHORT TERM...RGZ LONG TERM...CRM AVIATION...REK MARINE...REK/RGZ/DRH/CRM

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