Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 171042 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 253 AM EST Sat Nov 17 2018 .SYNOPSIS... High pressure along the East Coast will move offshore late Sunday. A weak coastal trough will develop along the Georgia and South Carolina coast Sunday night and Monday, possibly spreading a few showers onshore. High pressure over the Plains will push a cold front off the Carolina coast Tuesday. This high should maintain dry weather through Thanksgiving Day. && .NEAR TERM /THROUGH TONIGHT/... As of 300 AM Saturday...Elongated surface high stretching from the central Gulf coast to the OH Valley will start to consolidate north- northeast of the area today while the center to the southeast slowly fills. Forecast soundings show an abundance of dry air with precipitable water under half an inch through the period. Other than some occasional patches of thin cirrus skies will remain clear until late tonight, when cirrus may start to increase from the southwest. Cold advection continues today, although in a much weakened state. Lacking any warm advection, even 850 mb winds are out of the northwest until late tonight, temps will only warm slightly from yesterday as the airmass slowly modifies. Partial thickness suggests highs in the low 60s for most areas. Lows also end up slightly warmer down to airmass modification and increasing high cloud after midnight, upper 30s to lower 40s. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...The upper air pattern should slowly amplify early next week as a ridge builds across the Rockies and a trough deepens across the Great Lakes and Mississippi Valley. The subtropical jet will become quite active with a 120 kt jet streak passing just to our south on Sunday, and a merged polar- subtropical jet setting up overhead on Monday. Fortunately thermal gradients and advection will remain weak in the low levels. Surface high pressure over New England on Sunday will move off the coast on Monday. A weak coastal trough developing along the GA and north FL coast will build northward along the SC coast Sunday night. Without strong forcing aloft or significant local baroclinicity this trough should not strengthen appreciably. Low-level wind fields will respond to the trough, and models show a shallow layer of overrunning developing within a zone of veering winds between the surface and about 5000 feet AGL Sunday night into Monday. Given the shallow depth of moisture, weak winds, and only meager isentropic lift I`m not increasing PoPs beyond 20-30 percent. The best chance of rain appears to be late Sunday night into early Monday morning when I`ve got a couple hundredths of an inch of potential QPF in the gridded forecasts. High temperatures both Sunday and Monday should range from 63 to 67 degrees, warmest along the coast. I`ve bumped up forecast lows Sunday night to the upper 40s inland and lower 50s near the coast with the expectation of more clouds around. Clouds should decrease Monday night and allow lows to fall into the mid 40s inland and upper 40s near the coast. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 300 PM Friday...High pressure will shift off the coast by Sunday, and the airmass will moderate allowing temperatures to recover into the mid/upper 60s most areas. A coastal trough could support a few showers over coastal waters, but any precipitation should remain away from land areas. Sunday night, the coastal trough will sharpen and could push a few showers into coastal counties. Otherwise, increased cloud cover will hold low temps in the lower/mid 40s inland and in the 50s on the coast. Monday, weak surface cyclogenesis along the coastal trough, perhaps supported by a weak shortwave trough aloft, could translate to isolated/scattered showers. latest forecast pushed slight chance into coastal areas but per area consensus held PoPs below 15 percent with no mention of showers inland. The, high pressure and cooler temperatures should prevail through Thursday, before low pressure brings the next chance for rain to the area late this week. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... As of 12Z...There will likely be some scattered frost this morning with temperatures hovering just above freezing in many spots. Any light fog will dissipate by 12-13Z. Light gradient today, just light northeast flow with winds becoming calm again at sunset. Some light fog possible at the end of the forecast period. Extended Outlook...VFR Sat/Sun and possible MVFR Mon with an approaching disturbance off the coast. VFR Tue/Wed. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 300 AM Saturday...Winds will remain northerly through the period, veering from northwest to northeast during the day. Elongated surface high to the west will shift north of the waters, causing winds to veer. Not much change to the current gradient is expected through the period and wind speeds will remain around 10 kt. Seas will run 2 to 3 ft with occasional 4 ft possible in the vicinity of 20 nm, mainly during the first part of the period. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...High pressure centered over New England on Sunday will provide a light easterly wind across our coastal waters. A weak coastal trough developing along the coast of GA and north FL will spread northward across the SC coastal waters Sunday night. Most models show a weak low developing somewhere just south of Cape Fear on Monday, moving eastward and away from the area Monday night. Upper level support will remain quite weak, and since there shouldn`t be a significant temperature gradient across the area it makes sense that the coastal trough and subsequent low pressure development will remain weak. Wind speeds should remain less than 15 knots through the period, and the primary wave should be a 9-second southeast swell. LONG TERM /TUESDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Weak low pressure will push offshore early next week, and high pressure will build from the north. As a result, offshore winds 10-15 knots with gusts as high as 20 knots will turn toward the north/northeast late this period. Combined seas will build to 2 to 4 feet and will include a 9-10 second period swell from the east-southeast. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Frost Advisory until 8 AM EST this morning for SCZ017-023-024- 032-033-039. NC...None. MARINE...None. && $$ SYNOPSIS...TRA NEAR TERM...III SHORT TERM...TRA LONG TERM...99 from CHS AVIATION...43

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