Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 291451 AFDILM Area Forecast Discussion National Weather Service Wilmington NC Issued by National Weather Service CHARLESTON SC 1051 AM EDT Wed Mar 29 2017 .SYNOPSIS... Relatively cooler and drier high pressure will build in from the north beginning today. Showers and thunderstorms are expected on Friday as warmer and more humid air returns ahead of an approaching cold front. The cold front will sweep offshore late Friday night. Some of the thunderstorms may be strong to severe Friday. The weekend should be dry as high pressure takes hold. Then early next week, a southern stream system will again bring the risk for showers and thunderstorms. && .NEAR TERM /THROUGH TONIGHT/... As of 1030 AM Wednesday...A cold front is south of the area this morning. A weak pressure pattern will become better defined as the potent storm system crawling through the Central U.S. pushes high pressure down the east coast. With some very modest cold air advection there should be some convective cloudiness mostly across northern areas. Some mid level clouds may move across the area tonight from a glancing system to the south. Guidance is in good agreement on daytime highs a little lower than Tuesday with middle 70s eastern areas, where there will be more clouds and possibly 80s again inland. Thursday morning lows will be in the lower to middle 50s. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... As of 300 AM Wednesday...A strong area of high pressure centered across eastern Canada at the start of the period and ridging south across the Carolinas will drift E with the ridge axis moving offshore during Thu. Low pressure across the Missouri Valley Thu will move ENE across the Mid-West, ending up offshore of the Mid-Atlantic states late Fri night. Its accompanying warm front should reach the eastern Carolinas late Thu night and then move to our N on Fri. A cold frontal passage is expected later Fri night. Still looks like a wet period beginning late Thu night and on Fri with widespread showers and thunderstorms developing and then coming to an end with the passage of a cold front late in period. The combination of upper level support and strong and deep moisture return and lift should bring widespread half inch to one inch rainfall amounts with amounts in excess of one and a half inches possible. There is a risk for strong to severe thunderstorms during this time. 0-6 km effective bulk shear parameters have become more conducive for severe weather. Instability does grow with mixed layer CAPE values on the order of 500 to 1000 J/kg. These CAPE values are certainly conservative when we talk about severe weather in the Carolinas this time of year. The instability may be somewhat limited given that rainfall is expected to develop Thu night as isentropic upglide increases sharply ahead of warm front. Clouds and rainfall should help to mitigate the instability, especially early on, but a period of dry slotting may allow clouds to thin during Fri which could support greater instability and increase the severe risk. Highs on Thu will be in the upper 60s to lower 70s with sunshine giving way to increasing clouds Thu afternoon. Lows Thu night will be in the upper 50s to lower 60s with temps having a tendency to rise overnight. Highs on Fri will be in the mid and upper 70s. Any significant breaks in the clouds will allow temps to surge into the lower 80s Fri afternoon. Lows late Fri night will drop into the mid and upper 50s with around 60 at the beaches. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 300 AM Wednesday...In the wake of this system, dry weather and above normal temps are expected for the weekend as mid- level ridging builds across the area and surface high pressure to our N ridges S. Attention then will turn westward as next potent southern stream system along the Gulf Coast Sun night lifts to the NE and drags a warm front to the N. This will again bring deep moisture into the Carolinas, and with that, showers and thunderstorms early next week. Timing differences have decreased slightly and it looks like the greatest risk for showers and thunderstorms will be Mon night. Showers and thunderstorms should be increasing from the SW and W Mon afternoon with the risk decreasing from W to E during the day Tue as broad low pressure consolidates offshore of the Mid- Atlantic states Tue and Tue night. Drier air will work into the eastern Carolinas during Wed. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... As of 12Z...VFR conditions expected through the valid TAF period. Few to scattered stratocumulus will persist at the terminals and may briefly become broken as a push of colder air noses in from the NE this afternoon and tonight. The lowest of these clouds will develop around 3500-4000 ft. Could be some patchy fog/ stratus late tonight and at this time will include mention of stratus at KFLO with a scattered deck around 1 kft. Extended outlook...Flight category restrictions are probable in showers and thunderstorms late Thu night through Fri eve. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1030 AM Wednesday...Northerly flow is developing behind a front to the south. Speeds will remain modest along the lower end of a 10-15 knot range. A stronger northeast surge will develop later today with winds increasing to 15- 20 knots where they will remain through tonight. Once again leaning toward the lower end of the range. Regarding seas, some lingering five footers will abate later this morning with 2-4 feet ensuing. Later tonight some five footers will once again develop across the outer waters. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 AM Wednesday...A Small Craft Advisory is expected for all waters late Thu night and into Fri night. A strong area of high pressure centered across eastern Canada at the start of the period and ridging south across the Carolina waters will drift E with the ridge axis moving offshore Thu. Low pressure across the Missouri Valley Thu will move ENE across the Mid-West, ending up offshore of the Mid- Atlantic states late Fri night. Its accompanying warm front should reach the Carolina waters late Thu night and then move N of the waters on Fri. A cold frontal passage is expected later Fri night. Significant shower and thunderstorm activity is expected to develop Thu night and continue through Fri before ending Fri night. The wind direction at the start of the period will be NE. Winds will veer to easterly Thu afternoon, SE Thu night and S and SW on Fri. SW winds Fri night will shift to NW toward Sat morning. The strongest winds will occur Fri into Fri night, 20 to 25 kt, increasing Thu night and decreasing later Fri night. The highest seas, 5 to 7 ft and up to about 8 ft near Frying Pan Shoals, are expected later Fri into Fri night. Seas will be building Thu night and subsiding later Fri night. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 AM Wednesday...Small Craft Advisory conditions possible late on Mon and Mon night. Low pressure will be intensifying south of New England Sat morning. Its attending cold front will be offshore by the start of this forecast period. Low pressure will continue to intensify as it moves E and then NE during the weekend. High pressure centered across eastern Canada will build south across the Carolina waters during the weekend with the ridge axis moving offshore Sun night. Next in series of potent southern stream systems will be approaching from the W on Mon. Its attending warm front is expected to move across the waters Mon night. NW winds will generally dominate Sat although an inverted trough poking N may cause winds to back, especially across southern waters ahead of reinforcing cold and dry push. Winds late Sat night and Sun in the wake of this push will be NE. The wind direction will veer to E later Sun afternoon and then ESE Sun night. The wind direction will become SE during Mon. The highest wind speeds during this period are expected on Mon when they are expected to increase to 20 to 25 kt late day and Mon night. Wind speeds Sat through Sun night should be mainly 5 to 15 kt. Seas will be 3 to 4 ft Sat morning, subsiding to mainly 2 to 3 ft Sat night and then 1 to 2 ft Sun. There will be a tendency for backswell to slow the slow the rate of subsiding seas through the first part of the weekend. Expect seas will reverse higher late Sun night and Mon, possibly reaching Small Craft Advisory levels Mon night. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE... is the U.S. government's official web portal to all federal, state and local government web resources and services.