Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 202325 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 725 PM EDT Sun May 20 2018 .SYNOPSIS... Scattered showers and thunderstorms can be expected much of the upcoming week, as humid air of tropical origin remains across the region. Rain chances will increase late Wednesday into Thursday as a cold front drops into the Carolinas. High pressure to the north may bring a brief drying trend Friday. A return to a tropical airmass with renewed shower chances will occur next weekend. && .NEAR TERM /THROUGH MONDAY/... As of 3 PM Sunday...Scattered convection along the coast will shift inland for the late afternoon and early evening period. Bulk of this activity is being driven by diurnal instability and will start to wane during the evening hours. Flooding will be a concern while convection is present with storms that do develop being efficient at producing heavy rainfall and having storm motions under 10 mph. Lows overnight will once again end up above climo, but likely a degree or two cooler than the last few nights. Boundary layer winds overnight should be sufficient to prevent widespread visibility restricting fog, but patchy fog is possible. Bermuda High and 5h western Atlantic ridge will extend westward into Mon as mid-level low/trough over the eastern Gulf of Mexico shifts slightly farther west. This helps move the tropical moisture tap that has been over the area for the last few days farther inland. It will also allow for some mid-level dry air intrusion. This should lead to lowering precip chances overnight and Mon. Precipitable water drops under 1.5 inches early Mon afternoon and by the end of the period will be under 1 inch for many areas. Although clouds will linger in the area do expect to see more breaks of sunshine, pushing temperatures above climo in most areas. Despite heating do not think there will be a lot in the way of showers and thunderstorms. Mid- level lapse rates are marginal at best and ML CAPE is forecast to be under 1000 J/kg. Couple this with the mid-level dry air and precip chances will be limited. Sea breeze should develop which will provide some lift and do expect to see some showers along it. Storm motions will again be under 10 kt, but storms should produce less rainfall. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...Mid level ridging will be in place initially and keep conditions mostly dry for Monday night into a good part of the day Tuesday. Some significant moisture will return later in the day Tuesday and with some modest height falls showers and thunderstorms, at least a decent coverage, come back into play. Temperatures will be a little cooler Tuesday vs Monday via more cloud cover and convection with highs mainly in the lower 80s. Overnight lows remain on the mild side struggling to drop below 70. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 300 PM Sunday...More of the same Wednesday as Bermuda high pressure offshore persist producing warm and humid conditions with scattered showers and thunderstorms across the Carolinas. A brief break in the pattern is forecast late Wed into early Fri as a mid- level trough digs into New England driving a surface cold front into the area. Guidance is now insistent that this feature will stall overhead Thursday, which seems likely based off the continued southerly flow impeding its southern progress. This front in the vicinity will serve as a focus for convection Thursday, which combined with PWATs near 2 inches will likely lead to widespread showers with isolated tstms. On Friday this front will waver/dissipate with another round of convection likely, although coverage should be less than Wed or Thu. Thereafter, forecast becomes much more uncertain as a wave of low pressure develops in the tropics. Most extended guidance develops this low, but then tracks it slowly with highly variable solutions. At this point it is far too early to mention any tropical development, but it is likely that tropical moisture pooling near Cuba will again lift north into the Carolinas. This creates what at this point is almost a broken record forecast - increasing rain and thunderstorm chances with heavy rain possible next weekend. Of course this will need to be monitored closely as next weekend is the Memorial Day weekend and unofficial start to summer. Temps through the extended will feature highs around to slightly above climo, and lows well above normal as diurnal ranges are limited by clouds cover and humidity. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... As of 00Z...MVFR/VFR conditions prevail attm but IFR conditions will return overnight. Fog will probably be light, with IFR ceilings predominating. After sunrise, conditions will improve to VFR by about midday. There is a small chance of showers and thunderstorms with the highest potential of thunder inland. For now, showers and storms are covered with vicinity in the terminal forecasts. Extended Outlook... Decent chances for rain through Thursday with intermittent MVFR or even IFR conditions. VFR Friday. && .MARINE... NEAR TERM /THROUGH MONDAY/... As of 3 PM Sunday...Bermuda High will maintain southwest flow over the waters through the period. Speeds will be in the 10 to 15 kt range, but near shore directions will back to south or southeast on Mon as the sea breeze develops. Seas running 3 to 5 ft this afternoon fall to 2 to 4 ft overnight and 2 to 3 ft on Mon, mainly made up of decreasing southeast swell. SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...Bermuda High Pressure will be in charge of conditions across the coastal waters through the short term period. Winds will be primarily from the south in a range of 10-15 knots. Early on speeds will lean toward the lower end of the range increasing a bit overnight Tuesday into Wednesday morning. Really no surprises with the wave spectrum with overall 2-4 feet. LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 300 PM Sunday...SW winds of 10-15 kts persist Wednesday as Bermuda ridging remains entrenched. A cold front will drop into the region late Wednesday night and Thursday, briefly turning winds to the W/NW before the gradient eases considerably as the front wavers and then dissipates across the area into Friday. This brings a period of light and variable winds much of Thursday before easterly winds develop Friday, becoming south late at 5-10 kts. 3-4 ft seas will be common Wednesday thanks to a combination of a SE swell and SW wind wave, but these will deamplify as the swell weakens and winds ease Thursday. Wave heights will fall to around 2 ft Thursday, and then remain there through the end of the week. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...III SHORT TERM...SHK LONG TERM...JDW AVIATION...31

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