Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 220145 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 945 PM EDT Mon May 21 2018 .SYNOPSIS... Other than an isolated shower this evening, skies will partially clear out overnight. Ridging from the Bermuda high will extend westward and onshore across portions of the forecast area through Wednesday. Some drier air in the mid levels will accompany this ridging and help limit the amount of convection that occurs Tue into Wed. Scattered showers and thunderstorms will make their return and become more numerous Wed afternoon and continue thru the late week period as a cold front sags into the area from the north before finally dissipating Friday. The upcoming holiday weekend looks unsettled as a tropical airmass returns and brings the likelihood for showers and thunderstorms. && .NEAR TERM /THROUGH TUESDAY/... As of 900 PM Monday...This update will clear out the threat for showers and thunderstorms this late evening thru the overnight as illustrated by latest 88D trends and HRRR. Have further increased the area of patchy fog, now encompassing the entire ILM CWA from 06z-12Z. With mid level drying via latest model soundings, the FA may actually catch glimpses of the moon and stars. A low stratus deck of clouds may put an end to that toward late overnight to daybreak Tue. Some tweaks to tonights lows with no category changes. Previous....................................................... As of 300 PM Monday...The deep tropical moisture plume responsible for at many days of clouds and wet weather has temporarily shifted westward, leaving the eastern Carolinas with just some scattered showers today along the seabreeze front. The upper level ridge supporting the Bermuda high offshore is responsible for allowing the drier mid level air to advect across the area from the southeast. Models show deeper moisture may start to return as soon as late tomorrow afternoon across the Pee Dee region of South Carolina as a trough moving across the Great Lakes knocks upper level heights down and allows a westerly veering of the 700-500 mb flow to develop. Today`s scattered showers should die away this evening from south to north as the core of the drier mid-level airmass advects onshore. Model-computed precipitable water values fall to 1.0 to 1.2 inches tonight, a far cry from the 2.0 inch values we had over the weekend. PW could return to 1.5 to 1.7 inches tomorrow afternoon along I-95, and a chance of showers is back in the forecast accordingly. Lows tonight should range from the upper 60s inland to around 70 on the beaches. Some fog could even develop late tonight as winds become light. GFS MOS has been running consistently too warm for highs, so our forecast for Tuesday is much closer to a NAM/ECMWF consensus: mid 80s inland with lower 80s near the coast. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM Monday...A northwest flow will be in place by the end of the period after a transition from somewhat weak ridging. This flow will allow a weak backdoor cold front to move across the area at least briefly. Precipitable water values will have recovered nicely especially by Wednesday afternoon and with good sea breeze convergence and some distant forcing from the approaching front likely pops remain in place. For overnight Tuesday and Wednesday there will be a smattering of activity as well. Essentially no changes to the temperature forecast. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 300 PM Monday...A brief break in the pattern is forecast Thu into early Fri as a mid-level trough digs into New England driving a surface cold front into the area. This front will stall over the area Thursday and dissipate into Friday. While scattered showers and storms will remain possible Thu and Friday, it is possible that northern areas of the FA will get a break from the showers and storms and may see a little lower humidity for about 24 hours. As southerly flow returns to the area Friday into the weekend, shower and storm chances will ramp back up again for the holiday weekend. Temperatures through the extended range will remain in the lower to middle 80s by day and upper 60s to lower 70s at night. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... As of 00Z...The two main concerns this TAF period will be possible patchy dense fog, and possible convection on Tuesday in the afternoon at the inland terminals. Moisture profiles look favorable for fog, particularly inland, although CRE may get into the act. The winds at the boundary layer are marginally favorable. Tuesday, another summer like day with cu forming along the sea breeze by midday. Some isolated convection is possible, but for the coastal terminals the window will be small, say from 17-19Z. The best chance for convection will be at the inland terminals as the next system approaches. CAPES should be favorable for thunderstorms after 18Z. Extended Outlook...MVFR and possibly IFR conditions will increase late Wednesday into Thursday as a cold front drops across the area. && .MARINE... NEAR TERM /THROUGH TUESDAY/... As of 900 PM Monday...The sfc ridge axis from Bermuda high pressure will extend westward and onshore basically along or just south of the NC-SC state border. This will result in SSW-SW winds across the NC waters north of Cape Fear. South of the Cape to South Santee River, expect mainly southerly directions. The sfc pg remains conducive for speeds around 10 kt except 10-15 kt this evening near shore due to the dissipating sea breeze circulation. Significant seas will remain elevated, around 3 ft, with 4 footers across the outer waters off Cape Fear. The SE ground swell at 8 to 9 second periods will be the primary driver for the significant seas overnight thru Tuesday. Previous....................................................... As of 300 PM Monday...Bermuda high pressure well offshore is extending a ridge axis westward toward the South Carolina coast. A front stalled across the North Carolina/Virginia border should move north and farther away from the Carolinas tomorrow, allowing modest southwesterly winds to continue. Isolated showers should end quickly this afternoon as the seabreeze moves inland from the coast, but isolated showers are possible again Tuesday morning into the early afternoon hours. Although there is certainly a small wind wave out there, the majority of our wave energy is due to an 8-second southeasterly swell measured at 4 feet at Frying Pan Shoals buoy. This swell should continue into Tuesday. SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM Monday...For the most part a south to southwest flow of 10-15 knots will continue across the waters. There is a wind shift very late in the period to a weak offshore flow via a front or what is probably an outflow pushing offshore. As usual this time of year the push will be rather weak and fleeting. Significant seas will be 2-4 feet. LONG TERM /THURSDAY THROUGH SATURDAY/... As of 300 PM Monday...A cold front will briefly turn winds to the W/NW Thu before the gradient eases considerably as the front wavers and then dissipates across the area into Fri. This brings a period of light and variable winds Thu before E-SE winds develop late Thu into Fri with a turn to the south Saturday. Winds look to be 15 KT or less with seas of 2 to 3 feet through the period. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...DCH NEAR TERM...DCH/TRA SHORT TERM...SHK LONG TERM...RAN AVIATION...MRR

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