Area Forecast Discussion
Issued by NWS Wilmington, NC
Issued by NWS Wilmington, NC
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796 FXUS62 KILM 122306 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 706 PM EDT Sun May 12 2024 .SYNOPSIS... Mostly dry weather continues through Monday. High rain chances arrive for Tuesday through Wednesday with an approaching storm system. Dry weather and weak high pressure returns for Thursday and Thursday night before rain chances return for Friday and beyond with the next storm system. && .UPDATE... Only minor tweaks made to previous forecast. 0z aviation discussion included below. && .NEAR TERM /THROUGH MONDAY/... High pressure settles overhead this evening bringing calm winds and clear skies. Weak return flow pushes inland early this evening as NW winds relax. This additional surface moisture advection could lead to a better chance of ground fog along the Grand Strand overnight. Radiational cooling overnight will bring temperatures in the low 50s with a few of our typical cold spots dropping into the upper 40s. Swamps and low lying areas could see patchy ground fog inland as well. High pressure slides offshore throughout the day and southeasterly winds become reestablished across the region. An ejecting shortwave to our south and west will bring increasing upper level cloud cover. Increased low level moisture advection will bring an afternoon cumulus deck and within this deck, some afternoon showers will develop across the southern Pee Dee through early evening. Showers will be light initially with the best lift and heaviest precip arriving after sunset. Highs in the lower 80s due to clouds and onshore flow. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... The approach of a closed low from the central plains states will send multiple shortwaves across the area during this period, which should combine with increasing deep-layer moisture to produce considerable rainfall totals by Wednesday morning, particularly near the coast. With surface high pressure offshore at the start of the period, increasing moisture aloft and isentropic ascent over a warm front will yield lowering/thickening clouds and perhaps some scattered light showers during Monday night. As better forcing for ascent arrives attendant to a lead shortwave in tandem with anomalous pwats exceeding 1.75" (reaching or exceeding the 99th percentile for this time of year), more widespread rain is expected to overspread the region on Tuesday morning. With increasing elevated instability as the warm front nears, convective elements may enhance rainfall rates, leading to locally heavy rainfall until the warm front lifts through, which is progged to occur during the afternoon. Although the probability is low due to showers and abundant cloud cover through most or all of the daylight hours, a marginal risk for severe weather is outlooked for most of our SC zones on Tuesday as there will be plenty of wind shear available, but the limiting factor will be whether much surface-based destabilization can occur. With another shortwave hot on the heels of the first one, expect showers and at least isolated thunderstorms to continue affecting the area from Tuesday evening into the night without much of a break in between. However, as this second shortwave passes overhead and a surface cold front slides through from the west, expect shower coverage to decrease considerably during the latter half of Tuesday night. Temperatures will be limited by thick cloud cover and shower activity with advection primarily driving temperature changes. Morning lows on Tuesday should fall into the middle 60s before rebounding into the mid-upper 70s, warmest south. With only weak cool advection arriving on WSWrly low-level flow behind the cold front, morning lows on Wednesday should end up in the mid-upper 60s, mostly depending on how low dewpoints go behind the front. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... With the cold core associated with the closed mid-level low tracking overhead on Wednesday, lapse rates will steepen and should help to yield weak to moderate instability during the afternoon, given enough surface heating occurs. With 30-40 kts of effective shear in play and up to around 1000 J/kg of DCAPE shown in forecast soundings, the severe weather risk is certainly not zero. The key question is whether any organized convection will come to fruition as multiple impulses rotating about the low will likely yield scattered to perhaps widespread shower activity, thereby keeping surface-based instability low. Even if organized convection does not occur, showers may contain gusty winds and small hail as wet-bulb zero heights fall throughout the day. Highs should reach the middle 80s assuming the cold core remains just far enough north to prevent widespread cloudiness. A second cold front is expected to drop southward as the mid- level low and its associated surface reflection move offshore over Wednesday night. Ridging quickly builds in and dry weather ensues for Thursday and Thursday night before another collection of shortwaves and vorticity impulses bring wet weather for the weekend, although confidence in the timing and evolution of these shortwaves is rather low at this time. Thus, PoPs for Friday afternoon through Saturday are largely held in the 40-50% range for now. Of course, temperatures will depend on the final outcome of these shortwaves, but overall highs are expected to reach the low-mid 80s from Thursday onward with morning lows in the middle 60s, both of which are slightly above-normal. && .AVIATION /23Z SUNDAY THROUGH FRIDAY/... VFR. Few high clouds will begin to move in from the west overnight, thickening and lowering during the day Monday aided by moisture return around offshore ridge. Afternoon diurnal cumulus may develop given enough sunshine ahead of thicker mid- clouds. Atmosphere still quite dry for widespread fog concerns overnight. However, increasing dewpoints from the south and decent radiational cooling (high cloud dependent) may allow for isolated patches of ground fog. Chance for shallow fog at CRE overnight, especially with adjacent ICW, but not confident enough for TAF inclusion. Light winds overnight will turn southerly by tomorrow afternoon. Extended Outlook...Flight restrictions may occur Monday night into Tuesday with the next weather system moving in. Improving conditions into Thursday. Another system approaches the area for next weekend. && .MARINE... Through Monday...High pressure overhead this evening will gradually push offshore overnight. Light and variable winds will become SE tomorrow morning. Winds increase to 10-15 knots during the afternoon ahead of an ejecting shortwave from the Southeastern US. Showers will develop ahead of this disturbance late tomorrow afternoon, primarily in the SC nearshore waters. Showers and storms move northward into tomorrow evening. Seas 1-2 feet. Monday night through Friday...A complex low pressure system will send a warm front through on Tuesday with SSE flow turning to SSW behind it during the day. Seas rapidly increase from 2 ft early in the period to 6+ ft around midday Tuesday with wind gusts also peaking around 25 kts. Thus, SCA conditions are expected from midday Tuesday through Tuesday night with conditions subsiding below SCA criteria around midday Wednesday. A cold frontal passage early on Wednesday will veer winds to WSWrly with gusts possibly scraping 25 kts and seas hovering around 4-5 ft during the afternoon, so while an SCA is not likely by definition, conditions will be close to criteria. A second cold front is expected to drop in from the north on Wednesday night into Thursday morning with winds veering to northwesterly and subsiding through the day while seas fall to around 2-3 ft. Weak high pressure briefly takes control for Thursday night into Friday, with variable flow at or below 10 kts ending up at southeasterly ahead of the next system poised to affect the area over the weekend. && .ILM WATCHES/WARNINGS/ADVISORIES... NC...Coastal Flood Advisory from 1 AM to 4 AM EDT Monday for NCZ107. SC...None. MARINE...None. && $$ SYNOPSIS...ILM UPDATE...VAO NEAR TERM...21 SHORT TERM...ABW LONG TERM...ABW AVIATION...VAO MARINE...21/ABW