Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 291725 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 125 PM EDT Mon May 29 2017 .SYNOPSIS... Today should be the hottest day of the week with temperatures in the 90s away from the beaches. Thunderstorms may return tonight and Tuesday ahead of a cold front. This front should stall across the area Wednesday and Thursday, returning north again on Friday. && .NEAR TERM /THROUGH TONIGHT/... As of 1030 AM Monday...No changes necessary to the forecast with the mid morning update. 06 UTC and hourly guidance from high resolution models still show any chances for convection this evening. Previous discussion follows: A strong round of convection last night beneath a mid-level impulse has moved offshore, with a surface trough exiting the coast this morning. While mid and high level debris cloudiness will again scatter through the sky this morning, subsidence behind the departing impulse and increasingly dry air behind the convection will create a hot but sunny Memorial Day across the area. Elongated high pressure which has been stretched along the Gulf Coast for days now, will recenter offshore today in response to mid- level ridging blossoming up the Southeast coast. This thickness advection will push the strongest band of mid-level westerlies NW of the area at least through this evening, and the combination of subsidence beneath this along with the factors mentioned above will create a hot and dry day. Today is forecast to be the hottest day of this stretch, with widespread 90s forecast even right to the beaches as westerly wind pins the sea breeze at least into the late aftn. However, drier air aloft noted on soundings will allow for the dewpoints to mix out, and thus have kept all heat index values just below 100 degrees today - but still the hottest so far of 2017. Guidance is in very good agreement that a vorticity impulse rotating SW to NE around the ridge will spawn another round of convection this evening W/SW of the area, and then push NE into the CWA. Most of this activity is forecast to occur tonight, but forecast soundings suggest considerable MUCape of 1000-15000 J/Kg of MUCape above the nocturnal inversion along with 35-40 kts of 0-6 km shear. This will likely manifest as increasingly organized convection beneath the mid- level impulse, and another MCS with the potential for strong winds and hail may move across the area tonight. Inland locations may have the best chance with this setup, but have carried CHC POP for nearly the entire CWA tonight. Any convection will move offshore before the end of this period, leaving drier conditions and mins a degree or two either side of 70. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 300 AM Monday...500 mb high pressure will move farther offshore Tuesday and Wednesday to near Bermuda. Upper level low pressure will dig a trough across the Great Lakes. In between these two systems will be a flow of mid to upper level moisture originating from the western Gulf of Mexico streaming northeastward across the Carolinas. This moisture should remain overhead Tuesday, but will thin out below 600 mb on Wednesday. Tuesday appears to have favorable conditions for convection, perhaps arriving in two rounds. The first could be ongoing as the sun rises Tuesday morning as the last in a series of Monday night vort maxes pass overhead. After a lull in the late morning through early afternoon hours, another round of convection should develop during the mid to late afternoon hours with the arrival of a second vort max. Forecast PoPs have been bumped up to 40-60 percent, highest just inland from the coast where seabreeze convergence should exist. Model forecast CAPE as large as 3000 J/kg will coexist with weaker mid-level winds than we`ve seen the past couple of days. Despite the good buoyancy the organized severe weather threat is overall not as high as we saw yesterday or today. A weak cold front sinking southward from the Mid-Atlantic region will settle into the area Wednesday morning. Any northwest winds behind the front will be fleeting as Wednesday afternoon`s seabreeze should send the boundary back to the north. A cooler and much drier lower atmosphere will make it harder to generate showers and storms Wednesday and our forecast PoPs are only 20 percent. Forecast highs are in the upper 80s both days, with nighttime lows in the upper 60s to near 70. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 300 PM Sunday...GFS/ECMWF in agreement on the evolving H5 pattern in slowly migrating a broad but low amplitude trough eastward across the Great lakes and Ohio valley then into New England and SE Canada this period, while holding an upper ridge of varying amplitude over Florida and the Bahamas. This will allow a series of weak fronts and upper disturbances to move to our coasts, offering daily chances of thunderstorms. Late May/early June heating coupled with PWATS values between 1.50-1.80", and numerous surface boundaries, will support convection much of the extended forecast period. Next weekend potentially could turn wet, as enhancement of column moisture is drawn from the Gulf of Mexico by low pressure over Texas on Saturday, tracking to the Ohio Valley during Sunday. With the abundance of clouds, daytime temperatures will run near normal for the season, middle to upper 80s, but above average minimum temperatures in the upper 60s to low 70s. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... As of 18Z...Somewhat of a repeat of Sunday`s scenario with mostly VFR conditions expected through the period. There is the possibility of thunderstorms developing later this evening across the western areas and traversing the entire area slowly west to east overnight, hence the numerous PROB 30 groups in the TAF`s. Extended Outlook...MVFR/IFR conditions are possible in thunderstorms Tuesday, mainly during the afternoon and evening. More typical scattered showers and thunderstorms are possible Wednesday through Friday. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1030 AM Monday...A very light offshore flow is still in place with the latest buoy observations but this should be concluding in the next couple of hours with more of a synoptic southwest flow developing. No changes to the forecast. Previous discussion follows: Weak trough will move offshore this morning, causing winds to shift to the west while easing to 5-10 kts. This change will be short lived however, as high pressure expands from the south, winds will quickly return to the S/SW and increase once again to 10-15 kts and persist at these speeds through tonight. The exception will once again be within the near shore sea breeze circulation, where a local backing along with gusts up to 20 kts are forecast this aftn/eve. A low amplitude SE swell will again be masked by a 5 sec SW wind wave, and seas will become uniformly 2-3 ft today and tonight. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 300 AM Monday...1023 mb high pressure anchored offshore well south of Bermuda will move little through the period. This should maintain a light to moderate southwest wind across the Carolina coastal waters. A weak cold front will slide into the area from the north Wednesday morning, however any shift to northwesterly winds appears to be brief as the afternoon seabreeze should push the front back inland. Seas should average 2 feet through the period. Thunderstorms will be a concern for mariners, particularly Tuesday and Tuesday night as models show a series of upper level disturbances and good moisture crossing overhead. By Wednesday the atmosphere dries out enough to hopefully make thunderstorms more isolated in coverage. LONG TERM /THURSDAY THROUGH FRIDAY/... As of 300 PM Sunday...Near typical summer-like marine conditions this period as SW winds prevail with 2-3 foot seas. High pressure will remain centered just to the SE and E of Bermuda, and weak troughing inland should maintain SW wind flow Wed to Fri. The sea spectrum will be comprised of S-SSW waves 1-2 feet every 5 seconds and ESE waves 1-2 feet every 8 seconds. TSTMS will be active this period, moving generally from land to the coastal waters, and some may be strong from afternoon heating. Getting a radar update before heading out may be in the best interest of safely this period as we transition into a more active lightning and TSTM wind gust season. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...TRA NEAR TERM...JDW/SHK SHORT TERM...TRA LONG TERM...MJC AVIATION...SHK MARINE...

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