Area Forecast Discussion
Issued by NWS Wilmington, NC

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483 FXUS62 KILM 261132 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 732 AM EDT TUE JUL 26 2016 .SYNOPSIS... High pressure will expand across the Carolinas, maintaining uncomfortable levels of heat and humidity this week. Isolated to scattered showers and thunderstorms are possible each afternoon and evening. The chances increase heading into early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 645 AM Tuesday...Ridging surface and aloft will be the main players across the ILM CWA this period. Expect the diurnally driven sea breeze to develop by noon, and progress inland this afternoon and early evening. The low and mid levels of the atmosphere remain quite warm, ie. 500 mb progged temps will be -3 to -4 degrees Celsius. This will create a convective lid across the area basically preventing any thunderstorm development. Even the forcing along the sea breeze will have trouble breaking through this lid. As a result, have kept pops below the isolated threshold of 15 percent. Even if an isolated storm develops, it will not last long in this environment. The low level nocturnal jet will develop this evening and peak during the pre-dawn Wed hours. The mixing in the low levels should prevent fog development overnight. Used a consensus of the GFS and NAM mos guidance since both are at the top of the max/min temp verification here at ILM. Heat advisory criteria will be met for the majority of the ILM CWA today. In addition, the forecast worked out to where heat indices will begin exceeding thresholds a bit earlier. As a result, will change the start time of the advisory from 2 pm to noon. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 400 AM Tuesday...Ridging aloft and at the sfc will dominate the weather across the ILM CWA this period. The upper ridging and warm temps aloft will limit lapse rates and maintain the convective lid across the fa this period. Some weakness in this lid could occur especially on Thu, in which the sea breeze could end up with a few or more than a few isolated storms along it. The sfc ridge axis from the high`s center well offshore, will shunt slightly southward this period. This will result in sw-wsw winds on Wed and mainly wsw-w winds on Thu. This westerly direction may also result in isolated storm(s) drifting into the ILM CWA from CAE or RAH CWAs. The sfc pg will remain semi- tightened this period, resulting with active overnight winds around 5 mph, and 5 to 15 mph, during the midday thru early evening hrs. The winds associated with the inland progressing sea breeze will keep speeds in the higher end of this range. Wind gusts of 20+ mph will occur along the immediate coast at the height of the sea breeze and could approach these gusts again at the coast during the overnight period due to the mixing of the nocturnal low level jet to the sfc. Basically, sfc mixing will keep fog formation to a minimum at best. Used a consensus of the GFS and NAM mos guidance for daily max/min temps due to their better performance verification-wise as of late. With mid to upper 90s for highs and sfc dewpoints slightly increasing to the 75 to 80 degree range, the late morning thru early evening heat indices should easily surpass heat advisory thresholds and is currently advertised in the Hazardous Weather Outlook. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 330 AM Tuesday...Atlantic ridge of high pressure will slip farther to the south and east and weaken into early next week as trough moves east from the mississippi valley. This will allow h5 heights to slip and temps to lower slightly, as well as, reduce the subsidence and dry air aloft giving way to increased chance of shwrs/tstms heading into the latter half of the weekend and early next week. Initially expect only isolated convection along sea breeze front with main convective development farther west along piedmont trough and farther north along lingering frontal boundary on Fri. The persistent moist SW flow around atlantic high will bring pcp water values up above 2 inches over the weekend into early next week. This will combine with enhanced lift as mid to upper trough moves east into the Carolinas to produce stronger and more widespread shwr/tstm activity...especially Sun/Mon. By Late Mon, it looks like front/trough will move east into local forecast area. Temperatures in the mid 90s on Fri into Sat will drop down slowly, aided by lowering h5 heights and increasing clouds and convection into early next week. Heat indices will remain high, remaining between 100 and 105 most days. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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As of 12Z...Except for low confidence brief MVFR cigs at the coastal terminals early this morning as the sea breeze boundary develops, VFR expected through this 24 hour TAF valid period. Light SW-WSW winds will back to the S-SW as the morning progresses, highest speeds around 15 KT in the afternoon at the coastal terminals. A subsidence inversion will keep any convection isolated at best. Even if development occurs activity will not last long. Winds will slowly veer TO SW-WSW and decrease this evening. EXTENDED OUTLOOK...Isolated to scattered afternoon convection through Saturday may create periods of MVFR/IFR. Otherwise expect VFR.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 645 AM Tuesday...High pressure will ridge across the area waters from the high`s center well offshore from the Southeast U.S. States. The Carolinas trof...aka Piedmont...will orient itself across the western Carolinas. Enough of a sfc pg will result across the ILM waters, producing SW 10 to 15 kt winds. Nearshore this afternoon and evening, winds will become temporarily SSW at 10 to 20 kt due to the inland progressing sea breeze. Significant seas will range between 2 and 3 ft today, and up to 4 ft for the ILM NC Waters late tonight. This due to SW winds around 15 kt with gusts 20+ kt across all waters due to the mixing of the low level SW jet to the ocean sfc. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 330 AM Tuesday...The ridging from the sfc high will be suppressed slightly to the south of its current location this period. This will increase the westerly component in the wind directions during this period. The sfc pg will also tighten slightly as a result of the ridge axis oriented further south. The daily inland progression of the sea breeze may be limited due to the increase in the westerly component of the winds...and speeds. A daily nocturnal low level jet will develop each evening and peak during the pre-dawn hrs. Overall, looking at sw-wsw winds at 10 to 15 kt except up to 20 kt during the overnight periods...and...nearshore during the peak of the sea breeze cycle, from the late afternoon thru mid evening hrs. Significant seas will run 2 to 4 ft with the 4 footers primarily occurring during the overnight periods and possibly nearshore in the aftn/mid evening. Convection, if any, will mainly be isolated. LONG TERM /FRIDAY THROUGH SATURDAY/... As of 330 AM Tuesday...South to SW flow will continue between Bermuda High pressure and Piedmont trough inland. Winds will basically remain between 10 and 15 kts, but should become gusty each aftn due to sea breeze and may increase again overnight in nocturnal jet. This will produce a spike in seas late aftn into the evening with overall seas remaining in the 2 to 4 ft range. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Heat Advisory from noon today to 7 PM EDT this evening for SCZ017-023-024-032-033-039-053>056. NC...Heat Advisory from noon today to 7 PM EDT this evening for NCZ087-096-099-105>110. MARINE...None. && $$ SYNOPSIS...RGZ NEAR TERM...DCH SHORT TERM...DCH LONG TERM...RGZ AVIATION...MRR is the U.S. government's official web portal to all federal, state and local government web resources and services.