Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 221735 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 135 PM EDT FRI JUL 22 2016 .SYNOPSIS... Seasonable temperatures today will yield to hotter weather over the weekend. The heat wave will last into the early or middle part of next week all while rain chances remain minimal. && .NEAR TERM /THROUGH TONIGHT/... As of 1000 AM Friday...Massive ridge across the middle of the country responsible for the extreme heat through the Plains will shift eastward today, with a piece of the ridge extending into the Carolinas by this evening. As this ridge axis spreads east, a weak mid-level low off the east coast will get driven SW, allowing for heights to rise across the area. 850mb temps this morning on the local U/A soundings were around 16C, and are progged to rise to 18- 19C, as a string of some very hot temperatures develop beginning tonight. Highs today will rise into the low 90s, but dry air evident on WV imagery will mix down this aftn/eve, and heat indices will rise "only" into the upper 90s to around 100. Sea breeze convergence may be enough to spawn a few isolated showers/tstms today, but very dry mid-levels and a capping inversion will limit growth, and even lightning will be difficult to achieve this aftn. The NSSL WRF has a lot of convection today, but the much less robust NAM and HRRR are preferred. Any convection will wane after dark, and a warm/humid night is forecast with mins dropping into the mid 70s. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 330 AM Friday...Will continue to hold onto the idea of less than 20 POPS this fcst period, with mainly isolated tstorms along the sea breeze and possibly tstorms drifting in from the west. Even with the development and persistent Piedmont trof across the central Carolinas, convection will be hard pressed to develop and push through the convective lid. This aided by a subsidence inversion aloft as well as warming temps aloft, ie. models indicate 500MB temps only dropping to -4 degrees C, resulting in limited lapse rates that are not very conducive for Tstorm activity during this 2 day period. The central U.S. high de-amplifies some and broadens it`s coverage across the entire southern U.S. from coast to coast by Sunday. The ILM CWA will remain under its umbrella. Will have to watch the mid-level Low that develops offshore from Florida late Saturday, with models pushing it onshore across the central and northern Fl peninsula late Sunday. Not much of an effect this far north illustrated by the models but bears watching to see if it will increase convection probabilities late this period as it does south of the ILM CWA. Once again stayed closer to the GFS Mos guidance which shows increasing temps, both max and min, during this period. In addition, it slowly increases the sfc dewpoints to widespread 70s. Heat indices will be just shy of advisory criteria on Saturday but Sunday should push to and above 105 degrees. Will convey this within the hazardous weather outlook. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 3 AM Friday... The long term will be characterized by very hot and humid and generally rain-free conditions. The main questions appear to be the degree and length of the heat and when meaningful rain chances return. Early in the period upper level ridging will be broad and covering much of the lower CONUS (though there may be a weak upper low retrograding across FL/NE GOMEX). Locally this ridge will bring hot conditions and suppress precipiation despite increasing low level moisture in SW flow around Bermuda high and east of piedmont troughiness. Heights are not as high nor are BL temps as the last heat wave earlier this month as the core of the heat appears to stay relegated out west. Even so we will see mid to upper 90s and heat indices in the advisory realm through at least Tuesday. Previously it appeared that this setup would start to break down on Wednesday but now this may be a bit slower. And indeed some guidance is showing a slight abating of the heat by then this is likely due to the MOS increased bias towards climatology further out in time. Have reduced the amount of "cooling" and increase in POPS shown in previous forecast. This is especially supported by the 00z ECMWF. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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As of 18Z...High confidence in VFR through the Valid TAF period. Bermuda High will bring warm temps aloft and subsidence which will help to squash any significant cumulus buildups. Thus, have left any mention of showers and thunderstorms out of the valid TAF period. Few to sct cumulus will continue into the eve, 3-4 kft with cirrus above that. Once the heating of the day is through, we only expect some cirrus late eve and overnight as the cumulus clouds slowly dissipate. Southerly winds will be 10 kt or less through the early eve and then less than 5 kt overnight. EXTENDED OUTLOOK...Brief periods of MVFR/IFR from isolated afternoon convection Sunday through Wednesday. Otherwise expect VFR.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1000 AM Friday...Weak Bermuda high pressure will expand slowly this aftn and evening, with winds becoming SE to SW tonight at around 10 kts after being light and variable through this aftn. A weak sea breeze will develop as well, but little change in overall conditions in the near shore waters are expected. These light winds will ensure the 3ft/9sec SE swell remains the dominant wave group, producing 2-3 ft seas through tonight. SHORT TERM /Saturday THROUGH SundAY NIGHT/... As of 400 AM Friday...Ridging across the area from high pressure centered well offshore from the SE States will persist thruout this period. The Piedmont trof across the central Carolinas will develop on Saturday and persist into early next week. The slightly tightened sfc pg between the 2 wx features will result in sw winds at 10 to occasionally 15 kt speeds each day. Models are now indicating a weak mid-level low that develops offshore from the Florida coast by Sunday and pushes it westward across the central and north Florida coasts late Sunday. Some wind speed enhancement across the local waters may result from this low late Saturday thru Sunday. Significant seas will run 2 to 3 ft with the 4 footers primarily off Cape Fear Sat into Sun. The 2 foot ese ground swell will mainly dominate the sig. seas, however, at times the 3 to 5 second period locally produced wind driven waves may prevail over this ground swell. LONG TERM /MONDAY THROUGH TUESDAY/... As of 3 AM Friday...Seasonable lack of variability in the forecast for the long term. South to southwesterly flow well established between the bermuda high and piedmont trough. If anything changes at all it may be a slight lengthening of the dominant period as the weak swell energy competes in the frequency spectrum with the shorter period wind wave. Even so combined seas leading to a dominant height of 2-3ft. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...JDW SHORT TERM...DCH LONG TERM...MBB AVIATION...RJD

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