Area Forecast Discussion
Issued by NWS Wilmington, NC

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324 FXUS62 KILM 220837 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 437 AM 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 330 AM Friday...Mid and upper levels illustrate a ridge axis extending from the amplified South Central U.S. High will lie across or just north of the ILM CWA this period. Since the ILM CWA is downstream from this axis, NVA and subsidence aloft will result in a convective lid across the area. The GFS idea of low instability looks more realistic when compared to the NAM and thus will adhere to its fcst. Forcing along the mesoscale diurnally driven sea breeze may allow a tstorm or 2 to break thru this lid and for that indicated a 15 to 20 POP along the sea breeze as it progresses inland. Otherwise, looking at scattered diurnally driven cu dissipating around sunset. Popcorn type showers or tstorms will develop offshore after midnight but do not expect them to move onshore. Stayed closer to the GFS Mos guidance which has been performing better than the NAM and European Mos respectively as of late. && .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. With a subsidence inversion aloft as well as warming temps aloft, ie. models indicate 500MB temps climb to -4 degrees C, resulting in limited lapse rates not very conducive for Tstorm activity during this 2 day period. The central U.S. high de-amplifys 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 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. 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 increasing RH. 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 /08Z FRIDAY THROUGH TUESDAY/... As of 06Z...Predawn fog will generally be MVFR at worst at coastal terminals. Inland still not quite clear as to whether IFR or even LIFR develops. Some guidance hitting FLO with LIFR (though oddly not LBT). Since FLO has a higher dewpoint depression than LBT at this time have limited to IFR and relegated to tempo. VFR for the rest of the forecast for all terminals. Winds lt and var through the overnight hours. around mid-morning winds will become southerly 5-10 kts, highest at the coastal terminals. EXTENDED OUTLOOK...Brief periods of MVFR/IFR from isolated afternoon convection Saturday through Tuesday. Otherwise expect VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 330 AM Friday...Weak ridging from the center of high pressure well offshore from the Southeast States will extend across the area thruout this period. Looking at a land breeze to start this morning that will eventually transition to a se to s direction by midday and persist through tonight. With the sfc pg rather relaxed, speeds will run 10 kt or less. The exception will come from a weak sea breeze circulation that will result in wind speeds at 10 to possibly 15 kt this aftn thru early this evening. Significant seas will run 2 to 3 ft with the ese 1 to 2 foot 8 to 9 second period ground swell dominating, power-wise, when looking at the spectral density plots thru tonight. Isolated popcorn convection just offshore early this morning will fade away by late morning, then re-occur during the pre-dawn Sat hours. 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 push it westward across the central and north Florida coasts late Sunday. Some wind speed enhancement across the local waters may result from this low on Sunday. Significant seas will run 2 to 4 ft with the 4 footers primarily off Cape Fear. 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 the 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. && $$ SYNOPSIS...MBB NEAR TERM...DCH SHORT TERM...DCH LONG TERM...MBB AVIATION...MBB is the U.S. government's official web portal to all federal, state and local government web resources and services.