Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 230542 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 140 AM EDT SAT JUL 23 2016 .Synopsis... An area of high pressure aloft will expand from the central U.S. across the mid-Atlantic states and Carolinas through early next week. This will bring a period of hot temperatures to central NC. && .Near Term /Overnight/... As of 720 pm Friday... Central NC lies on the eastern periphery of a deep upper level ridge (centered over the lower Midwest) and on the western periphery of an upper level trough stalled offshore the Southeast coast. Similar to yesterday, diurnal destabilization this afternoon has been strongest in the W/SW Piedmont (1000-2000 J/kg MLCAPE) and weakest (500-1000 J/kg MLCAPE) in eastern/coastal NC where subsidence prevails on the backside of the upper level trough stalled offshore. Small amplitude disturbances /DPVA/ rounding the NE periphery of the 300 mb ridge over the central Appalachians could track into western NC this eve/tonight, however, the `sphere of influence` of such disturbances should remain west of central NC as they track S/SSW along the eastern periphery of the H3 ridge. As a result, forcing for ascent this evening will be confined to shallow convergence attendant a weak Piedmont trough and convective outflow. With the above in mind, expect scattered convection to largely remain confined along/west of Highway 1 and to gradually weaken/dissipate within a few hours after the loss of heating/insolation. Expect lows generally in the lower 70s, though a few rural/low-lying areas in the N/NW Piedmont may fall as low as 68-70F. -Vincent && .Short Term /Saturday and Saturday Night/... As of 345 PM Friday... The environment on Saturday should be similar to today, although PW values are expected to rise steadily, with thicknesses continuing to climb. We`ll also be on the anticyclonic side of MCVs dropping southward through the southern Appalachians, with no other dynamic forcing mechanisms evident. So we`ll be relying on purely thermodynamic lift, it appears, focused on differential heating in the higher terrain as well as subtle boundaries, a few of which may be leftover from the current convection over western NC. Will expand the low shower/storm chances a bit from today`s pops, but still expect coverage and upscale growth to be limited by warm and somewhat dry mid levels. Thicknesses and new guidance indicate highs of 94-98, and with dewpoints dropping no further than around 70 over much of the area, heat index values should peak in the 99-104 range for a couple of hours. This is below advisory criteria, so will stick with a mention in the HWO for now, but this will certainly be revisited tonight. Lows Sat night in the low-mid 70s, not allowing much recovery from the heat stress. -GIH && .Long Term (Sunday through Friday)... As of 245 PM Friday... To begin the long term period, the strong upper ridge that provided multiple days of intense heat across the Central Plains will have dampened and became elongated in east-west fashion, extending into the region. As it does, heights will rise over central NC through the weekend. As such, max low level thickness values are progged to top out in the low to mid 1440s on Sunday (slightly lower than previous runs), with similar values on Monday. This combined with mostly dry conditions and temps not cooling off much as night, temps will be able to rise well into the mid 90s, maybe even the upper 90s (warmest on Sunday). This combined with a moist air mass may necessitate the issuance of a heat advisory, most likely across at least the eastern half of the forecast area, where heat index values will approach or exceed 105 degrees. With regards to precip chances, overall they will stay rather low through early next week, but will not be zero as there will be a persistent Piedmont trough that could be a focus for convective development, as well as the sea breeze and/or any weak disturbances that move through aloft. The aforementioned ridge will continue to dampen and shift more offshore through the middle of the week. Also, a shortwave trough is progged to cross southern Canada and the Great Lakes Monday into Tuesday. This will propel a cold front towards the region Tuesday into Wednesday, but as can be expected this time of the year, there is disagreement with just how far south it will make it and it will likely stall near or just north of the area and then meander for a few day. Another shortwave crossing the Ohio Valley will approach towards the end of the week. Therefore, with us gradually losing the influence of the upper ridge and with a cold front in the vicinity, precip chances will start to increase, at least back to the normal diurnal range, especially towards the middle to end of the week. The increased cloud cover and precip chances should allow temps to "cool" back to the low to mid 90s (however, still slightly above normal). -KRD && .Aviation /06Z Saturday through Wednesday/... As of 140 AM Saturday... VFR conditions expected to prevail across central NC through Monday as an area of high pressure aloft builds over the region. While isolated thunderstorms will be possible each late afternoon-early evening through Monday, probability of convection affecting a specific TAF site is too low to mention in the terminal forecast at this time. Patchy MVFR fog will be possible early each morning, primarily between the hours of 10Z-12Z. While VFR conditions will likely dominate through Wednesday, there will be periods of MVFR conditions associated with either early morning fog, or late afternoon/early evening convection. && .Climate... Record high temperatures and the year in which the record was most recently set at Raleigh, Greensboro, and Fayetteville. Sat Jul 23 Sun Jul 24 Mon Jul 25 RDU 105/1952 101/2011 102/2010 GSO 99/1952 99/1914 101/1914 FAY 103/2011 105/1952 103/1914 && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...Vincent SHORT TERM...Hartfield LONG TERM...KRD AVIATION...Hartfield/mlm CLIMATE...BLAES

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