Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221948 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 345 PM EDT FRI JUL 22 2016 .SYNOPSIS... A hot mid level ridge of high pressure will expand from the central U.S. across the mid-Atlantic states and Carolinas into early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 330 PM Friday... A band of storms which formed over the higher terrain of NC earlier this afternoon continues to drift toward the SE, approaching our western counties, while other very isolated cells form further east over the eastern Piedmont where PW is slightly greater. These are being assisted by weak DPVA but are facing a bit of hostility in the environment with marginal to poor mid level lapse rates, very weak deep layer shear, and slightly below normal PW. However, given the good low level lapse rates, MLCAPE up to 2000 J/kg, and downdraft CAPE over 1200 J/kg, these western cells still have a favorable environment to work with, so will adjust pops a bit to expand slight risk further east and raise pops on the far western fringe of the CWA for the next several hours as this convection eases toward the SE. A few of these storms could generate enhanced downdrafts given the high D-CAPE, along with heavy rain due to slow movement. The latest CAM runs show convection gradually diminishing by mid evening in our CWA, and will trend pops down accordingly after nightfall. With light winds and high dewpoints, would expect to see another round of patchy light fog late tonight. Movement of convective debris cloudiness from the NNW late tonight along with a light breeze should curb radiational cooling from a hot ground overnight, so temps should be warmer than last night, falling to 70-75. -GIH && .SHORT TERM /SATURDAY THROUGH 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 /18Z Friday through Wednesday/... As of 1205 PM Friday... High probabilities of VFR conditions persisting through the next 24 hours. Warm and dry air aloft will suppress most shower/storm activity over Central NC this afternoon through midday Sat, with clouds generally scattered and bases above 4 kft. Any isolated storms would be circumnavigable. The better chances of a stray storm would be near INT/GSO and FAY, although chances are too low to include as a prevailing condition. As always, erratic gusty winds and lightning can be expected in and near any storms. There is a small chance for patchy shallow MVFR fog in low-lying areas late tonight into early Sat morning at all TAF sites, but chances are too small to mention at this time. Surface winds will remain light through Sat, mainly from the southwest under 10 kts. Looking beyond 18Z Sat: A few storms are possible late Sat afternoon into Sat night, primarily at INT/GSO/FAY. Areas of MVFR fog may develop late Sat night into Sun morning. Shower/storm chances will start to improve late Sun into Sun night, with scattered daily storms possible through Wed as the air mass moistens more deeply over Central NC. Fog is possible early each morning Mon-Wed. -GIH && .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...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...KRD AVIATION...Hartfield CLIMATE...BLAES is the U.S. government's official web portal to all federal, state and local government web resources and services.