Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 270137 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 935 PM EDT TUE JUL 26 2016 .Synopsis... Strong high pressure aloft will extend over the Southeast U.S. through the work week, as weak disturbances pass by just north of the region. A cold front will approach from the northwest on Friday, then stall out just to our north and west next weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 330 PM Tuesday... Scattered showers and storms have already begun to fire over the mountains, foothills, and into the northern and western Piedmont, where CINH has vanished and MLCAPE has already risen well over 2000 J/kg. Deep layer bulk shear still isn`t great but is better than in the last several days, as shortwave energy tracks eastward across the OH valley and mid-Atlantic, nudging the westerlies slightly to the south and inducing sufficient acceleration aloft to boost values to around 20 kts across northern NC this evening. Have retained isolated to scattered showers and storms through the evening, starting first over the Piedmont (better coverage north and fewer storms south), then shifting eastward into the NE Piedmont and northern/central Coastal Plain through the evening before weakening and dissipating with loss of heating overnight. This scenario is supported by the latest CAM runs. A few storms could become strong, given the degree of instability, improving wind field aloft, and high downdraft CAPE over 1000 J/kg, but the mid level lapse rates remain meager with no good low level mass convergence, so widespread strong storms aren`t expected. Persistence will be followed for lows tonight, in the lower to mid 70s. Temps over much of the CWA won`t drop below 80 until well after midnight, exacerbating the adverse health effects of this ongoing hot spell. -GIH && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... As of 345 PM TUESDAY... The two main concerns for Wed are the storm threat and the heat. The mid-upper level ridge will remain centered just to our SE while extending across the Southeast states, while the weak mid level wave continues to pass by to our north, crossing the mid-Atlantic coast. Deep layer bulk shear will remain marginal, and the warm mid levels will continue to curb instability over the southern sections of NC. But both factors will be sufficient for convection initiation and maintenance Wed afternoon across the northern CWA. With a thermodynamic environment tomorrow similar to that of today, we should again see scattered storms mainly across the north Wed afternoon, lasting into the evening before weakening and exiting. Once again, a few strong storms are possible, but weak lapse rates and marginal winds aloft will limit this potential. A few debris mid clouds from this evening`s convection may linger early in the day to temper heating slightly, however thicknesses and forecast soundings still support persistence, with highs again in the mid to upper 90s, and dewpoints starting out in the mid-upper 70s before dropping to 70-75 in the afternoon with mixing. Heat index values are expected to top out near or above 105 over all but the NW Piedmont tomorrow, so will go forward with another heat advisory, along and east of a line from Albemarle to Burlington to Kerr Lake. Lows Wed night in the mid 70s. -GIH && .LONG TERM /Thursday through Tuesday/... As of 230 PM Tuesday... Beginning Thursday, the high pressure system gets suppressed ever so slightly to the southeast and allows the remnants of the frontal boundary over VA to creep southward, increasing pops a bit for the northern tier of the CWA but otherwise points south should remain fairly dry but afternoon showers and thunderstorms will be favorable east of the Piedmont trough. Thursday night a wave is expected to develop just north of the area and move northeastward leaving Friday fairly dry. Afternoon convection will be possible again Friday and Saturday afternoons as the upper level flow turns more southwesterly. By Sunday, central NC becomes increasingly squeezed between a surface high to our southeast and another to our northwest. This will set up a more active pattern over the area which will funnel moisture into the area. This should help keep skies cloudier and bring temps down a few degrees for the beginning of next week. Early next week an upper trough develops to help push the frontal boundary through the area and hopefully provide some relief to temperatures. Until then expect continued highs in the mid 90s with heat index values approaching 105 degrees. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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As of 935 PM Tuesday... Humid airmass in place still supporting widely scattered thunderstorms this evening. Eastern TAF sites will need to be monitored through 04Z for isolated lingering showers and storms, otherwise VFR conditions will prevail through the 24 hour valid period. Expect another round of convection tomorrow under similar heat and moisture conditions, mainly across the northern tier during the late afternoon...with activity migrating slowly south in the evening and early night. Winds through the period will be light...less than 8 mph...and generally westerly... Looking beyond 18z Wed: Mostly VFR conditions are anticipated, although late night and early morning MVFR fog is possible each day through Fri, with a better chance of sub-VFR fog/stratus Sat/Sun. Scattered showers/storms are again expected Wed afternoon, mainly at the northern TAF sites. Storm chances will drop once again for Thu and Fri, before rising again over the weekend.
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&& .RAH WATCHES/WARNINGS/ADVISORIES...
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Heat Advisory from noon to 8 PM EDT Wednesday for NCZ008>011-023>028- 039>043-073>078-083>086-088-089.
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&& $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...mlm

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