Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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644 FXUS62 KRAH 250743 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 343 AM EDT THU AUG 25 2016 .SYNOPSIS... High pressure will extend across the region through the remainder of the week, as a strong upper level ridge builds overhead. && .NEAR TERM /THROUGH TONIGHT/... As of 345 AM Thursday... On the eastern periphery of a 596m ridge at 500mb, water vapor imagery and dynamic trop maps depict a compact tropopause disturbance diving south across the area this morning. This has only resulted in a few extra clouds and will go mostly unnoticed. the aforementioned ridge will build eastward over the TN Valley today, continuing the warming trend and dry conditions over central. Some CAMs suggest convection over the higher terrain will progress southeast into the Piedmont late this afternoon, but limited moisture and instability will make it hard for much more than an isolated storm to reach the northwest Piedmont. Highs 89-93. The surface ridge axis will shift east tonight, favoring a little better cooling over the coastal plain, with lows ranging from the upper 60s to around 70 east to west. && .SHORT TERM / FRIDAY THROUGH FRIDAY NIGHT/... As of 345 AM Thursday... The center of the upper ridge -forecast at 594dm- will shift east and be centered over southwest VA on Friday, bringing the 850mb thermal ridge across northwest NC and southern VA. 850mb temps around 21C favor highs in the upper 90s, and while mixing may not be quite that deep, highs should be on the upper end of guidance, 93-96. dew points creeping back into the lower 70s area while will spell a return of humid conditions and heat indices back around 100F. A weakening cold front is forecast to drop into VA Friday evening, but ahead of the front lows on Friday night will be in the lower 70s for most areas. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 240 PM Wednesday... Fri-Sun: Quite warm to start this period, followed by moderating temps, and very low precip chances throughout. Strong mid level ridging will remain the dominant weather feature heading into the weekend, with its center drifting slowly from the western Carolinas early Fri ENE to over eastern VA/NE NC by Sun, all the while maintaining dry and stable mid-upper levels over our area. A surface cold front approaching from the NW Fri will drop into and through NC over the weekend, causing a dip in thicknesses from much above normal Fri/Sat to near or just slightly above normal starting Sun. With a weakening low level wind field and no opportunity for moisture influx at any level, any convection ahead of or with the front will be feeble and very isolated, likely limited to a few cells drifting slowly off the higher terrain (extreme NW CWA) and along an inland-drifting sea breeze (far SE CWA) late in the day Fri, with perhaps a bit better (but still low) coverage Sat afternoon over the southwest CWA near weak upglide and low level mass convergence near the Piedmont trough. The front settles to our south Sun with a high pressure ridge centered off New England nosing narrowly to the SW through central NC, supporting a drop in max temps from the mid 90s Fri/Sat to around 90 or the lower 90s beginning Sun. Mon-Wed: Starting Mon, the mid level ridge weakens and flattens yet continues to extend W-E across the region. Low level flow from the east or ENE may be sufficiently strong and onshore-directed to boost low level moisture profiles and increase diurnal sea-breeze convection chances in the SE CWA on Mon, although the limited deep moisture should keep coverage low. Models still vary quite a bit with the tropical wave now over the northern Leeward Islands which may be driven toward the WNW by the mid level ridge and may affect a portion of FL and/or the Gulf Coast by early to mid week. Model solutions continue to range widely, with the GFS remaining weak with an erratic motion and the so-far-strongest ECMWF solution showing a slowing trend with the 12z/24 run, which all results in reduced confidence in any details this far out. At the very least, the increasing easterly low-mid level component should draw increasing amounts of Atlantic moisture into the eastern Carolinas, and we should see an increase in daily showers and a few storms mainly east as we head into midweek. We will, of course, continue to monitor the tropical wave, although by all accounts it will not be a direct factor in our weather through at least Wed. With thicknesses holding a bit above normal, temps are expected to peak around 90 to the lower 90s Mon-Wed, with lows mostly in the lower 70s. -GIH && .AVIATION /07Z THURSDAY THROUGH MONDAY/... As of 145 AM Thursday... High confidence in predominately VFR conditions through the TAF period, as strong high pressure remains in control of the region. As was the last last night, there will likely be a period of IFR or LIFR vsby after 08z at RWI, with MVFR vsbys more likely at RDU AND FAY. Confidence is much higher at RWI. All terminals will return to VFR by around 12z. Outlook: Persistence of high pressure over the region will continue to promote VFR conditions, with early morning fog possible each morning. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...BLS NEAR TERM...BLS SHORT TERM...BLS LONG TERM...26 AVIATION...BLS

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