Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 190129 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 929 PM EDT THU AUG 18 2016 .SYNOPSIS...
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A series of mid-level disturbances in generally westerly flow aloft will track across the Southern Middle Atlantic states, atop a lee surface trough over the same areas, through Saturday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 925 PM Thursday... A couple of MCV`s are evident in regional radar and model analyzed vorticity data this evening between KINT and KIGX. These disturbances appear to be situated on the south side of a SRN stream mid-upper jet axis stretching from the Mid MS Valley to the Middle Atlantic coast. At the surface, a generally E to W-oriented surface trough /former weak frontal zone/ was analyzed from the NC Outer Banks WWD across the NE NC Piedmont, where it intersected a NE to SW-oriented lee/Piedmont trough extending across the WRN Carolinas. A relatively well-defined, and slightly NWD-retreating outflow boundary also remains evident in KRAX data this evening, from SRN Wilson Co. WWD to NRN Lee and SRN Chatham Co. Recent HRRR solutions that have depicted the development of a large convective cluster over central NC this evening seem overdone, given radar trends of the past several hours. Nonetheless, the current minimal coverage of showers and storms in central NC may indeed experience a slight uptick during the next few hours from the Central and SRN Coastal Plain WWD into the ERN Piedmont, as the aforementioned MCV`s track EWD and interact with the E to W-oriented surface trough and outflow boundary. It will otherwise remain very mild, and humid/muggy, with lows in the lower to middle 70s.
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&& .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... As of 350 PM Thursday... Shortwave impulses interacting with moderate instability within the moist 2-2.25 PWAT airmass pooling invof the stalled surface trough will support scattered to numerous showers and storms Friday afternoon and evening. While deep layer shear of 20 to 25kts is progged to be a bit stronger, instability is forecast to be less than recent days with MLCAPE in the 1000-1500 J/Kg range. So still expect a low end/isolated severe threat. High PWATS around ~2" will also support the threat of heavy rain and localized flooding of urban and poor drainage areas. Storm coverage and intensity should decrease with loss of heating, but presence of stalled surface trough and intermittent of DPVA from shortwave disturbances tracking through the area justifies continuation of small chance pops overnight. High temps are expected to be in the upper 80s to lower 90s. Low temps in the lower to mid 70s. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 315 PM Thursday... Saturday and Sunday: With mostly zonal flow aloft and a lingering frontal zone to our south, Saturday will feature plenty of moisture available for convection but only marginal shear and instability. One thing that could help is a small shortwave disturbance that moves across the area and could provide some additional lift for convection, particularly in the east. Temperatures mainly in the upper 80s. Sunday the attention will turn to the approaching cold frontal system to the west. Models have been speeding up the passage of the front the last couple of runs and that trend continues with both the ECMWF and the GFS brining in pre-frontal convection Sunday afternoon and evening with the actual front moving through very early Monday morning. As far as convection on Sunday is concerned the best chances should be across the south where the front will set up a little better with diurnal heating. The good 30 kt shear looks to be hanging back behind the front and will not line up with the best instability. Therefore not expecting much as far as severe weather goes and the front should move through fast enough that flooding should not be as big of a concern as it has been early this week. Temps in the upper 80s to low 90s. Monday through Thursday: After the cold front pushes through early Monday a much drier and more comfortable airmass moves in for much of the work week as high pressure moves overhead. High temperatures are expected to be in the mid 80s with lows in the mid 60s and dewpoints in the upper 50s to low 60s. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... As of 800 PM Thursday... Outflow moving west through the coastal plain and an upper disturbance crossing the Blue Ridge have been largely inactive today but may still pop a few showers or an isolated storm this evening, mainly from RDU south to FAY through midnight. Otherwise, VFR conditions are expected, with a period of sub-VFR possible at INT by 12z given the brief shower that passed over that terminal this evening. Another upper disturbance tracking near the NC-VA border on Friday and a continued hot and unstable airmass will support the potential for scattered storms after 18z. Looking ahead: Scattered afternoon/evening showers and storm will be possible through the weekend in advance of a cold front passage early Monday. In addition, patchy morning stratus/fog will be possible, especially for locations that receive afternoon/evening showers/storms. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...CBL LONG TERM...RE AVIATION...BS/CBL

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