Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 180708 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 308 AM EDT Fri Aug 18 2017 .SYNOPSIS... A weak surface trough will hold over eastern North Carolina today, while a second stronger trough sits over western North Carolina. An upper level disturbance and accompanying weak surface cold front will cross the region from west to east late this afternoon through tonight. The front will stall out over the coastal Carolinas on Saturday, as weak high pressure builds over the western and central Carolinas through the weekend. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As of 1005 PM Thursday... 00Z upper air analysis depicts a weak zone of speed convergence exists between 850mb-500mb immediately west of central NC. This region of lift interacting with available moisture may trigger isolated convection overnight across central NC. This threat appears a bit higher over our western counties versus east. With precipitable water values around 2 inches in the west, any showers/storms will be efficient rain producers, dumping locally heavy/excessive rainfall. In addition, steering flow rather weak at 10kts. Otherwise, expect a mixture of clouds/stars until 08Z when areas of low clouds or fog will begin to develop, especially in the coastal plain. Muggy, with overnight temps in the mid-upper 70s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... As of 345 PM Thursday... Short wave ridging across the Carolinas will give way to falling heights as a short wave trough dives from the upper Midwest into the Ohio Valley by late friday night. The associated cold front will approach the southern Appalachians friday morning and then move across central NC Friday night reaching the coastal region of the Carolinas on Saturday morning. Another convectively active day is expected on Friday with widely scattered showers and storms expected to develop around midday, especially across the eastern Piedmont and Coastal Plain. Some of the higher resolution convection allowing models suggest that the majority of the convection will be attendant to the surface front and will move into the RAH CWA from the west late in the afternoon and then move southeast across the area during the evening. It will remain humid on Friday with dew points in the lower to mid 70s which combined with highs of 89 to 95 will result in heat index values of 100-105. Dew points today over performed and were in the upper 70s across the Coastal Plain and if that occurs again, a heat advisory would be needed. Will hold off for now and defer to the mid shift to issue any headlines. -Blaes && .LONG TERM /SUNDAY THROUGH THURSDAY/...
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As of 310 AM Friday... Sunday will begin with a frontal zone along the NC coastline and continental high pressure moving into the area from the northwest. This should give us very low precipitation chances for Sunday and keep flow very stagnant over the area with very little forcing aloft or at the surface. A similar pattern in place for Monday but the offshore surface high becomes a bit more dominant, meaning southerly return flow increases and potentially some more clouds and shower activity but lagging continental high to the north should keep us relatively dry and hopefully keep cloud cover suitable enough for eclipse viewing. The Piedmont Trough should be more active on Tuesday and coupled with a few shortwaves moving in from the southwest, will result in a slight increase in precip chances on Tuesday afternoon but still only lower end of the chance range. On Wednesday a stronger surface low in the northern stream will bring a cold front to central NC and with it, our best chances for rain for the week. This front will linger over the eastern part of the state through Thursday, keeping precip chances higher in the east. Expect temperatures in the low 90s through the period until Thursday when the front will drop temps back into the mid 80s.
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&& .AVIATION /06Z FRIDAY THROUGH TUESDAY/... As of 125 AM Friday... VFR conditions are expected for much of today through tonight at most central NC terminals, with a few exceptions. At RWI, periods of IFR conditions, primarily IFR cigs with MVFR to IFR vsbys, are expected early this morning, from 06z to 13z, after which time these low cigs will quickly mix and disperse to VFR. Scattered storms are possible near FAY/RWI early today, starting as early as 15z with the potential lasting through the afternoon, although they will remain scattered and not a prevailing condition. More numerous showers and storms are expected starting after 20z at INT/GSO, spreading eastward to RDU then to RWI/FAY during the 22z-06z time frame. MVFR to IFR conditions with very heavy rain and strong gusty and erratic winds are possible with any of these showers and storms later today into early tonight. Looking beyond 06z Sat, any lingering showers will be diminishing soon after 06z as a front passes to our east and weak high pressure builds in from the west. MVFR vsbys in fog are possible early Sat morning at RDU/RWI/FAY and early Sun morning at RWI/FAY. But otherwise, VFR conditions and dry weather are expected Sat through much of Mon with only a small chance of afternoon showers near FAY. The chance of late-day storms and early-morning fog returns late Mon into Tue, as the air mass over NC becomes increasingly hot, moist, and unstable. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...WSS SHORT TERM...BLAES LONG TERM...Ellis AVIATION...Hartfield

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