Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 250523 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 123 AM EDT TUE OCT 25 2016 .SYNOPSIS... High pressure will extend into our region today through Wednesday. A cold front will approach from the west on Thursday. && .NEAR TERM /Tonight/... As of 650 PM Monday... The dry cold front was a few hours slow in passing through central NC. The front extended across TN into southern VA at 630 PM, and was preceded by a surface trough. Both will push through the region by midnight. DAA and downslope flow behind the surface trough lowered the dew points by 10+ degrees (fell from 43 to 30 at Winston-Salem between 400 PM and 500 PM). However, the temperature remained in the upper 70s. The true CAA was tied to the cold front and was located north a few hours behind the surface trough and cold frontal passage. Therefore, the air will dry out further this evening but most importantly the actual temperatures will be very slow to fall. The evening will be very mild, even a few hours after the frontal passage. The SW wind at 10 mph will shift to the NW at 10 to 15 mph with the frontal passage. A few gusts to 20 mph will occur this evening. Expect plenty of 60s through the mid to late evening, finally cooling from the north later. The skies were clear ahead, along, and behind the front over the entire mid-Atlantic region, and are expected to remain so overnight. Later tonight, winds will diminish to light and finally some radiational cooling will take over. Lows by daybreak will be in the 40s (lower 40s N to upper 40s S). && .SHORT TERM /Tuesday through Wednesday night/... As of 330 PM Monday... Quiet and fairly uneventful through mid week. A portion of the surface ridge settles over central NC and modifies somewhat on Tue, then is followed by a weak reinforcing boundary dropping southward through NC Tue evening, and cool Canadian-rooted high pressure nosing in from the north through Wed. This ridge axis will be capped by an 850 mb anticyclone which will drift from the Mid South ESE across the Southeast states through Tue night before shifting off the coast late Wed. Further aloft, the mid levels will remain subsident and warming as a large vortex centered over the Canadian Maritimes and encompassing much of NE NOAM drifts NE and fills with weakening flow over our region as a shortwave ridge builds in from the west through Wed. All of this equates to little or no lift or moisture and a generally weak surface flow. The only issue of concern is the presence of the chilly ridge axis overhead Tue night accompanied by clear skies and light winds, fostering radiational cooling and bringing about the risk of patchy frost. Statistical guidance has trended slightly cooler in spots, and with otherwise favorable conditions, will introduce patchy fog over portions of north central NC with lows in the upper 30s. Otherwise, expect somewhat cool highs Tue/Wed in the mid-upper 60s. The surface ridge will then shift east off the coast Wed night with a light return flow helping to drive surface dewpoints back up through the 40s Wed night. Lows in the mid-upper 40s with mostly clear skies. -GIH && .LONG TERM /Thursday through Monday/... As of 350 PM Monday... Shortwave troughing will extend from south central Canada through the Great Lakes to the Mid South early Thu, shifting eastward Thu into Thu night. This will be accompanied by a strong surface low crossing the Great Lakes (and culminating in a triple point low over E PA and NJ) Thu through early Fri, and a trailing cold front that will drop SE through NC Thu night/early Fri. We will briefly be in the warm sector Thu, which will help drive up thicknesses to near or just above normal with temps expected to warm up into the upper 60s to mid 70s. Moisture depth does improve with PW reaching near 1.25", with decent mid level DPVA and minor upper divergence, although along-front mass convergence is apt to be small. Will retain chance pops Thu afternoon, peaking Thu night before departing early Fri morning. Projected instability appears minimal, and will keep it at just showers for now. The active northern stream across the north central and northeast CONUS/Mid-Atlantic persists through the rest of the week, with the aforementioned trough strengthening to a closed mid level low over MI Thu before shifting east and off the Northeast coast by early Sat, and another closed low close on its heels over the weekend. Another high pressure ridge builds into NC and overhead through Sat morning before shifting to our SE Sat afternoon in response to this fast flow. Expect minimal cooling Fri as the cooler thicknesses barely work into NC, then a warmup back into the 70s is anticipated Sat as we again get into return flow on the back side of the departing surface ridge. The next front pushing in from the north is likely to drop into or through NC on Sun or Sun night, but this too should be moisture-starved. Expect highs to cool back down a bit Sun and a bit more Mon, into the 65-70 range. The way-too-early outlook for Halloween night appears to be dry, with seasonable to slightly cooler than normal temps. -GIH && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... As of 123 AM Tuesday... There is a high probability that VFR conditions will exist across central NC through Wednesday as high pressure builds into then settles over the area. North to northeast sfc winds will occasionally gust between 15-18kts between 13Z-18Z. This high will drift east late Wednesday ahead of a cold front approaching from the west. Southerly return flow will advect low level moisture, likely resulting in the formation of a low stratus deck and MVFR ceilings by early Thursday morning. A few showers will accompany the front late Thursday and Thursday night. Afterwards, high pressure and associated VFR conditions will return for Friday and Saturday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...Badgett SHORT TERM...Hartfield LONG TERM...Hartfield AVIATION...WSS is the U.S. government's official web portal to all federal, state and local government web resources and services.