Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 100055 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 755 PM EST Fri Dec 9 2016 .SYNOPSIS... Arctic high pressure will build across the area through Saturday. A cold front will approach from the west late Sunday and move through the area on Monday. && .NEAR TERM /THROUGH TONIGHT/... As of 240 PM Friday... A chilly day (temps around 12-15 deg below normal) will become a chilly night, as arctic high pressure continues to build into the area from the NW. Passage of a weak sheared wave just to our north will bring a few high clouds mainly to the northern forecast area overnight (some of this cloudiness could be orographically enhanced late). But otherwise skies will be generally clear tonight, and this in combination with light surface winds will foster good radiational cooling, with thicknesses likely to be a bit lower than they were this morning. Expect temps to bottom out in the 18-24 degree range, with the cooler readings in outlying areas of the northern/western Piedmont. -GIH && .SHORT TERM /Saturday through Sunday night/... As of 335 PM Friday... Sat/Sat night: The surface high builds overhead through Sat night, as the mid level flow becomes more zonal. We should see an increase in high thin clouds, especially late Sat into Sat night, as weak perturbations and high level moisture move out of the Front Range and across the Mid-Atlantic region. Thicknesses will start out a bit cooler Sat morning than this morning, although this will be partially offset by some afternoon recovery, which should lead to highs similar to today, in the 40-45 range. Lows Sat night in the low-mid 20s, with light to calm surface winds and a veil of high thin clouds and patchy mid clouds overnight. Sun/Sun night: The 850 mb anticyclone will shift off the Southeast coast late Sat night into early Sun morning, inducing low level warm advection just above the slowly-departing surface high. This warm advection will strengthen over time Sun/Sun night, and models agree on increasing and deepening moist isentropic upglide, starting at 285K-290K, focused on the eastern CWA. Expect increasing clouds roughly from S to N Sun afternoon, trending to mostly cloudy areawide by sunset, and remaining cloudy Sun night. The column remains dry above the freezing level through Sun night, so any precip should be fairly light with pops no better than chance. With rising thicknesses balancing increasing clouds, expect still-cool highs in the 43-50 range. After a slight dip in temps Sun evening, readings should hold steady or rise a bit overnight. Lows 39-46. -GIH && .LONG TERM /MONDAY THROUGH FRIDAY/...
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As of 210 PM Friday... Initial low amplitude long wave troffing will produce fast and near- zonal flow across the central and southern tiers of the Conus through mid week. Return flow ahead of an initial front on Monday will produce a strong surge of warm air advection with highs ranging from upper 50s across the north to mid 60s in the south...5 to 10 degrees above normal. Moisture advection will cut off pretty quickly as low level flow turns westerly across the Gulf states...with chance PoPs during the day shifting to the east and diminishing post-fropa on Monday night. The frontal zone aligns parallel to the flow and forecast details are murkier heading towards midweek with considerable variability in model solutions. The frontal zone looks to remain south of the area...with small chance PoPs mainly across the southern tier... both Tue and Wed as surface high pressure races across the Ohio Valley. Highs will be on a gradual fall as the upper trof amplifies a bit and we should be in a predominantly cloudy regime. Highs Tuesday in the mid to upper 50s will fall to the low and mid 50s on Wednesday. Confidence in model solutions for the late week is even lower although colder air will continue edging southward. The upper flow is not highly amplified, however, which will block off the really frigid airmass north of the area. Regardless, highs will probably top out in the mid 40s after morning lows in the mid to upper 20s both Thu and Fri.
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&& .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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As of 745 PM Friday... Sprawling arctic high pressure will maintain continued VFR conditions and calm to light Nly winds through Sat. Cirrus will fill an otherwise clear sky beginning late tonight or early Sat. Outlook: VFR conditions should hold through the first half of Sunday as high pressure builds overhead. As a warm front approaches from the south, moisture will increase, and cigs will trend to MVFR, then IFR Sunday afternoon from south to north. There is a good chance for low level wind shear conditions Sun night into Mon morning with 35- 40 kt winds from the SW at 1500-1800 ft AGL. Adverse aviation conditions, including sub-VFR cigs and vsbys, are expected to dominate from late Sunday through at least Monday night -- and perhaps into Wednesday -- as waves of low pressure track along the frontal zone as it holds over or just south of the area.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...mlm AVIATION...MWS/Hartfield

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