Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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731 FXUS62 KRAH 100532 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1233 AM EST Sat Dec 10 2016 .SYNOPSIS...
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Cold high pressure will build across the area through tonight, then shift offshore Sunday. A cold front will approach from the west late Sunday and move through the area on Monday.
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&& .NEAR TERM /THROUGH TONIGHT/... As of 815 PM Friday... 1040+ mb surface high pressure was centered over the Northern Plains states this evening. Bitterly cold air was associated with this high. The high pressure continued to build and extend SE to encompass much of the central and eastern United States. Even though the arctic air is greatly modified as it reaches our latitude, the temperatures were still around 15 degree below normal for mid- December with the air mass. These numbers seem almost mild if compared to the temperatures directly under the high pressure over MT/ND/MN, where readings were 25 to 35 degrees below normal. Cold air advection continued over our region with the NW flow. The pressure gradient will continue to weaken overnight as the core of the high shifts SE toward the mid-Mississippi Valley region. Clear skies are expected with good to excellent radiational cooling as winds die off to less than 5 mph. Dew points were already in the teens and lower 20s. Expect lows to fall to 20-25 except around 18 in the rural Piedmont locations. && .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/... 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. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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As of 1230 AM Saturday... High confidence that VFR parameters will persist across central NC through 12Z Sunday as high pressure at the surface will be the dominate weather player. Westerly flow aloft will advect high level moisture across the area later today an tonight in the form of patchy cirrus. The high will shift offshore Sunday. the return flow on the backside of the retreating high will advect low level moisture into central NC late Sunday and Sunday night, resulting in MVFR, and eventually IFR ceilings. In addition, patches of light rain should develop Sunday night. An increasing low level jet may produce marginal low level wind shear parameters Sunday night, mainly in the form of speed shear rather than directional shear, as wind speed 35-40kts probable between 1500-2000ft. Variable aviation conditions expected Monday through Wednesday as a series of low pressure systems cross the southeast U.S. This will result in periods of MVFR or IFR parameters due to adverse ceilings.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...Badgett SHORT TERM...Hartfield LONG TERM...mlm AVIATION...WSS

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