Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 170724 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 225 AM EST Fri Nov 17 2017 .SYNOPSIS... High pressure will build overhead from the northwest today, and then move offshore tonight. A warm southwest flow will overspread the area Saturday, ahead of a cold front that will cross the region Saturday night. High pressure will return for Sunday through Monday. && .NEAR TERM /today through tonight/... As of 155 AM Friday... A subtle frontal zone now sitting across northern NC will continue to drop southward through the state early this morning, with little consequence other than briefly stronger winds form the N and NE and perhaps a few gusts. Otherwise, high pressure will build in from the NW today, settling overhead this afternoon, with rising heights aloft and deep subsidence within a dry column. Expect generally sunny skies through the day, with just a few high clouds. Expect highs about a category below normal, in the upper 50s to lower 60s, reflecting the low level thicknesses around 10 m below normal. Increasing high level moisture (around 325-335K) from the west tonight within strengthening upper northwest flow will bring increasing high clouds overnight, as the surface high drifts off the NC coast, with strengthening SW flow up to 25-30 kts at 925 mb evident over the NW CWA. Lows will be in the mid-upper 30s, coolest NE where the clouds will be thinner with lagging low level moisture and thermal advection. -GIH && .SHORT TERM /Saturday through Saturday night/... As of 225 AM Friday... A deep shortwave trough will shift quickly from the central CONUS early Sat eastward to the Mid-Atlantic and Northeast through Sat night, attending a well-defined surface cold front. A brisk low level flow will be strengthening and backing slightly from WSW to SW Sat/Sat night, which will draw higher PW and greater surface dewpoints into NC, so we`ll see tonight`s increasing cloud trend extend into Sat with skies becoming partly then mostly cloudy through the day. But no rain is expected Sat with the column remaining somewhat dry and weak to absent forcing for ascent until after nightfall. Despite the clouds, rebounding thicknesses with good mixing and prefrontal warm air advection should push temps up to above-normal maxes of 63-71. Strengthening SW flow through a deep layer ahead of the surface front and mid level trough will push PW values above 1.0", well above normal, and with the arrival of strong mid level height falls and improving upper divergence along with a 50+ kt 850 mb jet, the earlier likely pops sweeping across the area Sat night still appears justified. However, the quick-hitting nature of this system and the short window of low level moisture transport will greatly limit amounts, and most locations will see a tenth of an inch or less, with the higher values mainly in the northern sections, closer to the more intense dynamics (much of which will pass to our N). Will not have any thunder in the forecast, given the very low and short-duration forecast MUCAPE values (under 200 J/kg). Showers should be exiting the eastern CWA toward daybreak, as the cold front lags just behind, crossing the forecast area late. Lows are expected to range from the low 40s NW to the low 50s SE. -GIH && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 140 PM Thursday... No changes made to longer range forecast. Models continue to highlight a trough and surface low moving across the Great Lakes Saturday and Sunday with its associated surface front racing east across North Carolina Saturday night. Surface winds will be gusty as the pressure gradient tightens ahead of the front, with gusts of 20 to 25 mph by Saturday afternoon. The front will spill over the mountains Saturday afternoon, with likely PoPs in the western Piedmont early Saturday night. These likely PoPs will translate quickly across central NC, reaching the Coastal Plain after midnight before ending towards sunrise Sunday. Cool and dry high pressure will settle into the area Sunday, with rather low amplitude upper troffing lingering Sunday through Thursday. && .AVIATION /06Z Friday through Tuesday/... As of 1230 AM Friday... Confidence is high in dominant VFR conditions across central NC over the next 24 hours. Surface high pressure and a dry air mass will build over the area from the northwest today, bringing unrestricted vsbys and no cigs. The surface high will shift offshore tonight as a few weak upper level disturbances approach from the west, and these will bring an increase in high clouds starting late in the TAF valid period. Surface winds will be from the northeast today under 10 kts, although some gusts over 10 kts are possible early this morning as a weak cool front drops through the area. Winds will trend to light and variable late today into tonight. Looking beyond 06z Sat: VFR conditions will hold through Sat, with increasing and thickening high and mid clouds. Surface winds from the SW will strengthen after daybreak Sat, to sustained 12-20 kts gusting occasionally to around 25 kts through the day. A short period of MVFR cigs/vsbys in showers is possible Sat evening and night as a cold front crosses the area, resulting in a shift of winds from SW to NW Sat night. VFR conditions are expected starting Sun morning as high pressure returns, lasting through Tue. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...mlm/Franklin AVIATION...Hartfield

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