Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 270547 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1247 AM EST Mon Feb 27 2017 .SYNOPSIS...
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High pressure will move offshore today. A warm front will approach from the south tonight, then move north of the region Tuesday. Warm southwesterly flow will continue ahead of a cold front approaching from the west.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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As of 825 PM SUNDAY... Expect mostly clear skies followed by increasing upper level cloud cover (ceilings 12-25 KFT) after midnight. With mostly clear skies and calm or light/variable winds, expect temps to fall rapidly, reaching the lower 30s in the typical rural and low lying areas by midnight. Overnight lows will range from the upper 20s (typical cool spots) to low/mid 30s elsewhere, warmest in urban areas and locations affected by cloud cover. -Vincent
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 AM TUESDAY/... As of 250 PM SUNDAY... Surface ridge axis will extend west into the area from the parent high centered off the Mid-Atlantic coast. Resultant southerly- southeasterly low-level flow will allow for moderation of cP airmass with highs Monday a good 7 to 10 degrees warmer than Sunday. Highs ranging from lower 60s NW to upper 60s/near 70 SE. Strengthening southwesterly low-level WAA ahead of the sheared low- amplitude shortwave trough moving into region will result in increasing clouds by the late afternoon with isolated to scattered showers possible during the evening and into the overnight hours. The NAM is especially wet as it develops 500-750 J/Kg of elevated instability across the area, but believe this to be a bit overdone. Much warmer overnight lows in the upper 40s to lower/mid 50s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... As of 255 PM Sunday... Tue/Tue night: The most likely scenario is that the warm front will be pushing NNW into the area early Tue, with the morning hours featuring low stratus in the west, where the stable pool should linger, and partly cloudy in the east, with isolated light precip in the west supported by moist isentropic upglide. Models show the entire area mixing and destabilizing during the afternoon, although climatology would suggest that the NW CWA could stay somewhat stable all day. Models depict marginal to moderate instability developing mainly along and east of Highway 1 in the mid-late afternoon, with good low level moisture streaming in, improving deep layer shear, and decent mid level lapse rates of 7.0-7.25 C/km. Dynamics are slim however, with a fairly flat mid level flow, and only weak upper divergence. Will have a slight chance of showers in the afternoon in the west, with a better chance of showers and thunderstorms in the east, lasting into the evening before the loss of heating prompts a trend down to small shower chances and the development of stratocumulus overnight. These clouds should mix out with heating Wed as we`ll be firmly in the warm sector, with a stout gusty breeze from the SW ahead of the cold front, which should push SE through the area Wed evening or Wed night (the GFS is several hours faster than the ECMWF and NAM). GFS instability is a bit higher Wed afternoon as compared to Tue, reasonable given the even greater influx of low level moisture, and if the slight cap noted around 800 mb on GFS forecast soundings comes to fruition, in conjunction with the GFS`s projected 7.5-8.0 C/km mid level lapse rates and strengthening deep layer bulk shear to 55-65 kts, we could get rapid development and intensification of convection during the afternoon, especially over the eastern CWA, with some late-day severe storms possible. This convection should remain supported by a pocket of strong upper divergence as it shifts over eastern NC through late evening, followed by frontal passage, although high clouds should persist over the area through Wed night as the positively tilted mid level trough will still be well off to our NW. With warm thicknesses, expect highs of 70-77 Tue except for mid-upper 60s NW. Morning thicknesses Wed around 1380 m, nearly 60 m above normal, will support highs from the mid 70s NW to lower 80s SE. Thu through Sun: A generally tranquil period with dry weather likely. The cold front will be pushing southeast ward off the coast Thu morning. Broad mid level troughing will persist over central/eastern Canada and the northeast CONUS into Sat, with the core of the polar low transferring from Hudson Bay to Newfoundland. An initial ridge of high pressure nosing in from the WSW Thu will bring thicknesses that are close to seasonal normals. Then, energy that swings through the trough base across the Mid Atlantic/Northeast on Friday will bring a reinforcing dry cold front southeastward through the area, followed by chilly high pressure that will build overhead by Sat morning. This should knock temps down to below normal for Fri night/Sat, with a good chance of orographically enhanced high clouds over the Piedmont early Sat within fast perturbed mid level flow. Temps should moderate for Sun as the highs drops to our SE with return flow and weak lee troughing for the latter half of the weekend. -GIH && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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As of 1245 AM Monday... High confidence in VFR today under influence of high pressure. A light south-southwest wind will develop today as the high moves east. Mid and high level clouds will increase this evening as a weakening upper level disturbance moves overhead and a warm front lifts north into the Carolinas. More substantial stratus, MVFR to IFR, will likely come after 06Z, but there is a small chance some MVFR ceilings, along with a few weakening showers, could develop at GSO and INT by 06Z Tuesday. Outlook: Stratus developing early Tuesday will burn off prior to midday, with scattered showers and storms possible during the afternoon and evening. A more substantial threat of sub-VFR is expected late Wednesday and early Thursday a cold front crosses the region. VFR will then return for the end of the week.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...SMITH NEAR TERM...VINCENT SHORT TERM...CBL LONG TERM...HARTFIELD AVIATION...SMITH

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