Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 201812 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 112 PM EST Mon Feb 20 2017 .SYNOPSIS...
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High pressure will extend along the East Coast through early Tuesday. A weakening upper-level disturbance will cross the Southeast states Tuesday night into Wednesday.
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&& .NEAR TERM /THROUGH TONIGHT/... As of 950 AM Monday... Forecast is on track. Plentiful sunshine is a near certainty beneath dry high pressure at the surface and deep ridging and stable/warm air aloft. Observed thicknesses are higher than yesterday morning by around 10 m, although they shouldn`t rise quite as high through the afternoon as they did yesterday, given that the surface ridge will be building down the Eastern Seaboard. Temps are already in the mid 50s to lower 60s, comparable to yesterday`s pace, so still expect highs from around 70 NE to the low-mid 70s elsewhere, with light winds veering from NE to E then SE through the day. -GIH Earlier discussion from 315 AM: A narrow upper level ridge extending from the eastern Gulf into southern Ontario coupled with a dry air surface ridge building southward along the East Coast will maintain mostly clear skies, and very mild conditions for this time of year. While the low level flow is northerly, it`s a neutral flow, meaning little if any cold air advection. Thus, afternoon temperatures should be fairly comparable to Sunday`s, in the 70-75 degree range. Tonight, the low level flow becomes ely as the parent high to our north moves a little farther to the east. This ely flow will advect moisture off the Atlantic and into central NC. Due to the upslope component of the flow, the rising/lifting of the moisture should cause a layer of stratus clouds to develop late tonight/early Tuesday morning in vicinity of the Yadkin River Valley, possibly spreading into our western counties including the Triad region. This moisture band is fairly narrow so no precipitation should be generated from these clouds. Elsewhere, expect mostly clear-partly cloudy skies, with patchy fog possible. Overnight temperatures will vary from the upper 30s-around 40 northeast to the mid 40s over the far south and west. -WSS && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 315 AM Monday... Tuesday, the low level ely flow will advect a cooler air mass into central NC, resulting in afternoon temperatures 4-6 degrees cooler than today`s high temperatures. In addition, expect to see more clouds, though still partly sunny. Tuesday night, the low level flow will continue to slowly veer to a south-southeast direction in response to the departure of the high pressure system and the approach of an area of low pressure from the southwest. The tightening pressure gradient will enhance the low level sly flow and attendant warm air advection, leading to increase isentropic lift/upglide and the possibility of a few showers breaking out overnight night across the western Piedmont. Additional lift may be supplied by increasing divergence aloft. Thus, have tweaked PoPs up 10-15 percent from the previous forecast with chance PoPs covering portions of the western/southern Piedmont after 06Z Wednesday. If model trends continue or remain consistent, solid chance/low end likely PoPs may be warranted. At this time, not anticipating rainfall amounts of any significance, with amounts of just a few hundredths expected. Overnight temperatures near 50-lower 50s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 230 AM Monday... A closed low aloft will move east-southeast into the Gulf of Mexico on Wednesday (well south of the North Carolina). Meanwhile, the weak remnant northern stream trough will move over Central NC. There is a slight chance for light rain on Wednesday as the trough passes overhead. However, accumulations should be minimal as the best moisture will be well south of the area. At the surface, the southerly return flow will increase over Central NC on Wednesday, resulting advection of warm, moist air into the region. A moderating temperature trend is expected through Friday night. With the continued surge of warm air and the frontal passage not expected until the weekend, temperatures will remain well above normal through Friday night (highs in the low to mid 70s Wednesday, increasing into the upper 70s by Friday. Lows will follow a similar trend, low to mid 50s Wednesday night into the mid to upper 50s by Friday night). The models continue to differ with respect to rain chances through this part of the forecast, though a slight chance for rain cannot be ruled out, mainly across the west, Thursday through Friday. The best chance for any significant rainfall will come ahead of the fropa late Friday night through Saturday. The cold front is expected to move through Central NC on late Saturday. Cold air will advect in behind the front for Saturday night into Sunday as the surface high builds over/moves through the region. Expect a dry forecast on Sunday given the current timing of the front. Temperatures behind the front will be much closer to, but still slightly above, normal. && .AVIATION /18Z Monday through Saturday/...
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As of 112 PM Monday... High confidence in VFR conditions areawide through at least this evening, as high pressure builds in from the north, topped by warm and stable air aloft. Mostly just high clouds based above 18000 ft AGL are expected through tonight and Tuesday across the area, however at INT/GSO, increasing low level moisture within stable low levels late tonight may result in a few low clouds based below 900 ft AGL and perhaps shallow MVFR fog 08z-12z tonight. Elsewhere, no low clouds/fog are expected tonight. Winds will stay light from the NE, trending to ESE areawide over the next 24 hours, but speeds will be a bit stronger at RWI/FAY this afternoon. Looking beyond 18z Tue, VFR conditions will hold through Tue evening. We will see a chance for late-night and early-morning sub- VFR fog/stratus repeat areawide each day through the remainder of the week. MVFR to IFR conditions with a few showers are possible late Tue night through Wed as an upper trough crosses the region. A cold front will cross the area Sat, bringing a chance for showers and MVFR cigs. -GIH
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS/BLS NEAR TERM...Hartfield/WSS SHORT TERM...WSS LONG TERM...KC AVIATION...Hartfield

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