Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 210030 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 730 PM EST Tue Feb 20 2018 .SYNOPSIS... High pressure at the surface and aloft will extend across the Carolinas through Thursday, resulting in record warmth across the region Wednesday and Thursday. A backdoor cold front will move southward into the area Thursday evening into Thursday night but lift back north as a warm front late Friday and Friday night. && .NEAR TERM /THROUGH TONIGHT/... As of 635 PM Tuesday... Main adjustment to the near term forecast was to include the mention of patchy dense fog overnight into early Wednesday morning, primarily for locations west of I-95, and more so over the southern- western Piedmont. A mild evening in store for the region as an area of high pressure near the surface and aloft extends over the region. Sfc dewpoints near 60-lower 60s makes it feel more like late Spring rather than late February. The warm moist air over the relatively cool ground surface will aid in the development of low clouds and areas of fog. Unlike Monday evening which saw visibilities begin to deteriorate after 9-10 PM, do not expect conditions tonight to deteriorate until after midnight, and potentially not until a couple hours prior to daybreak. Forecast confidence is increasing that dense fog may occur over the Piedmont, especially west of highway 1, though confidence not high enough to warrant an issuance of a dense fog advisory. Will continue to monitor. The sfc dewpoints near 60-lower 60s indicative of a warm moist air mass. With no features approaching to result in a change in air mass, expect the mild conditions to persist well into the night. Min temps fairly uniform in the upper 50s to around 60. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 316 PM Tuesday... Very strong and near record strong upper level ridging will be along the SE U.S. coast Wednesday and Wednesday night. The flow around the high will continue to pump up the dew points and low level moisture. Essentially, this will be enough to create fog and stratus again tonight. However, it is expected to be less widespread and time consuming. Expect the stratus to burn off by mid morning, with partly sunny skies the rest of the day. Highs are favored to warm into the daily record territory. Readings in the mid 70s to near 80 are favored from NW to south, only tempered a bit by the amount of moisture in the air with dew points in the 60s. The warmest readings in the cool season (February in this case) are typically associated with very dry, downslope events characterized by dew points in the 20s/30s etc. So this particular warm episode event will be accompanied by record high low level moisture for February, leading to record high minimums - not so much as hot daytime highs. There should be an increase again of stratus late Wednesday night and early Thursday morning. Otherwise, partly cloudy with lows 60-65. && .LONG TERM /THURSDAY THROUGH TUESDAY/... As of 229 PM Tuesday... The last couple model runs have trended slower with the backdoor cold front on Thursday, thus allowing for another very warm and mostly dry day Thursday with highs from the mid 70s north to around 80 south. Latest guidance now suggest the boundary will move south into our CWA Thursday evening, then stall along or just north of the Hwy 64 corridor early Friday morning. As such will continue to show best chance for patchy light rain along and north of Hwy 64. Friday now looks to be a bit warmer with the boundary farther north and CAD airmass mainly across our northern Piedmont zones. As such, will adjust temps up a few degrees, with the warmest readings (70s) still expected across the southern half of our CWA, and 60s north near the VA border. Otherwise, dry wx on Friday. Saturday looks warm and dry now with SW flow increasing ahead of the trough and cold front moving across the MS valley. Highs will climb well into the 70s, with clouds gradually increasing from west to east as the trough approaches. It`s worth noting that the 00z ECMWF tries to drop another backdoor front southward toward the NC/VA border during the day Saturday, with rain chances across our northern-most zones. However given the strength of the subtropical ridge, for now the preference is to keep the backdoor front and its wx farther north. The next front moving in from the west is progged to cross our area during the daytime Sunday, and will bring the chance for showers and perhaps isold tstms with its passage. Given that the best upper energy is quickly lifting out and leaving broad SW flow in it`s wake, the front may stall just to our east, prolonging the risk for scattered showers, particularly across our eastern zones, into the daytime Monday. By Monday night however, the next short wave ridge will move in from the west with a sfc high building to our north, and that should clear out skies and bring a more seasonable airmass for Monday night and Tuesday. && .AVIATION /00Z WEDNESDAY THROUGH MONDAY/...
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As of 730 PM Tuesday... 24-Hour TAF Period: VFR conditions to start the TAF period will once again give way to MVFR cigs and visbys after midnight, generally between 06Z and 09Z Wednesday, then subsequently dropping to IFR/LIFR. There is still some uncertainty of if/when the cigs will scatter out, but generally expect a return to MVFR/VFR conditions by Wednesday afternoon, though there is a chance some terminals could stay broken IFR/MVFR into the afternoon. South-southwesterly winds will persist through the period, generally 5 kts or less overnight and 5-10 kts during the day Wednesday. Looking ahead: Given the persistent warm, moist airmass expected through Friday, there will be a chance for sub-vfr cigs/visbys during the pre-dawn/early morning hours through Friday morning. With a strong cold front moving in on Friday, expect the boundary layer to dry out, with generally VFR conditions expected through Monday. There will be a chance for some periods of scattered/broken clouds around 2-4 kft, but otherwise good aviation conditions are expected.
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&& .CLIMATE... RDU Records: Date | High Year | High Min Year ------------------------------------------ 02/20 75 1939 62 1939 02/21 76 2011 55 1939 02/22 75 1897 60 1897 02/23 79 1980 57 1962 02/24 81 1982 58 1985 GSO Records: Date | High Year | High Min Year ------------------------------------------ 02/20 74 1922 56 1939 02/21 74 2011 50 1954 02/22 74 1925 57 1980 02/23 74 2017 52 1922 02/24 79 1982 55 1985 FAY Records: Date | High Year | High Min Year ------------------------------------------- 02/20 82 2014 60 1939 02/21 80 1991 61 1953 02/22 77 2003 56 1989 02/23 80 1922 55 1922 02/24 83 1930 60 1975 && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...Badgett LONG TERM...np AVIATION...KC CLIMATE...RAH

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