Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 260356 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1156 PM EDT Tue Apr 25 2017 .SYNOPSIS... Low pressure centered over the eastern North Carolina will slowly drift northeast and off the coast tonight into Wednesday. High pressure will build in Wednesday and continue for the second half of the week. This will result in a considerable boost to the temperature with above seasonal warmth expected by the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... As of 950 PM EDT Tuesday... Patchy sprinkles across parts of the mountains are continuing to a decreasing trend on radar, and there are few reports within the surface observations. Bluefield, WV had some light rain a little while ago. The latest report is from Hillsville, VA. Little if any sprinkles are expected to survive after midnight as cloud cover starts to erode across western sections of the region first. With winds becoming light and variable or calm, plenty of surface moisture, and clearing skies, we are anticipating fog development to be common across the region overnight. Have tweaked hourly temperatures and dew points based upon the latest observations and expected trends into the early morning hours of Wednesday. As of 640 PM EDT Tuesday... The low pressure system that has affected the entire area through this past weekend is situated over the North Carolina coast and is forecast to slowly move out of the area during the overnight hours. Currently on radar, areas are seeing some lingering drizzle that will make way to patchy fog in the morning hours before clearing out for the day on Wednesday. Most recent solutions of the HRRR and RAP models show precipitation ending sooner in the Piedmont with only a few lingering sprinkles along and west of the Blue Ridge Mountains. Therefore, have adjusted the forecast accordingly. As of 255 PM EDT Tuesday... WSR-88D showed showers are diminishing or dissipated across most of the forecast area. However, there are still some pockets of drizzle and light rain. Low pressure centered over eastern North Carolina this afternoon will move northeast off the Atlantic coast tonight into Wednesday. High pressure over the Ohio Valley will build east tonight into Wednesday. HRRR and Hiresw-arw-east try to develop some isolated showers across the high terrain this afternoon into this evening. Believe any shower or light rain/drizzle will be limited. Mid level ridging builds in from the west this evening into tonight. For tonight, any clearing will set the stage for fog formation. Unless the stratus persists, anticipate development of fog per wet ground, diminishing winds and radiational cooling from the departing mid/upper level cloud cover. Low temperatures tonight will range from the mid 40s in the mountains to the lower 50s in the Piedmont. High pressure will build over the Southeast States Wednesday. Any fog Wednesday morning will quickly dissipate leaving sunshine for Wednesday afternoon. With increasing heights and warming thicknesses, 85h temperatures will climb to near +15 deg C for Wednesday. Temperatures may be a degree or two cooler than one would think, as the initial surge of warmth will go into latent heating and an attempt to evaporate all of this moisture laying around from the multiday rain event. High temperatures will vary from near 70 in the mountains to the upper 70s in the Piedmont. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... As of 258 PM EDT Tuesday... A low amplitude upper ridge will give way to a broad trof over the upper midwest with short wave shearing off to our northwest. This will drive a surface low from the Great Lakes into Canada and drag a trailing cold front into our region late Thursday into Thursday night with basically high chance POPs for scattered showers/some thunder. High pressure brings us a basically dry day for Friday before a warm front lifts north through the region Friday night with chance for showers/storms. By Friday, we develop a Bermuda high off the coast with ridging aloft and a deepening trof/closed low over the midwest. This will develop a deep southerly flow of warm and moist air that will pump the heat and humidity up by late in the week. Expect highs Friday to reach the mid 80s east of the Blue Ridge with upper 70s/lower 80s to the west. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 258 PM EDT Tuesday... We will be in a very summerlike pattern this weekend with very warm and humid conditions and an increasing chance for showers and thunderstorms each day, especially along the Blue Ridge. By Monday, the vertically stacked upper closed low over the midwest will move into the Great Lakes region. This will push a vigorous cold front into the area from the west with a good chance of showers and thunderstorms through Monday afternoon. High pressure will then build on for Tuesday with cooler weather and windy conditions. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... As of 730 PM EDT Tuesday... MVFR ceilings with pockets of IFR, light rain, drizzle and fog will continue until about midnight. The upper level low will slowly drift northeast tonight and away from the area Wednesday. The pressure gradient across the region will start to weaken, allowing winds to become light and variable overnight into Wednesday morning. Areas of low clouds and fog will develop tonight with IFR conditions expected into Wednesday morning. Conditions will become VFR by Wednesday afternoon. Winds will remain light and variable. Moderate confidence in ceilings, visibilities and winds during the TAF period. Extended Aviation Discussion... Better flying weather is expected for the second half of the week, though another front may bring scattered MVFR showers/storms Thursday afternoon and evening across the mountains. Drier and much warmer weather will return for Friday and Saturday with temperatures much above normal for the weekend. Can not completely rule out an isolated MVFR thunderstorms along the southern Blue ridge. Scattered MVFR showers and thunderstorms are possible Sunday and Monday. && .HYDROLOGY...
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As of 1145 PM EDT Tuesday... The upper low has finally moved out of the area and any remaining precipitation is generally in the form of drizzle. Additional QPF from this synoptic system will no longer be a factor. Main concern at this point is runoff into the lower end of the Dan and Roanoke River basins. Coordinating with SERFC and AEP, expected water releases from Smith Mountain Lake and Leesville Reservoir will be insufficient to push Alta Vista or Brookneal into flood stage, and in fact, the river at both of these locations is already falling and is just at action stage at this point. Further downstream at Randolph on the Roanoke, flooding will continue for a couple more days and the river will just touch moderate flood stage by Wednesday afternoon. More significant concerns along the lower end of the Dan River continue and will for a couple more days. The river has crested at Danville, just a tad under major flood. At Paces, the situation is a bit more serious as the river is now forecast to crest near 28.6 feet, well above the major flood level. Viewing the crest history, this is only the 9th time of record that the river has crested in the above the major flood level. Finally at South Boston, the current forecast has it cresting just below major flood. It is interesting to note that most of the previous major floods were associated with a tropical system, such as Hurricane Agnes in 1972 or Hurricane Fran in 1996. Will also continue the Areal Flood Warning for a bit longer along the upper reach of the Dan River due to continued flooding at points such as Wentworth, NC. For additional details on the river flooding, please refer to the AHPS page and specific FLS/FLWs issued from this office. As of 258 PM EDT Tuesday.... Significant rainfall has ended across the region allowing water levels to gradually subside at all locations except along the Dan and Roanoke rivers. The Dan is expected to crest early tonight above major flood stage at Danville, then begin falling later tonight. Crests at Paces and South Boston are not expected until late Wednesday. Further upstream, the Dan crested at moderate flood stage at Wentworth and will be falling slowly overnight. The Roanoke river at Randolph will experience moderate flooding with a crest late tomorrow. Please refer to the latest flood statements for further details.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK NEAR TERM...DS/KK SHORT TERM...MBS LONG TERM...MBS AVIATION...DS/KK/PM HYDROLOGY...MBS/PM/RAB

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