Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 260517 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 117 AM EDT Fri May 26 2017 .SYNOPSIS... Low pressure along the Mid-Atlantic coast will continue to lift northeast and away from the area overnight followed by high pressure on Friday. The high weakens Friday night allowing a warm front to lift north across the region before stalling. Weak disturbances will ride east along this boundary resulting in a return to periodic rounds of showers and thunderstorms for the holiday weekend. && .NEAR TERM /THROUGH TODAY/... As of 730 PM EDT Thursday... Upper low and a series of short waves will continue to bring showers across the area overnight. Eventually, downsloping northwest winds will limit rain chances east of the Blue Ridge after midnight. Rainfall amounts overnight should not contribute much to the already wet ground. As of 230 PM EDT Thursday... An upper low was positioned near the Mason-Dixon Line. Flow on the backside of this low is progged to increase to around 40kts this evening, and continue as such through the overnight hours. A Wind Advisory will remain in effect for areas near and west of the crest of Blue Ridge. While official wind advisory wind level speeds and gusts are not anticipated, the impact of increasing gusty winds and saturated soils will allow for trees to be blown down more easily. Central and eastern sections of the region have had a decent amount of sunshine this afternoon. We expect showers and storms to develop this afternoon and continue into the evening hours, supported by steep lapse rates aloft associated with the cold pool of the upper low. The relatively low freezing level will allow for just about any thunderstorm to have the potential for small hail, as well as, the stronger rain showers. By late this evening, flow across the entire region will be from the northwest, and subsidence will begin to win across eastern parts of the area. Look for precipitation to end, and for there to be a trend in clearing skies after midnight. In the west, the northwest flow will help maintain upslope clouds and scattered rain showers. These showers will continue through the night and into the morning hours on Friday. Coverage will decrease during the day Friday as low level winds start to slow and back. Clouds will also be on the decrease. Temperatures will continue to be on the cool side overnight. Expect low temperatures tonight across the mountains to range from the upper 40s to lower 50s. Across the Piedmont, low to mid 50s are forecast. On Friday, sunshine in the east, and sunshine in the west by the afternoon, will help yield high temperatures close to ten degrees warmer than those realized today. Expect the low to mid 70s across the mountains with upper 70s to around 80 across the Piedmont. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... As of 1100 AM EDT Thursday... Friday night through the weekend, an upper level shortwave ridge will be positioned across the Tennessee Valley. A closed upper low will slowly progress from south central Canada towards the Great Lakes region. During this period, anticipate central U.S. shortwave troughs to be funneled eastward between the flow of these two features into the Ohio Valley, all the while the Tennessee ridge slowly erodes. This will allow for increasing coverage of shower activity by the end of the weekend, especially by Sunday into Sunday night with the approach of a cold front. Temperatures Friday into Sunday will be near normal, with temperatures about five degrees above normal by Sunday. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 1030 AM EDT Thursday... During the period of Monday through Wednesday, an upper level low will gradually progress eastward through the Great Lakes region and into southeast Canada. A couple of associated cold fronts are expected to spiral ahead of this system and progress into the eastern part of the U.S. Model timing of these front places one moving through on Monday, and then the second on Wednesday, with the first of the two the most potent for our region. This scenario offers scattered showers in the forecast both of these days, with some isolated thunderstorms more probable on Monday as compared to Wednesday. Tuesday may not be completely precipitation free, but very limited on cover and due more to differential heating. On Thursday, guidance differs on the extent precipitation will be possible for the area, and much will be determined based upon how far the front on Wednesday exits the region, and to what extent a southern stream shortwave trough rides northeast along this front into, or near the area. Our forecast will reflect a model blend consensus of solutions, with better chances of showers on Thursday than not. Temperatures during this portion of the forecast will be a little over five degrees above normal on Monday, but trend to near normal conditions on Thursday. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... As of 105 AM EDT Friday... Upper low will gradually lift northeast and away from the area through Friday morning. However northwest flow around this system will continue to result in a few showers across the northwest mountains in the vicinity of KLWB/KBLF into early Friday. A broad area of IFR/MVFR cloud cover will remain over the mountains overnight with improving conditions east of the Blue Ridge where VFR cigs to clear skies can be expected. Visibilities will mainly be VFR, but pockets of MVFR visibilities are possible across western slopes. Wind gusts across the higher elevations will be in the neighborhood of 25 to 35 kts through Friday afternoon. These winds will mix down to the lower levels at times with heating during Friday. Extended Aviation Discussion... We will transition back into a wet pattern over the weekend as a frontal boundary enters and stalls over the area. A series of disturbances will bring showers and storms to the area. Anticipate at least some periods of sub-VFR conditions into Monday. The coverage of showers and storms should decrease by Tuesday resulting in more widespread VFR toward the middle of next week. && .HYDROLOGY... As of 110 AM EDT Friday... Small streams and creeks have been receding and most are below flood stage. However most will stay elevated into Friday as significant runoff continues and crests move down the mainstem rivers. Good drying on Friday should also aid in helping levels drop fall a bit quicker. We are in a river flooding scenario for portions of the Roanoke and Dan River basins with at least minor flooding on some of the downstream sections such as Randolph and South Boston likely to persist into the weekend. The New River and Greenbrier river are expected to stay below flood stage with near bankfull levels on the James especially downstream from Buchanan into Friday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Wind Advisory until noon EDT today for VAZ007-009>020-022>024- 032>035. NC...Wind Advisory until noon EDT today for NCZ001-002-018. WV...Wind Advisory until noon EDT today for WVZ042>044-507-508. && $$ SYNOPSIS...DS/JH NEAR TERM...DS SHORT TERM...DS LONG TERM...DS AVIATION...DS/JH/RCS HYDROLOGY...WP

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