Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 251855 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 255 PM EDT Thu May 25 2017 .SYNOPSIS...
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A broad area of low pressure extended from Ohio to the Delmarva Peninsula. High pressure will make a brief visit to our region on Friday. Wet weather returns to the area over the weekend as a frontal boundary stalls overhead, and a series of disturbances moves along it.
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&& .NEAR TERM /THROUGH FRIDAY/...
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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.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
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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.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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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.
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&& .AVIATION /19Z THURSDAY THROUGH TUESDAY/... As of 140 PM EDT Thursday... Upper low was making progress eastward across northern Virginia. Associated cold pool lapse rates and daytime heating will lead to convection this afternoon, mainly in areas along and east of the crest of the Blue Ridge. Broad area of IFR/MVFR cloud cover over KY/WV will advance into the region from the west, and impact areas in the west late this afternoon through the overnight hours. Visibilities will mainly be VFR, but pockets of MVFR visibilities are possible across the mountains. Low level winds will become northwest by this evening and allow for subsidence clearing in areas east of the Blue Ridge. Wind gusts across the higher elevations will be in the neighborhood of 25 to 35 kts. These prevailing winds allow for a continuation of upslope rain showers in the west, and these will continue into the day Friday. However, coverage during the day Friday will be on the decline. Extended Aviation Discussion... VFR conditions are expected on Friday as a shortwave ridge builds into the region. 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 pockets of sub-VFR conditions. The coverage of showers and storms decrease early next week, but remain at least scattered in coverage. && .HYDROLOGY... As of 100 PM EDT Thursday... Small streams and creeks have been receding and most are below flood stage. We are in a river flooding scenario for portions of the Roanoke and Dan River basins. The New River and Greenbrier river are expect to stay below flood stage. The upper level system moving in from the west will bring scattered to numerous showers and possible thunderstorms. Overall rainfall amounts on average will be under a quarter to half inch, in this scenario. Will have to watch for any training or heavier downpours, as it will not take much to cause flooding again given the saturated grounds and swollen creeks and rivers. Currently, we are not expecting enough for a flood/flash flood watch and activity should diminish/weaken after sunset. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Wind Advisory from 6 PM this evening to noon EDT Friday for VAZ007-010>014-016>020-022>024-032>035. Wind Advisory until noon EDT Friday for VAZ009-015. NC...Wind Advisory until noon EDT Friday for NCZ001-002-018. WV...Wind Advisory from 6 PM this evening to noon EDT Friday for WVZ042>044-507-508. && $$ SYNOPSIS...DS NEAR TERM...DS SHORT TERM...DS LONG TERM...DS AVIATION...DS HYDROLOGY...WP

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