Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 260723 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 323 AM EDT Fri May 26 2017 .SYNOPSIS... Low pressure will exit to the northeast of the region this morning followed by high pressure that should build in by afternoon bringing drier weather on gusty westerly winds. The high weakens overnight 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 SATURDAY/... As of 300 AM EDT Friday... Upper low to the northeast will continue to pull away this morning allowing brief shortwave ridging to slide east as the associated surface high builds south of the area. This should bring a period of drying as the flow turns more westerly and decent subsidence arrives per drying seen on water vapor this morning. However expect will see low clouds persist far west through around midday per northwest upslope including trapped low level moisture with a few light showers/sprinkles possible. Thus will keep some low pops going before drying wins out and all break into sunny skies this afternoon. Winds to remain gusty with some enhancement due to heating/mixing so will keep the impact based wind advisory in place this morning. Otherwise more insolation along with eastern downsloping and exodus of the 850 mb cool pool should allow for much warmer highs, with readings rebounding back into the 70s most spots and perhaps around 80 southeast. Upper ridge starts to flatten overnight in response to shortwave energy passing north which will allow a warm front to shift north passing west of the mountains late. An initial belt of stronger winds aloft will ripple a weak sheared mid level impulse east along the boundary with this feature approaching by early Saturday. This along a baroclinic zone separating much warmer/juicier air to the southwest and more of a capped environment to the east. Latest guidance has a cluster/band of showers zipping east with this wave perhaps reaching the far northwest counties by daybreak Saturday within the sharp westerly flow aloft. However latest soundings still indicate some residual dry air aloft which should help to weaken coverage. Thus only running with low chances northwest third late. Otherwise more clouds north and remaining mostly clear south overnight. Lows mostly in the 50s but could rise late including the ridges where may stay above 60 as warm advection aloft quickly returns. Overall reprieve from persistent rainfall will be short as the boundary stalls just northwest of the area Saturday with an impressive return of moisture per jump in dewpoints and subsequent humidity by afternoon. In return, models indicate quite an unstable environment developing with MLCAPE values better than 1500 J/KG given heating under decent jet energy aloft ahead of a secondary wave aloft arriving over the northwest late. This impulse could lead to an organized area of convection riding east behind the initial wave with fast moving storms impacting espcly northern sections, and perhaps elsewhere pending organization under the fast flow aloft. Therefore will keep likely pops northern sections with high/decent chance pops elsewhere in the afternoon including severe mention in the HWO per slight risk in the SWODY2 attm. Will feel quite warm given the coolness of late as highs under strong 850 mb warming look to zoom back well into the 80s east, and around 80 west pending early debris clouds. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/... As of 1100 AM EDT Thursday... Saturday night through Sunday, 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 should rise to about five degrees above normal by Sunday. && .LONG TERM /SUNDAY NIGHT 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 /07Z 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...JH NEAR TERM...JH SHORT TERM...DS LONG TERM...DS AVIATION...DS/JH/RCS HYDROLOGY...WP is the U.S. government's official web portal to all federal, state and local government web resources and services.