Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 212330 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 730 PM EDT Wed Jun 21 2017 .SYNOPSIS... High pressure will build over the southeast into Thursday. The remains of Cindy will get caught up in front Friday into Saturday as the front moves from the midwest to Virginia during this time. The front slides off the coast Sunday. && .NEAR TERM /THROUGH THURSDAY/... As of 300 PM EDT Wednesday... 5h ridge will build over the southeast thru Thursday while upper system in association with TS Cindy pushes into the TX/LA area. Models are showing vort energy moving northeast along with moisture by Thursday afternoon. At least some agreement to keep rain showers likely over the southwest VA to NW NC mountains Thursday afternoon, tapering to little to no chance around Lynchburg. Tonight, should see partly cloudy skies, but more clouds will move in from the southwest late along with low chance of showers. The low level pattern does not favor a great deal of rain, and limited threat of thunder, though pwats will surge to 1.0 to 1.5 inches late then 1.5 to 2.0 by the end of the day Thursday. Highest rainfall amounts through Thursday afternoon will be around a quarter of an inch in the NC mountains, so not expecting any flooding concerns. Dewpoints will rise and Thursday will feel more muggy than the past couple of days. Lows tonight start that trend with readings in the 60s, then with more clouds Thursday, especially in the mountains, temperatures should reach the 80s, with 70s over the Mountain Empire to the NC High Country. May reach 90 in places like Dillwyn, Keysville and Lynchburg. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 300 PM EDT Wednesday... The weather pattern across the region is expected to establish itself during this time period to be one with plenty of potential for rainfall, some on the heavy side. Thursday night into Friday morning, the remnants of T.S Cindy are expected to be moving north through the Lower Mississippi Valley. Concurrently, a cold front will be approaching the region from the northwest. The moisture fetch on the east side of the dissipating tropical system will start to be advected into our region, increasing the potential for showers across the region from southwest to northeast during this time period. By Friday afternoon, the cold front is expected to located just north of the Ohio River, with the remnants of Cindy near Paducah, KY. This will be the point that the moisture under the core of the tropical system starts to ride eastward along the cold front, and reach our region Friday night, with the focus of the best cover across our southeast West Virginia counties. By Saturday morning, the remnants of Cindy will be closer to the Mason-Dixon line, and flow on the backside of the system will help usher the cold front through our region, and precipitation chances will be on the decrease during the course of the day. For more information regarding the heavy precipitation concerns with this event, please reference the HYDROLOGY section of this discussion. Winds associated with the remnants of Cindy are not anticipated to be too strong across the region, but there will be enough of a gradient remaining so that gusts across the higher elevations in the 25 to 40 mph range will not be uncommon on Friday into early Friday evening. Temperatures during this portion of the forecast will average a few degrees above normal. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 130 PM EDT Wednesday... There are notable model differences during this portion of the forecast. Guidance starts out similar Saturday night with a cold front parked just to the southeast of the region. Lingering isolated showers will be possible across southeastern sections of the area. Where the models differ is the Sunday into Monday time period. Both models offer solutions of a reinforcing cold front sweeping through the area Monday, however, that concludes the similarities. The GFS, for the most part, offers very limited moisture associated with the feature. Its European counterpart offers a wetter solutions. This wetter solution is the result of this guidance bringing a shortwave trough eastward the Tennessee Valley along the first cold front, that interacts with the second cold front, producing a generous coverage of showers across the area late Sunday night and through the day on Monday. Our forecast during this time frame will represent a blended solution that offers the potential of showers, but not to the degree done so by the European solution. On Tuesday, both the GFS and ECMWF hint at a shortwave trough heading eastward through the Great Lakes region into New England. Both keep the bulk of the energy and moisture north of our region. Our forecast will reflect at best some isolated showers across far northern sections of the forecast area. High pressure and dry weather is forecast for Wednesday. Temperatures during this portion of the forecast will start around near normal and trend to slightly cooler than normal by Wednesday. && .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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As of 730 PM EDT Wednesday... VFR conditions will prevail tonight into Thursday. The only except will be patchy fog late tonight into Thursday morning. KLWB is the taf site with the best chance for fog. MVFR fog is possible at KLYH and KBCB. Mid and high clouds will increase overnight into Thursday ahead of a front, and moisture from remnants of Cindy. Winds will generally be southwest at 8kt or less. High confidence in ceilings, visibilities and winds during the taf period. Extended Aviation Discussion... Ceilings lower to MVFR Thursday evening into Friday with first surge of showers advancing SW to NE. More sub-VFR conditions through at least early Saturday with periods of moderate to heavy rain. Less threat of showers Saturday evening into Sunday so mainly VFR after Saturday morning, but fog Sunday morning is possible. Scattered MVFR convection is possible Monday.
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&& .HYDROLOGY... As of 320 PM EDT Wednesday... The combination of the the remnants of T.S. Cindy crossing the area in concert with the approach and arrival of a cold front may set the stage for very heavy, flood producing, rain across parts of the area Thursday night into early Saturday morning. An analysis of the 00Z/8PM NAEFS Standardized Anomalies of precipitable water around 1.75 to 2.00 inches across our region during the Thursday night through Friday night time period, which equates an anomaly of to +2 to +3 sigma across the area. Mean integrated water vapor transport is forecast to have an anomaly around +4 to +6 during this same time period. A review of the NAEFS Probabilities place a 50 to 70 percent of extreme maximum of precipitable water over southeast West Virginia mid-day Friday with 25 to 50 percent across a generous portion of the remainder of the area. The Day 3 Excessive Rainfall Outlook from the Weather Prediction Center places a Marginal risk of flash flooding across our region, with the slight chance on the western edge of our West Virginia Counties. WPC QPF numbers across our region during the Thursday through Saturday morning time period has roughly 0.50 to 1.25 across the Piedmont, with the highest amounts on the western parts of this region. Across the mountains, 1.25 to 1.75 is the average. Higher amounts near 2.00 inches are forecast across some of the higher peaks across the Mountain Empire region of southwest Virginia into the Northern Mountains of North Carolina. Western Greenbrier County, West Virginia is forecast to have some of the greatest amounts during this time period with totals around 2.50 inches possible. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...WP NEAR TERM...WP SHORT TERM...DS LONG TERM...DS AVIATION...KK/WP HYDROLOGY...DS is the U.S. government's official web portal to all federal, state and local government web resources and services.