Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 262310 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 710 PM EDT Sun Mar 26 2017 .SYNOPSIS... Low pressure near Chicago will move northeast through the Great lakes and weaken as it passes into Ontario tonight and Monday. A second area of low pressure will move northeast out of the southern Plains crossing the Mid-MS Valley Monday, and across the Ohio Valley into the northern Mid-Atlantic Monday night and Tuesday. These weather features will result in unsettled weather across the central and northern Appalachians through Tuesday. Temperatures will remain well above normal through mid week. && .NEAR TERM /THROUGH MONDAY/...
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As of 659 PM EDT Sunday...Radar and METARs continue to indicate ongoing, though weakening rain showers from Roanoke to Reidsville NC eastward into western portions of Appomattox County. These showers stand to dissipate per recent HRRR/NAMNest output. Also watching stronger convective development to the the west and south of our forecast area, primarily in central West Virginia, associated with vort max pinwheeling northeast into southern Ohio around parent upper trough extending southeastward from the upper Midwest. Past couple HRRR runs, which have generally handled the spatial coverage of convection to our west the best since it partly initializes off radar, continues to suggest that some possible scattered showers/possible rumble of thunder may slip into Mercer, Summers and western Greenbrier Counties in WV as well as our southwest Virginia Tennessee Valley counties next couple hours. As we progress toward midnight, upper trough lifts to our northeast, leaving us in shortwave ridging overnight. As forcing becomes nebulous at best, except for some additional upslope convergence along the southern Blue Ridge, PoPs should be at their lowest overnight with shower coverage being even more isolated than they presently are. Given rather saturated air mass would expect skies to stay at least mostly cloudy. Lows only fall into the 50s tonight. Previous near-term discussion issued at 300 PM follows... Radar indicated a 30 mile wide band of rain showers propagating east across the central CWA. As of 3PM the leading edge was along the 220 corridor from Clifton Forge to Martinsville. Movement was to the east at 20 mph. Leading rain band was associated with a front aloft, arcing from NW to SE from Low pressure moving through the Great Lakes. The actual surface front was over western KY/TN, with additional bands/clusters of showers and thunderstorms scattered across the Ohio Valley. The initial rain band over our CWA has outrun any surface instability and has been weakening with time. Rainfall amounts have been averaging between a tenth to a quarter of an inch, but as this band of showers continues to move east, the overall qpf will diminish with amounts of a tenth of an inch or less. Timing suggests these showers will reach Highway 29 corridor...Charlottesville, Lynchburg, Danville, between 5-6PM. Behind the front aloft, some partial clearing was taking place, the rain only lasting a couple hours in duration. Once this initial rain area moves east, will have to wait for the instability driven showers over KY/TN ahead of the actual surface front to move east. Models suggest most of this activity will dissipate during the overnight, but until then will threaten our western CWA (primarily west of I-77 in VA/NC and west of Lewisburg or highway 219 in WV) this evening with potential for both showers and thunderstorms and an additional tenth or two of rainfall before midnight. As the main upper level low slides by to our northwest overnight, dynamic support will decrease. The actual surface front is forecast to wash out before crossing the mountains so this will maintain a persistent mild southerly flow across the forecast area overnight. As such, there will be a continued chance of showers mainly along and west of the Blue Ridge overnight, although nothing severe per waning instability. Some patchy fog is also possible, but cloud cover should prevent it from becoming widespread. On Monday, a second storm system will be moving northeast out of the southern Plains, crossing the Mid MS valley during the day and into the OH Valley Monday evening. Response will be the development of more showers and thunderstorms with focus primarily to our west across the OH/TN valleys. Model soundings suggest some instability driven activity may develop over our CWA during the afternoon associated with weak convergence near the Blue Ridge. Attm will advertise chance threat for showers/storms Monday, but coverage generally less than 50 percent and no mention of severe attm. Certainly can`t rule out a stronger storm or two if temperatures rise into the 70s permitting surface based CAPE in the 1000-1500 range. Temperatures through Monday will remain mild with readings 10 to 15 degrees above normal, and remaining well above freezing.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM EDT Sunday... During this portion of the forecast, a Pacific based system is expected to impact the region. Guidance among the models is in good agreement of bringing a shortwave trough eastward along the Ohio Valley and then into the New York City region Monday night into, and through Tuesday. This track will keep the region on the mild side of the system until the passage of its associated cold front Tuesday morning into the afternoon hours. Scattered showers and isolated storms across the area Monday afternoon, will lingering into Monday evening. The scattered showers will continue through the overnight, with coverage increasing towards daybreak in the west. There may be an initial increase in coverage across eastern parts of the area through the evening hours, but decrease to isolated coverage early Tuesday morning. As the front crosses the region on Tuesday, showers will be in greatest concentration coincident and just in advance of the cold front. Instability is progged to increase enough to warrant isolated to scattered thunderstorms in this same general area, with the best potential shifting eastward during the course of the day. Coverage will quickly decrease Tuesday evening with the departure of the cold front to the east. Some lingering northwest flow upslope isolated showers are possible across portions of southeast West Virginia, neighboring counties of southwest Virginia, and south into the Northern Mountains of North Carolina. Coverage will be greatest during the evening hours with decreasing coverage as the nigh progresses. Wednesday into Wednesday night, an upper level shortwave ridge is progged to build over the area, all while surface high pressure noses south along the lee of the Appalachians. Look for any lingering isolated showers in the west to end by noon. Limited cloud cover is forecast for all of the region by Wednesday afternoon. As Wednesday night progresses, low level flow on the west side of the surface ridge will allow for moisture levels to increase. Anticipate increasing cloud cover, and eventually some patchy light rain across areas mainly near the crest of the Blue Ridge from roughly Roanoke, VA southwest into the Northern Mountains of North Carolina. Temperatures during this portion of the forecast will trend from roughly fifteen degrees above normal Monday night into Tuesday to around five to ten degrees above normal Wednesday into Wednesday night. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 300 PM EDT Sunday... The lee side ridge of surface high pressure will continue to prevail on Thursday, although low level flow not too far above the surface will start to increase as a closed upper low heads eastward through the central U.S. Look for light rain to increase across the area on Thursday, especially western and central parts of the region. The activity will take on more of a showery nature Thursday night as the upper system draws closer. On Friday, showers will be likely across most of the region with isolated thunderstorm possible across the western and southern parts of the area. The main system will track north of the area Friday night into Saturday, with its associated cold front across our region early Friday night. Look for an end of the shower activity for much of the area by Saturday morning. Lingering upslope showers on the backside of the system will be possible across southeast West Virginia and neighboring counties of southwest Virginia. Saturday night into Sunday, an upper level ridge will build over the area, allowing for a gradual decrease in the upslope showers in the west, and limited cloud cover in the east. Temperatures during this portion of the forecast will be around or slightly above normal Thursday and Friday, but trend to readings about ten degrees above normal for Saturday and Sunday. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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As of 710 PM EDT Sunday... VFR to VFR/MVFR presently across most of the terminals, and those conditions should continue through the next couple of hours. Of note is lower, more widespread MVFR ceilings along the southern Blue Ridge and into the NC mountains that will contribute to obscured mountains through much of the TAF period. Ongoing unrestricted showers from Roanoke and Lynchburg south to Danville and Reidsville should persist next couple of hours as well. Limited potential for in-cloud lightning in southeast WV next couple hours, but not expected to affect any TAF. Confidence in ceilings is low for the rest of the overnight, but expect OVC VFR to MVFR to be the primary ceiling conditions for the terminals. Generally reflected this uncertainty with a second SCT MVFR cloud group. Light south to southeast winds overnight. For Monday...ceilings should begin to become scattered to broken again. Potential for showers and thunderstorms again for tomorrow, though would tend to be sporadic/intermittent. Winds stay southerly around 6-10 kts. Extended Aviation Discussion... An active weather period with a series of vigorous upper-level low pressure areas tracking from west to east across the U.S. during the week. Areas of sub-VFR cigs/vsbys are possible, especially during the morning hours, in low clouds and fog. Coverage of showers and thunderstorms will be the greatest during the afternoon and evening coinciding with the peak heating of the day.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PM NEAR TERM...AL/PM SHORT TERM...DS LONG TERM...DS AVIATION...AL/PM is the U.S. government's official web portal to all federal, state and local government web resources and services.