Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 180202 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1002 PM EDT Mon Apr 17 2017 .SYNOPSIS... A cold front will move into eastern Virginia and North Caroline this evening and off the southeast North Carolina coast by Tuesday morning. In the wake of this front, a wedge of high pressure will build over the Mid-Atlantic region bringing noticeably cooler temperatures for Tuesday and Wednesday. Overrunning moisture will bring a threat of rain back to the southern part of the area on Tuesday and spread northward Tuesday night into Wednesday. && .NEAR TERM /THROUGH TUESDAY/...
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As of 950 PM EDT Monday... Shower activity across the region continues to wane. The greatest concentration is over parts of Southside Virginia and neighboring sections of north-central North Carolina. We expect this activity to continue to decrease in coverage as it exits to the southeast. Coverage is still expected to be on the increase again later tonight across mainly portions of the Northern Mountains and Foothills of North Carolina, as well as, neighboring sections of the Mountain Empire region of southwest Virginia. This increase will be thanks to an upper level disturbance, currently over central Tennessee, moving eastward into the Carolinas. The latest update will reflect a greater period of time with limited coverage of showers across our area between the departing activity in the southeast, and the arrival later tonight across the southwest. Have also made minor tweaks to reflect hourly temperature, dew point, and wind based upon the latest observations and expected trends into wee morning hours of Tuesday. As of 704 PM EDT Monday... Showers remain scattered about the region early this evening, generally in the New River Valley and into the North Carolina foothills and the Southside of Virginia. This activity generally located on the northern side of a wavy, nearly stationary frontal zone positioned to our south into the Tennessee Valley. RAP analysis also depicting a vort max located over northern Arkansas that may be encouraging the current area of showers and thunderstorms over the Tennessee Valley as well. Through late evening, coverage of showers should remain isolated to widely scattered and mainly confined from Grayson County eastward and southward. As this does so, will be watching for A re-development/northward shift in the frontal zone and accompanying rain showers as the upper wave approaches is expected during the overnight hours, resulting in an increase in PoPs in much of the North Carolina foothills and the High Country after 07z. High- resolution guidance and the 18z runs of the NAM and GFS are not particularly consistent with how far northward the showers extend, perhaps as far north as the New River Valley. Showers will also be fighting building ridge to the north. Didn`t feel the need to extend isolated showers overnight any further north than the Grayson Highlands at this point, but that is something to monitor as the night progresses. Otherwise, only changes made were to account for current observations. Previous near-term discussion issued at 415 PM follows... Cold front has shifted to just east and south of the Blacksburg forecast area this afternoon with a line of broken convection near the boundary moving into southeastern Virginia and north- central and northeast North Carolina. Scattered lingering showers behind the front, closer to where the boundary likely is at 850mb, are expected to fade through the late afternoon into evening hours. Have moved out showers and storms much more quickly next few hours so that the tonight forecast should have no mention of thunder in for any locations, and even chances for showers are fairly low. Late tonight, an upper level wave currently over western KY will approach and bring an increasing chance for light rain back into the southwestern part of the forecast area, especially NW NC and far SW VA. Light rain could continue at times into Tuesday across parts of the far southwest and south overspreading the wedge, but think this will have a hard time getting much past the NC/VA border. Only partial clearing expected across the far north well behind the front, but most locations will remain overcast. Winds shift northeast overnight as high pressure center moves east across Great Lakes and noses southward through NY/PA and northern VA. Temperatures will be cooler tonight behind the front and with shallow wedge building in, but most noticeably tomorrow compared to the highs today. However, even with wedge firmly in place, the air advecting in from the northeast is fairly dry and some sunshine is expected at times across the northeast. In locations where is remains overcast, and additionally there is rain continue into some of the day, temperatures will be well below normal and went as much as 5 degree below coolest MAV guidance. Might have trouble getting out of the 40s in places like Boone, but most locations will remain in the 50s in the mountains, with a few low 60s in Mountain Empire, perhaps toward Bluefield, and then mid to upper 60s in the Piedmont of VA. Tricky temperature forecast and suspect some areas across the south we may need to go even cooler, while others may end up being warmer farther north.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 230 PM EDT Monday... A strong surface wedge will be draped across the region and stretching south into Georgia Tuesday night and Wednesday. A short wave axis over the Tennessee Valley will push moisture over this wedge starting from the southern Appalachian mountains Tuesday, then northward over southwestern Virginia Tuesday night. A surface reflection is expected to form off the North Carolina coast late Tuesday night into Wednesday. This coastal reflection and the short wave axis, moving over the southern Appalachians, will nudge precipitation east off the Blue Ridge Wednesday afternoon and east of the piedmont Wednesday evening. The best isentropic lift and upslope flow is across all of the North Carolina mountains into southwestern Virgina Blue Ridge (Floyd and Patrick counties) Tuesday night into Wednesday morning. This lift and moderate rain will track along the NC/VA border Wednesday into Wednesday evening. Rainfall amounts, especially along the eastern slopes of the Blue Ridge will range from a half to one inch. Foothill and piedmont counties along the VA/NC border should see up to half an inch. Rainfall amounts north of 460 will range from a few hundredth towards the Southern Shenandoah Valley to a quarter of an inch in the Roanoke and New River Valleys. Rainfall intensity will also vary greatly from moderate to possibly heavy rain south of highway 460 to light rain and drizzle north. Low clouds and fog will also be present Tuesday night and Wednesday morning. Saturated soils and warm moist air from a passing warm front will bring areas of fog to the area again Wednesday night. Diurnal temperatures ranges will remain small while this wedge hangs over the region. Overnight lows will be in the upper 40s to lower 50s Tuesday night and Wednesday night. High temperatures Wednesday may warm into the upper 50s to lower 60s. Areas that see the wedge erode Wednesday (Mountain Empire and Bluefield) could see temperatures warm into the upper 60s to lower 70s Wednesday afternoon. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 240 PM EDT Monday... A warm front will move north of the region on Thursday. With the wedge gone, temperatures will warm into the mid to upper 70s across the mountains and lower 80s east of the Blue Ridge. A cold front slides across the region Thursday night into Friday morning. Mostly showers will accompany the front, but a few rumbles of thunder are possible. Temperatures Friday afternoon will be slight warmer than normal, mid to upper 60s west to mid to upper 70s east. High pressure builds in Friday afternoon and will keep the area dry until Sunday. A closed low tracking east from the Midwest is expected to bring strong to severe storms to the area Sunday. Models differ on the track of the upper low but agree on timing for Sunday. This weekend`s temperatures will depend on the timing and track of the low. For now, we will keep temperatures near guidance which is near normal. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... As of 714 PM EDT Monday... Ceilings/visibilities mainly VFR, outside of a temporary MVFR shower at Blacksburg and Danville through 01z. VFR is generally maintained through 04z, with lowering MVFR ceilings at Danville and perhaps as far west as Blacksburg, Bluefield and Roanoke after 04z. This is from a building ridge of high pressure to our north with associated easterly flow allowing for potential for MVFR ceilings. That said, confidence is medium to low on ceilings overnight; feel lowest ceilings by morning would be mainly along the southern Blue Ridge away from any TAF sites. Winds generally light and variable (though will trend north to northeast) through 04z, with light east winds overnight. Should see continued BKN/OVC VFR/MVFR into Tuesday. Ongoing clouds and rain will likely lead to continued obscured mountains in the North Carolina high country. Rain shield makes some northeastward advance into Blacksburg and Bluefield near the end of the valid TAF period, with potential MVFR ceilings/visibilities at these two TAFs. Should see easterly winds increase to speeds around 4-8 kts Tuesday. Extended Aviation Discussion... Surface high pressure will wedge southwest into the area later Tue-Wed resulting in a more stable air mass and allowing the front to be pushed a little further south, thus no threat for convection during the Tue-Wed period with the possible exception of KBLF late Wed. Some showers could get as far north as KDAN late Tues perhaps resulting in MVFR conditions but at this time they appear more likely to remain to the south. By Thursday, the front will return north as a warm front as a new front approaches from the northwest once again. Showers and thunderstorms will be on the increase Thu-Fri as this front also drifts into the area and stalls. This front will return to the north as a warm front Saturday as a much stronger weather system moves into the southeast U.S. Between the wedge Tue-Wed and the frontal systems in/near the area through the week, multiple and extended periods of sub-VFR aviation conditions are expected through the week, but most likely by later in the weekend. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...SK NEAR TERM...AL/DS/SK SHORT TERM...RCS LONG TERM...RCS AVIATION...AL/SK is the U.S. government's official web portal to all federal, state and local government web resources and services.