Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 230525 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 125 AM EDT Sun Jul 23 2017 .SYNOPSIS...
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A cold front should pass south of our region by Monday. High pressure will arrive to bring slightly cooler conditions by the middle of the week.
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&& .NEAR TERM /THROUGH TODAY/...
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As of 110 AM EDT Sunday... Updated to account for latest radar trends, with high-res models showing best coverage tracking from KY to southern WV into far SW VA/NW NC through dawn, while activity in the piedmont moves out. Previous discussion from Saturday evening... A short wave moving by to our north is helping the frontal boundary sag a bit closer to the area early tonight. This will allow convection along the front to brush the northern portion of the region mainly along and north of the Interstate 66 corridor. However, the entire overnight period is rather muddy as the remnants from waves of convection upstream move in our direction and may be able to affect the area, while lingering boundaries from earlier convection may be able to generate some new activity in residual pools of instability. Believe the best course of action is to play the POPs early from convection dropping in from the north, then allow broader POPs in the west later tonight. Convective debris clouds will have an impact on overnight low temperatures. Believe there will be enough cloudiness around to keep us a degree or two above last night with low/mid 70s east of the Blue Ridge and mid 60s/near 70 to the west. Previous discussions... 745 PM EDT Saturday... Activity associated with a wavy frontal boundary to our north will remain very close to the boundary and gradually work its way south during the night in a much weaker fashion. Confidence in activity for tomorrow is still only in the chance range, much of which will depend on how much cloud cover and convection there is in the morning. Will not make any changes to tomorrow`s pops for now. SPC still holding a SLIGHT RISK for tomorrow. 330 PM EDT Saturday... High resolution models hint at another round of convection arriving west of I-77 by early Sunday morning. Cloud cover from upstream convection could limit high temperatures from climbing as high by Sunday afternoon compared to Saturday afternoon. Still, it will be quite hot and humid, and the cold front may reach the VA/NC border by the afternoon. This situation should allow enough instability and lift for more scattered showers and thunderstorms to develop in this area toward the evening.
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&& .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... As of 230 PM EDT Saturday... For Sunday evening, weather forecast models are hinting at a line of thunderstorms entering our far western Virginia/northern North Carolina counties during late evening as an upper level disturbance passes overhead. Believe any storms would diminish in intensity quickly as they cross the ridges and move into downslope flow. Have introduced a period of higher rain chances across the west for the possibility of this system, however admit that confidence of the occurrence/timing/location of any organized line of storms moving in from the west is marginal. The coming overnight forecast shift will have the benefit of an updated set of models to have a look at and will make adjustments to these rain chances accordingly. Outside of these storms, convection is expected to diminish after sunset with the loss of daytime heating. Widely scattered showers and thunderstorms can be expected for Monday despite a cold front approaching from the northwest. Slightly drier air and stronger northwest wind flow will help to inhibit convective development, though those storms which do develop may pulse up to strong/severe intensity for brief periods of time, capable of producing localized damaging winds. The cold front will enter the southeast West Virginia counties during late Monday evening, and gradually loose momentum as it continue south across our area. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 1230 PM EDT Saturday... Looking to Tuesday, long-range weather models are indicating that the cold front may not pass completely across our forecast region, possibly stalling near the Virginia-North Carolina border as high pressure shifts from the Great Lakes toward New England. Will hold close to the previous forecast of a higher chance of spotty afternoon showers/storms south of Highway 460...closer to the front. Passage of high pressure off the coast on Wednesday will bring cooler easterly windflow to the mid-Atlantic, resulting in likely the coolest afternoon temperatures of the week. Upslope wind flow will make for the best chances of shower/thunderstorm activity across the mountains. Winds will shift more southerly by Thursday, resulting in a return of warmer temperatures and higher humidity, and greater coverage of afternoon showers/storms, more so across the mountains. A cold front will slowly make its way across the mid Atlantic on Friday and Saturday, again resulting in scattered showers and thunderstorms both days, a few of which may become severe for brief periods of time. && .AVIATION /05Z SUNDAY THROUGH THURSDAY/...
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As of 115 AM EDT Sunday... Lots of uncertainty this period in placement of convection as models are all over the place. Confidence is the first 6 hrs of the taf cycle higher per radar trends which favors BLF/LWB to have a few showers, possibly thunderstorms around til 09-11z with better coverage BLF south toward VJI-TRI corridor by 12z. For today will be sticking with VFR and not having any fog outside convection, per increasing high clouds. Storms overall look to be potentially to be in a lull between 12-18z, awaiting heating and next upper disturbance to move in from the Ohio Valley ahead of a cold front in the afternoon. Overall looks like best organized activity will be in the LWB- LYH corridor and points north, though models also favor BLF and points west, while bringing an area of storms into far SW VA after 00z, with less coverage Danville until late in the period. Will keep token VCTS in all sites, as at least widely scattered coverage will occur in the afternoon, and will amend as necessary or hone in better toward the 18z tafs while monitoring radar. Winds will be SW-WSW through the period at speeds of 4-6kts overnight and 8-10kts after 14Z Sunday with low end gusts possible at most sites. Aviation Extended Discussion... The cold front currently to our north should be near the NC/VA border by Monday evening. This leaves a baroclinic zone in or near the area through much of the extended period. Additional upper- level disturbances are progged in northwest flow to impact the area, leaving an unsettled weather pattern in place. The most likely areas to see convection, at least during the first part of the week would be near the NC/VA border, mainly affecting KDAN. Late/night early morning fog can be expected in the usual locations, otherwise outside these concerns and scattered convection, mainly in the south, look for mostly VFR cigs/vsbys.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PW NEAR TERM...MBS/PW/RAB/WP SHORT TERM...NF LONG TERM...NF AVIATION...RAB/WP

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