Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 240452 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1152 PM EST Fri Feb 23 2018 .SYNOPSIS... A strong cold front will slowly approach the Appalachians and central mid Atlantic region from the west, as high pressure remains wedged down east of the mountains. This will keep temperatures generally well above normal with an increasing chance for showers through the weekend. The front will push through the area on Sunday and after some lingering showers on Monday, high pressure will build in with gradual improvement and cooler temperatures for the first part of next week. && .NEAR TERM /THROUGH SATURDAY/...
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As of 1131 PM EST Friday... Have continued to delay onset of higher pops in the west as ridge holds firm keeping main area of deep convergence and convection well west of the forecast area. Should start to see some advance toward our WV mountains by 4am. Other weather issue late this evening is dense fog in the piedmont. For now have a special wx statement covering this, but may have to throw a dense fog advisory if conditions persist, but most models are variable on visibilities through dawn. Previous evening discussion... Convection fairly isolated at the moment over SE WV, and seeing lack of deep moisture convergence will lower pops across the west this evening, following close to the Consshort. Otherwise, seeing clouds continue to erode early this evening, but should see another surge west toward the west overnight, with mid/high clouds moving in from the west/southwest. Previous discussion from early afternoon... Wedge is eroding along the periphery and as a consequence, temperatures range from the middle 70s well west of the Blue Ridge to the middle 40s in the piedmont. Expect the erosion to continue with the central portion of the wedge persisting through the afternoon. Starting to see some showers popping up in the west thanks to some shortwave energy and weak instability where heating has occurred. Expect the chance for a shower/possibly a rumble of thunder to extend just about up to the Blue Ridge by late in the day. The main frontal boundary will continue to reside off to our west, but weak synoptic forcing and some short wave energy will continue to stream over the region from the southwest with lingering effects of the wedge across the piedmont. Expect this will result in an increasing chance for showers overnight, followed by a good chance for showers/perhaps isolated thunder on Saturday enhanced by good isentropic lift. Expect temperatures to be a bit more uniform tonight and Saturday as the wedge loses some character, but we will remain well above normal for late February.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... As of 215 PM EST Friday... Residual surface front will remain across far northern sections of the region Saturday night ahead of a stronger cold front that will approach from the west late. This should allow most of the area to stay within the warm sector overnight with best chance of showers north early on followed by increasing pops over the far west toward daybreak with the pre-frontal showers. Lows mild, mainly 50s under clouds and strong southwest flow aloft which may keep some spots above 60 for lows. Weakening cold front looks to cross the region Sunday aided by a narrow ribbon of shortwave energy while best support lifts well out to the north. Models continue to trend a bit slower while producing less rainfall with the GFS/Euro both showing the best swath of showers west of the Blue Ridge through midday and then mainly southern sections in the afternoon where a bit more weak instability will reside. Still iffy on any thunder chances given the overall weakening trend and deep westerly flow but will leave in an isolated mention from UKF to around MTV for now. Otherwise likely to categorical pops with QPF of a quarter to half inch mountains at best and generally less than a quarter inch out east. Will again be quite warm with highs 65-70 west to mid 70s southeast pending any sunny breaks. Still a lot of uncertainty to start early next week as the passing front gets caught up in southwest flow aloft and stalls across the Carolinas Sunday night into Monday. Guidance continuing to maneuver around with another wave along the boundary to our south as disorganized shortwave energy gets sheared northeast ahead of a bit stronger northern stream trough. Blend would suggest better rainfall chances near the VA/NC border with some drying north and more clouds in between. However latest ensembles support deeper moisture farther north and since carrying at least chance pops across most of the area will stay the course and await later trends at this point. Will cool down by Monday night as the final wave exits with lows in the 30s, otherwise lows 40s/low 50s Sunday night and highs 50s/low 60s Monday. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 100 PM EST Friday... Initial shortwave ridging within the fast westerly flow aloft will bring a brief drying period for Tuesday into early Wednesday as surface high pressure passes overhead Tuesday and to the coast by early Wednesday. However the run of quiet weather looks to be brief as the flow again backs/amplifies by midweek ahead of a strong upper low that will eject out of the southwest states into the Great Lakes and Mid- Atlantic region by Friday. Pieces of mid level energy ahead of the main upper system will give rise to overrunning across a warm front to the southwest by later Wednesday with this boundary crossing the region Wednesday night/Thursday as the main surface low tracks into the upper Midwest. Quick return of deeper moisture per model Pwats suggests an increasing threat for showers/rain from southwest to northeast later Wednesday and across the region Wednesday night into Thursday ahead of the trailing cold front. Upper trough looks to deepen across the region with a switch to colder northwest flow by Friday in the wake of the cold front. This likely to produce some upslope rain/snow showers with breezy/windy conditions elsewhere with more sunshine returning out east. Temperatures mainly 50s/60s for highs early on with warmest Thursday under strong southwest flow ahead of the front and then much cooler Friday under cold advection resulting in highs 40s mountains to low/mid 50s east. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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As of 1145 PM EST Friday... Dense fog has set in at LYH/DAN and other airports in the piedmont. At the moment think these two terminals will be the only ones affected in the tafs thru 12z-14z. Aside from this will be seeing VFR ceilings further west, with potential for fog in the high end IFR range at ROA. Models continue to slow down rain threat until later this morning and mainly affecting airports west of the Blue Ridge and north of a BLF-ROA line. Will see dense fog wane at LYH/DAN by 13-14z, then improve to VFR by 15-16z. Ceiling and vsbys should stay at or above 3kft for most of the afternoon outside of showers. Will have to see how much fog and low clouds form Sat evening as winds subside, but appears where it rains Saturday will see some fog into Sat night. Confidence high on cigs/vsbys in the east through 12z and less beyond for all sites, especially after 00z Sunday. Extended: During the day Sunday, showers become more widespread as a cold front crosses the region from the west. Sub-VFR conditions may well extend through Monday as the front stalls out to the south allowing for showers to linger in the region throughout the day. High pressure builds over the region Monday night into Tuesday which should bring drier conditions, at least temporarily.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...MBS/WP SHORT TERM...JH LONG TERM...JH AVIATION...JR/MBS/WP CLIMATE...PM

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