Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 242313 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 613 PM EST Sat Feb 24 2018 .SYNOPSIS... Low pressure was over Arkansas with a warm front extending into the Mid Atlantic region. The low will move northeast tonight and Sunday which pushes the warm front into New England and a cold front across much of the eastern United States on Sunday. High pressure will be over the area on Tuesday. && .NEAR TERM /THROUGH SUNDAY/... As of 545 PM EST Saturday... Updating PoPs based on radar trends with showers across the mountains. These showers will move north and out of the area by 900 pm. As of 215 PM EST Saturday... Primary axis of precipitation this evening will extend from central New Jersey to southern Indiana to central Arkansas with scattered showers in the warm sector. Will have higher probability of precipitation this evening when the models bring a band of deeper moisture across southwest Virgina, northwest North Carolina, and southeast West Virginia. Expecting a lull in the precipitation late tonight. Any chance of thunderstorms this afternoon and evening will be largely driven by daytime heating. Widespread showers and isolated thunderstorms will reach the area on Sunday morning along with the cold front. Bath county to Buckingham County will be close to the surface warm front this evening so will be trending temperatures down a couple of degrees in that area. Otherwise temperatures will remain mild and above normal overnight ahead of the front. Clouds and precipitation will hold down warming on Sunday. Even with a minimal heating potential on Sunday, Convective Available Potential Energy forecast to be around 500 J/KG Sunday afternoon so may keep threat of isolated thunderstorms in east of the Blue Ridge. Overall timing of front was very similar in all the guidance. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... As of 215 PM EST Saturday... Cold front expected to move through a large part of the forecast area will continue to largely govern sensible weather conditions Sunday night into a part of Monday as well. By majority of today`s 12z NWP solutions, this front will tend to get hung up or stall from the VA Tidewater region southwest into north-central NC and into the Deep South. A weak mid-level trough coming out of the southern Rockies/Plains region should induce a weak low/wave to form on the frontal zone Sunday night, rippling along the stalled boundary into the first half of Monday. Still is some level of uncertainty on the exact position of the frontal zone Sunday night, which mostly affects the northward extent of rain chances on the cool side of the boundary; that said, it`s reasonable enough to expect some brief northward return of the stalled front Monday as the weak low/wave moves across. Though showers may extend as far north as Route 460, highest confidence of rain is from Route 58 in southern VA into northern NC where frontal boundary may linger. It`s also a little less certain on when rain chances are greatest - the NAM and 00z ECMWF suggests it rains a good part of this period, with the GFS/Canadian shows the best period of rain being in the after- midnight timeframe. While the ECMWF is considerably wetter than most guidance, that the rain will probably be falling on the cold side of the front should keep rain rates more gradual, so not anticipating any hydrologic issues at this stage. Best chance of clearing and cooler nighttime temperatures is toward the northwest due to cool advection and some radiational cooling from building ridge. These areas also should see at least peeks of sun on Monday as well versus the cloudier southern tier. Will show lows in the 40s/lower 50s, but in the southern areas will show little significant rise in temps Monday into the upper 50s. Highs elsewhere are also in the upper 50s, despite starting off cooler with better prospects for sun here. Passage of the weak low along the front then pushes the front into the Carolinas Monday night with the center of an expansive ridge settling over the Canaan Valley in WV. This is pretty much ideal radiational cooling which should help to plummet temperatures into the 30s, perhaps near 40 in the northern NC Piedmont. Though I`m not overly confident as yet to put in the grids, with the likelihood of wet ground and developing radiation inversion, may have some overnight patchy fog with best chance perhaps where it rained Sunday night/Monday. Tuesday by and large is uneventful. In-situ CAD profile will probably begin the day with easterly flow against the southern Blue Ridge, perhaps leading to some scattered lower clouds but it`s otherwise a largely dry, mostly sunny forecast. CAD then erodes by afternoon with southerly/veering low-level profile. This will spread increased cloud cover in the western Appalachians/southern Blue Ridge Tuesday night. Appears best chance for light rain is along the southern Appalachians in GA/southwestern NC, but will carry lower Chance PoPs for the pre-dawn Wednesday hours up to Ashe County. Highs Tuesday should have no trouble reaching at least the upper 50s, and areas in Southside/Piedmont should reach the mid 60s again. For temps Tuesday night, sided on cool side of guidance given at least some radiational cooling before clouds overspread Tuesday night - with lows in the upper 30s to mid 40s. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 100 PM EST Friday... 12z global guidance points to a more active weather pattern late in the week. A southern stream mid-level trough and organizing surface low coming out of the southern Plains will be the source of this active weather period, and at least on a synoptic scale, may not be too dissimilar to the one underway today (Saturday). This should be a potentially wet period overall at least for the end of the week, before conditions begin to trend somewhat drier and more typical for late February/early March. Elongated warm front pushes across the region on Wednesday/Wednesday night. This will focus at least steady light showers through Wednesday. The most active day at this point appears to be on Thursday, as a powerful digging shortwave with good 500 mb height falls/diffluence aloft combines with warm, moist warm sector (PWATs > 1 inch) and approaching cold front to lead to high chances for rain. Good veering profile from surface southeasterlies to southwest 500 mb winds along with the aforementioned height falls/forcing could support potential for thunder as well for part of the region. Beyond that, it`s too early to speculate on any further potential impact though. Thursday is nonetheless a day to keep close tabs on in the upcoming workweek. Will indicate high Likely to low Categorical PoPs with this system. The southern stream trough then phases with northern energy and evolves into a closed upper low Thursday night into Friday. This will lead to precipitation becoming more orographic/NW flow variety as the surface low becomes nearly stationary off Southern New England. Though much of region should trend cooler and generally drier, may see some rain or upslope, elevation-dependent wet snow in the western mountains Friday (850 temps fall to 0 to -4C). Temperatures should continue to run above to well above normal through the rest of the workweek, then begin to trend closer to normal into the upcoming weekend. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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As of 613 PM EST Saturday... Flight conditions will be VFR into tonight across southwest Virginia, northwest North Carolina and southeast West Virginia. Isolated to scattered showers are expected through the evening. Probability of occurrence was too low to include in area TAFs except LWB. MVFR of lower ceilings are possible north of a warm front tonight. NAM, RAP, and GFS all keep the boundary north of KLYH but only medium confidence overall with the forecast position of this front. The main cold front crosses into the region from the west on Sunday. High confidence of widespread showers after 12Z with occasional MVFR visibility. Extended: Sub-VFR conditions may extend through Monday and Monday night as the front stalls to the south allowing for showers to linger across southern Virginia into much of North Carolina throughout the day. High pressure builds over the region into Tuesday which should bring drier conditions and VFR, at least temporarily. By Thursday rain and MVFR to IFR ceilings may return to the region.
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&& .CLIMATE... Records For... Feb 24th Site MaxT/Year Warm Min/Year BLF 71/2017 53/2017 DAN 79/2012 51/1996 LYH 79/2012 53/1985 ROA 80/1985 52/1943 RNK 73/1975 49/1975 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS/RCS SHORT TERM...AL LONG TERM...AL AVIATION...AMS/RCS CLIMATE...PM

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