Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231859 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 259 PM EDT Thu May 23 2019 .SYNOPSIS... A weak cold front will progress across the forecast area later tonight into Friday. Warm and humid weather under an upper-level ridge of high pressure will maintain itself Friday, with limited thunderstorm chances. A cold front will progress into the northern mid-Atlantic region Saturday into Sunday. && .NEAR TERM /THROUGH FRIDAY/... As of 258 PM EDT Thursday... Widely scattered showers and storms continue to form in two main areas: now moving into Summers and Greenbrier Counties as well as more isolated activity into the foothills of the Blue Ridge west of Roanoke. Air mass is moderately unstable with surface based CAPEs between 2000 J/kg with an axis of 3000 J/kg just east of the Blue Ridge. Appears that westerly flow has led to more limited surface convergence with coverage of storms isolated to widely scattered. A few storms may still prove capable of gusty winds especially north of Route 460 as ongoing line moves into the more unstable air. After these initial showers and storms move eastward, guidance also has some consistency in bringing a second round of showers or storms toward our far northwestern and western counties - the Alleghany Highlands westward into the Greenbrier Valley - though they differ on precise evolution and how far east into the forecast area these showers/storms progress. The cluster of storms the guidance is keying on which turns northwestward toward our area perhaps is the cluster of storms now near the Louisville area. So while trended the forecast dry for the overnight for most areas west of I-81, kept a mention of showers and thunderstorms going until midnight for the Highlands southwestward into southeast WV. These aren`t likely to be severe but may still be capable of evening lightning strikes through midnight. A rather muggy evening tonight with lows in the mid-upper 60s and dewpoints in the mid 60s. The trough moving into the Northeastern states will weaken/flatten the top of the Southeast ridge, with stronger ridge axis across the Missisippi Valley into the upper Midwest. This will encourage more of a northwesterly flow aloft for Friday. After any leftover showers fizzle in the far western mountains, most of the area sees mostly sunny skies. While the atmosphere becomes moderately unstable again, models show a little more capping along with less forcing for ascent. This should keep any convection pretty well suppressed. A few models were developing some showers or storms mainly southwest of I-77 running along or just south of the 500 mb height gradient; did leave slight to low chance PoPs for showers and storms in this area. This threat appears conditional on some triggering source in the northwest flow aloft and/or residual low-level boundaries left behind from today`s storms. GFS progs CAPE values around 1000-1500 J/kg with 0-6 km shear values less than 35 kts; implication being that any storms may be more pulse variety than organized. Highs into the 80s to low 90s; should have heat indices in the mid 80s to mid 90s warmest in Southside. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 259 PM EDT Thursday... The upper ridge over the eastern part of the country will remain in place and keep the Appalachians and central mid Atlantic region with summery weather through the weekend. A transitory surface wedge of high pressure east of the mountains will push off the North Carolina coast on Saturday. The circulation into the warm frontal boundary on the backside of the wedge will fuel thunderstorm development especially west of the Blue Ridge with some stronger storms possible thanks to enhanced shear near the warm front. Convection will linger into Saturday night before dissipating during the overnight hours as the warm front pushes off a bit to our north. Sunday looks to be mostly dry with a few isolated showers/storms. However, indications are pointing to an MCS developing Sunday evening along the lingering warm frontal boundary to our north. While the main push of this MCS looks to be through OH/PA/northern WV, the southern flank may sag far enough southward to impact southeast WV and the I-64 corridor Sunday night. Will be watching how this situation develops and fine tune any potential severe weather impacts Despite a wedge on Saturday temperatures will remain well above normal through the weekend. By Sunday temperatures will once again be in the low/mid 90s east of the Blue Ridge with generally mid/upper 80s to the west. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 259 PM EDT Thursday... The axis of the upper ridge will be to our east by Wednesday, then flatten considerably as the pattern becomes essentially zonal by the end of the week. Expect the depth of the warm air under the ridge to help suppress convection with generally isolated/widely scattered thunderstorms mainly in the mountains on Monday and Tuesday, though will have to watch the lingering frontal boundary on Monday. Then by midweek, the progressive zonal pattern will bring an increasing chance for showers/thunderstorms ahead of a cold front that will move through on Thursday. Temperatures will remain well above normal for most of next week with hazy, hot, and humid conditions. Highs will generally be in the low/mid 90s east of the Blue Ridge with 80s to the west. Lows will be quite balmy with readings generally in the mid/upper 60s, a bit cooler in the valleys west of the Ridge. && .AVIATION /19Z THURSDAY THROUGH TUESDAY/... As of 113 PM EDT Thursday... Lingering low stratus has finally started to thin out away from Southside into the NC Piedmont; but the main concern for the remainder of the afternoon is for scattered strong/severe thunderstorms. Threat appears greatest for most TAFs except Danville, and have included SHRA VCTS in association with a likely line of storms progressing eastward from central WV now through 00z. Storms may be capable of lightning, gusty winds capable of localized turbulence, and brief IFR visby from heavy rainfall. Storms should weaken as instability wanes after sunset, though a few additional showers capable of brief restrictions toward Lewisburg late this evening. Kept TAFs at mainly VFR, but will be quick to issue TEMPOs for any convective threat this afternoon/tonight. Winds outside of thunderstorms mainly southwest 6-10 kts. Should see mainly VFR conditions through 18z Friday. May see isolated thunderstorms build up southwest of I-77 into the mountains of northwest NC very late in the 18z TAF period, but not likely to affect any TAFs. Winds west to northwest 6-9 kts. Forecast confidence is moderate on thunderstorm potential, and moderate to high on aviation categories outside of thunder. EXTENDED AVIATION DISCUSSION... VFR conditions are expected across the region Friday thru Sunday. Exception is with evening/overnight fog but confidence low on development attm. SCT MVFR showers and thunderstorms are possible Monday in the west. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AL NEAR TERM...AL SHORT TERM...MBS LONG TERM...MBS AVIATION...AL is the U.S. government's official web portal to all federal, state and local government web resources and services.