701 FXUS61 KRNK 201135 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 735 AM EDT Thu Jun 20 2019 .SYNOPSIS... A cold front will move across our area today, exiting the piedmont this evening. Less humid weather follows for Friday under high pressure. A warm front pushes north across the area over the weekend with humidity returning along with a threat of storms. && .NEAR TERM /THROUGH TONIGHT/... As of 250 AM EDT Thursday... Trend in convection over the southwest VA Mountain Empire is downward/weakening. Still some isolated rumbles of thunder and heavy rainfall appears possible, but nothing strong or severe. The high- res models are showing this activity shifting east toward the New River Valley and Southeast WV before dawn, though a bit of differences between all of the convective allowing models in terms of coverage. Will lean toward a weaker scenario and keep pops in the slight chance ranges to the Blue Ridge to low likely in the southwest. East of this complex some clearing allowed for dense fog to form in a few spots, but as more clouds move in, the visibilities should improve somewhat. Today looks fairly active. This morning cluster of showers and embedded vort should spread a low level boundary east toward the piedmont, but this may occur before mid morning. However, models are showing limited coverage in the east and more sunshine, as we wait for the main upper trough to move across in the afternoon. Shortwave energy and convection appears likely ahead of this main axis, as flow aloft sharpens and bulk shear increases. With a bit of sunshine to fuel the airmass, especially east of the mountains, sending MLCAPES of 1500 to 2000 J/Kg across southside VA into the NC piedmont coincident with 0-3km bulk shear of 35 to 45 kts, severe thunderstorms are possible this afternoon. 0-1km SRH increases to around 100 , and with QLCS a tornado may also be possible. The Storm Prediction Center has increased the threat to enhanced across southside VA into the NC piedmont, with the slight risk advanced further west to the NC mountains, and I-81 corridor, with marginal west into SE WV, though some parameters off the models suggest a secondary max of severe with the shortwave later in the afternoon in WV, where lapse rates may increase with the cooler trough overhead, leading to hail. All of this will be mentioned in the hazardous weather outlook. Additionally, since the PWATS stay elevated in the 1.5 to 1.9 inch range, all storms will be rain efficient. However, most of the storms will be moving fast from generally west to east at 20 to 35 mph, so limited threat of localized flooding, especially in the mountains. Will still mention this as well, given how wet we have been lately. The main cold front should track the mountains by early afternoon, then move east of the piedmont by 8-9pm. This system is more like an early spring system in terms of having better flow and low level moisture following the front this evening into tonight, and allow for showers to persist in the mountains through dawn in scattered fashion. The drier air arrives late tonight into Friday. Today will maintain the mugginess, but highs in the west may be a little cooler as residual clouds and showers arrive this morning, but some sunshine will also make an appearance at times, so expect highs in the 70s, possibly around 80 in the valleys. The foothills and piedmont should surge well into the 80s, and just could pop 90 east of Danville. Tonight, should see temps and dewpoints a little cooler at least in the mountains, with lows in the upper 50s to around 60, to mid 60s east of the Blue Ridge. Confidence is high on threat of storms and the severe threat being mainly damaging winds today, especially for areas south of a Stuart to Charlotte Court House line into NC. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... As of 300 AM EDT Thursday... Northwesterly post-frontal cool advection upsloping winds across the western flanks of the Appalachians should maintain a threat for some lingering light scattered showers into Friday morning from the NW NC mountains north into portions of SE WV, with the threat likely to end in NC and SW VA before noon, and by mid-late afternoon in SE WV as upper trof lifts off to the north and east and as high pressure builds into the region. East of the Blue Ridge, downsloping winds should maintain dry conditions. All areas should experience slightly below temperatures and a notable change (decrease) in dew points. However, any reprieve in relatively wet weather as of late will likely come to an end on Friday night into Saturday as yet another convective complex on the nose of the return of warm and moist air is expected to ride around the periphery of a developing upper ridge over the Gulf of Mexico, finally turning east and then southeast from out of the central plains toward the mid-Atlantic region - resulting in an increasing threat for showers/storms to move east to at least areas west of the Blue Ridge late Friday night into Saturday morning - and all areas by afternoon as warm moist advection increases coupled with daytime heating and influence of residual outflow boundaries from earlier upstream convection. Slowly increasing heat and humidity as the Gulf of Mexico upper ridge continues to build, and a continuation of ridge-running convective complexes will then likely maintain a threat for scattered showers/storms for the rest of the short-term forecast period (Saturday night through Sunday night)- even during nighttime periods when less overall activity would normally be expected. Timing/arrival of each convective complex is still somewhat problematic since each has yet to develop, and will be mesoscale in nature rather (than synoptic-scale) - each of which also having a significant potential to impact cloud cover and temperatures (especially by day, when contamination by cool outflow boundaries will significantly influence the normal diurnal temperature curve). Overall, though, expect a return to a sultry airmass that will linger into the beginning of next week. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 AM EDT Thursday... Amplified upper ridge axis from the Gulf of Mexico north into the TN and OH valley will gradually shift east toward the Blacksburg forecast area by Monday - along with corresponding increasing heat and humidity. GFS has advertised 850 mb temperatures in the low +20s C by Monday, which will likely push temperatures east of the Blue Ridge into the low 90s, with heat indices in the mid to upper 90s. Later Monday, a rather strong shortwave trough aloft looks to topple the ridge and will drag a weakening cold front across the Appalachians and mid-Atlantic region. This should bring with it a greater chance for thunderstorms areawide; while a few strong storms possible, too much uncertainty to place in the HWO or in the zone forecast. A bit cooler, although temperatures likely still to run close to or just above late-June climatology for Tuesday- Wednesday, with a diurnal threat for storms. Forecast confidence is overall moderate for this period. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... As of 730 AM EDT Thursday... The fog and low clouds were intermittent and as more clouds and showers move in from the west stratus and fog will erode around 12-14z. Not a complete washout in terms of rain, but should see storms in and around all taf sites at least a couple times during the day. Best chances will be this morning in BLF and this afternoon at BLF/LWB and DAN. Stronger storms more likely toward DAN this afternoon with severe winds possible, but will see how storms evolve. Otherwise, mainly VFR except MVFR or lower if storms move over TAF sites. Winds are going to be out of the west-southwest ahead of the front today, then turn westerly by later this afternoon in the west and this evening in the east. Some gusts over 20kts likely. Precip should exit this evening, except lingering upslope showers near LWB/BLF. Cigs will be VFR except MVFR to IFR in BLF/LWB. Confidence is moderate for this taf issuance. .Extended Aviation Discussion... VFR conditions with lighter winds will follow for Friday into early Saturday as high pressure builds overhead. Scattered showers and thunderstorms could return during late Saturday through Monday with MVFR conditions possible in the strongest storms. MVFR may also be possible due to any low clouds or fog during the early morning hours, especially in the mountains. && .HYDROLOGY... As of 125 AM EDT Thursday... Appears threat of flash flooding will not be as high given less coverage Wednesday. Storms today will still be rain efficient, but storm motion will be faster, so they should not linger over the same area. Some places could see 2 to 3 episodes of storms during the course of the day, so these areas may need to be watched, especially the mountains. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PW/WP NEAR TERM...WP SHORT TERM...WERT LONG TERM...AL/WERT AVIATION...PH/WP HYDROLOGY...WP