Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 230747 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 347 AM EDT Sat Jul 23 2016 .SYNOPSIS... Strong high pressure aloft to the west will continue to bring increasing heat and humidity over the weekend. A series of weak surface cold fronts approaching from the northwest should gradually bring an increasing threat for showers and storms early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 235 AM EDT Saturday... Strong upper ridge west of the mountains will continue to expand east over the next 24 hours with heights slowly building as a piece of the high noses east into the Mid-Atlantic. Resultant 850 mb temps near +24C or better will accompany the ridging this afternoon as decent subsidence remains in place despite lingering rather moist pwats. This should bring one of the hottest days seen so far with mid/upper 90s east and 80s to perhaps touching 90 in spots over the mountains. However dewpoints again look to drop off enough east of the ridges in the afternoon despite only weak flow to preclude heat advisory headlines at this point. Still could see an hour or so where indices touch 103-105F piedmont, espcly if the flow ends up more southwest and dewpoints stay up, so continued HWO mention for now. Otherwise given little support aloft, expect more isolated convective coverage at best, with storms driven by differential heating/weak convergence mountains and perhaps the eastern lee trof. Latest suite of solutions suggest best low chances across the northwest NC mountains and possibly the Va Highlands, with shotgun 20ish pop elsewhere for isolated afternoon pulse storms at this point. Any residual convection should fade with loss of heating with another warm overnight in place as higher dewpoints return and debris clouds linger before clearing late. Will leave in some low pops mainly west early on for more outflow driven shra/tsra, otrw cutting to patchy fog overnight with lows from the mid 60s valleys to the low/mid 70s east. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 309 PM EDT Friday... As the surface frontal boundary drops south Sunday, its looses its definition stopping near the area. Showers and thunderstorms will be on the increase in advance of this front and in its proximity once it stalls. The best chance of a storm will occur in the west. The region will remain on the hot and humid side of the front. High temperatures on Sunday will range from the mid 80s in the mountains to the mid 90s in the Piedmont. Heat index values are forecast to surpass 100 degrees for one hour or two across the far southeast portion of the region Sunday afternoon. By late Sunday night, a shortwave trough approaching through the upper Mississippi valley will help to buckle the stalled front north as a warm front. This will keep hot and humid conditions across the area, and briefly shift the main focus for additional showers and thunderstorms north of the area. Added the mention of patchy for to the western valleys. Low temperatures Sunday night into Monday morning will range from the mid 60s in the west to the lower 70s in the east. On Monday, the trough axis of a disturbance will be approaching the western portions of the area by Monday afternoon and act as a focus for additional showers and thunderstorms. The greatest concentration will be in the west. High temperatures Monday will the mid 80s in the west to the mid 90s in the east. Monday afternoon some heat index readings may briefly top 105 degrees between roughly South Boston, VA and Charlotte CourtHouse, VA. We will continue to highlight the heat in the Hazardous Weather Outlook. Scattered convection will continue into Monday evening with some decrease by late Monday night as the trough axis moves east of the region. Low temperatures Monday night into Tuesday morning will range from the mid 60s in the mountains to the lower 70s in the Piedmont. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 309 PM EDT Friday... The large upper ridge will extend from the West coast to the East coast through Wednesday. Towards the end of the week, there is a gradual lowering of H5 heights as ridge splits and develops a Bermuda ridge and desert SW ridge. In the northern stream, a shortwave will drop southeast out of eastern Canada and crosses through New England on Tuesday. A frontal boundary will settle across the Mid-Atlantic and Southeast Wednesday into Thursday. A wave of low pressure along the front will slow the progression of the boundary. The placement of fronts are always a challenge in the summer. Low level moisture will continue to increase into the end of the period. Afternoon and evening showers and thunderstorms are possible Tuesday into Midweek. Temperatures will be above normal early next week and return to normal by end of the week. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... As of 1250 AM EDT Saturday... Continued mainly VFR this period with fog being the only real issue late tonight into early Saturday. As such will stay with the previous forecast of bringing KLWB to LIFR around 08z/4AM, while including a brief tempo for MVFR at KBCB. Should see good flying conditions prevail on Saturday under scattered/broken cu including isolated convection, mainly along the southern Blue Ridge espcly toward KGEV/KTNB. However uncertainty too great to include any shra/tsra mention given likely spotty nature to convection. Extended aviation discussion... Strong high pressure aloft centered across the Midwest will attempt to build eastward into Sunday, then retreat back to the west early next week. Our region will remain on the eastern periphery of the upper high and thus subject to weak disturbances in northwest flow aloft tracking around the Great Lakes and into the Mid-Atlantic. Moisture and instability will be sufficient for isolated pop up thunderstorms, but a slightly better coverage will be possible early next week as weak front moves into the area, stalls, and lingers over the region for several days. Hot and humid conditions east of the Blue Ridge this weekend which may impact density altitude. Late night and early morning fog will still be possible at the usual sites almost every day, and those chances increase if any rain occurs during the afternoon or evening at any of these sites. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/RCS NEAR TERM...JH SHORT TERM...KK LONG TERM...KK AVIATION...JH/RCS/SK/WP

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