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Area Forecast Discussion
Issued by NWS Blacksburg, VA
Issued by NWS Blacksburg, VA
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325 FXUS61 KRNK 270025 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 825 PM EDT Wed Jun 26 2024 .SYNOPSIS... A weak cold front will slowly track south through the Mid Atlantic and Carolina states through Friday and resulting in showers and thunderstorms tonight. Another front with thunderstorms comes across the region Saturday and Sunday. The humidity will remain high through the weekend. && .NEAR TERM /THROUGH THURSDAY/... As of 800 PM EDT Wednesday... Key Messages: 1) Severe threat low, increasing threat for flooding issues with more rain expected overnight...mostly over by 4 AM. 2) Additional chance for thunderstorms over the Piedmont tomorrow with front stalled in the area. First wave of convection over areas north of Highway 460 has devolved into a large area of moderate rain over the Greenbrier Valley and the southern Shenandoah Valley. Rainfall rates of 1-2 inches per hour have been noted and we continue to monitor for any flooding issues, mainly for Summers and Greenbrier Counties in WV. Thankfully, precipitation has largely moved out of those areas, but additional rainfall is expected later tonight ahead of a SE moving cold front. This activity is expected to push across the entire area, with periods of rain through about 4 AM before tapering off. The severe threat has waned considerably this evening, and at least through the morning hours, expect the main concern to be moderate to heavy rainfall as outlined in WPC`s Mesoscale Precipitation Discussion. The front is expected to stall in the vicinity, and could be the focus for additional convection tomorrow afternoon, mainly in the Piedmont. Rainfall cut temperatures down a good 10-15 degrees over the course of an hour or two. It will still be muggy overnight with rain showers and temperatures in the low to mid 60s for the mountains, and the upper 60s/low 70s for the Piedmont. Confidence in the above scenario is high. As of 215 PM EDT Wednesday... Key messages: - Scattered thunderstorms tonight - Front may stall on Thursday Convective temperatures have been reached across much of the area leading to the development of isolated thunderstorms along the southern Blue Ridge, through the New River Valley and in southeast West Virginia. Plenty of instability with Convective Available Potential Energy in the 800-1500 J/kg range and downdraft CAPE up to 1200 J/KG. Most likely probability for wind gusts exceeding 50kts north of Route 460. Much of thunderstorms will be pulse variety with outflow and merging cells aiding in triggering storms. A pre-frontal trough will push through the region tonight followed by the weak cold front. The surface front advances to the North Carolina border but the 850 front never making it that far south. This leaves areas of convergence over Virginia tonight and Thursday. Thunderstorms will continue overnight and into Thursday morning. Surface dew points have climbed back into the upper 50s to mid 60s. This will keep temperatures mild overnight. The cloud cover and any rain will inhibit heating on Thursday. This will hold maximum temperatures in the 70s and 80s. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... As of 130 PM EDT Wednesday... Key Messages: 1. Daily chances of showers and thunderstorms through the period. 2. Near to above normal temperatures. Lingering showers and thunderstorms may continue overnight Thursday into early Friday morning, mainly in the eastern counties of the forecast area, following the passage of a cold front. Surface high pressure develops over the northeastern US, building down into the Mid Atlantic behind the front for Friday, bringing some cooler and drier air to the area. Not expecting much of a drop in high temperatures with this airmass, but a few degrees lower than earlier this week, and Friday will likely be the coolest day of this forecast period. Easterly flow around the high will bring some moisture into the area from the Atlantic, and could trigger some afternoon showers and thunderstorms over the southern Blue Ridge of Virginia and North Carolina. Heading into the weekend, ridging aloft develops over the southeastern states, and 500mb heights increase over the Mid Atlantic, suggesting a warming trend in temperatures. An upper trough amplifies over the Great Lakes late in the forecast period, and a warm front lifts northward over the area through Saturday, putting the area in the warm sector of the surface low pressure system, so temperatures and dewpoints will increase through the day. The cold front approaches the region from the Midwest, increasing probabilities for more widespread convection by Saturday afternoon. NBM thunderstorm probabilities range from 50% to 70% by late Saturday, as dewpoints rise via the southwesterly flow. However, chances for more organized convection increase with the passage of the actual front. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 145 PM EDT Wednesday... Key Messages: 1. Showers and thunderstorms possible Sunday, though timing is uncertain. 2. Near normal temperatures, slightly cooler Monday and Tuesday. An upper trough digs into the Great Lakes and northeastern US into Sunday, bringing a surface frontal system through the eastern states. Ample moisture and warm air ahead of the front will contribute to increasing instability, which will increase potential for showers and thunderstorms on Sunday. Better forcing for storms comes along with the front, and the trough will bring additional upper level support, and would lead to more organized convection, though those better dynamics appear to stay farther north, over the northern Mid Atlantic and Northeast, at this time. With uncertainty due to model differences in the timing of the frontal passage, and with the system still being several days out in the forecast period, confidence is lower on potential for severe storms. However, with above normal precipitable water values, storms would have the potential to produce moderate to heavy rainfall, and though most of it would be beneficial with the very dry antecedent conditions across much of the forecast area, there is a marginal risk for flooding of urban and low lying areas. Behind the front, high pressure returns to the area for the beginning of the work week. Temperatures will drop a few degrees in the cooler and drier airmass over the region, closer to seasonal normals. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... As of 815 PM EDT Wednesday... First batch of thunderstorms has morphed into areas of moderate to heavy rainfall near LWB and north of ROA. Additional rainfall is expected later tonight ahead of a SE moving cold front. This activity is expected to push across the entire area, with periods of rain through about 8Z before tapering off. After 8Z, we could see a few more hours of light rain, but it remains broken to overcast, limiting fog. Most likely spot for IFR/LIFR conditions will be LWB. Otherwise, MVFR ceilings and visibilities are possible overnight, with improving conditions to VFR after 14Z. Additional SHRA/TSRA/MVFR conditions possible tomorrow, mainly for LYH and DAN, with the front near that area. Moderate confidence for this TAF forecast. EXTENDED AVIATION OUTLOOK... Isolated showers and thunderstorms are possible again each afternoon and evening Thursday and Friday. A greater coverage of thunderstorms and associated MVFR flight conditions, is expected along and ahead of a cold front on Saturday and Sunday. Monday is expected to be drier and VFR, with a majority of the showers and thunderstorms south of the region. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AS/SH SHORT TERM...AS LONG TERM... AVIATION...AMS/BMG/SH