UPDATE 7AM, 8/29/2020: A showery morning is on tap for the Roanoke and New River valleys, a far cry from what was once the fifth strongest hurricane on record to make landfall in the U.S. The remnants of Hurricane Laura are moving through with a gloomy sky and periods of showers, with amounts of rain likely to be well under 1 inch at most locations in the region. The circulation center of the diffuse system is a bit north of earlier forecasts, it is arriving a bit faster in our region at the coolest and least unstable time of day, and some of the rain has dried up with downslope flow crossing southwest to northeast across the mountains. Some breeziness will develop later today as the rain begins to pull away, but not damaging winds, with sunshine likely popping out for the afternoon. There is a slight chance some thunderstorms could develop this afternoon along and east of the Blue Ridge, but it appears this activity will be more likely to the east, where there remains a tornado risk with strong shear aloft in central and eastern Virginia. A warm, dry Sunday is in the offing before some unsettled weather in the week ahead. END UPDATE
UPDATE 10:30 PM, 8/28/2020: No major changes with going forecast. The mass of rain associated with what was once Hurricane Laura is over eastern Tennessee and Kentucky, headed generally eastward. Thunderstorms and bands of rain have developed intermittently ahead of the mass of rain as moisture is pulled northward by the circulation of Laura. It appears this will push across the region mainly during the morning on Saturday, with widespread 1/2 to 2 inch rainfall amounts, locally up to 4. Winds will pick up somewhat to the 15-25 mph range with some gusts over 40 mph in higher elevations and near some squalls that manage to pull down stronger winds from aloft. There is a minimal risk of a few tornadoes in our region, but that threat will maximize over central and eastern Virginia later Saturday with daytime heating destabilizing. All in all, it will be a rainy, breezy morning that might not look like anything that was once a destructive hurricane, but we will probably see some sunshine by mid to late afternoon. END UPDATE
UPDATE 4PM, 8/28/2020: A flash flood watch has been issued on this Friday evening for most of Southwest Virginia west of Roanoke, as far east as Carroll, Floyd, Montgomery and Craig counties. This watch is not for the core of Laura's remnants, which will move through Saturday, but for storms that have developed in northwest North Carolina and northeast Tennessee and are slowly moving northeast generally along the I-81 corridor and Blue Ridge. The heaviest storms will be capable of rainfall rates exceeding 2 inches per hour on this Friday evening, posing the risk of flash flooding. While the watch does not cover Roanoke or locations to the east, some storms with locally heavy downpours are also possible in those areas. While this is not part of the structure that once was Hurricane Laura, its remnant circulation over Tennessee is enhancing moisture flow into our region from the south with counterclockwise rotation. Laura's remnants will move through on Saturday morning, with a quick push of squally rain and thunderstorms. END UPDATE
The remnants of Hurricane Laura are on track for a Saturday arrival over Southwest Virginia, with a quick rush of squally rain and storms, possibly some fairly strong gusts of wind, especially in higher elevations, and maybe a few tornadoes, more likely east of the Blue Ridge. But it would not be shocking if your particular location got a stronger storm on this Friday than what happens on Saturday.
The "regular" weather stuff is still happening, and a wave of upper-level energy moving ahead of Laura, combined with heat and humidity, will trigger scattered storms on this Friday afternoon and evening. The strongest storms have the potential for torrential downpours of 1 to 2 inches in a short time and damaging downburst winds. As is typical, most locations will not see these impacts, either getting lighter rain or nothing, maybe hearing some distant thunder. Any storms on this Friday will not be directly connected to Laura.
The old circulation center of Laura is expected to take a track near Interstate 64 across the middle of Virginia. A band of rain and storms is expected to precede the circulation center on Saturday, morning to midday for our region. At this point, this does not look like any kind of widespread disaster for our region, and might seem fairly tame for a lot of people. Widespread rainfall of 3/4 to 2 inches appears likely, but some spots could get more in stronger storms, posing the threat of localized flooding, especially anywhere that gets under heavier rain on this Friday. Huge rainfall totals exceeding 6 inches, as sometimes happen with old tropical systems passing through our region, appear highly unlikely, given Laura's speed and the tendency for its moisture to spread out rather than remain concentrated.
Winds will pick up, but probably only to the 15-25 mph range for most, especially below 2,000 feet in elevation. Some higher gusts exceeding 40 mph may occur at higher elevations. Wet ground and fully leafed trees will enhance potential for some trees to be knocked down, possibly into power lines for sporadic power outages.
The atmospheric shear of Laura's old circulation center will cause storm cells to spin more readily than we typically see, and some of these could produce either localized downburst winds of up to 60 mph, isolated tornadoes, or both. The greatest chance of this occurring will be east of the Blue Ridge, where a slightly later arrival of Laura's squalls may allow for more daytime heating and therefore greater destabilization to lift storm tops high enough to be more affected by that spin.
Most of Laura's direct impact will be over by about mid-afternoon in the Roanoke and New River valleys, with some showers possibly circulating in from the northwest on the backside of Laura. It would not be shocking to see the sun during the afternoon.
Somewhat cooler and much drier air will filter in behind Laura and a passing cold front, bringing a sunny, warm Sunday with decently cool mornings in the upper 50s and lower 60s both Sunday and Monday. The week ahead will bring more unsettled weather with periods of showers and storms with mostly seasonable temperatures, 80s highs/60s lows.
There is more potential tropical trouble to monitor in the Atlantic, with two systems that may develop into tropical cyclones, but they are several days away from any potential effect to the U.S. The long range pattern shows the potential for fall-like temperatures to make themselves known at least in the central U.S., possibly expanding to the east, by the second week of September.
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