UPDATE 3:40 PM, 10/10/2018: The flash flood watch for our region has been expanded northwest to the Interstate 81 corridor, including Roanoke and most of the New River Valley. Widespread rainfall of 1-3 inches is expected, with locally heavier amounts, especially near the North Carolina state line and along the Blue Ridge south of Roanoke. Flooding could develop quickly anywhere a heavier rain band can remain over a given location for an hour or more. END UPDATE
UPDATE 2:35 PM, 10/10/2018: Hurricane Michael made landfall at about 2 p.m. near Mexico Beach, Florida. Tyndall Air Force Base was within the eye. Its maximum sustained wind at landfall was 155 mph, which is the top edge of Category 4, and the fourth strongest ever for a U.S.-landfall storm. Its central pressure was 919 millibars, or 27.14 inches of mercury, the third lowest pressure ever recorded for a U.S.-landfalling hurricane (trailing only Labor Day 1935 and Camille in 1969). Large-scale destruction from wind and surging waves is ongoing in the Panama City Beach to Appalachiacola stretch of the beach. Significant wind damage, with millions of customers losing electrical power, will likely continue far inland as the hurricane-force winds only gradually diminish as the storm acclerates, tropical storm force winds (39+ mph sustained) continuing even across the Carolinas. … Periods of rain will continue for Southwest Virginia, possibly heavy at times, this evening into Thursday, with widespread 1-3 inches of rain and locally more. END UPDATE
It's really bad to wake up to see a soon-to-be-landfalling hurricane is a strong Category 4 storm and still strengthening. That is the nightmare unfolding for the Florida Panhandle, where a devastating impact appears imminent from Hurricane Michael, with maximum sustained winds at 145 mph and storm surge likely to go well over 10 feet, maybe 20 feet. Hurricane impacts will extend well inland across the Panhandle into southeast Alabama and Georgia, with tropical storm force winds reaching the Carolinas, as it will take some time for winds that strong to cycle down after landfall.
For Southwest Virginia, we are well outside the zone of significant wind impacts, but Michael-influenced rains have already begun and will continue tonight and Thursday. Southeasterly flow, rotating around Michael, against the mountains has lifted moisture to create numerous showers this morning. Later today, a band of locally heavy rain over the Carolinas will likely move northward into our region. This is a "predecessor rain event" (yes, that is a real weather term), a heavier rain band that often develops well north of a tropical cyclone, as its moisture and influence collides with other atmospheric factors.
Michael's main rain shield will lift northeastward on Thursday, as the storm's circulation center tracks southeast of us across the Carolinas. We'll be caught between Michael and an approaching cold front, which will provide another source of lift to enhance rainfall. Over Wednesday and Thursday, widespread rainfall totals of 1-3 inches are likely over our region, with some localized heavier amounts. The speed of Michael's movement will help limit rain totals from what they could be, but even at that, widespread rain on still-moist soils and the potential for localized heavier bands will raise concerns for flooding -- as is any nudge west in the inland movement of Michael, that could raise our rain totals. A flash flood watch has already been issued for counties near the North Carolina state line most likely to see direct Michael rainfall impacts, but that may be extended north and west as the situation unfolds.
Once this cold front passes by, we dry out and cool off to seasonal norms for the weekend (60s highs, 40s lows).
Reinforcing cold fronts arrive next week to deepen the fall-like weather, possibly even bringing frost on a few mornings mid to late next week. Some moisture from the remnants of Tropical Storm Sergio way out in the Pacific Ocean may get caught ahead of the first front, bringing a chance of showers on Monday, but this will pass through quickly.