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Ex-Hurricane Sally brings a cool, mostly slow rain, but localized flooding south of Roanoke
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Ex-Hurricane Sally brings a cool, mostly slow rain, but localized flooding south of Roanoke

Only $5 for 5 months
Flash flood watch 091720

Rain will fall areawide, but heavier rain is possible in the green-shaded areas south and east of Roanoke, more so in North Carolina toward Southside Virginia.

This is not going to seem much like a hurricane-induced rainfall for the Roanoke/New River valleys and much of Southwest Virginia on this Thursday. It will be slow -- light to moderate mostly -- and feel a bit chilly, with temperatures holding in the upper 50s and lower 60s, mostly.

And that's because, largely, it isn't anything special or different than what we often see in cooler months of year, as moisture is lifted over a cooler dome of air near the surface, something called an "overrunning" event, when a low-pressure system tracks south of us with cooler air firmly wedged against the mountains. It just so happens that the low-pressure system in question is the remnant circulation of what was a strong Category 2 hurricane that made landfall at Gulf Shores, Alabama, on Wednesday.

Widespread 1-2-inch rainfall amounts appear to be likely, maybe a little less or a little more in a few spots, along and north of the I-81 and U.S. 460 corridors (Bristol to Wytheville to Roanoke to Lynchburg). South and east of that corridor, enough of the heavier rain from the south may nudge in for some 2-4-inch amounts, which could spur localized flooding if it comes down pretty hard for a while on top of already soggy ground from so much previous light rain.

The old circulation center of Sally is expected to track well south of us, through the Carolinas. The heaviest core of rain will occur just north and east of that track, in warmer air where convection will develop. Cooler air in our region will dampen convection, lessening the intensity of rainfall, but some of the old core of Sally might scrape into southern Virginia by tonight and early Friday. That's why a flood watch has been issued south and southeast of Roanoke, expanded one county west to include Franklin and Patrick counties.

A major Canadian cold front blasts through on Friday, sweeping Sally's remnants aside, and initiating an autumnal period that will be sweater- and pumpkin spice-worthy. Weekend high temperatures will stay below 70, maybe even below 60 in some spots, and lows will fall into the 40s, with some typically chillier spots in rural valleys dipping into the mid to upper 30s. Do not rule out seeing patchy frost in the coldest spots.

It will only gradually warm up next week with no rain expected for several days. Additional cold fronts and, possibly, the counterclockwise flow of what is now Hurricane Teddy approaching the Maine-Nova Scotia are in some form will augment the fall cool next week. 

Contact Kevin Myatt at Follow him on Twitter @kevinmyattwx.


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Since 2003, Kevin Myatt has penned the weekly Weather Journal column, and since 2006, the Weather Journal blog, which becomes particularly busy with snow. Kevin has edited a book on hurricanes and has helped lead Virginia Tech students on storm chases.

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