Saturday Weather Briefing: Heavy rain/flash flood threat increasing for this weekend...

Good Saturday to everyone across the region, we continue to monitor what looks to be a very wet next couple days. Since yesterday we have seen a trend take place that suggests that heavy rainfall and flash flood threat is increasing for the Western Carolinas.

 

As of early this morning a warm front has surged northward through the region helping deliver a moist and unstable atmosphere across most of the Southeast US including here in the Western Carolinas. A few rain showers moved through overnight and for the morning hours we have overcast skies with occasional bouts of shower activity.

 

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For later today we see the pieces coming together throughout the atmosphere that is going to lead to heavy rain potential. At the surface a frontal boundary will be centered West of the Appalachians across the Tennessee Valley and that will be a focus for rainfall. At about 5000 ft altitude, southerly slow will strengthen as high pressure in the Atlantic has winds around its rear side transporting a good bit of Atlantic and Gulf moisture northward.

 

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Once you get to the jet stream level, a deep southwest flow that has plenty of Gulf moisture and even some moisture of Pacific origin moving northeast, uninterrupted into the Southern Appalachian Region. These features are coming together to help produce widespread heavy precipitation.

 

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Precipitable Water values of between 1.3 and 1.5 inches will quickly advect northward and into the Western Carolinas by this evening. This kind of moisture content is very high for the second week of February. Its something more like you would see in the late Spring rather than the heart of winter.

 

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So…the combination of a surface boundary, high moisture content and south to southwest flow (upslope) aloft is leading to the heavy rain potential.

 

Computer models yesterday tried to focus the heaviest precip west of the Appalachians in association with the surface boundary but overnight that has shifted east into the Apps and for our coverage area, the Foothills in particular. A conveyor belt of upper level energy on southwest winds is going to produce multiple rounds of steady/heavy precip. It will begin in earnest later this afternoon and will be underway tonight and going through the morning hours of Sunday and beyond

 

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This is really a best case scenario for heavy rain genesis as the front is slow moving and we have deep moisture in place…so this has the potential to be a big rainmaker. And with recent wet weather, it could lead to flash flood issues especially on Sunday. Another factor to play into the rain potential will involve just how much convective activity may try to form as warmer air is being pulled in.

 

The latest WPC outlook has widespread 2-3 inch rainfall totals with local amounts of 4+ inches through Monday morning, that looks like a solid forecast at this time in regards to our area. WPC has also updated its excessive rainfall outlook putting areas west of the mountains in a slight risk…that could easily be adjusted east in later updates…

 

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Residents of the Western Carolinas should be prepared for the possibility of some flash flooding later this weekend. Our weather team will continue to monitor the situation and will post any additional watches or warnings that are issued by the National Weather Service.

 

Have a great Saturday and remain Weather Aware all weekend.

 

 

 

Daniel Crawley

Foothills Weather Network