Valleywx.com: Tonight’s Severe Weather Threat Marginal

Posted on: 10:02 am, December 19, 2012, by , updated on: 03:31pm, December 19, 2012

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When it comes to severe weather, “marginal” is one of the best words you can hear. Marginal means that some of the ingredients are in place, but they are either not in balance or just not mixing well. A “marginal” threat means we probably will not have to deal with widespread strong or severe storms; however, it only takes ONE storm to make a big impact, so we will remain vigilant and watch each storm closely to make sure you are informed of any threat that may be coming in on you.

Last night’s model runs indicated a trend toward slower movement of the storms, and that led us to believe the threat could be a bit more elevated than previously thought. Now, we are seeing that those indicators were outliers – they do not fit the trend, so we are discounting that elevated threat.

This morning’s data suggests we could still have some relatively strong storms, and there is still a low chance (under 10%) of one or two of those storms turning severe by mid-morning. It is something we will monitor on a case by case basis.

The Storm Prediction Center has not included any of the Tennessee Valley in the Day 2 Severe Weather Outlook; there is little reason to believe this will change through tonight or tomorrow.

Here’s the Bottom Line:

    Timing: Right now, storms are expected to move into The Shoals between 5 AM and 8 AM. Some showers and storms will develop over South and Central Alabama in this time frame as well. Those developing storms will cut off a lot of the good low-level inflow of warm, humid air, and that should prevent significant severe weather in the Tennessee Valley. Showers and storms will rumble across North and Central Alabama through mid-morning and move out between 12 PM and 3 PM.

    What you need to do: Just be alert. We don’t recommend sitting up all night worrying about this. It is a “marginal” threat. Have a NOAA weather radio ON and programmed, or check out some of the smart phone apps that can alert you to a severe weather warning: WHNT App Recommendations.

    What kind of storms? Most likely, we will deal with a decaying (weakening) squall line moving across the Tennessee Valley after sunrise Thursday. The tornado threat is not totally zero, but is tiny. The severe weather threat is not zero, but is is quite low as well. Any severe weather would like come in the form of wind gusts exceeding 60 MPH; that would be a very isolated incident if it occurs.

    The wind ahead of the storms will be gusty. We could have some non-thunderstorm winds in excess of 40 MPH on the ridgetops tonight and Thursday morning. That could blow down trees and knock out power to some communities even where no “severe” weather occurs. Be aware as you are out driving that tree branches, garbage cans, and other objects can get blown out in the road even when no storms are present!

    Stay up-to-date here on the blog, WHNT News 19, and our mobile offerings:

    WHNT.com’s Maps & Radar Page
    Mobile Apps
    Alabama SAF-T-NET