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A Closer Look at the Potential for Strong Storms Midweek

Posted on: 10:43 am, January 27, 2013, by , updated on: 10:48am, January 27, 2013

There continues to be the potential for strong to severe storms this week, thanks to a very dynamic and potent storms system expected to develop and traverse the central/southern Plains and track east Tuesday and Wednesday.  Forecast models are indicating a line of showers and storms moving across the Tennessee Valley sometime late Tuesday, into Wednesday.  Below are two images from the Storm Prediction Center.  The first is the Day 3 Convective Outlook, outlining an area from Texas, to the Great Lakes, with a chance for severe storms.  The second image is the Day 4-8 Severe Weather Outlook highlighting from eastern Mississippi, to Pennsylvania, a heightened risk for severe storms. You will notice that the Tennessee Valley is included in both images, due to the fact that the first image goes through 6:00 am, Wednesday morning and the second goes beyond that period.

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It will already be gusty across the Tennessee Valley as the system nears, with sustained wind between 15-25 mph Tuesday, gusting higher than that.  The strong southerly wind will help move moist, warm air into the region, allowing for temperatures to rise into the upper 60s and low 70s across the Tennessee Valley.  Forecast models are indicating dewpoints to reach into the low 60s, to possible mid 60s south of the Tennessee River ahead of the cold front that will bring the showers and storms, with the richer moisture staying south of North Alabama.

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There will also be a lot of wind energy with this system as wind speeds in the upper atmosphere will exceed 100 knots, or 115 mph on the eastern side of the upper trough as it intensifies across the southern plains.

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Models still disagree on the exact timing of when the showers and storms will enter Alabama.  Showers are possible Tuesday evening, before the main line of showers and storms likely enters Northwest Alabama sometime between 12:00 am – 6:00 am, or later and progresses east. Below is a look at the RPM model, one of the slower models showing the line of storms only just crossing the Mississippi River by 6:00 am Wednesday morning.

RPM

If the line doesn’t start moving through until daybreak Wednesday, then there will be higher instability and therefore a greater chance for stronger storms. This line will be quickly moving east across the region and may pick up speed as it does so.

What To Expect:
The likely scenario is that a line of showers and storms will develop just ahead of the cold front and track east across the region sometime after midnight late Tuesday night and into Wednesday.  Expect gusty wind ahead of the system, with 40-50 mph wind gusts a good bet as the line moves through, with likely a few storms reaching severe limits with wind speeds greater than 58 mph. All modes of severe weather are possible, meaning there is some potential for storms to rotate, especially if discrete cells develop ahead of the leading line of storms.  Therefore there is a tornado threat and this is something we will continue to monitor.  Exact details are still unclear, but the main threat looks to be strong to damaging winds, with the stronger storms, due to the amount of wind energy with this system, that will likely be transferred to the ground by strong thunderstorm down drafts and out flow boundaries.

Expect a wet morning commute Wednesday, with the possibility of strong storms around…something to plan ahead for, it may take a few extra minutes to get to work/school. With heavy rain likely in the stronger storms, ponding is possible on the roadways and with gusty wind, driving will be somewhat hazardous, it will be important to use extreme caution especially if storms are moving through early Wednesday and to take your time getting to your destination.

Rainfall Totals:
Heavy rain is also expected as this storm system moves through.  Below is the Hydrometeorological Prediction Center’s 5-Day Total Precipitation forecast, showing the Tennessee Valley likely receiving between 0.25″-1.25″ of rain, with likely higher amounts in heavier storms.

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Thankfully swollen creeks and rivers have had time to recede, since the flooding rain in mid January, but some rivers are still running above normal, they may need to be monitored, depending on the rainfall rates within individual showers and storms. As of right now, no major flooding issues are expected.  Some of the models are also hinting at a potential for a brief changeover from rain to flurries/light snow on the backside of the system as cold air rushes in.  Due to the ground being so warm and wet, no accumulations are expected.

How to Prepare:
This is not a storm system to lose sleep over or stress about, just be sure you have a way to get weather warnings if they are issued and check back here frequently for updates to the forecast.

- Jennifer Watson

Twitter: @JWatson_Wx

Facebook: Jennifer Watson WHNT

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