January Severe Weather Threat

By: Michael Knight
By: Michael Knight

It may still be January, but we are watching for the threat of severe weather late this afternoon and evening.

It's not a secret, yesterday (Tuesday) was beautiful! Temperatures made it into the 70s and it is likely to happen again today. However, this time of year and through the spring, we never get to enjoy one air mass (cold or warm) for too long. This time, the warm air has moved in from the south, and now a cold front is sweeping east across the country to bring in a new and much colder air mass.

On this surface map you can see the cold front and the stationary front that separate the different air masses.

As the cold front surges forward, pushed by the cold air mass, it actually digs under the warm air. As the warm air is lifted on top of the cold air, it creates the line of thunderstorms you see just on the western fringe of West Virginia.

The cold front and the line of storms are going to push through our area later today. That is why the Storm Prediction Center has put us in the slight risk category for Severe Storms.

This is a map from the SPC, showing much of the southeastern US under the slight risk. Specifically damaging winds are our most likely threat.

The cold front will be the trigger and the lifting mechanism to fire off these storms. However there is another piece of the puzzle, making these storms so potent.

When we talk about severe weather, generally we have two major things to consider, wind shear and instability. In general, the larger they both are (within reason), the more likely severe weather will be.

Today, instability will remain low. This means the air is stacked in the atmosphere in a way so that it doesn't want to rise, it is content where it is.

The wind shear on the other hand will be very high. This means the wind speed and/or direction are changing quickly with height. Even with our low instability, we have enough wind shear to maintain the line of strong thunderstorms and create the potential for damaging wind gusts.

This image shows the threat for damaging winds, specifically.

Timing: The squall line of storms is moving rather quickly. Models have settled in on these storms reaching the western portions of our viewing area around 3/4 p.m. and pushing east throughout the evening. They should be in the central Shenandoah Valley around 6/7 p.m. There are indications that there will be another push for storms around 10/11 p.m. as the cold front officially sweeps through the area.

We will have to be mindful of strong winds in general all day, and potentially damaging winds associated with thunderstorms, along with the potential for flash flooding.There is currently a flash flood watch for our entire viewing area through late Wednesday night.

Stick with TV3 through the evening and George and Aubrey will have you covered online, and on air.

 Follow Meteorologist Josh Knight on Facebook and Twitter.

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