Mother Nature is about to unleash a nearly three-day rampage of severe storms across a huge area of the United States. Everyone will need to be wary as the potential for tornadoes, large hail and destructive winds threatens the Great Plains, Midwest, Southeast and Mid-Atlantic from late this afternoon through Friday night and early Saturday (April 17-20, 2019). Truckers will need to stay alert and pay attention to quick changes in the weather, and may be delayed by numerous wet Interstates and flooded secondary routes across the eastern half of the country.
At the surface, a low pressure system is developing over western Kansas, with a cold front extending southward into New Mexico. The front marks the boundary between warm, humid and unstable air to its east – across the Great Plains and portions of the Midwest – and the cooler, drier, stable air to its west. Storms typically develop near fronts because this is where the most dramatic differences exist between air masses. Meanwhile, low pressure aloft will add energy and spin to the atmosphere, increasing the odds for storms to become severe.
Typically, an organized line of storms develops near the front. However, discrete storm cells that look like popcorn patterns on a radar screen can develop well ahead of fronts. These cells, given the right environment, can strengthen rapidly and begin rotating into supercell thunderstorms. Supercells can then form funnel clouds that, upon reaching the ground, become tornadoes. This could happen in many areas as this system moves eastward each day, possibly in/near some communities that were hit last weekend.
Ranking the Risks
Tornadoes will definitely be a concern, but we probably won’t see a major outbreak across every state in the system’s path. However, along its three-day journey, certain areas will be more prone to tornadoes than others, and regional or localized severe storm outbreaks are a good bet. Tonight, the highest risk is from Austin and Dallas, Texas to Oklahoma City and Wichita; Thursday it’s from most of Louisiana to Pensacola, Florida, northward to Tupelo and Birmingham; and Friday it is across the Carolinas and southern Virginia.
All types of severe weather are possible – tornadoes, large hail and destructive straight-line winds. Frequent dangerous cloud-to-ground lightning is likely, and many places could experience flash flooding. What type of severe weather will strike specific areas depends on the day and the locations.
The National Weather Service (NWS) defines a severe storm as one that produces any one or more of the following:
• Hail at least 1 inch in diameter (around the size of a quarter)
• Winds of at least 58 mph (50 knots)
NWS meteorologists will often issue a Severe Thunderstorm Watch or a Tornado Watch for a large number of counties up to 12 hours before they expect severe weather to occur. Once severe weather is observed and reported by someone in the field, or indicated on radar, the NWS will issue a Warning.
Here’s the easiest way to remember the difference between a Watch and a Warning:
• Watch = Watch the skies; severe weather may develop; pay attention to local forecasts.
• Warning = Take action; severe weather is heading your way.
Having a NOAA weather radio with battery backup is the best way to stay aware of impending severe storms. You can receive Watches and Warnings 24/7, even if the electricity goes out and cell towers get knocked out of service. It could end up being your only source for life-saving weather information.
So, please remain “weather aware” and stay safe!