Thursday severe weather threat: damaging winds and isolated tornadoes

Posted at 9:41 PM, Mar 13, 2019
and last updated 2019-03-13 23:22:59-04

WEST MICHIGAN -- Severe weather is probably the last thing on everyone's mind after the winter we just came through. All the more reason why we need to be vigilant in our coverage and keeping everyone informed. A strong, but dying low pressure system over the central portion of the country is creating hurricane wind speeds of 75 mph and blizzard conditions across Denver and the central/northern Plains of the Dakotas.  That same system will drive temperatures in Michigan between 65 and 70 on Thursday, but it will come with wind and the threat of strong to severe storms Thursday afternoon. Below is a snapshot from our forecast model valid at 6 A.M. Thursday.

See the snapshot from our forecast model valid at noon on Thursday. Notice a secondary line of storms just starting to develop. These have the potential of becoming severe.

We'll likely see some showers and thunderstorms overnight into Thursday morning, but those will not be severe. It's the redevelopment of storms in the afternoon that may pose issues. A strong wind field, a turning motion in the atmosphere, and other upper level dynamics may spin up a brief tornado or two or some damaging straight line winds of 60 mph or more. We believe the target time for West Michigan is about noon through 6 P.M. See the severe weather threat graphic below. The areas in yellow have a higher risk of severe weather.

There are two important mitigating factors for this severe weather we should mention. A temperature inversion, or cap as meteorologists call it may help prevent significant thunderstorm development. This is where temperatures actually warm above the surface and prevent air from keeps a lid on the atmosphere and creates negative buoyancy. If the air was cooler aloft, the air below it (at the surface) would want to rise because it's warmer. Positive buoyancy would allow thunderstorms to develop and continue to flourish. The other thing? A mainly cloudy day will keep heat and energy from building in the atmosphere and fueling these storms. More sun = more heat/energy and power to fuel these storms. It would also help break the cap or inversion. Think of it this way: if you shake up a bottle of soda and leave the lid on, nothing happens. But shake it and pop the lid and you'll see explosive development of that soda rushing out of the bottle or can. The atmosphere acts much the same way!

Our primary threats include damaging straight line winds (60 to 70 mph) and/or the possibility of isolated brief tornado spin-ups of an EF0, EF1, or EF2. Thunderstorms aside, we will see sustained synoptic winds (from the low pressure system itself) from the south at about 20 to 30 mph with gusts of 40 to 50 mph possible. See severe weather threats graphic below.

By Friday the system has moved into Canada and colder air will be filtering in. See our forecast model below.

Area rivers are expected to rise with all the rain (between .50" and about an inch) plus the snow melt. Make sure to fire up your NOAA weather radios and keep a close ear/eye on FOX 17. Get the complete forecast at