Strong Low-Pressure System Will Bring Threat of Severe Thunderstorms to Midwest, Great Lakes, Ohio Valley Late This Week

Linda Lam
Published: February 21,2017
The threat of strong to severe thunderstorms is expected to develop in portions of the Midwest, southern Great Lakes and Ohio Valley late this week as a strong low-pressure system pushes a cold front through the Midwest and into the East.
Areas east of the Rockies have been experiencing spring-like temperatures this week, but this late-week system will bring an end to the record warmth.
(MORE: Dozens of Record Highs Will Be Broken as Spring Fever Continues)
On the back side of this low-pressure system, temperatures will return closer to average for most areas. In addition, snow and gusty winds are expected.
For some areas, Friday will feel like spring, but winter will be in the air by Saturday.
(MORE: Snowstorm Will Give Midwest, Plains a Reality Check Late This Week)

Severe Setup

An area of low pressure will move through the Rockies and into the Plains by Thursday. This system will begin to develop and become better organized Thursday and will track toward the Great Lakes through Friday.

Setup for strong to severe thunderstorms late this week.

One of the ingredients necessary for severe thunderstorms is warm, humid air. There will be plenty of warm and moist air ahead of the cold front, which will help thunderstorms form across the Midwest and Ohio Valley.
Dew points in the 50s will reach as far north as the southern Great Lakes, contributing to instability of the atmosphere.
(MAPS: 10-Day Forecast)
Moderate to strong wind shear, or the changing of wind – changing wind speed and/or direction with height – is also expected to be in place.
These ingredients may come together to produce a few strong to severe thunderstorms as the cold front pushes east. The exact track of this system is uncertain, which is important for the forecast details, so be sure to check frequently for updates.

Severe Weather Forecast

Showers and thunderstorms will increase in coverage on Thursday as the storm system strengthens.
A few isolated severe thunderstorms may develop late Thursday afternoon in northeastern Kansas, northern and central Missouri and into southeastern Iowa. A few storms could produce large hail and damaging wind gusts.
Thursday Night

• The chance for strong to severe thunderstorms will spread east Thursday night into Illinois, northern Indiana and southwestern Michigan.
• The primary concerns will be damaging wind gusts and large hail.
• FORECAST: St. Louis | Springfield, Illinois | South Bend, Indiana

Thursday Night's Forecast

Friday

• The best chance for severe thunderstorms will be from Illinois into Indiana, southern Michigan, western Ohio, western Kentucky and northern Tennessee.
• Damaging wind gusts will be the biggest concern, although large hail and an isolated tornado are also possible.
• FORECAST: Chicago | Indianapolis | Detroit | Louisville, Kentucky

Friday's Thunderstorm Forecast

Saturday

• The cold front slides into the East to start the weekend, bringing the risk of isolated severe thunderstorms into the mid-Atlantic.
• The main concern will be damaging wind gusts, but large hail and an isolated tornado cannot be ruled out.
• FORECAST: Philadelphia | Washington D.C. | Norfolk, Virginia

Saturday's Forecast

Locally heavy rain is also possible, which could result in localized flooding and hazardous driving conditions.

Is This Unusual?

It's important to remember many areas that could see severe thunderstorms late in the week don't regularly experience severe weather during the winter and may not be prepared.
Meteorological spring begins March 1, so it is not rare to see a more spring-like low-pressure system to develop at the end of February.

In the "possible" lighter red are locations that have a 0.10 percent probability of a tornado within 25 miles of a point by late February. The "most likely" darker red shading is for locations that have a 0.20 percent probability of a tornado within 25 miles of a point by late February. Based on 1982-2011 averages.
(NOAA/Storm Prediction Center)

However, as the map above illustrates, tornadoes can form in parts of the Midwest and Ohio Valley in February. Even areas not shaded in red can experience severe weather in late winter.
(MORE: Tornadoes in February)
Warm temperatures are usually one of the limiting factors in severe thunderstorms forming farther north in the winter.
It is not uncommon to experience above-average temperatures in late February, but this current prolonged period of record warmth is noteworthy and will likely help in the development of severe weather this week.
MORE: Tornadoes in San Antonio, Texas

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