Will Storms Spoil Warmest Day of Year So Far?
There is little doubt we will soar into the 70s today marking the warmest day in over 6 months.
What isn't as certain is if we will see some strong or even severe storms late today and tonight. The Storm Prediction Center has most of us in the marginal risk for severe weather today with far southern suburbs and northern Indiana in the slight risk category.
Damaging winds and large hail appear to be the biggest threat but a few tornadoes can't be ruled out. For those in the marginal risk category there is a threat of some isolated severe thunderstorms that would generally be short-lived. For those in the slight risk category the risk is for scattered severe storms and among them could be some isolated intense storms. This chart from the SPC has greater detail on the definition of all the risk categories.
Wind shear could be a contributor to severe storms should they form. There are two forms of shear, speed or directional. Directional shear means a change of wind direction with height while speed shear means a change in wind speed with height. There will be both types of wind shear at play later today.
The biggest question concerning the threat of severe weather is if we will 'break the cap'? Here is the definition of a 'cap' according to the National Weather Service:
A layer of relatively warm air aloft, usually several thousand feet above the ground, which suppresses or delays the development of thunderstorms. Air parcels rising into this layer become cooler than the surrounding air, which inhibits their ability to rise further and produce thunderstorms. As such, the cap often prevents or delays thunderstorm development even in the presence of extreme instability. However, if the cap is removed or weakened, then explosive thunderstorm development can occur.
A cold front crossing through this evening might help to initiate some storms that if the environment is sufficiently unstable, could turn severe.
Be alert and have more than one way to receive severe weather alerts. Stay safe!
Here is my 7 day forecast:
Today: Partly to mostly cloudy, breezy & warmer, sct. t-storms late High: 76
Wednesday: Partly/mostly sunny, evening shower possible Low: 49 High: 67
Thursday: Partly/mostly cloudy, shower possible late Low 38 High: 49
Friday: Partly to mostly sunny Low: 32 High: 50
Saturday: Partly to mostly cloudy, pm sct. showers Low: 37 High: 54
Sunday: Mostly cloudy, pm sct. showers Low: 41 High: 51 (45 Lakefront)
Monday: Mostly cloudy, sct. showers Low: 34 High: 40