Summary:
Severe weather threats for Friday night and into Saturday morning remain low, but risk areas have expanded, highlighting the potential for isolated damaging wind gusts, large hail, and even a brief, weak tornado or two across much of Southwest Michigan.
NWS SPC Severe Weather Outlook For Friday Night Into Saturday Morning:
NWS SPC Severe Weather Outlook For Saturday Afternoon:
Discussion:
Risk areas for severe weather Friday night into Saturday have been expanded quite significantly to the North and East across the area with the level 2/5 Slight Risk now encompassing much of Southwestern Berrien County and the level 1/5 Marginal Risk now covering areas South and West of a line from Manistee to Big Rapids to Jackson which is about half of our coverage area, so overall a decent sized expansion of the risk area.
In terms of the weather environment and related hazards, not much has changed since yesterday (see previous discussion below), except that confidence in better northward extent of moisture and related surface instability amongst plenty of wind shear has increased, and hence, while probabilities for an all-hazards severe weather setup remain low, the areas of risk have been expanded as aforementioned.
With regard to the daytime hours on Saturday, storms should be clearing our area by late afternoon at the latest, and so while we remain in a General Thunderstorm risk for Saturday at this time, we do expect that any re-development of severe weather hazards will remain to the South and East of our coverage area. We will continue to monitor this.
With the overnight timing of this threat, we plan to post updated SPC Outlooks and any relevant forecasts tomorrow morning, and then we will do either a YouTube Video update or a livestream (see links on our Live Coverage page here) tomorrow afternoon or evening with additional details and our overall thoughts on specific severe weather hazards.
Previous Discussion:
(Issued at 8:44 AM ET Wednesday, March 12, 2025)
Our first severe weather threat of 2025 is now on the table for portions of Western Lower Michigan Friday evening into Saturday morning as a strong low-pressure system drives a swath of showers and storms, many of which will likely be severe, across much of the Midwest and Great Plains.
As we know, thunderstorms, and especially severe thunderstorms, generally need 4 key ingredients to mature and sustain themselves: moisture, wind shear, forcing for ascent, and instability. Sometimes, however, a lack of 1 or 2 of those ingredients can be overcome by an abundance of the other ingredients.
In this setup, Michigan and the Great Lakes region at large will generally be removed from the area of greatest moisture and instability, however, wind shear will be plentiful. This will allow for a non-zero severe weather risk across parts of our area in what is known as a "High-Shear-Low-CAPE" setup.
As the low-pressure system moves eastward, we will see wind shear across the area, which is more than favorable for the development and sustainment of thunderstorms and for the mixing of strong to even damaging wind gusts down to the surface. However, the lack of other key ingredients will hinder the initial development and overall longevity of thunderstorms, so our overall risk for severe weather is not overly concerning but is non-zero nonetheless.