Monitoring severe storm threat tonight in Metro Detroit


The brief line of thunderstorms that crossed the area midday brought lightning, heavy downpours, and penny-size hail to some of you but, given the very fast forward speed of these storms (65 mph), they were gone pretty quick.  We’ll be windy and warm the rest of the afternoon so, if you want to get outside for some recreation or work, it’ll be a splendid spring afternoon to do so.

Another round of thunderstorms should develop and cross the area this evening, and these storms do have the potential to bring some severe weather our way.  However, there’s a big question mark about the exact orientation of this batch of storms, and this gives me a great teaching moment opportunity.  Check out the two computer model forecasts below for 9:00 p.m. Monday evening:

Both of these are from our in-house RPM model.  The one on the left was produced by the 8:00 a.m. run of the model, while the one on the right was produced by the 11 a.m. run of the model.  The 8:00 a.m. model has what appears to be a substantial area of severe storms affecting areas mainly north of 8 Mile.  The 11:00 a.m. model has those storms well north of I-69 (this model does bring in some scattered storms farther south a couple of hours later).  That makes a HUGE difference in terms of how many people are impacted.  So how do I forecast an event like this when there is such great disparity in the model runs?  By looking at what’s happening way back to the southwest, where the storms should develop this afternoon, and compare what’s happen now to what the models suggest “should” be happening now out there.  Based upon what I’m seeing at the time I’m writing this article (3:00 p.m.), it appears that the 11:00 a.m. model run may have a better handle on things, so I think the better chance to see strong or severe storms will be north of M-59.  Ben Bailey and I will have to monitor this, and he’ll have our updated forecast philosophy coming up on Local 4 News at 4, 5 and 6. 

Despite this uncertainty, there’s enough confidence that SOME part of our area may see severe storms Monday evening that the Storm Prediction Center has broad brushed the threat and put all of southeast Michigan in the Slight Risk for severe weather.  Large hail and damaging wind gusts are the primary threat, with a low chance for a brief, weak tornado west of US-23. 

A Severe Thunderstorm Watch has already been issued for a large area that includes western lower Michigan, but does NOT include southeast lower Michigan.  Also, due to the heavy rain threat over the northern part of our area, the National Weather Service has issued a Flood Watch for Genesee, Lapeer, and Sanilac Counties until 8:00 a.m.

This is a good evening to make sure that you have the FREE Local4Casters weather app downloaded on your phone…just search under “WDIV” in the app store.  When you open the app, it opens right onto the radar page, which you can pan or zoom with your fingers.  Check the app often for any developing storms.

Storms should be gone after midnight, with mild overnight lows in the mid to upper 50s (14 degrees Celsius).  Southwest wind at 10 to 20 mph.

Mostly cloudy skies to start our Tuesday should eventually become partly cloudy.  Expect a cooler day with highs in the low to mid 60s (17 degrees Celsius).  West wind at 10-20 mph.

Partly cloudy Tuesday night, with lows near 40 degrees (5 degrees Celsius).

Mostly sunny on Wednesday, with highs in the upper 50s (15 degrees Celsius).

Mostly clear Wednesday night, with lows near 40 degrees (4 degrees Celsius).

Partly cloudy to mostly cloudy on Thursday.  Most models keep us dry with only a slight shower chance late in the day.  Highs in the upper 50s (15 degrees Celsius).

Becoming partly cloudy Thursday night, with lows in the low 40s (6 degrees Celsius).

Partly cloudy on Friday, with highs in the low 60s (16 degrees Celsius).

Partly cloudy Friday night, with lows near 50 degrees (10 degrees Celsius).

We have a chance of thunderstorms on Saturday (not an all day event), with highs in the low 70s (22 degrees Celsius).

Showers and thunderstorms are likely Saturday night, with lows in the upper 50s (14 degrees Celsius).

Any showers or storms first thing Easter morning should end, leaving us dry for most of the day.  Highs near 70 degrees (21 degrees Celsius).

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