Hot, steamy weekend with some thunder chances

Get ready for a hot weekend. Highs will be near 90 degrees Saturday through Monday with muggy dew points. There will also be spotty storm chances, some of which could be severe. 

Steamy weekend with some storm chances 

Friday will be very warm with lots of sunshine. Almost all of Minnesota will again be dry. It won’t be quite hot just yet, but highs will be in the mid-80s with upper 80s in western Minnesota and a couple low 90s.

Overnight Friday night temperatures will drop just into the 60s to low 70s across the state.

There’s the possibility of some spotty storms developing late Friday night into early Saturday. Most forecast models agree storms will happen, but where they develop and their timing vary.

Here’s forecast solution No. 1, the most aggressive outlook:

Here’s the least aggressive version:

Note that even the aggressive scenario has activity fizzling out as it moves toward the Twin Cities and southern Minnesota. This may lead to some morning clouds but we’ll still heat up in the afternoon.

Both scenarios also develop more storms late in the day somewhere in northern Minnesota that could then drift south. Where they develop will be key to what makes it where.

Whatever storms that do develop will have the chance to become severe. There’s a slight risk (level 2 of 5) of severe storms Saturday for a swath of Minnesota due to this possibility.

We’ll be on the edge of the heat dome in Minnesota where minor, upper-level disturbances combined with a low level jet stream (winds at 4,000 feet above the ground that accelerate at night) will have the potential to spark activity occasionally into Monday. 

The best chances will be at night and north of the capped atmosphere (mid-level warm air that prevents storms). These upper-level disturbances are shown as red and purple blobs and swirls:

Unfortunately, it’s a pattern that’s difficult to forecast placement and timing of storms beyond 36 hours or so. It’s also possible where these develop that it will keep temps cooler with the left over cloud debris.

In between any thunder chances and leftover clouds from them, it will be steamy. Highs Saturday, Sunday and Monday will be near or above 90. Sunday looks to be the hottest day. 

The heat index could reach 100 degrees in places as we’ll have the heat combined with dew points of 70-plus degrees on Sunday afternoon. A heat advisory may be coming.

Cooler and drier air moves in for Tuesday and much of next week, bringing a comfortable break. 

Thursday’s interesting weather phenomena

We finally saw a dry day, but the same rare phenomena that led to slowly moving, pop-up and crashing storms the day before led to some other notable weather tidbits.

With very light winds both at the surface and aloft, you could see how unevenly things heat up in our region and how air moves when not mixed with other forces.

The first was urban heat island-induced cumulus clouds much of Thursday afternoon. On the image below, note the nearly stationary cumulus field over Minneapolis and St. Paul.

That’s because on any sunny day, the cities’ paved surfaces and buildings add a couple of degrees of temperature, which in Thursday’s scenario was enough to create an extra batch of clouds which are generated from surface-based instability.

You can see this via 5 p.m. temperatures of the Twin Cities versus surrounding areas:

Let’s look at the above satellite loop again. Note the clear skies over Lake Mille Lacs and the breeze it generated that pushed cooler air inland, creating clearer skies and pushing clouds away.

If you look at the temperature map again, you’ll note temperatures are several degrees cooler (or stable) over the lake and immediately inland from the lake. The Lake Mille Lacs breeze even generated a couple of brief, pop-up light rain showers.

This is something you’d more typically see from sea breeze-land interactions in Florida than central Minnesota: