90 degree heat and humidity on the way

WEST MICHIGAN -- It may only be early June, but 90 degree temperatures are likely as we head in to this upcoming weekend. Along with the heat?

A far more humid air mass more indicative of the southern states or tropical locations. The heat and humidity will start to ramp on Saturday, but likely peak on Sunday and Monday.

So what will drive in the tropical air mass? It will be a pattern shift and a change in our upper level jet stream. Below is a snapshot from one of our computer forecast models valid on Thursday morning. It's about 18,000 above the surface, or the 500 millibar level for you pilots and weather geeks, but it shows us the trough and ridge pattern.

A trough over the Great Lakes means the jet stream dips far south. It typically means cooler-than-normal temperatures and can be characterized by unsettled weather. A ridge over the region means the jet stream is pushing or bulging north in to Canada. It allows for warmer-than-normal temperatures and is usually characterized by dry, quiet weather and high pressure systems. The image below shows an upper level low pressure system and trough over West Virginia/Ohio/Pennsylvania.

If we look at the same level on Sunday below, note the upper level low and trough in the Pacific Northwest (it will actually be cold enough for snow in the higher elevations), while our region shows a warm ridge beginning to build and lift to our north.

We've got a weak disturbance floating through the state on Friday that could generate a shower or thundershower, but I think many areas may be missed. That means no real rain chance until at least the middle of next week. Take a look at the air mass at about 5,000 feet above the surface, or around 850 millibars for the weather geeks. Below shows colors in light green over Michigan...which equates to temperatures in the upper 70s. The image is valid for Thursday morning.

The next image below is valid for Sunday morning and also shows the different air masses at 5,000 feet. Note how the colors over Michigan are significantly warmer in the orange. Those colors equate to temperatures. Safe to say...the heat and humidity are on the way with readings around 90. That would be our first 90 this season!

The other noteworthy item is the moisture in the air itself. Take a look at dew point temperatures today below. Dew point is a measure of moisture in the air. The higher the dew point temperature, the stickier it feels outside. The lower the dew point, the drier the air mass. Dew points in the 40s this time of year indicate a very dry air mass. Very comfortable, low relative humidity. As the air temperature increases, the capacity for that air to hold more moisture increases too. I would expect dew point temperatures to reach the mid/upper 60s or higher Sunday and Monday.

Better make sure to have the A/C serviced if it needs it. Overnight lows likely won't fall below the mid/upper 60s on some of those nights. We had 18 90 degree or higher days in 2016. About 10 is normal or average. Generally, July tends to be the hottest month with four 90 degree days, followed by June and August with two each, and another one in May and September. We'll see if we can top that this summer. The beach may very well be the best place to be this weekend, but don't forget the sunscreen. These are the most intense UV rays we see in Michigan this time of year. The image attached to this story is compliments of EARTHCAM and is their webcam from Berrien County on Silver Beach. Make sure to get the complete West Michigan forecast at www.fox17online.com/weather. Stay cool!

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