Ozone “spike”; “Dry front” today; Dense smoke from CO fires now over MN

161 – “Unhealthy” Air Quality index for Twin Cities at 6pm Wednesday

“Ozone Spike” caused by heat, sunlight & stagnant air

“Dry Front” pushing through today

50s dew points Comfy behind the front

93 degrees – high in the metro Wednesday

8 days at or above 90 degrees so far in 2012 at MSP Airport

5 more days of 90 degree heat possible in next week

14 days of 90 or above in an “average” metro summer

(We could be close by next weekend?)

72 wxs.png

Source: Twin Cities NWS

Dry Front:

How do you spell relief?

For most of us it’s called a cold front…but in this case it’s really more of a “dry front.”

We’ve seen a remarkable change in air masses occur the past 24 hours in Minnesota. It was downright comfy Wednesday morning with a dew point of 57 at MSP Airport at 7am Wednesday. By last night, it felt like sitting in a sauna as we watched my son’s baseball team play at Veteran’s Field in Minnetonka as the dew point hit 73 at 10pm last evening.

This morning? A breezy frontal system is pushing though a few clouds and even some attempted showers, and dew points are again crashing into the comfy 50s in most of Minnesota.

Have I thanked Canada for the amazingly refreshing exchange of air masses lately?

Even though temps will remain warm to hot behind the front, dew points will linger in the 50s today and tomorrow over most of Minnesota.

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Source: Iowa State University

Thank goodness for AC (and a good night’s sleep) last night!

It could have been worse?

Temps peaked at 93 at MSP Airport Wednesday.

That’s about 2-4 degrees cooler than I thought ti would get yesterday. The nose of the most intense heat made it up to about Mankato and New Ulm where temps nudged 100 degrees.

72 highs.PNG

Source: Twin Cities NWS

The torrid details from the Twin Cities NWS.

So How Warm Was it Wednesday?

The afternoon of the 27th saw the immense heat that had been building the past several days to our southwest show up in a big way across southern Minnesota in particular. The warmest observed reading at an aiport today was 99 at New Ulm, though a couple of 100 degree readings were observed at mesonet stations in the Mankato area.

Widespread 100 degree highs were observed across Kansas up into the Omaha area, with highs greater than 90 working up to about the I-94 corridor. The worst of the heat has by far been observed in Western Kansas, where Hill City saw their second day in a row with a 115 degree high and 5th day in a row with highs greater than 110.

We will see a small respite from the heat through this weekend, but extended forecasts show the warm dome of high pressure returning next week into the following week, with the first two weeks of July looking to get off on a rather toasty note across the northern Plains into the Upper Mississippi River Valley.

72 heat why.gif

Upper air analysis shows Twin Cities on the northern edge of heat dome Wednesday.

Source: Twin Cities NWS

“Ozone Spike:”

You could just see and feel the haze and thickness in the air last night.

Smoke from Colorado wildfires was clearly visible high above. And low level “ozone” spiked to unhealthy levels Wednesday evening.

Check out the readings form MPCA Wednesday.

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Source: MPCA

The combination of heat and sunlight and pollution causes a chemical reaction that produces ground level ozone on summer days. The stagnant air means that ozone accumulated and hung around…as levels spiked late Wednesday.


Source: MPCA

One thing I don’t get is why some Minnesotans are so “bonfire happy” that they need to have bonfires on nights when there is little or no wind, it’s 90 degrees and it already feels like the jungle. Thick smoke just hangs and spreads around the neighborhood, even blocks away.

I love a bonfire as much as the next guy on a cool crisp fall evening, A bonfire last night? Really?

Smoke gets in your eyes:

You could clearly see smoke in the air from the western wildfires Wednesday over Minnesota. Check out the latest “Firedetect” images from NOAA/NESDIS tracking a plume of “dense” smoke right over Minnesota.

72 dense.PNG


Get used to it.

Until those fires are doused by the probable onset of “monsoonal thunderstorms” in July and August it’s going to be a long haul for smoke plumes as they drift downwind over Minnesota and the Upper Midwest.

Outlook: More 90s ahead?

Our cool front today lowers temps a bit and brings a much drier air mass.

But the overall pattern the next two weeks looks favorable for adding more 90 degree days to the mix.

72 90s.PNG

Source: Iowa State University

Wednesday was the 8th day at or above 90 so far in 2012 at MSP. Looking at the maps, it seems we’ll flirt with 90 several days in the next week and we could add as many as 5 more days of 90 degree heat by the end of next week before a cooler & drier air mass nudges south next weekend.

That would put us at around 13 days of 90+ by July 6th, about the halfway point of summer heat in Minnesota. The “average” for the metro is 14 days in summer. I could easily see us racking up 20…maybe even approaching 25-30 days of 90 degree heat by summer’s end at this pace.

By all indications it’s going to be a long…hot summer.

Hopefully we’ll fall far short of the 44 days of 90 degree heat we sweated through in the infamous summer of 1988.


  • no A/C


    How long is the drier weather going to stick around? As you’ve discussed a lot recently, it really IS the humidity that’s the kicker. Are these ongoing temps in the 90s through next week going to be tolerable, or swampy like last night?

    Thanks for the good coverage!