Updraft: September 15, 2009 Archive

Stagnant air mass increasing metro haze

Posted at 8:25 AM on September 15, 2009 by Paul Huttner (4 Comments)

MPCA air qulity data shows particulate matter has increased the past two weeks.

You can literally see it in the air.

Those lazy hazy days of summer came in September this year.

Haze levels and particulate matter have increased in the Twin Cities the past two weeks. A persistent ridge of high pressure has created nearly stagnant air conditions in the metro. Light winds and calm air have been common the past few days, and that has allowed pollution levels to build in the area.

According to MPCA data, the level of particulates has been on the rise since September 2nd. The forecast is for levels to rise slightly the next few days.

In the Twin Cities, the highest wind the past three days has been a mere 7mph. You can see from the observations at Twin Cities Airport, the air has been calm for many hours. This means there is little horizontal movement of air, and no fresh air masses sweeping in off the Canadian Prairies. As a result fine particulate matter less than 2.5 microns in size from auto exhaust and wood smoke is just hanging around.

Everything's a trade off in life and sometimes in weather too. Our mild air mass will linger this week, and so will pollutants. If you're looking for cleaner air it will come next week with a Canadian cool front. The trade off is, it's going to start feeling like fall with much cooler temperatures.

Enjoy our last spell of summer in September through the weekend!

PH

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Here Comes Fall: Season's first frost in sight

Posted at 3:16 PM on September 15, 2009 by Paul Huttner (1 Comments)

NOAA 6-10 day temperature outlook forecasts below average temperatures next week for the Upper Midwest.

You knew it wouldn't last forever.

A major pattern change will bring much colder weather and possibly the season's first frost to much of Minnesota including the metro next week. A strong Canadian cold front will move into Minnesota Sunday and should arrive in the metro with a chance of showers later Sunday night.

Behind the front look for windy and much colder conditions next week. Temperatures could be as much as 20 to 30 degrees colder by late next week. That would mean highs in the 40s in northern Minnesota and in the 50s in southern Minnesota. Overnight lows could plunge into the 20s up north with lows dipping into the 30s in the south.

If the current forecast models verify, we could see the season's first frost in much of southern Minnesota by next Wednesday morning. That would be about two weeks earlier than average. Next Wednesday is the 23rd. The average date for the first frost at Twin Cities Airport is October 6th.

There will also be chances for frost Thursday and Friday mornings next week as chilly Canadian air pours into the region. Hopefully most crops will have reached maturity with the late season surge of warm weather the past two weeks.

Want some good news?

It looks like our summer-like weather will hang on into the upcoming weekend. We should enjoy lots of sunshine highs near or into the 80s right into the upcoming weekend. It's a great time to plan that next summer like barbeque for this weekend.

This has been a remarkable and possibly record setting streak of 80 degree weather in September.

PH

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