September-like air mass; monitoring rain chances

The weather maps are giving a hint of the end of summer.  Sept. 1 marks the first day of the meteorological autumn, but until then let's make the most of what's left of August.

You surely noticed the big drop in dew points and the comfortable relative humidity this afternoon!  Temperatures had the feel of "back to school."

The mid-afternoon satellite image was very much like that of autumn with an expansive cumulus cloud shield sweeping across northern Minnesota.

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Image:NOAA

Note the thunderstorms that erupted in the warm and humid air in northern Illinois and northwest Indiana.

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I stepped away from the weather lab for a time, only to return and find the computer models were now trending toward wetness extending into southern Minnesota at midweek.  Two computer models even brought generous rain on Wednesday night up beyond the Twin Cities.

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GFS model of precipitation expected from 7 p.m. to 1 a.m. Wednesday night.

Now compare that to the North American Model for the Wednesday night, which pushes the heavy rain even further north.

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NAM of precipitation Wednesday night. Image:NOAA

In the forecasting world could this be the possible flip-flop-flip.  You can expect to see meteorologists in the Twin Cities cautious about their forecast wording for midweek.  In the olden days, my early years, we would prefer to hold off on bold predictions of rain until the model was consistent and we drew closer to the event.

Don't be surprised to see the proverbial 30 to 40 percent chance of rain on Wednesday night get bumped up if the models show the trend again on Tuesday morning.

The National Oceanic and Atmospheric Administration's forecasters at the Weather Prediction Center  are indicating a northerly shift in the rain threat as well.

 

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Rainfall ending at 7 p.m Thursday. Image:NOAA

Overcast skies are likely to hold down temperatures in southern Minnesota on Thursday.  Northern Minnesota could be comfortably cool.

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Maximum temperatures forecast from the National Weather Service for Thursday.

Pete Boulay of the Minnesota State Climatology Office posted this observation of yesterday's tornado in Benton County on Facebook.

"On August 24, 2014 a tornado touched down 4 miles west of Granite Ledge in rural Benton County and damaged trees and windows. It was the 2nd longest stretch without a tornado for a county in Minnesota. The last time a tornado touched down in Benton County was June 16, 1992. The longest stretch is Carlton County that has not seen a tornado since June 21, 1986."

Tuesday morning's low temperature will be on the cool side.

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7 a.m. surface pressure, temperature and wind forecast from the Rapid Refresh Model.

Do you remember the heat spell we were going through this time last year? On Aug. 25, 2013 we set a new record high of 96 degrees at the Minneapolis-St. Paul International Airport.  The following day, the airport recorded a maximum of 97 degrees.