Warm September to take a big turn, extended spell of clouds and cool coming

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Early Tuesday morning low temperatures dipped below 50° for the first time in Indianapolis since May 22nd, dipping to 48°.  Some cooler locations included 44° Martinsville and 45° in Lafayette and Crawfordsville.

The first nigh below 50° is a little behind schedule, the average date of the first sub 50° night in Indianapolis is September 10th.  The latest first night in the 40s dates back to October 10th 1910.



A strong west-southwest wind is behind a 27° temperature jump since daybreak.  Sunshine and warm winds produced high temperatures back into the mid 70s Tuesday.  While not as warm as recent days, this will go into the books as a 'normal' day.  Since September 1st 20 days have been above normal, 3 days normal and only 4 days below normal.

We haven't had a below normal day in over two weeks.  to date September 2016 and Fall ranks 9th warmest  on record. To date it is the warmest start to Fall and a September since 1941!


The bright skies overhead will be replaced drastically on Wednesday by a upper level, cloud and rain producing low pressure overhead.  Clearly evident on visible satellite images late Tuesday, the system will settle south and park itself overhead for several days.  Closed and cutoff from the main branch of the jet stream, the weather will be repeat performance from Wednesday thorough Saturday.  The lack of any steering winds aloft will allow the system to linger.

Visible satellite image Tuesday afternoon

Visible satellite image Tuesday afternoon


High temperatures will fail to reach 70° for the next four afternoons.  An afternoon below 70° is late this year.  We typically have our first sub 70 degree afternoon on September 7th.




Pattern flip-flops are rather frequent this time of the year as summer tries to hang around and fall asserts itself.  While chilly to close out the month of September, afternoon highs at mid-October levels, a return to warmth is likely again  early next week.  high temperatures could reach the lower 80s again by Tuesday.

Forecast upper air pattern next Tuesday. Warmth returns to the eastern U.S.

Forecast upper air pattern next Tuesday. Warmth returns to the eastern U.S.

Forecast 6-10 day temperature probability

Forecast 6-10 day temperature probability centered on October 3rd to the 7th