A Cool and Active Month of May
The ups and downs continued into the month of May, which followed a relatively cool March and another warmer than average month in April. May came in back on the downswing, and not only turned out on the cooler-than-average side, but was also fairly active in terms of rain and severe weather.
April was a high-ranking month for temperatures across much of the region, and even a record-breaker for Ohio. This changed in a big way in May, as a cool finish to the previous month bled into the first week of the month. This was a cloudy and damp period as well for the Midwest, with much of this week seeing measurable rainfall. A storm system even brought a daily record for total rainfall in Indianapolis with 2.17” on the 4th.
It was the cool weather, however, that really stood out for the first nine days of May. Chicago Metro’s mean high temperature of 57.1 degrees during the stretch of the 1st thru the 9th fell well short of the normal 66.7 degrees, and placed as the 3rd coolest on record. In addition, it was a top-ten cool period for the entire Midwest as a whole. Dayton, with 100 plus years of records, only failed to have a daytime high get out of the 40s 18 times. The rare instance was met on the 5th with a high that only reached 49 degrees. Furthermore, Cincinnati’s low of 30 during the morning of the 8th tied a record dating back to 1947 for coldest daily minimum.
Temperatures made a sudden rebound after this, as the middle of the month went into late-spring and early summer form with highs in the 70s and 80s, especially from the 13th through the 19th. This volatility in temperatures allowed for an outbreak of severe weather in Northern Illinois, resulting from a potent cold front swooping down from the Northern Plains. Widespread wind damage was reported between the I-80 and I-90 corridors, even all the way toward the lakeshore into the Chicago Metro. This same front translated to the rest of the Midwest in the following days, with reports of wind damage in Southwestern Ohio on the 19th.
— Devin Pitts (@DevinWxChase) May 17, 2017
May was not done yet in terms of severe weather, and even brought quite a scene to Dayton later in the month. On the 24th, upper level low pressure once from the Northern Plains was able to dive well south into the Ozarks thanks to an unusually strong jet stream for so late in the spring season.
The high wind shear produced by this set up, combined with a surge of Gulf moisture was able to produce a cluster of tornadoes right over southwestern Ohio. Late evening commuters were able to get a solid glimpse of one of the twisters which was even faintly caught on highway cameras. Widespread reports of damage did result, with surveys categorizing the tornadoes on the low-end of the Enhanced Fujita Scale at EF-1 with up to 100 mph winds.
— Mark Tarello (@mark_tarello) May 25, 2017