The warm and humid conditions of last weekend help set the stage for numerous thunderstorms this week across much of the state. Recall that the weather of last weekend produced widespread readings in the 90s F around the state, including a record high of 98°F at Winnebago on the 11th, and a record high of 96°F at Lake Wilson on the same date. Many observers also reported near record dew points in the 70s F, leading to Heat Index readings over 100°F in many places. This represents a large quantity of water vapor which does not allow the air to cool off much at night. As a result, Tracy set a new record warm minimum temperature on the 10th, with a reading of 73°F.
All of the water vapor in the atmosphere served as fuel for thunderstorms, which became widespread across the state over June 11-14. Over those 4 days many areas received from 2-4 inches of rain. A few highly localized amounts were even greater causing some short-lived flooding concerns. You can read more about the distribution of these storms at the Minnesota State Climatology Office web site.
Some climate stations reported new daily rainfall records as a result of these thunderstorms. These included: on the 11th Lake City 2.03 inches; on the 12th Thorhult 1.70 inches; on the 13th Eveleth 2.51", Dassel 3.19", Embarrass 1.96", and Stillwater 1.54"; on the 14th Amboy 2.00"; and on June 15th record values were reported for La Crescent 1.78", Melrose 1.80", Caledonia 1.51", Harmony 2.07", Houston 2.83", Waseca 3.19", and Forest Lake 2.00".
The strong thunderstorms on June 14th produced tornadoes in Pipestone, Traverse, Big Stone, Le Sueur, and Blue Earth Counties. All were relatively short-lived and produced relatively little damage. Very strong winds up to 60mph were also reported from portions of Nobles, Jackson, Cottonwood, Brown, and Watonwan Counties.
As a result of the rainy week, many climate stations are already reporting total monthly rainfall that exceeds the June normal. This continues a recent climate trend for June, as 15 of the most recent Junes have been normal or wetter than normal on a statewide basis.
New seasonal climate outlooks:NOAA Climate Prediction Center released new seasonal climate outlooks this week. The new outlooks covering the period from July-September favor warmer than normal temperatures over a vast area of the USA, including Minnesota. The outlooks also favor wetter than normal conditions for most of the southern half of Minnesota.
Weekly weather potpourri:Weather for Grandma's Marathon along the north shore of Lake Superior this Saturday from Two Harbors to Duluth looks good. Starting in the morning with increasing cloudiness, light south winds and temperatures in the upper 50s F to low 60s F. There will be a 40-50 percent chance of showers by mid-morning as temperatures warm into the low 70s F.
Recently NOAA scientists revisited the sources of carbon dioxide emitted into Earth's atmosphere each year. Human activity as a source of carbon dioxide far outweighs any other sources.
The UK Met Office has another interesting article this week about the trend in atmospheric carbon dioxide, showing that 2016 will be the first year with concentrations above 400ppm on a year round basis since measurements began at the Mauna Loa Observatory in 1958.
A recent study from the School of Public and Environmental Affairs at Indiana University reveals that the public is more likely to believe climate scientist's warnings about climate change if they see that these scientists are practicing conservation and reducing their own environmental footprints.
MPR listener question:The other night at the Pub 500 in Mankato we got into an argument about which month brings the most 2 inch thunderstorm rains. I am sure it is June because I have had so many hay cuttings ruined by heavy rains in June. My neighbor insists it is more common in August? Who is right?
Answer:For the Mankato area you are correct. Over 30 percent of all historical thunderstorms that brought 2 inches of rain or more have occurred in the month of June. August has brought about 20 percent of such storms. There is some geographic disparity in this climate attribute across the state. For most of southern Minnesota, June indeed has the highest frequency of heavy thunderstorm rainfalls, with the second highest frequency in August. In northern counties the highest frequency is in August, and along the north shore area near Lake Superior there is a second high frequency of such storms in September, while the lake surface remains warm from accumulated summer heat.
Twin Cities Almanac for June 17th:The average MSP high temperature for this date is 80 degrees F (plus or minus 8 degrees F standard deviation), while the average low is 60 degrees F (plus or minus 7 degrees F standard deviation).
MSP Local Records for June 17th:
MSP weather records for this date include: highest daily maximum temperature of 97 degrees F in 1933; lowest daily maximum temperature of 54 degrees F in 1876; lowest daily minimum temperature is 42 degrees F in 1960; highest daily minimum temperature of 75 degrees F in 1921; record precipitation of 1.72 inches in 1883; and no snowfall has occurred on this date.
Average dew point for June 17th is 56 degrees F, with a maximum of 74 degrees F in 1994 and a minimum of 39 degrees F in 1958.
All-time state records for June 17th:The state record high temperature for this date is 102 degrees F at Campbell (Wilkin County) in 1933. The state record low temperature for this date is 22 degrees F at Tower (St Louis County) in 2000. State record precipitation for this date is 8.67 inches at Minnesota (Lyon County) in 1957 ; and no measurable snowfall has occurred on this date.
Past Weather Features:The warmest ever June 17th occurred in 1933 when nearly every part of the state (except communities along Lake Superior) reported record high temperatures in the 90s F. Eight climate stations reached the century mark.
Over June 16-18, 1957 thunderstorms produced hail and heavy rains across many parts of the state. Many farm fields were flooded by 2-4 inches of rain. Especially hard hit were southwestern counties where rainfall totals ranged from 7-9 inches. Some fields had to be replanted.
A very cold on the morning on June 17, 2000. Many northern counties reported morning lows in the 30s F, while Embarrass and Tower reported readings in the 20s F. As far south as Wabasha County some ground frost was reported.