Rain Helps Some Areas:
Since last Friday (Aug 11) several days have brought widespread showers and thunderstorms to the state, especially western and central areas. Many climate observers have reported greater than one inch of rain, and some have reported 2 inches or more. August 13 and 14 brought the most significant rains to many areas, and in some cases record daily rainfalls, including on August 14th:
3,14” at Kimball
2.95” at Browns Valley
2.80” at Milan
2.42” at Wheaton
2.41” at Artichoke Lake
1.85” at Benson
1.43” at Milaca
1.40” at Madison
With these rains overall soil moisture conditions improved in some areas (over 40 percent now rated adequate) and drought conditions diminished by some percentage points in the Moderate and Severe categories.
At the State Fair:
CATHY WURZER AND I WILL BE HOSTING THE 27TH ANNUAL MPR STATE FAIR WEATHER QUIZ FROM 2PM TO 3PM ON AUGUST 28 AT THE MPR STAGE (CORNER OF JUDSON AND NELSON) . PLEASE DROP BY IF YOU ARE AT THE STATE FAIR THAT DAY. THE WEATHER QUIZ WILL BE BROADCAST ON MPR ON TUESDAY, AUGUST 29, FROM NOON TO 1PM ON THE PROGRAM “MINNESOTA NOW.”
The "Sunday Effect"
This term was coined in the 1970s by atmospheric chemists who found that air quality in urban areas seemed to have a distinctive pattern based on day of the week. Best air quality tended to occur with higher frequency on Sundays (when traffic and industrial activity was relatively minimal), and the worst occurred on Wednesdays (during the peak of the work week). Further studies have found that there are also patterns of sunshine, temperature and precipitation that may be correlated to day of the week as well.
A recent study in England (Wilby and Tomlinson) showed the highest frequency of sunny days in the winter falls on Sunday and the lowest frequency on Wednesday, though this pattern is less evident since the U.K Clean Air Act of 1968.
Studies of temperature and precipitation patterns associated with day of the week have produced mixed results in the USA. Some cities show lower precipitation on Sundays and higher precipitation during mid-week.
Weekly Weather Potpourri:
The Weather Underground featured a story this week about evacuating Yellow Knife in Canada’s Northwest Territories due to the risk of wildfires in the area. That area desperately needs rain to calm the wildfires, which have been numerous this year.
MPR listener question:
What is the driest August in the state climate records?
Answer:
The driest August on a statewide basis was in 1930, when the average rainfall for all reporting communities was just over one inch. The driest August for an individual community was at Beardsley in west-central Minnesota (Big Stone County), which recorded only 0.01 inches in 1969. The driest August in the Twin Cities climate record was 1925, with only 0.20 inches.
Twin Cities Almanac for August 18th:
The average MSP high temperature for this date is 81 degrees F (plus or minus 7 degrees F standard deviation), while the average low is 63 degrees F (plus or minus 7 degrees F standard deviation).
MSP Local Records for August 18th:
MSP records for this date: highest daily maximum temperature of 98 degrees F in 1976; lowest daily maximum temperature of 61 degrees F in 1890; lowest daily minimum temperature of 41 degrees F in 1977; highest daily minimum temperature of 77 degrees F in 1916; record precipitation of 2.26 inches in 1907. No snowfall on this date.
Average dew point for August 18th is 59°F; the maximum dew point on this date is 79°F in 1995; and the minimum dew point on this date is 36 degrees F in 2004.
All-time state records for August 18th:
The state record high temperature for this date is 107 degrees F at Browns Valley (Traverse County) in 1976. The state record low temperature for this date is 24 degrees F at Tower (St Louis County) in 1975. The state record precipitation for this date is 5.78 inches at Artichoke Lake (Big Stone County) in 1935. No snowfall has been reported on this date.
Past Weather:
This Sunday marks the anniversary of a remarkably destructive storm which passed through both Minneapolis and St Paul on August 20, 1904. It is thought that this storm started near Aberdeen, SD about 6pm as what is now known as a mesoscale convective system or cluster of thunderstorms. Later the storm intensified over Renville County and moved east through McLeod, Carver, Hennepin, Ramsey and Washington Counties. Severe damages occurred in Glencoe, Waconia, Excelsior, St Louis Park, Hopkins, Minneapolis, St Paul, and Stillwater. It was estimated that as much as $1.5 million in damages occurred, with 15 storm related fatalities. Anemometers at the Weather Bureau in downtown St Paul registered wind gusts up to 110 mph, while an unofficial anemometer on the roof of the Pioneer Press building registered winds of 180 mph before it blew away.
The storm peaked after sunset, between 8:30 and 10:00 pm, and rainfall was so intense, over an inch per hour, that observations about the character of the storm are not conclusive. No funnel was observed in the Twin Cities, but some of the damages provide evidence of tornadic-like winds. In fact some evidence in the Waconia area and the destruction of portions of the High Bridge in St Paul, indicate perhaps an F-4 tornado (winds of 207 mph or higher). Greenish-yellow clouds and hailstones were reported. A total of 2.56 inches of rainfall occurred over 24 hours in St Paul, with 1.23 inches coming in only 35 minutes. The evening dewpoint in St Paul was a sultry 70 degrees F.
Patrons of the Tivoli and Empire Theaters in St Paul became alarmed and sought shelter in nearby stone buildings as glass windows broke and roofs were torn off. It took Northwestern Telephone Company over a week to restore phone service to 7000 customers.
Record-setting heat dominated the Minnesota landscape on August 18, 1976. Most climate stations reported a high temperature of 90°F or greater and 14 counties reported an afternoon temperature of 100°F or higher. The morning low at Montevideo and Redwood Falls was 78°F.
The very next year, August 18, 1977 brought record cold temperatures to much of Minnesota. Roseau, Marshall, and Kittson Counties in northwestern Minnesota reported frosts, while many other places reported morning low temperatures in the 30s F. The high temperature at Fergus Falls only reached 64°F.
Outlook:
Sunny, dry, and warm over the weekend. Chance for showers up north by Monday but remaining mostly dry elsewhere. Temperatures will remain above normal through much of the week and cool down towards next weekend.
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