A monthly electronic newsletter summarizing Minnesota's climate conditions and the resulting impact on water resources. Distributed on the first Thursday of the month.
State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
distributed: October 3, 2019
What happened in September 2019:
- Precipitation for September 2019 finished well above normal statewide. The preliminary average for Minnesota was 6.32 inches or 3.04 inches above normal. There were four areas that finished with twice the normal. The counties that saw the most precipitation include: Roseau, Lake of the Woods, Pine, Sothern Aitkin, Northern Mille Lacs, Pipestone, southern Fillmore and Houston Counties. The highest rainfall total found was Mabel in southern Fillmore County with 12.51 inches and at the other end of the state at Norris Camp in western Lake of the Woods County with 11.72 inches. Nearly every location in the state finished with above normal precipitation.
[see: September 2019 Precipitation Total Map | September 2019 Precipitation Departure Map | September 2019 Climate Summary Table | September 2019 Percent of Normal Precipitation Map]
- There were several heavy rain events in September:
- The first of the rainfall events for the month was September 10-12. Rains, along with thunderstorms and many downpours soaked Minnesota over a 48-hour period, beginning in the evening of Tuesday September 10th and ending in the evening of Thursday September 12th. The rains were associated with a slow-moving, large, and rather intense low pressure system that formed in Colorado and made its way through the Northern Plains and Upper Midwest. This complex weather system generated three waves of heavy rain and thunderstorms. For the entire 48-hour event, rainfall approached 10 inches in the hardest-hit areas of southwestern Minnesota, exceeded three inches over large swaths of central and southern Minnesota, and were greater than one inch over the majority of the state.
[see: Rain and Flooding, September 10-12, 2019]
- The next event was over northern Minnesota on September 20-21. Heavy rains pounded parts of far northwestern Minnesota on September 20th and 21st, leading to some of the highest 24-hour totals of the year anywhere in the state, as well as at least minor flooding. Roseau, Hallock, Thief River Falls, Baudette, and Warroad all received over 3 inches of rain, and many automated and citizen-volunteer sites received 5-6 inches during the this event. The highest total of 7.12 inches came from the official National Weather Service cooperative observer at Norris Camp, in Lake of the Woods County. All but 0.02 inches of that came in 24 hours, making this a "200-year storm" for that location.
[see: Heavy Rains, September 20-21, 2019]
- Another event occurred at the end of the month from September 28-30. Warm, muggy air fueled more thunderstorms that dropped one to two inches of rain over northwest Minnesota, with another heavy swath from Brainerd to Pine County. 4.85 inches fell at Moose Lake in Carlton County.
[see: September 28-30, 2019 Rainfall Event ]
- September 2019 was more summerlike than autumnal and finished warmer than normal with the average statewide temperature about three degrees above normal. The Twin Cities hasn’t had a below normal September average temperature since 2010. The warmest temperature found in the state was 91 degrees at Granite Falls and Marshall on September 18. The coldest temperature of the month was 26 degrees at Babbitt, Celina and Hibbing on September 28.
[see: September 2019 Climate Summary Table | 2019 September Departure from Normal Temperature Map]
Where we stand now:
- Seasonal precipitation totals (April 1 through October 1) ranked above the historical median over a large area of southern, central and north west Minnesota. A slice of north central to northeast Minnesota was near normal to below normal. Some parts of southern Minnesota were ranked nearly the wettest on record.
[see: Seasonal Precipitation Ranking Map]
- The U. S. Drought Monitor map released on October 3, depicts not only no drought indicator present in Minnesota, but none in any of the surrounding states as well. Last year at this time 75% of the state was free of any drought designation. The U.S. Drought Monitor index is a blend of science and subjectivity where drought categories (Moderate, Severe, etc.) are based on several indicators.
[see: Drought Conditions Overview]
- The U.S. Geological Survey reports that stream discharge levels are much above normal to high across southern, central and northwest Minnesota, with normal to above normal streamflow across the northeast.
[see: USGS Stream Flow Conditions]
- Water levels on most Minnesota lakes vary depending on lake and location in the state. Mille Lacs level had stabilized in September, but then with heavy rains late in the month it rose about a half a foot. Minnetonka was at 929.21 feet with 100 cfs flowing through Grays Bay Dam. The fall drawdown target is 928.6 feet, which is the goal for ice in level. White Bear Lake was at 925.06 feet on October 3, about the same as it was a month ago. Water has been flowing out of White Bear Lake since late April. Rainy Lake was in the median range for early October and Lake of the Woods was in the 90th percentile for the date. Lake Superior was forecasted to be at 603.28 feet on September 27, thirteen inches higher than the monthly average for late September and one inch above the highest recorded monthly mean for September set in 1985.
[see: Mille Lacs Lake Water Level | Lake Minnetonka Water Level | White Bear Lake Water Level | Lake of the Woods Control Board Basin Data | Corps of Engineers Great Lakes Water Levels]
- The Agricultural Statistics Service on September 30 reports that topsoil moisture across Minnesota is 0 percent Very Short, 2 percent Short, 63 percent Adequate, and 35 percent Surplus. Corn that was dented or beyond was two weeks behind the five year average and soybeans were eight days behind average. Damp field conditions is making harvest a challenge. Soil moisture levels at Lamberton are well above the historical median. The soil moisture level at Lamberton is 1.78 inches above the historic average and is the fifth autumn with soil moisture levels above the historical average.
[see: Ag ricultural Statistics Service Crop Progress and Condition | U. of M. Southwest Research and Outreach Center (Lamberton) | U. of M. Southern Research and Outreach Center (Waseca)]
- The potential for wildfires is currently rated by DNR Forestry as Low across Minnesota. Historically, 80 percent of all wildfires in Minnesota occur during April and May.
[see: Fire Danger Rating Map]
- It looks like the wet pattern from the beginning of October is forecast to continue though the month. The October precipitation outlook leans towards above normal precipitation across the entire state. October precipitation normals range from about one-and-a-half inches in northwest Minnesota to about three-and-a-half inches in Cook County. Southern and central Minnesota range by about one-and-three-quarters of an inch in the southwest to about two-and-a-half inches in east central Minnesota.
[see: Climate Prediction Center 30-day Outlook | October Precipitation Normal Map]
- The October temperature outlook leans towards equal chances for below, normal and above normal temperatures throughout Minnesota for October. Normal October high temperatures are in the 60's to start the month, dropping to the low 50's to upper 40's by month's end. Normal lows are in the 40's early in the month, falling to the 30's by late October.
[see: Climate Prediction Center 30-day Outlook | October Temperature Normal Map]
- The 90-day temperature outlook for October through December has a tendency of above normal temperatures. The 90-day precipitation outlook for October through December indicates equal chances of below-normal, near-normal, or above-normal conditions across most of Minnesota, except for the southwest where there is a slight tendency for above normal precipitation.
[see: Climate Prediction Center 90 -day Outlook]
- The Winter Outlook (December-February) from the Climate Prediction Center depicts equal chances for below-normal, near-normal, or above-normal temperature conditions statewide. Precipitation chances continue to have a fairly strong tendency for above normal precipitation in the state.
[see: Climate Prediction Center December-February]
- The National Weather Service produces long-range probabilistic river stage and discharge outlooks for the Red River, Minnesota River, and Mississippi River basins. These products address both high flow and low flow probabilities.
[see: National Weather Service - North Central River Forecast Center]
From the author:
- Summer made a brief reappearance on the last day of September. High temperatures in the mid to upper 80s with dew point temperatures in the low 70s were common across southern Minnesota. The Twin Cities had a dew point temperature of 72 degrees for three hours during the afternoon of September 30. This is the highest dew point temperature seen so late in the year.
[see: Summer-Like Mugginess: September 30, 2019]
Upcoming dates of note:
- October 17: National Weather Service releases 30/90 day temperature and precipitation outlooks
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Pete Boulay, DNR Climatologist