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: August 3, 2017
What happened in July 2017:
- Precipitation totals were mixed for July 2017. There were locations in the state that had a quite wet July. South central and southeast Minnesota had some of the wettest conditions. Locations such as Waseca (6.56 inches or 2.14 inches above normal) and Minnesota City (7.33 inches or 3.09 inches above normal) lead the pack with surplus moisture. On the other end of the spectrum was north central and west central Minnesota both averaging 1.3 inches below normal. Morris reported .92 inches, the third lowest precipitation total for July at that location since 1886. This is 2.96 inches below normal. Norris Camp only had a quarter of an inch for July or 3.38 inches short of normal. Many locations in the state ranged from about one half to an inch and a half below normal. The Twin Cities was in this lot with 3.12 inches or .92 inches below normal. The preliminary average precipitation total for the state is 3.29 inches or .61 inches below normal.
[see: July 2017 Precipitation Total Map | July 2017 Precipitation Departure Map | July 2017 Climate Summary Table | July 2017 Percent of Normal Precipitation Map ]
There were a number of storm events in Minnesota for July 2017. There were around nine tornadoes reported in the state for July. Most were of the weak variety. - Storms developed during the evening hours of July 9, 2017 causing wind and hail damage, along with two tornadoes. The largest hail reported was grapefruit-size (4 inches) two miles southwest of Winthrop in Sibley County and also near Lafayette in Nicollet County. Reports indicated a weak tornado near Courtland in Nicollet County and one near Lake Crystal in Blue Earth County. Heavy rains up to four inches fell in Nicollet County.
[see: Tornadoes and Severe Storms: July 9, 2017] - Over a span of about 12 hours, five tornadoes were reported in Minnesota. Three tornadoes were spotted in northwest Minnesota during the evening of the 11th. Two of these crossed the Red River from North Dakota. The strongest tornado was ranked EF-2 with estimated winds to 130mph that passed just south of Halstad in Norman County. Heavy rains fell in a swath from just south of Grand Forks to St. Croix Falls, Wisconsin. Amounts ranged from one half to two inches. Two weak tornadoes were reported in the Forest Lake area in the early morning hours of the 12th.
[see: Severe Storms: July 11-12, 2017] - Severe thunderstorms formed in the hot afternoon air on July 17, 2017 over west central Minnesota with golf ball-sized hail reported south of Fergus Falls and a semi-truck trailer blow over on Highway 10 northwest of New York Mills. Some welcome rains fell in the Elbow Lake and Wadena areas eastward to the Brainerd Lakes area.
[see: July 17, 2017 Severe Weather Event] - Strong thunderstorms dumped heavy rains, especially along the Mississippi River from the Twin Cities to La Crosse on July 19-20 2017. A cluster of storms moved across southern Minnesota during the morning hours of July 19th and dropped up to two inches of rain in the Mankato area. Thunderstorms then redeveloped in the evening over the southern Twin Cities and then trekked down the Mississippi River, with the heaviest rain falling on the Wisconsin side of the border. The highest 24-hour rainfall total found in Minnesota was 6.02 inches measured by a MNgage observer in Wabasha.
[see: Heavy Rains and Severe Storms: July 19-20 2017] - Isolated, but severe thunderstorms spawned two weak tornadoes in remote terrain in Beltrami and Clay Counties. These storms also brought rainfall to from west central to North central Minnesota amounting from one half to nearly and inch.
[see: Severe Storm Episode from July 21, 2017] - July 2017 finished a tad warmer than normal for Minnesota. The preliminary average statewide temperature for the state was 70.4 degrees, which is .1 (one tenth of a degree) above normal. The warmest temperature found was 101 degrees at Browns Valley in west central Minnesota on July 17th, and the coldest temperature found was 37 degrees at Embarrass on July 14th. The Twin Cities wound up being 1.5 degrees above normal for the month and clocked five days of 90 degrees or above for high temperatures, very close to the 30 year average.
[see: July 2017 Climate Summary Table | 2017 July Departure from Normal Temperature Map ]
Where we stand now:
- Seasonal precipitation totals (April 1 though August 1) are ranked near or above the historical median over eastern Minnesota and below the historic median in the west. The north west and north central parts of the state have been missed by the passing showers more often and a large area is below the 15th percentile in ranking. A small area in south west Minnesota is also well below the historical median as well.
[see: Seasonal Precipitation Maps] - The U.S. Drought Monitor map, released on August 3, depicts 17 percent of the state in the Moderate Drought category, mostly in northwest and north central Minnesota and a small part of southwest Minnesota. This is an increase since early July. 32 percent of the state is in the Abnormally Dry category, a bit of a decrease since early July. 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 values are normal to below historical medians across Minnesota, with above normal flows in the southeast and northeast. The Mississippi River at Grand Rapids fell below the tenth percentile on July 27 and leveled off since then.
[see: USGS Stream Flow Conditions] - Water levels on most Minnesota lakes vary depending on lake and location in the state. Mille Lacs was near the median lake level for July. On July 5, Minnetonka was at 929.05 with 12cfs flowing through Grays Bay Dam. White Bear Lake was at 923.21 feet on August 3, a rise of 1.08 feet from one year ago. Rainy Lake and Lake of the Woods were in the median range for July. Lake Superior was at 602.89 feet on July 28, two inches higher than the monthly average for July.
[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 July 31 reports that topsoil moisture across Minnesota is 3 percent Very Short, 23 percent Short, 72 percent Adequate, and 3 percent Surplus. Soil moisture levels at Lamberton on July 15 are 1.19 inches short of the historical median, with the top two feet having very little moisture. Soil moisture is adequate at Waseca. The West Central Research and Outreach Center at Morris noted at the end of July that while crops generally looked good, rain is needed. The third crop of alfalfa has suffered from a lack of rain and row crops are starting to show stress.
[see: Agricultural Statistics Service Crop Progress and Condition | U. of M. Southwest Research & Outreach Center (Lamberton)] - The potential for wildfires is currently rated by DNR Forestry as Low across central and southern Minnesota, with the far north, north central and northeast sections where the fire danger is Moderate. Historically, 80 percent of all wildfires in Minnesota occur during April and May.
[see: Fire Danger Rating Map]
Future prospects:
- The August precipitation outlook leans towards equal chances for below, above and normal precipitation across the entire state. August precipitation normals range from about two-and-a-half inches in northwest Minnesota to about five inches in southeastern counties.
[see: Climate Prediction Center 30-day Outlook | August Precipitation Normal Map] - The August temperature outlook leans towards equal chances for below, above and normal temperatures for central and northern Minnesota, with a slight tendency for below normal temperatures in southern Minnesota. Normal August high temperatures are around 80 degrees to start the month, dropping to the mid-70s by month's end. Normal lows are around 60 degrees early in the month, falling to the mid-50s by late August..
[see: Climate Prediction Center 30-day Outlook | August Temperature Normal Map] - The 90-day precipitation outlook for August through October indicates equal chances of below-normal, near-normal, or above-normal conditions across Minnesota. The August through October temperature projection offers a tilt for above-normal conditions statewide.
[see: Climate Prediction Center 90-day Outlook] - 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:
- Some well-needed rains fell across central Minnesota during the morning hours of August 3rd. Some of the heaviest rains fell on the parched west central Minnesota area with Montevideo seeing 2.10 inches of rain and Browns Valley seeing 1.27 inches. One of the highest amounts found so far was 2.43 inches near Long Prairie in Todd County. The rains largely missed the dry areas of northwest and north central Minnesota. The Twin Cities only saw .28 inches of rain through Noon on August 3. If you have any questions or comments about the HydroClim Newsletter, please let me know.
Upcoming dates of note:
- August 17: National Weather Service releases 30/90 day temperature and precipitation outlooks
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Pete Boulay, DNR Climatologist