HydroClim Minnesota for Early May 2018
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: May 4, 2018
What happened in April 2018:
- April will be a month that will be long-remembered as cold and snowy, with a delay to spring and late lake ice outs. April monthly precipitation totals wound up below normal for most places in central and northern Minnesota, to slightly above normal in the southeast boosted by ample April snowfalls.
[see: April 2018 Precipitation Total Map | April 2018 Precipitation Departure Map | April 2018 Climate Summary Table | April 2018 Percent of Normal Precipitation Map]
- The main weather event of April 2018 was the thunder blizzard from Apri1 13-16. This was the largest April snowstorm in the Twin Cities. A wide swath of eight to eighteen inches fell from southwest to west central Minnesota. Heavy snow closed the Twin Cities International Airport for seven hours and dropped over an inch of liquid precipitation in the areas that saw the heaviest snow bands. This blizzard marks the first time since the 1991 Halloween Blizzard that the Twin Cities was under a blizzard warning and this snowfall also ranks as the 12th largest snowstorm on record for the Twin Cities.
[see: Thunder Blizzard: April 13-16, 2018 | Top Twenty Twin Cities Largest Snowstorms]
- Not only will April be remembered for the snow, the persistent cold for the first 22 days of the month will be long remembered. Even with much warmer air for the last week of the month, April 2018 finished in the top five coldest at many locations, including the fourth coldest in the Twin Cities and was the coldest April since 1950. It was the 2nd coldest April in St. Cloud, the coldest April in Rochester, the 4th coldest at International Falls and the 6th coldest in Duluth. Extremes for April ranged from a high of 84 degrees on April 30 at the Twin Cities and other locations, to a low of -11 east of Ely on April 8. Below-zero temperatures were found for places as far south as Redwood Falls which saw a low temperature of -3 on April 4. St. Cloud had its latest minimum temperature of zero on record on April 5.
[see: April 2018 Climate Summary Table | 2018 April Departure from Normal Temperature Map | April 2018 St. Cloud Climate Table]
Where we stand now:
- Seasonal precipitation totals so far (April 1 through May 1) ranked below the historical median across the north half of Minnesota and above the historical median for southern counties.
[see: Seasonal Precipitation, Percent Normal and Ranking Maps]
- The final snow depth map of the season was produced on April 26. Snow depths on that map range from one to seven inches across the Lake Superior highlands. The landscape was snow-free for the rest of Minnesota.
[see: Snow Depth Map: April 26, 2018]
- The U. S. Drought Monitor map released on May 3 shows a persistent area of Moderate Drought in Koochiching County. This pocket of moderate drought has been in place since the summer of 2017. Due to the dry conditions in April, an area of Abnormally Dry conditions expanded a little into northwest Minnesota. The rest of Minnesota is drought free. 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 above to much above normal in southern and central Minnesota. Streamflows are mixed in the north ranging from normal to below normal. There was a significant delay in snow melt and rivers were affected by ice for much of the first half of April. Some minor flooding did take place in late April along the Minnesota and Mississippi Rivers and also along the Red River of the North.
[see: USGS Stream Flow Conditions]
- Water levels on most Minnesota lakes vary depending on lake and location in the state. Mille Lacs lake level for April was still affected by ice. On May 3 Minnetonka was at 929.54 with 250 cfs flowing through Grays Bay Dam. Levels in April were affected by ice cover. White Bear Lake was at 923.33 feet on May 2, a rise of .12 feet from one year ago and a rise of 4.49 feet from the record low of 918.84 measured January 10, 2013. The most recent high level for White Bear Lake is 923.62 on 5/27/2017. Rainy is at the lower end of the normal band for the time of year. Lake of the Woods is well below normal and on April 26th was at 1057.5ft, less than the 5th percentile for that time of year. The late snowmelt and the scant precipitation were the main culprits. Lake Superior was at 601.97 feet on April 27, nine inches higher than the monthly average for April.
[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 reported on April 30, that topsoil moisture supplies across Minnesota are 0 percent Very Short, 3 percent Short, 64 percent Adequate, and 33 percent Surplus.
[see: Agricultural Statistics Service Crop Progress and Condition]
- The potential for wildfires on May 3, rated by DNR Forestry as ranging from Moderate across most of Minnesota to High for east central and parts of central Minnesota. There was also a pocket of Very High Fire Danger Rating just of the west of Upper and Lower Red Lakes. Warm, dry and windy conditions were present at the end of April and the beginning of May to elevate the fire risk.
[see: Fire Danger Rating Map]
- The frost has left the soil in most Minnesota locales. Some frozen soil remains in northern counties and in parts of west central Minnesota.
[see: Corps of Engineers Snow, Ice, Frost Data | National Weather Service Frost Depth Datanbsp; | MnDOT Road Frost Depths]
- 2018 is a near-historic late lake ice out in Minnesota. As of May 3, there are still many larger lakes with ice cover across central and northern Minnesota including Mille Lacs, Upper and Lower Red, Leech, Winnibigoshish, Lake of the Woods and Vermilion. The progress of lake ice out was about three weeks to almost a month behind across southern Minnesota and about one to two weeks behind across northern Minnesota. It appears as though the long-standing records from 1950 in the north will not be broken, but 2018 still stands as one of the latest ice out years of record for many lakes, and somewhat reminiscent of 2013.
[see: 2018 Lake Ice-Out Dates | DNR Conservation Officer Reports]
- The May precipitation outlook has above normal precipitation for all but the far northwest. May precipitation normals range from just over two inches in northwest Minnesota to just less than four inches in southeastern counties. The historical probability of measurable precipitation for any given day in May ranges from 25 percent in the northwest to near 40 percent in the southeast.
[see: Climate Prediction Center 30-day Outlook | May Precipitation Normal Map]
- The outlook for May calls for above normal temperatures across not only the state but for the entire country. Normal May high temperatures are in the low to mid-60s early in the month, rising to the low to mid-70s at month's end. Normal May low temperatures are in the mid-30s to near 40 to start the month and climb to the mid-40s to low 50s as the month ends.
[see: Climate Prediction Center 30-day Outlook | May Temperature Normal Map]
- The 90-day precipitation outlook for May through July indicates equal chances of below-normal, near-normal, or above-normal conditions for most of Minnesota, and a tilt towards above-normal conditions in northeastern counties. The May through July temperature projection indicates equal chances of below-normal, near-normal, or 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:
- Spring crop planting was behind in April due to poor weather conditions. Soil temperatures were also quite cold, causing a delay in seed germination. A warming trend at the end of April and early May began to warm the soil and the sunshine was welcome by many in the state. The weekly crop report from Waseca noted that soil temperatures that were below freezing at a two inch depth were now close to a 60 degree average by May 2. Spring field work had begun with even a little bit of corn being planted. Tilling was taking place at the St. Paul Campus Agricultural plots on Monday, April 30. [see: Minnesota Department Of Agriculture - 6 Inch Soil Temperature Network | Weekly Crop Update: Southern Research and Outreach Center - Waseca, MN]
Upcoming dates of note:
- May 17: National Weather Service releases 30/90 day temperature and precipitation outlooks
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Pete Boulay, DNR Climatologist