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, 2013
What happened in September 2013:
- September rainfall totals were below historical averages in many Minnesota counties, especially in northeast and far southern sections of the state. September precipitation totals fell short of long-term averages by two or more inches in these areas. Above-average rainfall totals were reported in a handful of northwest and west central Minnesota counties. Across much of the southern three-quarters of Minnesota, rainfall totals from late June to early October were four to eight inches below normal. These rainfall deficits, along with very hot late-summer temperatures, reestablished drought conditions across much of the state.
- The heaviest rainfall event of September occurred on the 19th when severe thunderstorms rumbled through southwest, central, and east central Minnesota. Heavy downpours, hail, and damaging winds were reported. Isolated locations in Sherburne and Isanti Counties received two to three inches of rain in less than an hour.
[see: Severe Storms - September 19]
- Average monthly temperatures for September in Minnesota were three to five degrees above historical averages. Temperatures during the second week of the month were very warm, pushing into the 90s in many locations. Extremes for the month ranged from a high of 96 degrees at a number of south central Minnesota locales on the 9th, to a low of 26 degrees at Embarrass (St. Louis County) on the 17th and Brimson (St. Louis County) on the 22nd. Numerous frosts occurred in September in north central and northeast Minnesota, while the rest of the state has yet to observe freezing temperatures this autumn.
Where we stand now:
- April 1-to-date precipitation totals are highly variable across Minnesota. Spring and early-summer precipitation totals were ample to excessive in many locations, especially southeast Minnesota. Whereas, precipitation totals from the last week of June through early-October were substantially below average in all but the northernmost counties. The seasonal precipitation map offers a patchwork pattern of values above and below historical normals.
- The U. S. Drought Monitor, released on October 3, places sections of central, east central, southwest, and southeast Minnesota in the Severe Drought category. Large portions of the rest of the southern one-half of Minnesota are rated in the Moderate Drought category. The U. S. Drought Monitor index is a blend of science and subjectivity where drought categories (Moderate, Severe, etc.) are based on several indicators.
- The U.S. Geological Survey and the Minnesota DNR report that stream discharge values are below the 25th percentile at roughly one-quarter of Minnesota's gauging locations. For other stations, stream flow is near the middle of the historical distribution. Some of the lowest stream discharge values, relative to average, are found in north central Minnesota.
- Water levels on many Minnesota lakes are lower than average due to dry summer and autumn weather plus high evaporation rates caused by hot late-summer temperatures. Canadian border lakes are the exception. Heavier rainfall totals in these areas have kept lake levels near historical medians.
- In their September 30 report, the Minnesota Agricultural Statistics Service reported that topsoil moisture was 52% Very Short or Short. Subsoil moisture was said to be 63% Very Short or Short. Soil moisture measurements made at two University of Minnesota Research and Outreach Centers in mid-September and early October indicated below-average conditions at these southern Minnesota locations.
- The potential for wildfires is currently rated by DNR Forestry as Moderate in many western and southern Minnesota counties. The fire danger is rated Low in central, east central, and northeastern Minnesota.
- The October precipitation outlook indicates equal chances of below-normal, near-normal, or above-normal conditions throughout Minnesota. Normal October precipitation ranges from one and one-half inches in northwestern Minnesota, to over two and one-half inches in portions of northeastern Minnesota.
- The October temperature outlook tilts towards above-normal conditions in most Minnesota counties. Normal October high temperatures fall from the low to mid-60s early in the month, to the upper 40s by month's end. Normal October low temperatures drop from the low 40s early in the month to near 30 by late October.
- The 90-day precipitation outlook for October through December offers equal chances of below-normal, near-normal, or above-normal conditions across Minnesota. The October through December temperature projection also calls for equal chances of below-normal, near-normal, or above-normal conditions for all Minnesota locales.
- 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.
From the author:
- Heavy autumn rains have fallen in many communities in the southern two-thirds of Minnesota during the past 24 hours. The area's rivers are showing little response to the precipitation, indicating that the soil moisture profile is making a claim on this water. More heavy rain is anticipated over the next 72 hours.
Notes from around the state:
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Greg Spoden, DNR Climatologist