Michigan drought update for July 5, 2012

Dry pattern to persist into the second half of July.

Scattered showers and thunderstorms brought much-needed moisture to extreme northwestern, central and eastern sections of Michigan, but rainfall totals in other areas were negligible. Symptoms of plant water stress were evident in many spots, especially across the southwestern Lower Peninsula where rainfall deficits since May 1 are now approaching 6 inches in some cases (8 to 9 inches is the climatological norm). The moisture stress was exacerbated by unusually high temperatures during the past week, with 100-plus degrees Fahrenheit maxima reported in southern sections on June 28 and again on July 4.

While forecast guidance does suggest some relief to heat and dryness during the next week (and that we may be experiencing the peak of the heat wave conditions during the next one to two days), medium range guidance continues to suggest a general continuation of drier than normal weather into the second half of July. The magnitude of heat and dryness across southern Michigan and much of the central and eastern Corn Belt region to our south is very unusual, with similar conditions not observed since the great drought of 1988.

In the short term, look for at least one last day of excessive heat on Friday (July 6), with high temperatures well into the 90s and more 100 degrees Fahrenheit or better readings in southern sections of the state. As has been the case for the past several days, the combination of extreme heat and humidity will lead to the formation of some isolated thunderstorms, but areal coverage will remain limited and most areas will remain dry. A cool front is forecast to move from north to south across the state late Saturday (July 7) and bring a better chance for rainfall, beginning overnight Friday across the far north and spreading southward during the day Saturday. Best chances for rainfall with this system (scattered 0.25 to 0.50 inches totals with locally higher amounts) will be across northern sections of the state. Fair, cooler and less humid conditions are likely Sunday (July 8) through the middle of next week. Daytime temperatures should fall back to the upper 70s north to mid-80s south – while still a few degrees above normal, is still significantly cooler than the past few days.

Latest medium range forecast guidance suggests that the persistent upper air ridge responsible for the drought will shift from western sections of North America early next week back to the Midwest by late next week. Unfortunately, this pattern change will likely lead to a return of much above normal temperatures at some point during the next one to two weeks.

The latest NOAA Climate Prediction Center 6-to-10 day and 8-to-14 day outlooks (for July 10-14 and July 12-18) both call precipitation totals to continue to remain at below normal levels state- and region-wide. Mean temperatures during the 6-to-10 day timeframe are forecast to range from below normal levels across extreme eastern sections of the state to above normal levels in the west, warming to near to above normal levels statewide during the 8-to-14 day period.

Dr. Andresen's work is funded in part by MSU's AgBioResearch.

Related MSU Extension News article: Michigan drought update for July 12, 2012

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