Michigan drought update for July 12, 2012

Some hints of a pattern change are forecast.

Following the passage of a cool front last weekend (July 7-8), a high pressure system slowly moved across the region, leading to somewhat cooler temperatures during the past few days, but also to a general continuation of dryness across the state. Drought conditions worsened in many areas, especially across south central and southwestern sections. As noted in Michigan drought update for July 5, 2012, the magnitude of heat and dryness across southern Michigan and much of the central and eastern Corn Belt region to our south has not been observed since the great drought of 1988.

In the forecast, while generally warmer and possibly drier than normal conditions are expected to continue in the short term, there are some hints of a more significant change in the one- to two-week time frame. Following another dry day Friday (July 13), the combination of a weak, upper air disturbance passing across the region and a northward surge of Gulf of Mexico-origin moisture will bring at least a chance of scattered showers and thunderstorms late Friday night through Sunday (July 15). Best chances for rainfall will be Saturday afternoon and evening (July 14), and – for a major change – across southern sections of Lower Michigan.

Most rainfall amounts will remain in the 0.25- to 0.50-inch range where rain falls, although some isolated 1-inches are also possible. Unfortunately, as has been the case for several weeks, many areas will remain dry. A warm front is forecast to move through the state early next week and will bring warmer, more humid temperatures, but also a continuing chance for more showers and thunderstorms Monday through Wednesday (July 16-18). Temperature-wise, look for highs generally in the mid-80s to low 90s, and lows in the 60s to low 70s through early next week.

Most recent medium range forecast guidance suggests a gradual flattening and westward shift of the persistent upper air ridge that has been responsible for the central U.S. drought conditions. This is a notable change from past forecast guidance, as the forecast pattern should lead to more frequent chances for precipitation in Michigan. The latest NOAA Climate Prediction Center 6-to-10 day and 8-to-14 day outlooks for July 17-21 and July 19-25 both call for mean temperatures to remain at above normal levels state- and region-wide.

In a significant change from recent outlooks, however, the outlooks also call for normal to above normal levels of precipitation. While I, personally, am still hesitant to believe that this will materialize exactly as forecast (once they are in place, large, regional-scale droughts are difficult to bring to an end), it is still one of the first true signs of hope of more favorable weather conditions in many weeks.

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

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