Jeff Andresen, Agricultural Meteorology and Geography

This past Monday (September 21), showers and thunderstorms associated with the weather disturbance that recently brought extended heavy rain and flooding to much of the south and Ohio Valley ended an extended period of mostly sunny, dry weather across Michigan. Many areas had been dry since August 30. Forecast guidance is now suggesting some major upper air changes during the upcoming week leading to a cooler, more unsettled weather pattern.

In the short term, an upper “cut-off” low spinning counterclockwise across the central Great Plains is forecast to slowly move towards and through the Great Lakes region by the end of the weekend. While this feature remains to our west, high pressure across eastern Canada will bring fair, cooler, and less humid weather to the state Thursday and Friday. The cut-off low is forecast to move through the region this weekend with a good chance for showers and a few thundershowers beginning early Saturday continuing through Sunday. Rainfall totals in the 0.25-0.50 inch are generally expected with this system with some locally higher totals possible, especially across southern sections of the state. High temperatures the next few days will fall back to the mid- to upper 60's north to the mid-70's south through Sunday. Low temperatures will generally range from the upper 40's or low 50's north to the upper 50's south.

Further ahead, most recent guidance suggests a period of northwesterly flow aloft and much cooler than normal temperatures across much of the state next week following the passage of a strong cold front through the state late Sunday and Monday. The threat of showers will continue Monday and Tuesday with temperatures falling back to highs from the 50's north to 60's south and lows in the 40's. As high pressure settles over the region Wednesday and Thursday next week (with clearing skies and relatively calm nighttime conditions), there may be the potential for a frost or freeze event either of those mornings over large areas of the state. Stay tuned to latest forecasts.

In the medium range forecast period (one to two weeks ahead), the forecast guidance is having problems converging on a projected upper air pattern. As it stands right now, the NOAA Climate Prediction Center 6-10 day and 8-14 day outlooks for September 28 to October 2 and September 30 to October 6, call for below normal precipitation totals statewide. Mean temperatures are forecast to remain at below normal levels across the state during the 6-10 day period, moderating to near normal during the 8-14 day period. It is important to note that forecaster confidence in these outlooks is considered below normal due to the recent inconsistencies in the model guidance.