More wet weather

Forecast projects rains will continue possibly through the weekend of April 30.

With a deep trough across western North America, and an unusually energetic jet stream and large amounts of low-level Gulf of Mexico-origin moisture available across the central United States, active and sometimes violent weather has been the rule for much of the past week in the Midwest and South. This pattern is expected to continue through at least the upcoming weekend, with more widespread rainfall across Michigan and the Great Lakes region during the next several days. Cool and somewhat drier weather is possible by next week.

During the next 48-60 hours, two separate areas of low pressure are forecast to pass through the region. The first will move through during the day Tuesday (April 26), followed by a stronger second system Wednesday. Look for steady rains across northern Michigan overnight Tuesday and for scattered showers and thunderstorms central and south. Some snow is possible across western Upper Michigan. Widespread rain with embedded thunderstorms will redevelop from south to north across the state on Wednesday and continue before tapering off to showers Thursday morning. Rainfall totals of 1 to 2 inches are possible with these systems by Thursday morning with some isolated 2 inch-plus totals possible. Given wet soils in many areas, the rain may lead to some localized flooding.

Temperatures during the next several days will range from highs in the upper 40’s to low 50’s north to the 60’s south Wednesday, cooling to the 40’s and 50’s Thursday and Friday. Low temperatures will generally range from the low 30’s north to the upper 30’s to low 40’s south through Saturday. After another chance for showers and thunderstorms late Saturday into Sunday, drier weather is expected early next week.

In the medium range time frame, the 6-10 day and 8-14 day outlooks (covering May 1-5h and May 3-9) both call for a continuation of above normal precipitation totals statewide. With upper air troughing expected across central and eastern sections of the United States, mean temperatures are forecast to range from near to below normal levels during the 6-10 day period, and remain at below normal levels during the 8-14 day period. With some differences among the various forecast models used in the outlooks, forecast confidence is considered lower than normal.

New long lead outlooks change previous forecast

A new set of long lead outlooks was recently issued by NOAA’s Climate Prediction Center, and they differ somewhat from previous issuances. For the month of May, the outlook calls for the equal odds scenario (near equal odds of below-, near-, and above normal values) for mean temperatures statewide. Wetter than normal conditions are expected from the Pacific Northwest eastward as far as western Upper Michigan. For the majority of Michigan, however, the outlook calls for no direction on precipitation totals (i.e. the equal odds scenario). For the 3-month May through July period, the outlook suggests cooler than normal mean temperatures and for near to above normal precipitation totals for nearly all of the Great Lakes region.

This forecast change is related to expectations that the wetter than normal conditions across the region during the past few months will: 1) require greater than normal amounts of incoming solar energy to evaporate and 2) provide extra water vapor for precipitation during the next couple of months.

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