Cooler weather on the way

Most parts of the state are up to four weeks behind in growing degree day accumulations and the cool forecast will likely increase that gap.

An unseasonably warm air mass moved across the Midwest during the past weekend, setting off several rounds of severe weather and pushing temperatures across much of Michigan into the low and mid 80’s on Sunday, April 10. The unusual warmth set many new high temperature records (for the date) in southern and central sections of the state and led to some early vegetative development of perennial crops.

The upper air pattern responsible for the current active weather pattern, troughing across western sections of the continental United States and ridging across the east, is gradually expected to give way to troughing across central sections of the country by this weekend (April 15-17). This change will lead to a return of cooler and wetter than normal weather that is expected to persist for the next one to two weeks.

In the short term, look for fair and relatively mild weather statewide on Wednesday, with increasing clouds late in the day. The passage of a weak cool front will bring the chance for light rain showers overnight Wednesday. Rainfall totals will likely remain below 0.10”, with some areas remaining dry. Thursday should be mostly cloudy and dry.

Further ahead, an area of low pressure is forecast to slowly move from the central Great Plains northeastward through Michigan this weekend, leading to widespread rain and some snow across Michigan. Look for the chance of rain south and snow or mixed rain and snow north by late Thursday continuing into Friday. Rain is a good bet again across much of the state during the day Saturday before transitioning back to snow again late Saturday into early Sunday. Some minor accumulations are possible across northern sections of the state. Precipitation totals with this system are likely to be in the 0.5-1.0” category by Sunday morning, with some locally higher amounts.

Temperaturewise, a slow cooling trend is expected into the weekend. Highs are forecast to fall back from the 50’s north to low 60’s south on Wednesday to the upper 30’s north to upper 40’s by Saturday. Low temperatures are expected to range from the upper 20’s north to the mid and upper 30’s south through the weekend.

Current medium range outlooks for the next one to two weeks reflect the upper air pattern shift described above, with troughing expected to dominate the weather across the Great Lakes region. The latest NOAA Climate Prediction Center 6-10 day and 8-14 day outlooks (for April 17-21 and April 19-25) both call for cooler and wetter than normal weather across Michigan.

Finally, in the “what a difference a year makes” category, seasonal base 50F growing degree accumulations currently are generally running from one to two weeks behind normal across southern sections of the state while across far northern sections, the accumulations are several days to a week or more ahead of normal. This means that the current GDD totals are up to 4 weeks behind where they were at the same time last year (given last year’s record or near record early start), and given the cool forecast, look for that gap to become ever larger before the end of the month.

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