A Difficult Sunny Appearance

Posted at 9:15 PM, Feb 23, 2013

Ever wonder why we see reduced sunshine in West Michigan from November through about March? Prior to Grand Rapids I spent three years forecasting across the lake in Madison, Wisconsin. I can tell you the sun always seemed to shine in the winter there.

Simply put, the lake-effect influence on West Michigan puts a big damper on our sunshine throughout the winter months. If its cold enough, we may not get snow, but certainly lake-effect clouds contribute to quite a few gloomy days here. But we can’t always blame it on Lake Michigan.

We had a situation this past Thursday where we should have normally seen plenty of sunshine across the area with a dry airmass and no storm systems, low pressure area, or upper level disturbances overhead. So what happened? Probably the same thing we may deal with on Sunday and Monday!

When high pressure builds in to our region, it usually goes to work scouring out or clearing out the clouds. It creates what meteorologists call sinking air or subsidence. When the air is forced to sink, it tends to dry the atmosphere out. That leads to, contributes to, or promotes clouds NOT forming. It has the opposite effect of a low pressure system which creates rising air, cooling, condensation, and cloud formation. Anyway, we can sometimes get warmer temperatures just above the surface (aloft a few thousand feet). With high pressure overhead, this can create what meteorologists call a “subsidence inversion“.

The inversion tends to keep a lid on the atmosphere and prevent the cloud deck or moisture from mixing out and being broken up. Sometimes these inversions can be broken, but it’s increasing difficult during the winter months. High pressure systems that don’t clear our skies out are sometimes referred to as dirty highs. That said, we have a chance at seeing some sunshine (again) Sunday afternoon and Monday, but only if we can break the pesky inversion. If we can’t, clouds will stay locked in place.

In either case, we can confidently say clouds will rule on Tuesday with some sort of precipitation likely as a rather large, developing low pressure area tracks in to the Great Lakes from Texas. Preliminarily, I would expect the possibility on Tuesday of rain, freezing rain, sleet, and perhaps accumulating snow. Make sure to stay up on later forecasts. Get more too at