WINTER WEATHER EXPECTED OVER SOUTHWEST MICHIGAN SATURDAY

It may be late March but we can still get meaningful snow in Southwest Michigan through the month of April!

While we may well get a significant (shovel-able) amount of snow and enough ice accumulation in areas near or just north of I-96 Saturday, as typical of late March storms, most of the snow and ice will likely be gone by Sunday afternoon. Below is the model (GFS) forecast snow depth by Sunday evening at 8pm.

6th Lowest Frost Depth since 1999

It is worth noting for my top 3 warmest winters, the frost depth stayed under 6″.

Below is a table that shows the top 10 warmest winters since 1999, and the maximum frost depth. Note that except for 2016 and 2020, the frost depth was no greater than 7.5″.

Top 10 Warmest Grandville Winters since 1999

So, why was the frost depth so deep in 2016, even through it was relatively warm winter? It’s a function how persistent the cold temperatures were, in combination with the snow depth.

In 2016, through it was an overall warm winter, when the frost depth got to 11.5 inches in mid February the snow depth stayed under 3″. Meanwhile the 7 day running mean temperature fell to 16.5 degrees. This year our lowest 7 day running mean temperature was 17.8 degrees, not really all that much warmer than in 2016, however this year the snow depth during that time was between 12 and 16 inches. The point being, to get a deep frost depth you need less than 5″ of snow depth and a 7 day running mean temperature below 20 degrees.

PERSPECTIVE ON THE NORMAL MARCH HIGHEST TEMPERATURE AT GRAND RAPIDS

I want to point out what the typical March high has been since 1991 at Grand Rapids. There has been a slight negative trend from 69f to 68F in the past 30 years. The median maximum temperature for March is 69F . Having a maximum March temperature below 60 is unusual as you can see from the chart above. There have been 6 years out of 30 (20%) when this has happened.

How Warm Will Our Summer Be Over Southern Michigan?

This will be short version of this idea, I will post something with more detail next week (CPC issues a new forecast on Thursday) and I want to look at more information. Still what I know now is worth sharing.

The last forecast from CPC (Feb 16th) suggests a warm summer is slightly higher odds than does a near normal or cool summer but the odds are not great, 35% for warm, 33% for near normal and 32% for colder than normal.

However, if we look at all years when there was a La Nina during the winter (there was this winter) when the winter in Southwest Michigan was warmer than normal, like it was this past winter, we see from the charts below the spring it typically warmer than normal with near normal precipitation.

As for the summer we see the warmer than normal trend continues and precipitation remains near normal south of I-96 but it’s wet north of I-96

Since southwest Michigan had a warm winter, let’s look at what happens when the winter is warm, not caring about the state of ENSO.

Now here is something that may change that story! So far, most of southern Lower Michigan has not had a daily the temperature above 60F. The extended ensembles of both the GFS and ECMWF, while not ruling out one or two days with highs that warm, odds are very low at this point. Neither model means show highs that warm, it is only 1 or 2 out of 50 of the ECMWF that are forecasting highs that warm by the end of March. So below is a joint study by Gary Rizzo and myself on what happens at both Grand Rapids and Detriot.

So, this will be fun to watch how this plays out! We already know that if at Grand Rapids the daily high reaches 90F in May there will be a much higher than normal number of 90F days but it now seems we have a filter for below normal numbers of highs in the 90s.

Once again next week I will put info out on our coming summer, but I through it’d be fun to post this this week.