Jon Shaner: December 2009 Archives

There are many points in talking about the weather daily where we compare things to "normal" or "average" conditions.  You've probably noticed that snowfall the last two years (and so far this year) has been well above normal.

But how are the normals computed?  Well, the official "NORMAL" (although I prefer the term "average," since Michigan weather is rarely normal!) snowfall is the average of the totals for a 30-year period, currently 1971-2000.  Every decade, those numbers are recalculated, so we'll be due to adjust the averages at the end of 2010.

Where does that put us?  I checked the numbers from 1981 to present and found, as you might expect, that recent higher snowfall numbers push our overall average up a few inches, from 72.2" for the season to around 75.5".  December, January, and February averages go up, while the fringes of the snow season see numbers drop a bit.

If you take out some of the early-80s seasons with low snow totals, the effect is even greater.  From 1989-2009, the average has been about 80.9", with increases in every month except March and April.

It's obvious based on that information that snow totals have trended upward through the last couple of decades.  But how much of that is cyclical (there is evidence of ups & downs in such numbers back to the 1950s), and can any of it be attributed to climate change or other factors?  That's for us to try to gather data to analyze, and for future meteorologists to decide!

Good morning, everyone.  A few weather-related topics to cover, things to watch, etc. as I'm chilling out over the Christmas week...

- Upcoming weather to watch: parts of the Mid-Atlantic are going to get SLAMMED with snow Saturday.  The Richmond-Washington D.C.-Baltimore corridor will be under the gun Friday night into Saturday, with snow spreading northeastward from there through the weekend.

A couple of weak systems will slide through the Great Lakes this weekend, with each possibly giving us an inch or two of fresh snow.  Some lake-effect or lake-enhanced snow may develop from time to time as well Sunday and Monday.

After a midweek break, medium-range computer models are indicating a more potent system developing and moving into the Great Lakes.  However, they're not being very consistent about where exactly it will head, so it's way too early to say for sure whether it will cause travel problems around West Michigan.  As we like to say, "Stay tuned for later forecasts!"

- Copenhagen climate talks: As I'm typing this, President Obama and other foreign leaders are still sniping at one another about worldwide greenhouse gas emissions and how their respective nations will cut them over the next few decades.  Despite some general agreements, it's unlikely that groundbreaking changes are forthcoming.  The international community is always hesitant to impose real deadlines.  That creates a very easy return to everyday activity and an eventual changing of the target later down the road, or loopholes that allow nations to avoid the pain that would come with real change.  The politicians want to claim victory now, despite the fact that the promises may fall by the wayside later on.

I'm not on board with those who proclaim global doom because of climate change; but if the world decides to tackle this issue, I'd rather leaders do it quickly and efficiently rather than through finger-pointing and rhetoric.  Politicians are great, aren't they?  Another topic for another day.

- I'm off all next week through Christmas for some much-appreciated family time.  Kevin will carry you through the holiday, and I'll be back on Monday the 28th.  Until then, thanks for following FOX 17 Morning News and for supporting what we try to do in the weather department.  Merry Christmas!

-JS

As of Tuesday morning, here's the outline of our impending winter storm:

Snow will gradually spread into West Michigan during the day today, but minimal accumulation by this afternoon's commute.  Snow will continue to increase into this evening:

Here's an updated forecast before I turn things over to the next shift on this Thursday:

Lake-effect bands will continue as a rain/snow mix through midday, with a gradual shift inland and transition to all snow by late afternoon and early evening.

An upper-level disturbance is going to swing through tonight and disrupt the pattern a bit, generating a fairly heavy single band of lake-enhanced snowfall this evening and overnight.  The biggest question is where that band will set up?

As of early this morning, the heaviest accumulation looked to be down toward I-94... but over time this morning, each computer model has gradually shifted it northward toward Grand Rapids and, now as of 11 AM, the Muskegon area.  If that band sits still for a few hours, a narrow zone of 6"+ accumulations are possible, with only 1-3" outside of it.  If it swings through the area gradually, the snow will spread out more into a general 2-4" accumulation.  There will still be some decent lake-effect possible outside of that main swath, but that disturbance will be the main player.

Here's our latest computer model forecast of regional snowfall through noon Friday:



That dark blue area is the 6"+ zone (near Muskegon, in case you can't see the map outline), and the lightest blue is 2-4" (along and west of US-131 down to Kalamazoo).

Kevin will be updating the forecast tonight at 6:00 and 10:00.