Updraft: November 28, 2007 Archive

Forecasting snow

Posted at 7:06 AM on November 28, 2007 by Paul Huttner

It's one of the most difficult forecasts we make as meteorologists.

Snow.

When will it start? When will it end? Will it be heavy and wet, or dry and fluffy? And, of course, how much will we get?

All snow systems are not created equal. There are several different types of weather systems that produce snow in Minnesota. We blather about Panhandle Hooks and Alberta Clippers, but they really do have different characteristics, and different results for how much ends up on your driveway.

One thing these storms tend to have in common is the heaviest snow band often sets up about 60 to 100 miles north of the track of the surface low. At 7am this morning our weak Alberta Clipper is centered just north of the Twin Cities. Note the snow bands north of the low center in northern Minnesota on this surface plot below.

Minnesota surface map

As you can see the snow totals for northern Minnesota fit pretty well with the expected storm path.

Northeast MN snow totals

Saturday a different set up will shove warmer moist air over our cold dome near the surface. We call this overrunning, and it can produce widespread snow which can be heavy. If the map below "verifies" for Saturday, we could see heavy snow this weekend.

GFS Model run noon Saturday

Stay tuned!

PH

Speaking of snow

Posted at 1:23 PM on November 28, 2007 by Craig Edwards

It was shortly before 3:00 p.m. yesterday when the office manager from a snow plowing company phoned me for details about the upcoming snowfall. Word had it that an overnight snowfall was about to stir up some salting and sanding business in the metro area. The best I can promise you is a dusting. 'That’s why I hadn’t called you,' was the short answer.

Now Saturday might be another story, but details will be sorted out later this week.

When I became the chief meteorologist for the National Weather Service in the Twin Cities in December of 1991, the metro area had already accumulated 50 inches of snow. Yes, in 30 days, there was enough snow to call it a season. The average winter snowfall in the Cities is around 55 inches.

For the past 16 years, I watched in wonder how media weathercasters would tease with the promise or a calamity of snow. Government meteorologists, whom I supervised for 25 years out of my 34-year career at the Weather Service, tended to be conservative on the snow forecast.

Computer models were assessed, lessons of synoptic meteorology were applied, and tried and true cookbook rules of thumb were followed. Projected snow accumulations were based on consensus of sound meteorology by a staff of skilled meteorologists.

As Paul Huttner mentioned in this morning’s blog, snow is a tough element to predict. It’s even tougher when stakes are high. I don’t know what goes on behind the scenes, but it sure appears to me that my dear colleagues in the media have it even tougher. The forecast of snow becomes more than a weather element, it becomes a news story.

Yes, even in the land of snow and cold, the first inch of snow in the Twin Cities can be the No. 1 news story. Let’s see how Saturday plays out!
National outlook for weather hazards