Updraft: December 19, 2007 Archive

Irreconcilable differences

Posted at 7:12 AM on December 19, 2007 by Paul Huttner (2 Comments)

The Weather Lab models don't seem to agree about much when it comes to our chances for snow this week.

Take the GFS. Uncertain, quirky and mercurial. Not really able to settle on a particular track for the surface low. Not sure of two split storm centers or one. If we are to believe the GFS, it will snow, some, on Friday and into Saturday. The split pattern of two upper low centers usually produces lighter snow amounts for southern Minnesota, with more up north in the northern stream and more to the south.

GFS model forecast 6am Saturday

Then there's the NAM. Bold, certain, loud and quite possibly wrong. It keeps the storm center more compact and together as it tracks into Iowa late Friday night. This kind of a solution generally produces a band of heavier snow in southern Minnesota and western Wisconsin.

NAM forecast for 6am Saturday

The NAM has seemed to move just a little toward the GFS solution over the past 24 hours.

When meteorologists try to forecast snow storms, we watch for (and hope for!) day to day and run to run consistency in the computer output. No such luck this time.

Suffice to say if you are planning pre holiday travel Friday afternoon through Saturday, be ready for some snow. How much? We'll have to let the NAM, GFS and friends fight that out for a while longer.

PH

(2 Comments)

Fog lingers on the crystal ball

Posted at 2:26 PM on December 19, 2007 by Craig Edwards

Unintentional delivery of misinformation is a clever alibi for an ever changing weather forecast. Every now and then a meteorologist has to stick his or her neck out for a long range forecast on a busy travel period. We rely on multiple computer models to formulate our best guest, knowing that activity in the laboratory is always a work in progress.

Earlier this week our best computer models were strongly hinting at a troublesome weather event from Minnesota to Michigan on Saturday. Today, the fog is starting to lift from the crystal ball. It now appears that Mother Nature has decided to perform the splits. The heaviest precipitation may move well south of the Great Lakes.

While some snow is still possible Friday night into Saturday it does not look to present much of a calamity. But there is still time for shifts in the weather pattern, so don’t stray too far from a source of weather information.

As chief meteorologist Paul Huttner noted in the previous blog there are some inconsistencies in how the evolution of weather parameters will shake out on the weekend. Don’t cancel any travel plans, but remain flexible.
CE