Tuesday, December 9, 2008

Today...warm front-cold front combo


A warm front is approaching us this morning (see satellite picture) and the radar shows the advance of the associated rain (see image). Showers will develop over Puget Sound this morning, with most of the precipitation north of Centralia. Aloft the winds will strengthen from the SW and temps will warm a bit. The rain should lessen by dinner time and then pick up this evening with the passage of the associated cold front (the back line you see in the satellite picture).
Wednesday will bring some residual showers...particular in the mountains and Thursday should be dry. The big issue is Friday and this weekend.
There is still considerable uncertainty in the forecast for Friday--and particularly lower elevation snow. But it is clear that the weather will turn colder over the weekend and dry out.
The computer models have not locked on to a consistent solution for Friday...something I like to see to give confidence in the forecast. Most models bring precipitation in and the mountains will receive considerable snow. The latest run of the best local model produces a strong low that moves in later in the day...giving strong winds to the coast and southern Puget Sound and no general snowstorm. Just rain. The only wrinkle would be the chance of snow in a Puget Sound convergence zone that night and Saturday morning. We are going to have to wait at least until tomorrow to make a skillful forecast for this transition.
Finally, let me say that snow prediction is the most difficult type of prediction in the region. It is hard to snow here and the flow configuration has to be just right. Furthermore, the large scale atmosphere is going through a large reconfiguration...and skill is lessened during such periods. But that is why forecasting is fun!

5 comments:

Matt said...

Regarding snow in this area... it seems that we used to get a lot more snow. You see photos from the early 20th century of massive amounts of snow in downtown.

Did we really receive that much more snow, or does it just seem that way?

Cliff Mass Weather Blog said...

In fact there was much more snow during the 50s through mid 70s. And another period of enhanced snow was at the end of the 19th century/beginning of the 20th. These changes are probably not associated with any human induced global warming.

EA said...

It was great to hear you this morning on KZOK - usually I only hear you on KUOW, but it was a nice change of pace & Bob Rivers & his crew are always informative, funny & interesting.

Saw your book @ Costco the other day - that's the definitive sign that "you've made it"! Congrats. A wonderful read.

I put the winter tires on the car this morning - thanks for the heads-up.

Cliff Mass Weather Blog said...

EA..thanks...never thought that the book would reach Costco...the true mark of success. Again..no guarantee of snow...but colder air is heading this way!

Keeping one's head above water said...

My mom has a photo album full of pictures of me up until 1976 with yardfulls of snow. But even in the 80's we had some really good snow storms.