Monday, March 8, 2010

SNOW!! And the Faucet is about to turn on....

As predicted, some snowflakes were flying today around the Puget Sound lowlands, with dozens of reports from southwest Washington to Bellingham. See the video of snow in Federal Way: http://www.youtube.com/watch?v=sdfKPEM78xM

Several people asked how it can snow when temperatures were about freezing--in some cases with temperatures this morning in the upper 30s and lower 40s. Although today was somewhat on the extreme end of warmth for snow, there are few things to keep in mind:

(1) It takes about 1000 ft of above-freezing temperatures to melt snowflakes and today there was a large change in temperature in that thousand feet!

(2) The melting and evaporation of snowflakes in convective showers can cause the freezing and snow levels to drop rapidly.

A weak convergence zone kept the snow showers going for much of the morning and early afternoon, but now it is over. For awhile.

With clear skies and cold air over us, it is going to be REALLY COLD tonight, with temperatures falling into the 20s away from the water. Protect your delicate plants.

But the next round of fun is approaching. As shown in the latest infrared satellite photo a Pacific front is heading eastward towards us.

Rain from this system should reach the lowlands around dinnertime tomorrow and move through over night. This will be followed by a break into Thursday when a much more potent and far wetter system will reach us. Take a look at the predicted 24-h rainfall ending Friday at 4 AM (black is 2.5-5 inches!):

and 24-h later:


This is serious rain for the Olympics and north Cascades. Seattle City Light should be getting substantial precipitation behind their Ross Lake dam...perhaps they will be able secure lots of $ from California after all! The mountains will be getting substantial snow later this week, and there are more wet weather systems after that.

4 comments:

Jim said...

The roads are icing and fog is forming on some of the hills. Temp @ sea level on Vaughn Bay is 33 deg. F. The decks and roofs and sidewalks still have unmelted snow, so tomorrow morning looks to be a slick one.

The autobody shops and the hydro utilities will be happy with this forecast!

Broadview Missus said...

I'm not terribly surprised by the cool weather with a snowflake or two--March and April here in the Pacific NW have been known to host a very occasional snow shower.

But, I will be bummed if a cold snap does in the early tulips.So many this year!

epjmcginley said...

not sure how i lived without you cliff.

Daniel Kirkdorffer said...

Hmmmm... this is one forecast that doesn't seemed to have panned out. It has been pretty dry in Seattle the past couple of days? Olympic rain shadow effect at play here?