Sunday, December 14, 2008

End of snow today but cold here to stay

The air over us is cold enough for snow everywhere in Western Washington and it will be getting considerable colder over the next day. Later yesterday, the weak disturbance from the north began circulating snow showers into our region and with sufficiently cold air in place finally, light snow occurred during the evening and morning hours. The reports I have seen indicate general amounts of 1-2 inches, but with heavier falls north of the city and to the east..particularly in places with some elevation. The National Weather Service did a good job of forecasting these amounts yesterday afternoon (they went 1-3 inches). Of course, the mountain passes have secured 1.5 to 2 feet during this event.

So what is happening now (7 AM)? Some moisture is still rotating around the offshore low (see radar), but most of the snow showers...and particularly the heavy stuff, is on the eastern side of the Sound and Strait of Georgia.
The reason is that strong easterly flow has developed aloft over the western slopes of the Cascades. To see that look at the observations above Seattle (image) and the surface wind plot (image). Remember the way winds are plotted..the pennant points in the direction the wind is blowing and and a big line mean 10 knots and and small one is 5 knots. Two big lines is 20 knots, etc. The downslope easterly flow works against precip, but as it rises on the eastern side of the Olympics and Vancouver Island, it enhances the snow.
Strong winds from the NE are now blowing into Bellingham. This air is not only cold, but dry. Strong easterly winds are also blowing in the Gorge at locations such as Troutdale.
Anyway, today the offshore disturbance will move south and the showers we lessen. As the low moves south of us, the really cold air will be drawn southward and skies will clear. Having some snow on the ground will promote cooling, since snow is very good in radiating heat to space. So today will not get much above freezing, but tonight will be much colder...dropping down near 20F in most of the region...and into the teens in colder spots. The cold air will be in all week, with some minor modifications. We are still watching a weak system on Wednesday. Perhaps some snow showers. The question is a major system approaching over the weekend...things could get very interesting...but too soon to talk about that.

7 comments:

natchrl8r said...

Everyone missed the mark on Bellingham again. Though it snowed 4-5 inches in places that is not acknowledged by any weather service. I still feel that our forecast is only a slight modification of the Seattle forecast and not specific to us. Is there any meteorologist currently blogging specifically for Bellingham and Whatcom County?

Anonymous said...

Cliff Mass - Got your book last night (B&N in Federal Way has some copies). I love weather! I came from Minnesota where we had lots of interesting weather - and here it is the same, yet different. This is the forst "cold snap" where I will actually have to wear a jacket. People - be carefule while walking and driving on ice! :)

Cliff Mass Weather Blog said...

natchrl8r
I don't know of any experienced local meteorologist blogging Bellingham. Remember the staff at the NWS office are stretched thin..they have to deal with the local weather for a large area..get pretty overwhelming when everything is happening at once...like for this event!..cliff mass

natchrl8r said...

I totally appreciate that there's only so much a few people can do. I was just hoping. I am no meteorologist but I am getting better at reading between the lines (of blogs, bulletins and forecast discussions) to make my own forecast. Looking for professional corroboration. : )

John said...

The question is a major system approaching over the weekend...things could get very interesting...but too soon to talk about that.

Thanks for leaving us hanging, Cliff. :P

I am hoping that the higher elevations gets more snow if that big system does indeed develop. We need more snow on Mount Baker and Stevens Pass.

Anonymous said...

14 reports from Whatcom county
recorded on the cocorahs.org
website averaged 1.9" of snowfall
overnight. Although the winter
weather advisory was not issued
until 937pm, that forecast for 1-3"
agreed with most of the spotter
reports that came in today. I would
also point out that the forecast
for Bellingham is probably not a
'slight modification' of the
Seattle forecast when there is
strong Fraser outflow. That part
of the forecast was certainly well anticipated by all forecasters (and
very well simulated by mesoscale
numerical models).

Anonymous said...

boy, with all this global warming, i'm freezing to death ...