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Dec 19, 2008

Where Do We Go From Here?

Thursday night will be clearing and cold, with lows in 15-21 range. That means a hard freeze to all that is on the ground today.

Friday should be a lot like earlier this week -- sunny but
continued cold -- possibly a few degrees colder than this current spell
-- with highs 25-28 and lows Friday night from 10-18.

Saturday also looks dry and continued cold with highs in the
mid 20s. But clouds will increase Saturday night, keeping lows around

Those clouds are a signal of our next great forecasting
challenge -- a storm heading in for Sunday. This one presents a whole
new set of variables, because Mother Nature has a devious sense of
humor and a thick playbook, it seems.

This storm is coming in from the west/northwest, and it looks
pretty wet. Second, we'll not only have some arctic air here in Western
Washington, but even more in Eastern Washington. That air is very
dense, and thus has higher pressure.

As the low pressure of the storm approaches, forecasting models
are hinting now that we could see some very strong, gusty east winds in
the passes to the usual North Bend, Enumclaw, Gold Bar east-windy
places -- perhaps as high as 40-50 mph.

That's challenge A. Challenge B -- if so, that would be blowing
in a lot of cold air from Eastern Washington into Western Washington --
the "North Bend gets to feel like Bellingham does now for a while"
scenario, getting even more cold air into the region ahead of this

So when the storm arrives, in the areas outside the wind,
depending on how warm the storm is and how much cold air is around,
it'll likely start as heavy snow, then gradually change to rain.

But in areas where that east wind keeps feeding the cold air
in, this could present some freezing rain problems along the I-90
corridor. (Portland people can tell us all about this, since they have
frequent experience with a similar set up with the east wind blowing
out from the Columbia Gorge. In fact, this set up presents them with
similar freezing rain problems for their area.)

Bottom line: Sunday could be real messy. It might be lucky for
us if the system comes in cooler and it stays as snow because while
it'd be quite a bit of snow, ice/freezing rain would be worse. (About
all that's left is the blizzard and we'd have collected the entire set
of weather problems :) ) Highs will be somewhere between 31-38.

Some lingering snow showers Monday, then we dry out again for
the afternoon into Tuesday with partly to mostly sunny skies and highs
in the low-mid 30s and lows still in the 20s.

Another not-so-frigid system moves through on Christmas Eve,
but at this point, this is looking like the kicker of just snow to rain
and highs into the 40s, perhaps ending the cold spell. But a more
southerly track, and we could get that White Christmas after all :)