Tuesday, March 24, 2015

The Most Unusual Weather This Winter. Normal Weather.

Light rain and a chill in the air.  Some snow accumulation in the mountains.  Towering cumulus clouds and showers.  It seems so strange.  Normal weather.

Here is a plot of the temperatures at Sea-Tac Airport for the past 12 weeks, with the normal high (red) and low (blue) temperatures shown.
During the last few days our average high and lows were near normal. Amazing.

The freezing level dropped below 3000 feet today and the  snow level dipped to around 1500 feet for a short time.   Imagine that.  Paradise, on Mount Rainier, received over half a foot before it warmed a bit.  Here is a shot there near sunset today.

The NW Avalanche Center even has a high avalanche danger out for tomorrow.   First one this year?
The NW Avalanche folks have had plenty of time to repair instruments and complete advanced training this year.

And take a look at the 500 hPa weather map for this morning.  A trough of low pressure over our region.  Haven't seen that in a while.

But don't worry, the ridge from hell (actually from the tropics) is coming back with a vengeance.

A strong WARM front is right offshore and will move in tonight.  To illustrate this, here is the forecast for 11 PM tonight of sea level pressure (solid lines), surface winds, and low-level temperatures.  Look along the coast.  You see the shift from SE to SW winds, a kink in the pressure lines, and a transition from cold (green) to warmer (yellow) temperatures...that is the warm front.

As the warm front passes, our region will be flooded by moisture, warm air and strong SW winds that will dump lots of precipitation tomorrow (Wednesday).  Here is the precipitation total for the 24h period ending 5 PM Wednesday.  Several inches of rain in the mountains on top of the snow today...that is why the NW Avalanche Center folks are worried.
Then...ready for warmth?  A big ridge develops over us on Thursday and we bake, with lowland temperatures near 70F that day.  Remember!  The sun is much stronger now.   As strong as mid-September.  Remember your sunglasses and sunscreen...you will need them.


Bruce Kay said...

It seems a normal spring pattern, but the current avalanche hazard is actually an indication of abnormality, by two things.

1) the drought and high FL generated widespread surface crusts that has prevailed most of the season.

2) another bout of unseasonably high FL for the forecast. High even under the prevailing zonalflow and higher yet with the upcoming SW flow.

The CB's and spring showers are typical but the warmth is not, no matter which sector it comes from. If you ask me anyway. Your thoughts?

measuredmass said...

It's not the first 'High' danger rating this year from NWAC, but they sure have been rare.

January 18, 2015: http://www.nwac.us/avalanche-forecast/avalanche-region-forecast/1085/

Lucie Khadduri said...

For several hours today there has been a very distinct rain shadow from Olympia to Tacoma. I don't recall this happening very often, especially when winds don't appear to be from the NW.

Brian Blackmore said...

Thank you for unabashedly referring to the perpetual-motion, heat-generating, winter-ruining dynamo by a rather accurate name: "The Ridge From Hell".

Unknown said...

Somewhat related: Lee Grenci has an interesting post up about snowmelt due to rainfall, and how it doesn't happen quite the way most people think.


Papa Zu said...

Sorry slightly OT but I thought Cliff would be interested in new study supporting Cliff's evaluation of Jennifer Francis's research on Jet Stream wobble and colder winters.

'Climate Change Is Not Causing Extreme Winters'


P.S. If Cliff is ever interested in submitting article to Science 2.0 contact Hank Campbell to discuss.