Saturday, March 6, 2010

The Big Wet Chill

Well, we were all getting a little smug about this spring.

Day after day of warmer than normal temperatures, bulbs and trees blooming roughly a month early, and drier than normal conditions. El Nino winter was here and Seattle City Light and others worry about the low snowpack and lack of water for power generation. Summer had to be just around the corner.

Not so fast! Mother nature has other ideas...a big, wet chill is approaching and some of you, particularly those at higher elevations, may even see snow showers.

Lets review where we are. The following graphs show the temperature and precipitation conditions at Sea Tac Airport, with comparisons to normal conditions, for the past 4 weeks. You will notice that for nearly every day temperature was above normal (Saturday got to 59F, normal is 51) and rarely have nighttime lows fallen to the average values. Observed precipitation (red) is roughly two inches below normal.

The reason for our benign situation? The jet stream has been splitting with most of the action going south of us. Classic El Nino configuration...and this has been an El Nino year. Not global warming.

But this delightful situation is all going to change in a major way.

Sunday a weak front will approach and you can see it clearly on the latest satellite image.We will progressively cloud up during the day, with showers later in the afternoon and and tomorrow evening over the interior lowlands. Behind the front is MUCH colder air (see graphic of low level temperature--blue is cold--and sea level pressure). Thus, the snow level will plummet and by tomorrow evening it will be all snow in the mountains. There is the possibility of a weak Puget Sound convergence zone tomorrow night and Monday AM, bringing showers and perhaps a few snow showers to the lowlands. Monday and Tuesday will have showers before the next frontal system comes in late Tuesday. Temperatures rise with that Tuesday front and fall in its aftermath. The models even show some snow showers reaching the surface in a few locations on Wednesday (see graphic)...but I wouldn't bet on that now. Later in the week we get into a warmer, wetter pattern with southwest flow aiming at our region (see flow at midlevels below, winds are parallel to the lines).

What we do have now is a much stronger sun, so even with cold air over us, our maximum temperatures will be able to reach the forties. Remember, our sun now is equivalent to that of late September!

Let me note that what is happening is not that unusual
. A number of El Nino years have had warm and relatively dry late winters, only to be followed by a cool, wet spring that saves us. That is why it never pays to panic about water supply in March. But it is of course prudent now for dam operators to save all the water they can--little risk of floods at this point.


Bottom line: cool and wet week. January in March. Protect your delicate plants. Skiing will improve by mid-week. And perhaps Seattle City Light will get enough water to stop the threatened rate increase.

28 comments:

Avalanche said...

Yeah, what's that weird purple line on that 925 mb map!

With the sun slowly getting stronger now, snow levels and temperatures become more diurnal so that map might be over doing cool temps. for daytime hrs.

Because of that, really suprised not to see showers with 500mb cool pool at -36 Mon. afternoon.

Richard said...

Cliff, have you noticed this pattern before? It seems like there have been a number of recent years like this: where mild and even dry weather, starting (after big fall storms) anywhere from mid-december to mid-january, turns to chill and damp around mid- to late march. As a skier, I think I have noticed several of the past few years where lousy conditions through the main part of the season turned around to great conditions just after everyone gave up and started biking and playing tennis.

natchrl8r said...

Not surprised. While I am not cynical and appreciate every warm sunny day in winter, I tell my friends not to get suckered. Plant peas and potatoes. Hold off on most other vegies awhile. Spring-like conditions in February are typical, so are winter-like storms in April, 80 degree May days, 50's in June...

Variety is the spice of life and typical Pacific Northwet!

Chris and Amy's story said...

I'm glad I enjoyed the sunshine yesterday while it lasted!

Soupman said...

Cliff,
With this upcoming week of cooler and wetter weather, it's interesting that the 6-10 day and 8-14 day outlooks last week never showed a "B-A" as far as temps and precip. were concerned. Presume something changed that wasn't anticipated?

Must read blogs said...

well all the women who are due or really close to their due date will probably feel the effects of this low coming in.

Thomas said...

Cliff, why is a split jet stream associated with an El Nino condition?
Tom

Kevin said...

As someone who spends every spring from March to June out in the weather on a daily basis, I can tell you this: all the wailing and gnashing of teeth about low snowpacks and droughts needs to stop until the end of April. As a high school spring sports coach of 23 years, I typically spend at least three whole weeks from March through April getting absolutely dumped on, with the days in between being still relatively cold and rainy. The mountains are NOT done getting their snowpack until this period is over. This diabolical pattern often denies me the best skiing of the year right when I have no time to go. RATS!

Richard said...

Does this indicate that the El Nino pattern is ending?

Lance said...

rain mixing with snow at midnight on cougar mountain at 1000'

Mark said...

We planted the peas 2 weekends ago and already have our first sprout. Thanks El Nino!

Kenna Wickman said...

I just noticed snow flurries while in Kingston. Its 41F at ground level but it must be much colder at cloud level. Tiny crystals - but definitely snow, not hail or grappel.

Casey Burns

Bill Reiswig said...

Cliff...

"The reason for our benign situation? The jet stream has been splitting with most of the action going south of us. Classic El Nino configuration...and this has been an El Nino year. Not global warming."

I don't think anyone is in denial that this weather pattern is a El Nino event. Is it not the case however that the record warm temperatures this winter result from a (moderate) El Nino plus a wamed ocean/climate change? I don't certainly deny that an El Nino is in place, but it seems that you overstep the certainty that some component of the warming is not due to climate change.

Right here is the NASA data for January 2010... globally the 2nd warmest January ever:

http://data.giss.nasa.gov/gistemp/graphs/2010vs2005+1998.pdf

Is it not more technically accurate to say that the majority of the warm winter here in the PNW is due to an El Nino year, but that this climate event is embedded in an overall warming atmosphere and ocean?

Bill Reiswig said...

Oh, and thanks sooooo much to ma nature for the cooler weather. I have some powder snow backcountry skiing I still have to attend to!

Corie said...

Snowing hard in Spanaway right now,,,but its 39 degrees and not sticking..just falling enough to distract my students!

Kevin Purcell said...

Just sitting here at the computer on Capitol Hill and there are very small snow flakes falling outside. Weird!

Certainly light precip but it's mostly not liquid phase :-)

JP said...

In Shoreline I just saw a very brief very light sprinkling of very small snowflakes!

Tisane said...

Snowing delicately at Greenlake at 10:08am Monday March 8.

MP said...

Snowing up here in Bellingham too. It's funny snow, looks more like frozen rain than typical flakes but it is sticking a little bit.

mary said...

Two weeks ago, an old man in the woods warned me that there would be a cold snap before summer set in. The gravity of his prediction made me want to believe him, and look, it came true!

How did he know?

Patrick said...

A few very small flakes on the UW campus, mixed in with bits of sunshine.

Eric Eitreim said...

Light snow flurry in the Seward Park neighborhood. We are straight West of the Park entrance up the hill at about 250 feet.

Jay said...

OMG! It's Arctic Blast 2010...news at 11!

mainstreeter said...

Hail or Grauple in Olympia at 14:40. Sky is really dark

Avalanche said...

Well a couple days ago I was trying to figure out why there wouldn't be more showers with such cold air overhead, but i guess the other half of the equation would be more moisture to work with.

Jim said...

Snow showers at Sea Level on South Salish Sea. Really interesting coloring with plum and cherry tree blooms over the blooming bulbs. 37 deg. F @ 3 PM.

natchrl8r said...

Hmmph. I've been hearing this snow business, even from compatriots in Bellingham, but from my vantage there were brief morning clouds, Sunny and dry all day. No complaints. :)

Devon said...

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