March 24, 2010

A warm day and then rain

Today was very warm around western Washington, with some stations (like Sea Tac) breaking their all-time daily record. Now let me make one thing clear...breaking a daily record is not that unusual. We break a few of them every year for highs or lows. Breaking monthly or all-time records like last summer's 103F...THAT is impressive.

Here is a map showing the temperatures at 3 PM..near the time of highest temperatures (note: you can click on it to expand). You will note that some of the warmest temperatures (70-72F) are on the east side of the Puget Sound basin away from the water. You will also note some easterly flow.
Today was a good set up for warmth. First, we had only limited high clouds and sun is fairly strong now--the same sun as mid September. Second, we had an approaching trough that brought southerly flow and relatively warm lower-atmosphere temperatures into the region. To see this, take a look at the temperatures and winds at around 5000 ft for 10 AM Wed morning, shown below. The solid lines are the heights of the 850 mb pressure surface...think of it as like pressure, with the winds roughly parallel to the height lines. You can see the southerly winds bring warmer air (reddish colors) into our region. You will also notice the easterly and southeasterly flow over the Cascades. Easterly flow adds to the warming because air warms as it sinks and is compressed. That is why the warmest temps are over the Cascade foothills and the east side of the Sound.

But the warmth is over now. As seen in the satellite image below, a front is now entering the region and tomorrow will only reach the mid-fifties and there will be light rain. And we stay in a cooler, wetter pattern for a while, which will include some needed snow in the mountains.


  1. Next week's forecasts by the media seem to indicate breezy to windy conditions for Tuesday in particular.

    While I realize it's WAY too soon to be very accurate, anyone have any thoughts on this? Are we lining up another windstorm?

  2. Cliff—this afternoon I saw some clouds I don't really see often. Looked like jellyfish, or a solid small cloud with a whispy curvy tail headed down. Can you explain what those were?

  3. Why do the winds flow along the contour lines? Seems like they ought to flow across the lines, from high to low pressure.

  4. Is the low center in this pic...

    ...going to miss us?

  5. islandmeadowfarm...I did see some cirrus with fallstreaks yesterday...that is probably what you saw.

    Franz...your question is a good one...the reason is that this is the effect of the rotation of the earth. It is called geostrophic balance....cliff mass

    and Joseph...I don't see any low centers approaching us. The one you note is way, way offshore..cliff

  6. Yeah Cliff, it is why you are the professor, and I am but the student :)

    A deep low, spawned another deep low, but everything turned north and went just south of Alaska.

    They must have terrible weather up th...I mean "interesting" weather up there.

  7. The low way offshore seems to be strong enough to render this:

    From the Weather Center
    Special Weather Statement

    ... A vigorous Pacific frontal system will bring heavy precipitation
    and windy conditions to western Washington as it moves through
    the area Sunday night and Monday...

    A frontal system well offshore this afternoon will strengthen
    before moving through the Pacific northwest Sunday night and
    Monday. This system will follow closely on the heels of a weaker
    front moving through tonight and Sunday.

    The front will bring windy conditions to western Washington...
    especially along the coast Sunday night where sustained winds of
    40 mph and gusts to 60 mph are possible. The National Weather
    Service has posted a high wind watch along the coast for Sunday

    Sustained winds could reach 35 mph over some parts of the western
    Washington interior lowlands Sunday night... especially in the San
    Juan Islands... western Whatcom County... and Whidbey Island. A Wind
    Advisory may be needed for these areas. It will also be windy in
    the Puget Sound area Sunday night... and a Wind Advisory is
    possible there as well.

    The storm will bring significant precipitation to western
    Washington Sunday night and Monday. The heaviest precipitation amounts
    will occur over the south slopes of the Olympic Mountains... where
    local rainfall amounts will likely exceed 4 inches. This could
    drive the Skokomish River above flood stage Monday or Monday night...
    and the National Weather Service has issued a Flood Watch for
    Mason County.

    Another concern will be snowfall at higher elevations in the
    Olympics and Cascade mountains. The snow level will be around 4000
    feet Sunday night and gradually fall to around 2500 feet Monday
    night. Precipitation will fall as snow throughout the event at
    places like Hurricane Ridge... Mount Baker Highway... and Paradise
    at Mount Rainier. Snowfall totals of 1 to 2 feet are likely at
    these spots during the 36 hour period Sunday night through Monday
    night. Precipitation could start as rain over Snoqualmie and
    Stevens Pass but will eventually turn to snow. Winter weather
    advisories... or possibly warnings... for heavy snow could be


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