August 26, 2021

A Pacific Cold Front Moves Through, With Near-Perfect Weather Ahead

It feels like fall like now, as a Pacific cold front moves through the region.  

The winds have started to gust, temperatures have fallen into the mid to low 60s, and leaves are blowing around outside.

The front was apparent in the forecast this morning, as an area of lower pressure and a sharp wind shift (see surface map for 8 AM).  I have indicated the front with a blue line.


And as it passed through this afternoon, there was a band of light rain, clouds increased, and the winds strengthened.   Here is the radar around 1 PM..you can see the rain.


And by 5 PM, the front had reached the Cascades, with increased westerly winds behind it.  

Winds that wrapped around the Olympics and converged over Puget Sound, producing a Puget Sound convergence zone (see surface weather map at 7 PM).  Northwesterly flow north of Seattle, southwesterly flow to the south.


The air converging a low levels forces air to rise, producing clouds and precipitation, something you can see in the latest radar imagery.  Gentle to moderate rain is falling now in the north Sound.


I rode my bicycle down to Magnuson Park and took this picture around 7:30 PM looking northward.  The ominous clouds of the convergence zone were evident.  Look closely and you can see rain falling.


As our region has cooled, wildfires have declined.  And with onshore flow, air quality at the surface is generally good, except for downstream of the remaining fires (like the Schneider springs)

HRRR surface smoke forecast for 8 PM Thursday.

If you are worried about heatwaves and smoke, the forecast is very favorable.    A ridge of high pressure will build again over the weekend and temperatures will be nearly perfect...mid-70s.

And then a trough will build over the region on Monday and Tuesday, bringing temperatures only reaching the upper 60s (see upper-level map for Tuesday morning)


So a summer that started much warmer than normal, has a much cooler than normal ending.  Yin and Yang of the meteorological world.




5 comments:

  1. How unusual is it too get these cool troughs in late august and could this be the set up for a active fall/winter?,in 2013 it was active late august and in September then pretty boring afterwords.

    ReplyDelete
  2. To add cool weather symmetry to this hot, dry summer, we’d need a few days with highs around 40 and lows around 25, and a bunch of days with highs in the low 60s and lows in the 40s. Instead, we’re getting normal late summer weather.

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  3. Sure *seems* like we've been getting a lot of rain/drizzle forecast which isn't realized, (think i could count the raindrops before it stopped last evening). Probably my own hopeful misplaced anticipation when one sees rain in the forecast -sigh-

    ReplyDelete
  4. Thank you for this wonderful public service you provide! I appreciate very much your thorough and thoughtful explanations of weather phenomena,

    ReplyDelete

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