January 30, 2009

Dense Fog

There is dense fog around the Sound right now....that is generally a very good sign for day ahead. To get dense fog at low levels, one generally needs intense surface cooling...which generally requires clear or nearly clear skies aloft. You also need little mixing (otherwise you would have a thicker fog layer, which tends to be less thick at any one level). So in many areas, particularly away from the Sound, this fog should burn out during the next few hours.

There is a well-defined surface-based inversion over us right now (see graphic), with the cool, moist air only about 500-700 ft thick. Pilot reports at Sea Tac indicate the low clouds and fog top out at around 700ft.


  1. Good call, Cliff -- the sun is breaking through downtown, but at the same time, it seems clouds are increasing for tonight's system.

    Any thoughts on the arctic air outbreaks depicted in some of the long-range models, about 12 days from now? Fantasy land yet again?

  2. Never believe arctic air predictions more than 6 days out..usually never pan out...cliff

  3. Hey Cliff, any more info about tonight's possible CZ?

  4. Sorry to be a little off topic from your dense fog post, but I am very interested in the science of translating how incoming weather influences water wave conditions. It turns out wave conditions can be very nuanced, especially in regards to the Strait of Juan de Fuca. Cliff, do you tackle this topic in your book (future blog?) or can you recommend a good source/book that addresses this and is applicable to the NE Pacific? Thanks.

  5. We definitely had thick fog most of the morning here in Woodinville. I didn't/don't see any high wind predictions anywhere but I can tell you the greenbelt behind my house is scary at the moment.

  6. Yes, I was also a bit surprised about the high winds so far here in south Bellevue.

  7. Hey cool...I see we have another member on here from here in Woodinville. Nice.

    Like Ashely said... the fog was pretty dense morning and didn`t really go away till early this afternoon. Then skies became overcast and turning cloudy by late afternoon with some what breezy winds. My high today was 49 with low of 28.

    This front that came through sure was`nt much. Just a bunch high/mid level clouds eventually lowering stratus form type clouds. However, I see on radar that a fast moving band precip/ or CZ is currently pushing through here in Woodinville and that looks to be the only precip showing up right now.

    Maybe another CZ tomorrow morning? WRF-GFS12z from this morning shows a CZ over parts of North interior for the morning/ afternoon hours. Will see if happens.

  8. Hey Cliff...looking at the visible satellite loop from today, I do have to say that todays cold front sure had a nice edge to it, but fell apart when it moved inland and not really doing much other than having high-mid level clouds and then eventually a fast moving band of precip tonight.

  9. How is that a very good sign for the day ahead? It just means that the sky is too clear, and thus the bright blinding sun will soon be plaguing the area.


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