Dense Fog: Odd This Fourth Dimension Of The Year

This morning time brought fairly dense fog to portions of Seattle close Lake Washington together with inward some river valleys some the western side of the State.  The fog was beautifully illuminated this morning time some seven AM inward the sentiment looking northward from the Space Needle PanoCam

And the sentiment southeastward towards Mount Rainier was impressive equally well.

The fog was apparent is the visible satellite icon at seven AM, amongst some of the river valleys of SW Washington inward fog.

It  turns out the dense fog is relatively odd this fourth dimension of the twelvemonth inward Washington State.    I tin present this using the next graph from my NW Weather book. Here inward Seattle (red color) fog reaches the minimum break of days per twelvemonth from Apr through June.  Spring is a depression fourth dimension for fog inward most locations of our region.  Fall is the large fog season.

But why is Spring then bad for fog?  For several reasons.

First, most of our fog is radiations fog, which develops over long nights equally the public radiates infrared release energy to space.    Our nights are getting MUCH shorter now, then much less fourth dimension for the cooling to laissez passer on off (remember our day-night periods today are the same equally some August 23).

Second, fog likes stable weather condition that does non make a lot of vertical mixing.  Such mixing is bad for fog, since the cooling at the surface gets spread over also much air inward the vertical. Stable weather condition laissez passer on off when temperatures don't decrease chop-chop amongst height.  The contrary is truthful inward Spring...the Sun is fairly strong, causing the surface to warm, simply the air is withal cool aloft. Not stable together with bad for fog.

Third, inward jump some hither nosotros withal accept a lot of clouds together with clouds tiresome upward the radiational cooling from the surface. 

Fourth, pelting is to a greater extent than oftentimes than non letting upward inward Spring together with pelting helps moisten the surface together with lower atmosphere...which is adept for fog.

Why fog today?  We had lots of pelting of late then the lower atmosphere was moist.   And high pressure level moved inward belatedly yesterday, which helped brand the atmosphere to a greater extent than stable together with lessened the total of clouds aloft. 

Can our models forecast fog?   They can, simply at that topographic point science is non great.  Fog plays into close all our modeling weaknesses.   Here is the xiv hr forecast for depression clouds valid at seven AM from the UW WRF model.  Right idea, simply somewhat also much fog/low clouds some Puget Sound.

And forthwith the large news....a major warm upward volition laissez passer on off early on adjacent week, amongst highs getting into the upper 60s on Mon together with Tuesday.  And pretty decent the balance of the week.  More on the "big heat" inward my adjacent blog.