When is it foggy at the field? - RC Groups
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Nov 15, 2014, 11:49 AM
Team Hello Kitty
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When is it foggy at the field?

Now that the foggy season is back for the Sacramento Valley newer members may want to know when conditions are clear at our Davis field before driving out. Here are a few tools to help:

UC Davis airstrip conditions - This site is 5.7mi NW of the SVSS field and gives wind and visibility data updated every 20 minutes. It can be a good indicator of visibility conditions at our field but, and this is a big BUT, not always. In the last 5 years I have had a handful of days where the airstrip says clear but it's still socked in at our field.

I-80 at Chiles Road Caltrans webcam - This traffic cam is 5.4mi NE of our field and gives a good shot to the West (as of the date of this post) at the Western end of the Yolo Causeway. The SVSS field would be off the left edge of the camera view.

Here's how I use the above: if the Davis airstrip shows clear AND the Chiles Road webcam looks no more than a little hazy then I head off to the field. If the Davis airstrip shows clear but the webcam looks foggy I don't go.

Ultimately the best indicator of clear field conditions is when someone at the field sends an email to our Yahoo club list. Next best is getting an email from Jonathan Heritage who lives in Davis and has found strong correlation between fog conditions at his place and on our field.

Any other tools?

Last edited by SoaringDude; Nov 16, 2014 at 12:57 PM. Reason: Added note about Jonathan Heritage
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Nov 21, 2014, 11:13 AM
Team Hello Kitty
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How to read Davis airstrip "Clouds" codes

This AM is a good example of foggy conditions (see attached screenshots) per the Davis airstrip and I-80 camera. If you're new to the Davis airstrip web page you may not know how to interpret the Clouds data. The codes used are directly extracted from the raw METAR weather data feed that is being displayed. Here's what they mean:

CLR -- "Clear" = no clouds below 12,000 ft
FEW -- "Few" = 1/8 to 1/4 cloud coverage
SCT -- "Scattered" =1/4 to 1/2 cloud coverage
BKN -- "Broken" = 5/8 to 7/8 cloud coverage
OVC -- "Overcast" = full cloud coverage

The number next to the cloud coverage code indicates the elevation in hundreds of feet. e.g. 100 is 10,000 feet, 010 is 1000 feet, 005 is 500 feet.

So the conditions in this AM's weather data shows:
  • at 4:30am: clear (CLR) with 5mi visibility
  • at 5:55am: overcast at 200 feet (OVC002 i.e. fog) with visibility of 4mi
  • at 7:15am : broken at 300 feet (BKN003, i.e. a broken 7/8 fog layer) with broken clouds at 10,000 feet (BKN100) and visibility of 5mi
  • at 7:35am: overcast at 100 feet (OVC001, i.e. very low full fog layer) with 1/2mi visibility

In other words, no flying at our Davis field until later.

Last edited by SoaringDude; Nov 21, 2014 at 11:26 AM.

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