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I'm using 1800wxbrief.com to get all the information necessary to brief myself on an upcoming flight.

I have noticed each time I've done this, that the Surface Analysis chart shows light / spotted rain where I can be nearly positive there is none. When cross checking this chart with sites like weather.com, it is confirmed through their weather products that there is no rain in the area.

Do these Surface Analysis charts sometimes show spotty false positives?

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    $\begingroup$ I believe this is an artifact around the actual radar receiver, usually you see this right around the radar itself. $\endgroup$ – Ron Beyer Sep 20 '16 at 19:08
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    $\begingroup$ @RonBeyer -- yes, NWS radar products (weather.gov) sometimes show clutter artifacts when the underlying NEXRAD system kicks into high gain (i.e. clear air) mode. $\endgroup$ – UnrecognizedFallingObject Sep 20 '16 at 22:20
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    $\begingroup$ Some of those will be flocks of birds. $\endgroup$ – Michael Hampton Sep 27 '16 at 3:03
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Fog and other low-altitude moisture often shows as very light precipitation radar returns. I look at the multi-image radar loops for an area, and if I see that I call a "sparkling" radar return in the looping image, it's a pretty good bet for ground fog. The California central valley area (around Modesto and Stockton) is known for its winter tule fog: watch the radar returns from that area in the wintertime.

You can correlate the radar observations with ground visibility observations (airport METARs, the regular and special airport weather observations, include visibility and ceiling—cloud height and coverage—information), along with satellite visible and infrared images to view cloud presence and cloud top heights. When the visible satellite shows clouds and the infrared satellite shows very low cloud tops, that's a good bet for fog or a low-level stratus layer: both have low cloud tops, typically 400'-1,000' above ground level.

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  • $\begingroup$ Thank you for the great answer @ammPilot, and welcome to the site. $\endgroup$ – Ryan Griffith Oct 7 '16 at 0:55

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