After some overnight and morning cloudiness, the skies should clear off as Saturday progresses, and we will be looking at a mostly sunny Super Bowl weekend. Temperatures will also warm up into the low 50s through Sunday, and steadily climb into the low 60s by Tuesday or Wednesday. Even though a few clouds come back into the forecast picture mid-week, it looks to stay dry for the foreseeable future.

Leeside

So why is this area so tough to forecast? Let’s go back to the topography that I mentioned yesterday. Those same topographic forces that can produce air movement upward (wind flowing up the windward side of the mountains, creating rain and snow) are reversed when the air is flowing down our (the leeward) side of the mountains. Air forced downward is warmed and “un-saturated”, suppressing precipitation. It doesn’t really lose moisture, but warmer air will evaporate clouds, and without clouds, you don’t get precipitation.

Rain shadow

When you have dynamics that are producing precipitation on the other side of the mountains, it is tough to know whether the suppressing effect of leeward (downward) flow will stop the precipitation or not. So I have to decide if the rain in Sacramento will hold together all the way over here, or if it will disappear on the way down the mountains.

It’s a classic description of the “rain shadow” that you might have heard me whine about from time to time. It’s been the source of a lot of embarrassment in the past.

And I’m sure it will continue to do so in the future.

 

 

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