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West_Sat_Rad_Large_Pac

The weather picture will stay mildly warm and slightly unsettled for the next week or so. Friday should give us some clouds with an approaching cold front, but most of the showers from that front will likely stay to the north. Another wave of moisture comes up from the south late on Saturday, bringing a better chance of showers to the Reno area. A few scattered showers Sunday will lead to a dry Monday, then a series of stronger storms bring a better chance of valley rain and mountain snow starting late Tuesday and going through the middle of the week.

rain-shadow-effect

When you are talking about a rain shadow, many people mistakenly think that the Sierra “block” or “stop” the moisture from getting over the mountains. That’s not really how it works. Just as lifting air causes condensation/clouds/precipitation, descending air heats up, which evaporates the clouds and suppresses precipitation. As the air flows up the west side of the mountains, it increases rain and snow, but as it flows down the back side into western Nevada, it heats up and kills the precipitation producing process, unless some other lifting process is strong enough to overcome the backside drop. So the mountains don’t block the moisture… it just turns back into vapor and stays in the air, bypassing us until it gets lifted by some other process further to the east.

rain shadow 1

 

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