A fairly strong ridge of high pressure will keep us dry for the next several days, and temperatures that have been lagging behind seasonal averages will climb above the norm once we get into the weekend. A few clouds will pass over us Friday afternoon ahead of a weakening frontal band, but those should move out by the weekend leaving Saturday and Sunday mostly sunny. Highs Friday will be in the mid-40s and will climb into the 50s through Tuesday and may hit the 60s by mid-week.

Sierra

So why is it so challenging forecasting near mountains? In a nutshell, the mountains make it tough to forecast (at least on this side of the mountains) because they change the vertical motion of the air. In order to get rain and/or snow, air has to be forced upwards, either by topography (called orographic lift), or by dynamics in the atmosphere, such as a cold front, upper-level divergence, or lower level convergence (or a combination of any or all), just to name a few. The reason it has to do this is the air has to cool enough so that the water vapor it is will become saturated and condense into clouds. I’ve written other columns on why air moving upward gets colder, so I would just ask that you take my word on that for now. More tomorrow.

 

 

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