December 21, 2017 – Mainly dry weather through the weekend. Breezy northerly winds today. Potential for another weather system early next week.
Low pressure system that brought us precipitation yesterday has shifted into the Great Basin today. High pressure building over the Pacific has strengthened the pressure gradient, which is running about 5-6 mb between MFR and SAC. This will lead to some breezy north winds today. Dry weather expected with high temperatures running several degrees above normal as high pressure remains in control.
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Chilly overnights on tap too, coldest tonight into Friday morning as winds die off and clear skies allow for plenty of radiational cooling. Valley lows will likely drop off to around 30 degrees with teens in the mountains. A little milder readings are expected Friday and Saturday nights as some high clouds begin to spill into the area over the ridge. Model solutions show ridge flattening some on Sunday ahead of a system approaching the West Coast. Any precipitation will likely not reach the area until after Sunday night and, as is discussed in the extended discussion, model run to run consistency is low.
Extended discussion (Monday through Thursday)
Uncertainty continues in the forecast for Christmas Day. Model differences continue to be an issue, but overall looks like a system will pass through far Norcal. Will continue the potential for some light precipitation for Christmas Day, mainly over the northern and Coastal mountains. Uncertainty remains high, so will continue to watch trends to see if this potential increases and becomes more extensive. Drier weather is expected to return by mid week.