Cool nights and mild days on repeat

December 7, 2017 – Dry weather this week with cool nights and mild days.

Discussion

Beginning to sound like a broken record, but high pressure will remain in control for the foreseeable future. Another cool night across the area, with the exception being across the northern Sac Valley. Northerly winds have kept temperatures up again tonight, with Redding and Red Bluff still in the 50s as of 2am. Have nudged temperatures up there as guidance is not handling this well with a continued cold bias. Patchy fog has developed in the southern Sac and San Joaquin Valleys overnight but visibilities are currently running at 4 miles or higher. Shouldn’t be widespread as we head toward daybreak but will watch trends.

Otherwise, daytime temperatures will be above normal with full days of sunshine. Cool nights as clear skies will allow for plenty of radiational cooling. Lows in the valley will generally be around the mid 30s so patchy frost will be possible.

Extended discussion (Monday through Thursday)

A strong ridge of high pressure centered over the West coast will keep the extended forecast dry with above normal afternoon highs and slightly below normal morning lows. Light northerly winds will limit dense fog development in the area, though some overnight mist and morning haze are possible at times.

Hints of a possible inside slider on Thursday by the 12z European model have faded with the latest run (00z), keeping that disturbance well east of the region. The next possibility of precipitation for NorCal by any of the extended models isn’t until late Friday, but only the latest European shows a weak system brushing through far Norcal. At this point, it looks more likely that at least a weakened form of the ridge will persist for the foreseeable future.

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