Cold and foggy Central Valley, dry and boring on the coast; possible change?

It has been uncomfortably cold and damp lately in the Sacramento Valley, with daily fog (often extremely dense Tule fog, which makes for extremely dangerous driving conditions). Overnight  temps have also been steadily decreasing and last night fell to around freezing in some locales. Tonight will probably be the coldest right for a while around here, with lows dropping to near freezing nearly everywhere and below 32 in some locations. This means that some local areas may see ice fog tomorrow and Sunday mornings, which would make driving conditions even more hazardous than they already would be. Fog and low clouds will persist into next week thoughwith moderating overnight temps (35-45 instead of 28-38). The rest of the state will experience extremely uneventful weather for thenext 7 or 8 days. This is where the models really begin to diverge. The GFS and the ECMWF both indicate that a slight shift westward of the blocking ridge will bring about an enormous change in sensible weather days 9-14, with a deep Gulf of Alaska trough carving out a slice of Arctic air over Western Canada and sending in wouth. This would bring periodic precipitation and much colder temperatures, possibly with low snow levels (below 2500 feet at times). The problem, of course, is that we’re only talking about a relatively small translational shift of a blocking pattern that is extremely well established and may very well have more tenacity than the models are currently anticipating. It is possible that this may turn into a more inside-slidery type event, with cold temps, wind, and little to no precipitation. If the current model progs are right, though, it will be wet and cold in time for Christmas. This will not be a drought-busting pattern by any means even if the most aggressive model solutions come to pass, as this system has cold origins and not much of a moisture tap. Most precip will be convective in nature or forced by regional scale dynamics (as opposed to a large cold front on the synoptic scale). I would be more confident in this forecast if the models were forecasting a breakdown of the block or an undercutting jet stream, and currently this does not appear likely. As always, though, this could change. Stay tuned.

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