Cold(est?)

Today was quite cold across all of CA and the western United States. Some early morning snow showers in the higher valleys east and north of Los Angeles brought up to 2 inches of snow down to near 1000 feet, which was quite a spectacle for some and an entirely different thing for those who had to commute to work in it. Low temperatures generally did not break any records last night, though a few daily records fell along the NorCal coast and in the SoCal valleys. Today’s “high” temps were quite low…here in San Rafael, the frozen puddles in the shade remained frozen all day. Tonight, however, will be a different story. Dewpoints are extremely low this evening–here in the San Rafael, the 7 PM dewpoint was 1 degree F and dropping with calm winds and a temperature of 39 degrees. This will actually be the driest air in quite some time–probably since that Arctic outbreak back in 1998, in fact. Not surprisingly, temperatures could fall to the frigid levels seen during that event in the north. In the south, temperatures may actually be a bit colder this time around–closer to the historic 1990 CA cold event. Needless to say, agricultural interests in the state are very concerned, as temps in the prime citrus-growing areas will likely drop well below freezing and possibly below 20. Other crops will be at risk, too, and the trees themselves may be damaged in some places, not just the fruit. Frozen or burst water pipes and sprinkler systems will also occur. The only impediment to achieving these low temps may be the gusty NEly wind that is still blowing in some places. This could induce mixing and prevent some windier locations from reaching their potential minimums tonight. We shall see, as it appears that these winds have eased in recent hours. Even though the coldest air aloft will be present tonight, tomorrow night could be even colder than tonight in some places as the winds will be lighter and the dewpoints even lower (though I’m not quite sure how much lower they can go). Subfreezing minimum temps will continue through the week in many areas. 

The long term is very discouraging. There is an overwhelming model consensus that a powerful high will remain over the central and eastern Pacific through at least the next 2 weeks, bringing mostly dry weather to the entire West Coast. A weak cutoff low could drift in under the ridge and produce a little rainfall, but the overriding theme for the forseeable future will be unseasonably dry weather, yet it will still remain on the cool side. This, given the very dry antecedent conditions in the south and the moderately dry conditions in the north, is rather concerning. January should be the wettest part of the year in CA, but so far this year many places have seen little or no rainfall, and this is not likely to change in the coming weeks. This means the not-so-distant prospect of drought may be looming, especially in SoCal where virtually no rainfall has occurred this rain year. Another consideration: it appears that the moderate El Nino has already begun to weaken. Unless another Kelvin wave comes along to reenergize the warm episode, I feel that the potential for El Nino to influence North American weather patterns may be waning. Ironically, the most El Nino-like pattern so far this year is currently occurring, with the persistent E. Pac. blocking pattern, albeit a little farther south than would be expected, and associated dry weather in British Columbia and the PacNW (though the cold, dry wx. in CA is rather atypical). In short: We’re going to be very cold for a while and very dry for a long while. Certainly a year for the temperature-related record books…