Brief but rather intense heat wave for California; dramatic pattern change in the works

The weather has become notably more interesting over the past week across the state of California. A significant (albeit brief) heat event is unfolding across the state and is expected to peak on Tuesday into Wednesday. Inland areas will see temperatures well above 100 degrees, with 90s even relatively close to the coast, and some hotter Central Valley and Southern California locations will see 110 degree heat. Thursday will see moderate cooling across most of the state, but a much more dramatic drop in temperatures will be experienced going into the weekend.

Source: NCEP

A highly anomalous deep trough will dig sharply down off the West Coast, trying to pinch off into a cutoff low according to some recent model runs.  A deep low of this magnitude just north of California in August is not unprecedented, but is is highly unusual. The most obvious implications would be a continued drop in temperatures through early next week, perhaps to as much as 10-20 degrees below seasonal normals (perhaps in the lower 70s inland and even cooler near the coast). Also worth considering is the possibility of precipitation, especially since the GFS is now explicitly showing some precip over NorCal associated with the low. Given the time of year (still a high sun angle with warm-ish surface temperatures) and the projected depth of the low (relatively quite cold temperatures aloft for August), combined with the overwater trajectory of the low (increased moisture), some showers or thunderstorms would be a good bet if the pattern evolves as currently depicted.  There’s a bit of time between now and then, and a heat wave to get through first. This will certainly be interesting to watch evolve, however, and the long range ECMWF and GFS both indicate an increasingly active and amplified flow pattern over western North America over the next 1-2 weeks. Will we have an early fall this year? Stay tuned…


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