That might help increase the likelihood of downpours and possibly some isolated thunderstorms despite the relatively modest atmospheric river conditions most likely to be associated with next week’s system(s). Additionally, there are some early indications that there may be at least a modest amount of atmospheric instability associated with next week’s systems (possibly enhanced by unusually warm near-shore ocean temperatures along nearly the entire CA coast at present) and possibly some subtropical moisture in the mix as well. That’s generally favorable for the development of surface low pressure and storm strengthening, which is fairly unusual for this early in the season. In this case, though it’s not the atmospheric rivers themselves that will be responsible for the most significant weather: the favorable position of these low pressure systems will place California, at various points next week, under regions of divergent flow aloft thanks to multiple jet streaks moving overhead. The ECMWF ensemble is suggesting widespread precipitation throughout almost all of California over the next 10 days, with the possibility of unusually heavy early-season accumulations along the coast from around Santa Barbara northward as well as the Sacramento Valley and Sierra Nevada. At least one or two of these will be associated with (most likely) weak-to-moderate atmospheric rivers. This low pressure system will become “quasi-stationary” as it lingers offshore west of San Francisco for several days thanks to upstream blocking near the Aleutian Islands, allowing for the passage of both a primary and possibly multiple secondary cold/cool fronts over several days. By Monday, an unusually deep low pressure system will set up shop to the west of California and sit there for much of the following week–bringing multiple opportunities for (possibly significant) rain, wind, and mountain snow. Well, that relatively quiet weather pattern won’t last much longer in California.

Major early-season storm(s?) possible next week in California, especially north A slow-moving and unusually deep low pressure system will remain quasi-stationary just west of the CA coast by the middle of next week, potentially bringing multiple rounds of significant rain and wind from Monday through Friday. The one exception to this were portions of the northwestern interior of California, where dry lightning events did lead to significant fire activity for much of the summer (though it still paled in comparison to the scale and destructiveness of other events in recent memory). As predicted as early as mid spring, these conditions yielded greatly reduced vegetation aridity compared to recent extreme/record-breaking drought years–which reduced the likelihood of ignition in the first place, and (more importantly) minimized the level of fire intensity on those fires which did occur.

The real reason for this quiet fire season overall, though? The residual effects of a very wet winter and cool spring–combined with the unusual summer “top up” of soil and vegetation moisture across much of the state associated with Tropical Storm Hilary in August. Despite occasional modest precipitation in October, mainly in NorCal, most spots ended up near to below average in the (very) early season precipitation tally. While conditions were in fact significantly warmer than average over the past 30-60 days across much of the state, there were no individually extreme heatwaves (despite a few marginally record breaking days) and also no extreme wind events despite a few occasions of offshore flow. Although there several periods of elevated fire weather conditions, and while a couple of modest-sized fires in SoCal did occur (unfortunately burning several structures), September and October 2023 (and, as you’ll see below, almost certainly November 2023 as well) will be remembered for their notable lack of severe wildfire activity. ()Īs far as autumns go, 2023 has been mercifully calm from a weather and wildfire perspective across California.

Most of California was warmer than average, although northwestern California was mostly near or slightly below average. A pretty benign autumn weather pattern in CA (so far) Temperature departure from the longterm average across the Western U.S.

Meteorologist map california