A rather small but potentially significant trough has pinched off into a cutoff low near the far NorCal coast this afternoon. This cutoff low will slide south along the CA coast today, bringing marginally unstable conditions and the potential for some scatted showers and isolated thunderstorms virtually statewide over the next 24 hours. Snow levels may briefly drop below 4000 feet in the Coastal Mountains. This system will likely be out of the picture by Sunday. It is interesting to note how quickly this system appeared–nothing of the sort was progged for Friday and Saturday even 48 hours ago…
Calm weather will return to the state for Sunday and Monday. Thereafter, there is a very wide spread among the models as to the evolution of the flow pattern over the Eastern Pacific Ocean. An extremely complex series of events are ongoing–including a once-again strengthening and eastward-propagating MJO signal, the ingestion of Supertyphoon Nida into the westerlies over the next 48 hours, and the ongoing evolution of El Nino are making a clear picture beyond about day 4 very hard to come by. Given that all three of these conditions increase the chances of an active pattern in CA, I do expect the pattern to become more active (perhaps dramatically so) within the 1-2 week period. There is a significant chance, however, that this is going to occur much sooner–perhaps by Wednesday of this upcoming week. The Westerlies are likely to break through the mean ridge over the E. Pac. at some point in the near future, bringing the subtropical jet into CA. Some runs of the GFS have brought copious rainfall to all of California; some have been nearly dry for the entire 16-day run. This is a symptom of the complexity of the current pattern, and the extraordinarily high level of uncertainty is likely to continue for some days, with a likely trend towards a wet pattern. Stay tuned, as this pattern already has the potential to be much more interesting than anything we saw all of last year…
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