Extraordinary uncertainty abounds

California continues to bask under unseasonably warm and dry conditions this holiday weekend. I do expect another 48 hours of warm and dry weather before the prevailing pattern does begin to change on Wednesday. What is extraordinarily uncertain, however, is how this pattern change will manifest itself. The models–the GFS in particular–have been literally all over the map with solutions these past few days, and they continue to swing dramatically from run to run (yesterday alternately brought severe thunderstorms, widespread snow, or dry conditions to NorCal next weekend). The mean flow pattern does seem to be shifting–the persistent East Coast trough that has brought such extreme cold to the eastern half of the country will shift westward with time. The question though, is if this is enough to bring rain back to CA. Currently, a weak cut-off low is funneling some subtropical moisture into SoCal in the form of mid and high-level cloudiness. This may progress to some light showers by Wednesday, and perhaps some heavier downpours if a bit of convection can get going in the moist plume. NorCal, however, will be lucky to see a few hundreths out of this one. Most of SoCal will probably see under 0.25 inches, even then. In any case, the Sierra snowpack will be completely unaffected by this system. The second system–currently slated for next weekend–has the potential to bring more significant precipitation, esp. to NorCal. The problem is: none of the models seem ot be able to resolve what kind of system it will be–warm or cold, moist or dry, northerly or southerly. So…at this point…we’re just going to have to wait and see. One somewhat concerning note is that the GFS really isn’t bringing more realistic opportinities for rain in after this  weekend’s system, although it might be prudent to point out that the relaibility of the models beyond day 7, especially when a system on day 3 is still very much up in the air, is quite low. We really need the rain–and nothing on the horizon signals “drought buster” to me…


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