A very active pattern (!) to continue across CA for forseeable future

Filed in Uncategorized by on February 10, 2009 106 Comments

Well–what a difference a week makes. After a seemingly unbroken winter of boring weather patterns and unending dry spells (after two consecutive winters of rather staid weather regimes), we’ve managed to have severe thunderstorms, a tornado, flash flooding, and sea-level snow in the past 72 hours. Not all parts of the state have been “blessed” by these dramatic weather events; SoCal has received the vast majority of the significant weather (and even the precipitation) since the beginning of the new year. This will begin to change this week, however, as the entire state stands to see quite a bit of precipitation over the next 7-10 days. I’ll start at the beginning…

Short-term: Wednesday-Friday

A cold low will drop down into NorCal from the north tomorrow, weakening as it moves inland over the Central Valley. A cold convective regime will follow the initially weak cold front, and there could be a few isolated thunderstorms with small hail mixed in. Snow levels will be low–as low as 1000 feet in interior valleys in the north and around 2500 feet in the Bay Area. The Sierra foothills will see local snow to 1500 feet.¬† There will be a brief break statewide on Thursday, though there may still be some scattered showers near higher terrain. Friday will feature a stronger and colder low moving just offshore of CA. The initial cold front with this system will likely be stronger–potentially containing gusty winds and brief downpours. More substantial convective activity could follow this front on Friday as the low moves almost directly overhead and instability increases. Snow levels will be even lower with this system–less than 1000 feet in the far north, between 1000 and 2000 feet in the Bay Area, and near 1000 feet or less in the Sierra foothills. It would not surprise me a great deal if we see some reports of snow at even lower elevations—potentially even near the coast–especially in the north, particularly if we can get partial nighttime¬† clearing with resultant radiational cooling.

Long-term: Saturday through Tuesday

The pattern may get even more interesting as we head into the holiday weekend. Two significant storms–both of which will likely impact NorCal but the first potentially hitting SoCal harder–will occur between Saturday and Tuesday of next week. Details are still too vague, and small changes in track will account for large differences in experienced conditions. As currently progged, however,¬† both storms have the potential to bring heavy rainfall, strong winds, thunderstorms, and even low snow levels. More updates will be forthcoming in the week ahead. We may be well on our way to reducing the seasonal defecit–though it’s too early to start talking about mitigating the multi-seasonal defecit…