Note: Forecasts will not be issued on Thursdays and Friday through 15 March. Potentially, there could of other days on occasion (my father undergoing cancer treatment)
A cool, northerly wind flow pattern continues over the West Coast. A passing, upper air disturbance helped trigger showers yesterday afternoon (in L.A. County, only eastern most section). Another disturbance is forecast to move through the Southland tomorrow. So, another round of mainly, light showers are expected by the afternoon hours tomorrow. I initially wrote in for "showers likely" in the campus forecast, but upon looking at various, computer model output, I back tracked to a "chance of showers". Some model solutions trigger showers mostly to the east and south of L.A. County (rain shadow effect farther west). Except for some mountain locales, the threat for showers should temporarily end in the evening hours (lingering evening showers probable for parts of the Inland Empire and south into San Diego County).
A new, cold, upper low pressure aloft should move through southern California on Thursday. Cold air instability should trigger additional showers that day although much of the activity should be around the mountains. If pockets of sunshine occur during the day, there is potential for isolated thunderstorms in the mid/late afternoon (ending sunset as atmospheric instability wanes). The aforementioned low pressure should be moving out of the Southland late Thursday evening (ending the threat of showers all areas, including the mountains).
All of the recent disturbances have had limited, available, water vapor (no input of sub-tropical air). The forthcoming disturbances will be equally challenged for available, water vapor. So, except for a few isolated, heavier showers and thunderstorms, rainfall in the lowlands this week shouldn't exceed a quarter inch (much less in many cases). Snow levels will continue unusually low this week (as has been the case recently). It's possible that on Thursday, the snow level could briefly fall below 2000 feet in spots, especially on north facing, mountain slopes. At resort level, up to a foot of new snow could fall this week.
Things are forecast to quiet down this weekend and next week in southern California. Another storm should bring some wet weather to portions of northern California this weekend, but most model solutions don't show that wet weather getting this far south. It's still not a clear, majority, model solution, but high pressure aloft may finally linger over the state for more than a couple days next week. Some model solutions even favor slightly warmer than normal weather toward the end of the month (lasting at least a couple of days). There are some model solutions showing a storm reaching the Southland around the third of March, but that's not written in stone.
UCLA Forecasts and analyses are written by James Murakami
– posted: 2019-02-19