| Day | Date | High/Low | Forecast |
| Thu | 20th | 59/50 | Slight chance of morning showers; Rain developing in the afternoon, possibly heavy at times through early evening. Rain tapering to a chance of showers by late evening. |
| Fri | 21st | 61/51 | Chance of showers, mainly in the morning. Slight chance of showers in the evening. |
| Sat | 22nd | 67/52 | Partly cloudy morning; Mostly sunny afternoon. Mostly clear evening. |
| Sun | 23rd | 65/51 | Mostly sunny day with some high clouds. Some evening high clouds. |
| Mon | 24th | 64/50 | Mostly sunny day with some high clouds. Some evening high clouds. |
Synopsis
Despite an upper level low pressure remaining relatively close to L.A. County yesterday (recently departed storm), it turned out sunnier in many areas than I anticipated (didn’t affect my campus temperature forecast, luckily). Today, a new storm (third and last of a series) has started wet weather again in southern California. It’s a little disheveled in organization, but the computer models predict better, organized, storm dynamics later this afternoon and tonight. As the storm is accompanied by ample, water vapor, there should be areas of heavy to intense precipitation (radar already indicated a band over the eastern San Fernando Valley early this afternoon).
Though all the models show occasional, wet weather into tomorrow morning, they aren’t in total agreement on weather details (no surprise there). The current storm is expected to develop into another “cut-off” low pressure. Depending on just where the center circulation resides, areas of heavier precipitation may differ from the model consensus. Still, unless the low pressure moves slower than expected or stays farther off the coast, the bulk of wet weather should occur before tomorrow afternoon (at least in L.A. County). Steady rain in the lowlands may transition to on/off showers as early as sunset (already the case in Santa Barbara County). Areal coverage of showers should shift south of L.A. County by tomorrow evening (might begin by afternoon, if some model solutions are right).
Rainfall in the lowlands away from coastal facing mountains should between a third and one inch (similar to previous storm). Where thunderstorms form, storm totals up to two inches of rain may occur. Some model solutions show that the wettest region will be in the Inland Empire down into San Diego County (best storm dynamics predicted there). So, there is a chance the campus area won’t get as wet as with the previous storm. Snow levels with the current storm shouldn’t get below about 6000 feet (core of low pressure predicted to remain over water until landfall somewhere in northern Baja California). A few to several inches of snow, however, may accumulate at the local resorts.
Most of the Southland should dry out on Saturday. The except might be down in San Diego County and parts of the Inland Empire (depends on how quickly “cut-off” low pressure moves as well as its proximity to the aforementioned areas). Since most of the models show some off-shore flow, some modest daytime warming should occur in most areas (air flow more related to circulation around “cut-off” low pressure than more typical, high pressure related flow…should result in less than usual warm up). No return to seasonal normals, however, are expected through early next week.
Most models show moderately strong (for November) high pressure aloft by the middle of next week. A weak off-shore flow is also indicated. If this consensus holds up, warmer than normal weather should develop across most of the Southland (Wednesday-Thanksgiving Day). Widespread readings into the mid/upper 70s west of the mountains should occur. If deep layered, easterly wind flow develops (currently not favored by the models), it could warm into the low/mid-80s.
Cooler weather should develop by the latter half of the Thanksgiving holiday weekend. Other than that, the longer range models offer a wide range of weather scenarios. Because there’s been a lack of run to run consistency (includes the usually reliable, ECMWF model), I don’t have any confidence in any given solution. A period of occasional, wet weather may occur before month’s end (lasting several days into December). On the other hand, there are model solutions that include Santa Ana winds (a few offer strong winds) at the end of November/1st week December. Temperature range from below normal to above normal. Get out the weather forecast dart board.
Next issued forecast should be on Monday, 24 November (just one issuance next week due to Thanksgiving holiday).