| Day | Date | High/Low | Forecast |
| Thu | 7th | 63/49 | Some clouds possible but otherwise, sunny morning. Becoming partly to mostly cloudy by late afternoon with a chance of a brief shower. Clearing in the evening. |
| Fri | 8th | 67/51 | Sunny day. Mostly clear evening. |
| Sat | 9th | 67/51 | Mostly sunny day with some high clouds. Some high clouds in the evening. |
| Sun | 10th | 65/52 | Variable high clouds but mostly sunny day. Partly cloudy evening. |
| Mon | 11th | 64/52 | Amended…Partly to mostly cloudy through the evening. |
Synopsis
The storm that brought wet weather to southern California yesterday was centered in Arizona this afternoon. It was a longer duration storm than I expected, and rainfall in a number of locales (West L.A., for instance) was more than I anticipated. The UCLA auto-gauge recorded 1.75 inch rainfall. The official hand measurement won’t be done till Saturday, but I suspect the campus storm total is more like 1.5″ (still twice as much as the high end range of what I expected). Other spots around West L.A. included 1.51 inches at the Bel Air Hotel, and 1.08 inches at the Santa Monica Airport. Culver City reported in with 0.69 inch. Other than favorable, low level winds (to enhance rain output in areas away from the mountains), I couldn’t see any obvious reason for a rainfall bullseye around the campus area.
Satellite imagery showed an upper air disturbance around San Luis Obispo County early this afternoon. It’s helped trigger showers along a portion of the west San Joaquin Valley. As the disturbance travels southward, it should further destabilize the atmosphere in the mountains of southern California (mostly “home grown” rain clouds rather than a line of precipitation originating close to the upper air disturbance). While the most relevant precipitation (includes brief-lived thunderstorms) should remain over and adjacent to the mountains (particularly from San Gabriel range eastward), I wouldn’t be surprised if upper levels winds carry some of the shower clouds south into the coastal plain late in the afternoon (reason for chance of late afternoon shower in the campus area). Once the disturbance passes through and daytime heating ceases, things should quiet down quickly (i.e. clearing skies).
The various, numerical models show high pressure aloft taking over tomorrow (weakening on Saturday as well as moving off to the east). A marginal, off-shore flow is predicted. Some gusty winds in Santa Ana wind prone areas are probable for a time tomorrow, but significant wind (25 mph or higher) should be mostly confined to higher elevations (isolated, peak wind gusts could reach 50 mph tomorrow morning). Wind support should wane tomorrow afternoon. The warming effects from the off-shore flow are predicted to be limited. Some areas may not see much daytime warm up relative to what occurs today (most applicable near the coast). At best, some areas may warm back to seasonable levels tomorrow and Saturday.
A series of upper air troughs will pass through northern California this weekend into early next week (every 24 to 36 hours). The Saturday trough should produce minor precipitation to the northern third of the state (just weakens our high pressure down here). The Sunday into Monday trough should bring more significant wet weather to northern California. However, as storms go, it should be just an “average” intensity system. In southern California, a healthy, on-shore flow pattern is expected (widespread marine layer clouds west of the mountains and brisk winds for the interior sections). I also wouldn’t rule out marine layer induced drizzle/light rain in places (best chances up against coastal facing foothills/mountains). A somewhat better chance of marine layer drizzle may occur with a passing trough on Tuesday.
The longer range models show the “Pacific storm gate” closing on the state by the middle of next week (at least for a while). High pressure aloft should build off the state coast for a period of time. The models, however, aren’t in agreement on where the high pressure center will go later next week. The complication involves a predicted, “cut-off” low pressure somewhere in or near the Southwest. The positioning of this high pressure/low pressure couplet will determine whether Southland temperatures get much warmer than normal by the subsequent weekend or not. There are a few scenarios that even place the “cut-off” low pressure close enough to southern California for a chance of mountain/desert showers (mostly sunny in the coastal plain but temperatures only slightly above normal levels). The general consensus favors warmer than normal weather in the second half of next week (potentially continuing into the following week). However, warmest weather may not exceed the mid-70s (need high pressure to get close enough for more warming).
Looking further out in time (risky business…more in the line of speculation), there are some signs that a storm or two could reach the state after the 20th (spring begins evening of the 19th, astronomically speaking). The wet weather forecasts don’t show any strong storms, but this would indicate that the rainy season may not end early this season (open season through early April in most years).
Next issued forecast/synopsis should occur Tuesday, 12 March.