| Day | Date | High/Low | Forecast |
| Fri | 8th | 71/54 | Sunny day. Clear evening. |
| Sat | 9th | 70/52 | Mostly sunny day with some high clouds possible. Some evening high clouds. |
| Sun | 10th | 68/51 | Chance of early morning fog; Otherwise, mostly sunny day with some high clouds. Chance of late evening low clouds/fog. |
| Mon | 11th | 66/50 | Mostly sunny day except chance of early morning low clouds. Partly cloudy evening. |
| Tue | 12th | 69/52 | Sunny day and possibly breezy at times. Clear evening and possibly breezy at times early. |
Synopsis
The recent, strong (in places), off-shore flow event is essentially over (winds under 25 mph in the mountains). High pressure aloft will continue over southern California through tomorrow, but a marginal, on-shore flow should develop by tomorrow afternoon. That, in turn, should promote a shallow marine layer development. Although satellite imagery currently shows no low clouds/fog over the Southland waters, patchy fog could form as early as tomorrow morning (probably remaining over water though). At least, surface humidity along the coast should approach normal levels (end to “bone dry” air).
It was a bit warmer on campus today than I anticipated (73 degrees today versus 71 yesterday), but the return of on-shore flow should herald a cooling trend west of the mountains (actually should warm some in the interior as the flow of polar air into the Mohave desert has ended). The cooling trend should be slow and modest in magnitude in most areas (most effective in the coastal plain). Areas of dense fog may occur along the coast tomorrow evening into Sunday morning. However, as the marine layer deepens in response to strengthening on-shore flow (at least, that’s what the numerical models project), the fog should lift into a low cloud layer (probably widespread in areal coverage Sunday night or Monday morning. At this point, I’m unsure if a widespread, persistent, low cloud overcast will prevail (complexities of marine layer physics).
A weak, upper level trough will pass through the Southland on Sunday (main reason for return of marine layer clouds to the coastal plain). A second trough will follow on Veteran’s Day (current, predicted time line for passage through southern California is late Monday into early Tuesday). This trough will be strong enough to produce wet weather across much of northern California (modest snowfall in the northern Sierras possible). However, no widespread precipitation event is expected in the Southland. The trajectory of the storm should make it an “inside slider”. Some isolated mountain showers are probable over the north facing Tehachapi Mountains. Some marine layer induced light showers could occur west of the mountains from Orange County southward (may also include parts of the western Inland Empire), but any rainfall should be minor (less than what occurred last Saturday). The threat of wet weather should end by sunrise Tuesday.
With the passage of the “inside slider”, an increase in northwest to north winds should occur. This event looks to be weak (certainly compared with the recent wind event). Peak wind gusts on Tuesday in the higher mountains may reach 45 mph in places, but Santa Ana wind prone areas at lower elevations should stay mostly under 30 mph. The campus area will probably see a period of breezy weather, but varied, model solutions for wind magnitude leave me unsure just how windy it will actually get (may not get much above 25 mph). The off-shore flow will continue on Wednesday, but upper air support should weaken by then. Significant wind should be restricted to the usual, Santa Ana wind prone areas, but most wind gusts should be under 35 mph (includes higher elevations). The off-shore flow should be ending by Thursday.
The longer range models are trending toward a possible opening of the “storm gate” through California. This would occur by the subsequent weekend (affecting northern California a couple days earlier). At this point, the models aren’t showing any storms tapping into a significant, atmospheric river, but it could be the start of multiple storm visits of weak to moderate caliber. Of course, much could change between now and the subsequent weekend. It’s possible the storm track will stay a little too far north for relevant precipitation to reach southern California. On the other hand, a random, unforeseen circumstance could lead to a major storm. We’ll just have to wait and see (for now).
Next issued forecast/synopsis should be on Tuesday, 12 November.