| Day | Date | High/Low | Forecast |
| Mon | 11th | 78/63 | Sunny remainder of day. Mostly clear evening. |
| Tue | 12th | 78/62 | Chance of some early morning low clouds; Otherwise, sunny day. Chance of late evening low clouds. |
| Wed | 13th | 77/62 | Chance of early morning low clouds; Otherwise, mostly sunny day. Chance of late evening low clouds. |
| Thu | 14th | 76/62 | Chance of morning low clouds; Otherwise, mostly sunny day. Chance of evening low clouds. |
| Fri | 15th | 74/61 | Good chance of morning low clouds but mostly sunny by late morning. Evening low clouds likely. |
Synopsis
Upper level high pressure covers the West Coast today. Usually, such a high pressure in that location (center over the southern Sierras this afternoon) produces warmer than normal weather (different high pressure late last week responsible for much warmer than normal weather…UCLA reached 84 degrees on the 7th…first 80 degree day since 10 July and warmest day since it reached 84 degrees on 30 May). Such is the case for most well inland areas. However, low level on-shore flow has stayed just strong enough to mute the warming near the coast (UCLA maximum just 77 degrees so far…a degree below normal). That’s remarkable considering that marine layer clouds were nearly absent in L.A. County coastal plain this morning.
All the computer models predict high pressure will stick around for one additional day (just a tad weaker). So, tomorrow’s temperatures in most areas should be about the same as it got today. However, as often the case, subtle changes in the low level winds may produce slightly different conditions. Some of the models predict a coastal eddy tomorrow morning, which may lead to a return of widespread, early morning low clouds in the coast plain. Depending on where the eddy center winds up, it may or may not delay the sea breeze onset on the Westside (usually allows for some extra warming that otherwise may not occur). In any case, any temperature changes from today should be minor.
High pressure should continue its weakening phase through the rest of this week (part of it resulting from just an eastward migration). Like much of this summer, low pressure aloft is expected to develop along the West Coast (southern end pretty feeble for a couple days). In addition, low level on-shore flow should slowly strengthen through the remainder of the week (strongest at the end of the week). Marine layer clouds should increase in areal coverage and persistence by midweek. If some of the models are right, low clouds may reach most coastal valleys by Friday or Saturday (daily clearing there should still happen by mid-morning hours though).
The presence of low pressure aloft and a decent strength on-shore flow should promote slightly cooler than normal weather (includes interior sections). The cooler than normal weather should last till early next week. After that, today’s model consensus favors high pressure aloft building back strongly into the desert Southwest. That should lead to a new warming cycle in the region (similar weather to recent heat spells). Warmer than normal weather should last through the subsequent weekend. For now, I’m expecting the campus area will experience some 80 degree weather by late next week. However, I’ve erred with stronger than expected on-shore flow a number of times this summer (led to cooler than forecast weather at UCLA).
Surprisingly, a couple of brief-lived thunderstorms formed in the southern mountains (San Diego, Riverside Counties) yesterday. A low level surge of Gulf of California air and some increase in mid-level water vapor (light southerly winds importing moisture from Mexico) contributed to the event. Based on today’s model consensus, nothing more than some cloud build ups should occur today. No new “monsoon” incursion into the Southland mountain/desert areas are expected through this weekend. Some model solutions, however, do predict a modest moisture incursion sometime next week. It could occur as early as early next week, but today’s model consensus favors late next week. Of course, as I’ve mentioned in previous synopses, small errors in predicted wind flow can lead to noticeable weather differences.
Next issued forecast/synopsis should be on Monday, 18 August. (My on call jury duty postponed to the week of 22 September)