| Day | Date | High/Low | Forecast |
| Mon | 7th | 74/60 | Sunny remainder of day. Chance of some late evening low clouds. |
| Tue | 8th | 79/63 | Chance of some early morning fog/low clouds; Otherwise, sunny day. Some evening high clouds possible. |
| Wed | 9th | 81/64 | Mostly sunny day with some high clouds. Some evening high clouds. |
| Thu | 10th | 81/64 | Sunny day. Chance of some late evening low clouds. |
| Fri | 11th | 78/62 | Chance of early morning low clouds/fog; Otherwise, mostly sunny day. Chance of evening low clouds. |
Synopsis
An upper level low pressure continues to meander just to the west of the state (center a couple hundred miles northwest of San Luis Obispo earlier today). The low pressure has limited any warming trend in recent days (a little more than I expected last week). However, all the computer models weaken the low pressure and have it moving inland (well to our north) later this week. This will allow high pressure aloft to build into the Southwest starting tomorrow. The center of high pressure will meander like its low pressure counterpart, but it will happen somewhere in the Southwest or just to our south. If the model consensus holds up, high pressure will be here to stay for perhaps a couple weeks.
Typically, the predicted position and strength of high pressure would promote much warmer than normal weather in most of southern California (desert Southwest in general). A noticeable warming trend is expected, but the ultimate magnitude of warming remains to be seen (dependent partly on where the high pressure center resides as well as its strength). For the coastal plain, there is common (for summer) issue of low level, on-shore flow strength and how well defined the marine layer is. A shallow but defined marine layer can help shield the coastal plain from warm air aloft mixing completely down to the surface. I’ve been fooled a few times in the early weeks of summer. For this forecast, I kept a conservative stance on warming for the campus area. The various models weaken the surface on-shore flow but don’t eliminate it. Even if marine layer clouds fail to reach UCLA in the early morning hours, a sea breeze may temper the daily warming on a given day. Otherwise, the campus should warm into the mid to possibly upper 80s by midweek. For the coastal valleys, I’m confident of triple digit heat developing.
High pressure aloft should be centered just south of the border late this week, but it should weaken ever slightly. Most of the models show minor to modest cooling (as usual, best cooling nearest the coast). Should the high pressure stay stronger than expected or the high pressure center reside right over the Southland, any cooling trend will likely be minimal (including this weekend). A number of model forecasts show high pressure strengthening again early next week. It’s center should move north into southern Nevada or western Arizona. This could renew heating over most of the Southland (areas near the coast could be sheltered by a shallow marine layer). However, a number of model solutions show a fair strength, low level on-shore flow. That would somewhat limit any new warming trend. Warmer than normal would still be the case, however.
Only minor day to day changes are anticipated for later next week. The one unknown (at this time) is whether any relevant, “monsoon” moisture incursion will occur in southern California. One that was predicted for later this week (looking at models last week) now appears to be minor (some high clouds only). The model consensus keeps all relevant, “monsoon” moisture away from the Southland through mid-month (possibly several days beyond that). Of course, a slight error in predicted winds and moisture can infrequently result in significant weather differences. I’m relatively confident with the “monsoon” forecast for this week, but much less so for next week.
Next issued forecast/synopsis should be on Monday, 14 July.