| Day | Date | High/Low | Forecast |
| Mon | 8th | 72/59 | Mostly sunny with some high clouds remainder of day. Chance of evening low clouds. |
| Tue | 9th | 73/60 | Good chance of early morning low clouds; Otherwise, mostly sunny day. Mostly clear evening. |
| Wed | 10th | 74/61 | Chance of some early morning low clouds; Otherwise, mostly sunny day. Mostly clear evening. |
| Thu | 11th | 73/62 | Chance of early morning low clouds; Otherwise, mostly sunny day. Chance of late evening low clouds. |
| Fri | 12th | 73/62 | Chance of early morning low clouds; Otherwise, mostly sunny day with some mid/high clouds. Some evening mid/high clouds possible. |
Synopsis
An upper level trough exists along the West Coast today. It’s promoting wet weather in the western portion of the Pacific Northwest. It’s even managed to trigger light showers over parts of northern California (northern third of the state). The weak, southern end of the trough is just promoting on-shore flow and the marine layer clouds that go with the pattern.
The computer models predict high pressure aloft slowly building into the state (belt from west of California down through northwest Mexico). The pattern change should promote modest warming for much of the week, especially well inland areas. A weak upper trough in the sub-tropics (west of lower Baja California) is forecast to extend northward by Friday. Weakening high pressure should result. That, in turn, should lead to a minor cooling trend over the weekend (lasting well into next week, if today’s model consensus holds true).
I had expected a little warmer day today (slightly shallower marine layer), but there appears to be less vertical air mixing than past days (preventing better mixing of warm air above the marine layer down to the ground nearer the coast). More high clouds today than I expected may also be contributing (cutting down on solar heating). The models predict some light north winds above the marine layer tomorrow/Wednesday. At the least, the marine layer should get more shallow. There is some chance that the north winds will punch holes into the coastal low cloud field, but confidence in that scenario is low. Should that happen, however, UCLA may warm a few to several degrees higher than I “officially” forecast. Well inland areas should definitely see moderate warming through midweek as the marine layer gets shallow.
The aforementioned, sub-tropical trough may send variable mid/high clouds our way late in the week. It would be a minor, “monsoon” moisture surge but only well aloft. No chance of instability showers/thunderstorms is foreseen for the Southland mountain/desert region (shower threat staying south of the border except possibly southern most Arizona). It’s main weather effect on the Southland should be promoting slightly stronger on-shore flow. The marine layer should begin a minor deepening over the weekend (more extensive and persistent low clouds…in theory.
Most of the longer range maintain some form of trough over the Great Basin states. The trough should be close enough to prevent any relevant warming cycle next week near the coast. Some model solutions last week showed high pressure strengthening quite a bit by mid-month, but the models have since back tracked on that scenario. So, only minor weather changes are currently anticipated for next week.
Next issued forecast should be on Friday, 12 June. [Note: I will be going to a once a week forecast issuance next week…lasting through the summer.]