| Day | Date | High/Low | Forecast |
| Mon | 16th | 77/61 | Sunny remainder of day. Clear evening. |
| Tue | 17th | 79/62 | Sunny day. Clear evening. |
| Wed | 18th | 78/61 | Mostly sunny day except chance of early morning low clouds/fog. Mostly clear evening. |
| Thu | 19th | 74/60 | Mostly sunny day except chance of early morning low clouds/fog. Chance of late evening low clouds. |
| Fri | 20th | 73/59 | Good chance of early morning low clouds; Otherwise, mostly sunny day. Evening low clouds likely. |
Synopsis
[Note: I amended slightly all forecast highs. Remainder of morning, preliminary forecast was unchanged.]
A weak, upper level trough was passing through the Pacific Northwest and northern California today. The southern end of this trough was very weak, but it managed to “flatten” the ridge of high pressure over the Southwest. In turn, slightly stronger on-shore flow toward the low desert was noticed early this morning. Despite clear skies in most areas, I thought areas near the coast (campus included) would be a few degrees cooler today than it got yesterday. Such was not the case, and I decided to amend slightly the campus highs in today’s forecast (77 degrees for today is the current maximum for the day, as of this writing…just one degree lower than it got yesterday).
All the computer models show the Southwest ridge rebounding over the Southland tomorrow into Wednesday. Most model forecasts show a small decrease in on-shore flow along with modest warming aloft. Since the low cloud field was very limited in coverage early today (nothing visible on satellite imagery this afternoon), there should be minor to modest warming in the coastal plain tomorrow (more noticeable warming for more inland locales as is common by this time of year). Temperatures should level off Wednesday for well inland areas, but areas near the coast may actually cool a tad that day if some model solutions showing increasing on-shore flow verify (similar to today).
The various models show a new, upper level trough developing along the West Coast on Thursday. The weather effects on the Southland should be minor at first, but increasing on-shore flow should help re-organize the local, low cloud field. A return of widespread, coastal low clouds are anticipated by late this week. By the weekend, low clouds may reach most coastal valleys during the early morning hours. The low cloud pattern may be persistent at some coastal locales too (“June Gloom” episode for some coastal areas). Assuming a defined marine layer returns late this week, areas near the coast should get slightly cooler than normal (most other areas, west of the mountains, expected to be at seasonal normals).
The aforementioned trough should weaken early next week (as early as Sunday). Depending on how the low level wind flow changes, marine layer clouds may quickly become less extensive again. Chances of that happening should increase in the second half of next week when high pressure aloft should re-strengthen over the Southwest (normal feature by summertime…astronomically speaking, summer begins this Friday at 7:42 PM). This should lead to a new period of warmer than normal weather late next week…lasting at least a few days. How warm it gets is still uncertain (model disagreement), but weather similar to what’s expected tomorrow/Wednesday could be a possible outcome.
Next issued forecast/synopsis should be on Monday, 23 June.