| Day | Date | High/Low | Forecast |
| Fri | 23rd | 71/60 | Mostly sunny remainder of day. Evening low clouds likely. |
| Sat | 24th | 70/59 | Partial afternoon clearing; Otherwise, mostly cloudy through the evening. |
| Sun | 25th | 69/59 | Partial afternoon clearing; Otherwise, mostly cloudy through the evening. |
| Mon | 26th | 69/59 | Morning low clouds; Mostly sunny afternoon. Evening low clouds likely. |
| Tue | 27th | 71/60 | Morning low clouds but sunny by late morning. Chance of late evening low clouds. |
Synopsis
The most recent warm spell (first half of the week) didn’t get quite as warm as many computer models predicted. Currently, a weak, upper level trough is back along the West Coast. It and one more trough (Monday) should promote marine layer dominated weather through the Memorial Day weekend (nothing unusual for this time of year). Warmer weather is anticipated after Monday, but details of how warm remain to be decided (more on this a bit later).
A healthy on-shore flow pattern is forecast to continue through tomorrow. After the passage of the current trough tomorrow morning, a little weakening of the on-shore flow is expected. However, the various models aren’t inclined toward much weather change on Sunday. The predicted trough for Monday should reverse any weakening of on-shore flow that happens. In short, only minor day to day weather changes are expected.
Of course, the details of the weather are subject to change in some areas. The “behavior” of the low cloud field may not be uniform from one day to the next (usual complexities of marine layer physics). It’s possible that “May Gray” weather (i.e. persistent low cloud overcast) may occur on one or more days. In such a case, spotty, early morning mist would be possible (best shot up against coastal facing foothills/mountains). The cooler than normal weather may wind up more so for a day or two (i.e. a little cooler than I currently expect).
Most of the longer range models predict high pressure aloft exerting more influence next week. This should lead to a warming cycle for most of next week. However, the models disagree on how strong and how close that high pressure will get. A number of model solutions depict some weak, upper level low pressure sneaking through the ridge. Depending on where the low pressure winds up late next week, the warming trend could be limited (affecting mostly well inland areas).
One complicating detail concerns a scenario of the upper low pressure winding up southwest or south of southern California (valid next Friday). Many of the longer range models also predict the first tropical disturbance of the season forming south of Mexico (potential to become tropical storm Alvin). While not explicitly in the model forecasts, there is some chance that a low pressure to the southwest of southern California could guide tropical moisture (from the predicted disturbance) into the Southland. That could lead to very warm and muggy (for our region) weather (valid end of next week or over the subsequent weekend). In fact, such an early, “monsoon” moisture incursion could promote shower/thunderstorm weather. Of course, much of this is just speculation. There is another scenario where the aforementioned low pressure just promotes “June Gloom” weather for a day or two.
Next issued forecast/synopsis may be on Tuesday, 27 May.