| Day | Date | High/Low | Forecast |
| Thu | 23rd | 65/58 | Possible partial afternoon clearing; Otherwise, mostly cloudy through the evening. |
| Fri | 24th | 65/57 | Possible partial afternoon clearing; Otherwise, mostly cloudy through the evening. |
| Sat | 25th | 66/55 | Morning low clouds likely but mostly sunny by afternoon. Chance of late evening low clouds. |
| Sun | 26th | 66/54 | Morning low clouds likely but mostly sunny by afternoon. Chance of late evening low clouds. |
| Mon | 27th | 67/55 | Morning low clouds likely but mostly sunny by afternoon. Chance of late evening low clouds. |
Synopsis
Not much to say. A large, upper level trough over the western states is helping to promote widespread, persistent, “May Gray” weather in southern California. Low clouds have cleared in western Santa Barbara County and a portion of the western Inland Empire (not sure why in those locales only). Elsewhere, west of the mountains, clearing has been partial at best (solidly overcast in many locales, as of this writing). The computer models continue to forecast only minor day to day changes, with regard to the wind flow pattern affecting the Southland (sound like broken record?).
As I’ve stated in past synopses, small changes in the wind flow pattern can result in noticeably different “behavior” in the low cloud pattern (i.e. better clearing in some areas but not so much in others). Spotty mist/drizzle occurred early today, and the models favor a repeat performance tomorrow morning (best chance of measurable rain in San Diego County). However, depending on what the actual wind flow turns out to be, drizzle may not occur in the forecast locales. A passing upper level trough may also help disrupt the low cloud field by mixing dry air aloft down into the marine layer (satellite imagery today shows a large area of clearing west of southern California). Whether this actually occurs on a widespread scale is uncertain (I don’t have a particularly great track record on this point). In any case, there should be at least widespread, partly cloudy skies (west of the mountains) tomorrow and probably Saturday too.
Most of the longer range models show high pressure aloft building over the Southwest by Memorial Day. It’s not predicted to be well developed. Some model solutions show minor disturbances rippling through the high pressure on occasion next week. Some model solutions hint at low pressure aloft reclaiming the West toward the end of next week (fairly weak intensity though). While the high pressure should bring about weaker on-shore flow and warmer air aloft, the on-shore flow isn’t predicted to go away. The marine layer should get shallower, but depending on how well defined it remains, a solid blanket of low clouds may still move across the coastal plain and some coastal valley locales each morning next week.
Expect a modest but noticeable warming trend for well inland areas (seasonable to slightly above normal levels). However, don’t be surprised if “May Gray” weather continues for areas near the coast (campus included). In that situation, any warming trend should be quite minor or non-existent. I’ve forecast some warming trends at UCLA this month but with limited success. If on-shore flow increases again toward the end of next week as some models predict, a spate of widespread, “June Gloom” weather is probable (over the subsequent weekend).
Next issued forecast/synopsis should be on Wednesday, 29 May (only one issuance for the week).