| Day | Date | High/Low | Forecast |
| Mon | 16th | 76/67 | Mostly sunny day with some high clouds. Some evening high clouds. |
| Tue | 17th | 90/70 | Mostly sunny day with some high clouds. Some evening high clouds. |
| Wed | 18th | 87/69 | Mostly sunny day with some high clouds. Mostly clear evening. |
| Thu | 19th | 87/68 | Sunny day. Clear evening. |
| Fri | 20th | 87/66 | Sunny day. Mostly clear evening. |
Synopsis
The previous couple of days ended up cooler than I expected last week. Chalk it up to a weak on-shore flow promoting a shallow marine layer over the coastal plain. The marine layer was more shallow this morning (reason for dense fog in spots near the coast), but I had some doubts about how much warming would occur at UCLA. For the preliminary forecast, I went conservatively. Even a very shallow marine layer potentially could limit warming. Well, as of this writing, UCLA appears to have peaked at 84 degrees. Santa Monica Airport peaked around 75 degrees. Santa Monica Pier hasn’t exceeded 61 degrees (that should be considerably higher tomorrow).
All the computer models have strong high pressure aloft (for March) over the Southland tomorrow into Wednesday (shifting slowly east thereafter). A weak off-shore flow is expected although no significant wind in Santa Ana wind prone areas isn’t likely for lowland areas (peak mountain wind gusts only 35 mph though…nothing widespread nor persistent). Today’s warming trend should continue tomorrow (smaller increases on Wednesday for most areas). The campus record high for March 17 is currently 91 degrees (set in 1978). So, the record is within reach, assuming the low level, off-shore flow holds up. The campus record for the 18th is likely to fall (current record just 84 degrees. The all-time March record at UCLA is 94 degrees (26 March, 1988)…reachable though not expected.
I have high confidence is record heat for many areas west of the mountains (overnight, high minimum temperature records may also fall in places). However, most models show just a marginal, off-shore flow by Wednesday (surface pressure gradient off-shore toward the high desert but weakly on-shore toward the low desert). This could potentially hinder further warming (beyond what occurs tomorrow) for areas near the coast (less consequential for more well inland areas). I went with minor cooling for the Wednesday-Friday period, but confidence is admittedly low. Overall, the strong high pressure aloft will foster very warm conditions aloft (some hillside areas in the Santa Monica mountains and Hollywood hills may not cool below the mid/upper 70s in the overnight hours). So, it wouldn’t take much vertical air mixing to induce heating to 90 degrees near the coast.
All the models show considerable weakening of high pressure aloft toward the end of the week. Noticeable relief should begin this weekend (agreeable levels for most on Sunday). However, a return to seasonable temperatures (normal highs late March at UCLA in the upper 60s) may not come before the 25th. Many model forecasts show at least a couple of weak storms passing through the state on or after the 24th. The chief threat is for northern California although widespread precipitation appears unlikely. In southern California, the best scenario would be for marine layer induced drizzle. There is definite chance that little or no rainfall will occur this month in the Southland.
Next issued forecast/synopsis may occur on Thursday, 19 March.