| Day | Date | High/Low | Forecast |
| Mon | 23rd | 73/58 | Hazy sunshine remainder of day. Chance of late evening low clouds. |
| Tue | 24th | 76/59 | Chance of early morning low clouds; Otherwise, mostly sunny day. Mostly clear evening. |
| Wed | 25th | 75/59 | Chance of early morning low clouds; Otherwise, mostly sunny day with some high clouds. Mostly clear evening. |
| Thu | 26th | 76/60 | Chance of some early morning low clouds; Otherwise, mostly sunny day. Mostly clear evening. |
| Fri | 27th | 81/62 | Mostly sunny day. Mostly clear evening. |
Synopsis
After six straight days of reaching at least 80 degrees, UCLA didn’t get above 73 degrees yesterday (72 degrees, so far today). A shallow marine layer, along with a coastal eddy circulation and a full fledged on-shore flow, are the culprits. High pressure aloft is forecast to intensify over the Southland tomorrow, but it shouldn’t get anywhere as strong as one did last week (i.e. temperatures shouldn’t reach triple digits in the valleys). There should be no widespread return of seasonable temperatures is this week (some spots near the immediate coast have fallen back to normal levels, at least for now).
Although all the computer models predict a new warming cycle after today, there is some disagreement on how warm it may ultimately get. That uncertainty concerns the coastal plain. The models under predicted the brief cooling cycle these past two days (marine layer under played by models). I have little doubt that the marine layer will become shallower (i.e. less extensive, coastal low clouds). However, as long as a shallow but defined marine layer remains (predicted by some models), warming in the coming days may be more subdued in the coastal plain (even some coastal valley locales if on-shore flow stays strong enough).
For this forecast, I kept the warming trend for UCLA on the slow and modest side. As happens infrequently in the spring, numerical models sometimes dilute or even purge a marine layer too much. For this week, no full fledged off-shore flow is predicted to erode the marine layer significantly. Of course, if sinking air motion by high pressure aloft punches large holes in the low cloud field, my forecast could go bust. So, confidence for this week’s weather isn’t all that high (I’ve under predicted temperatures multiple times this month).
Whatever occurs this week, most of the longer range models predict a significant change in the wind flow pattern next week. An upper level trough is forecast to develop along the West Coast early next week. Temperatures should finally come down to seasonable levels in most areas of the state (below normal temperatures quickly following). More importantly, there may be chances for wet weather at times (mainly beginning of April). If anything occurs early next week in southern California, it should nothing more than patchy, marine layer induced drizzle or light showers. Later next week, a number of model solutions show a chance for widespread wet weather (a few solutions with a decent soaking storm…for early spring). My one concern is that the model trend has been to delay the wet event as the date nears. Will this be a April fools joke on forecasters?
Next issued forecast/synopsis may be on Thursday, 26 March…time permitting.