| Day | Date | High/Low | Forecast |
| Mon | 13th | 64/53 | Becoming partly cloudy in the afternoon with a slight chance of sprinkles; Possibly breezy at times. Clearing in the evening. |
| Tue | 14th | 68/55 | Some clouds possible but mostly sunny day. Mostly clear evening. |
| Wed | 15th | 68/57 | Partly cloudy day with mainly high clouds. Chance of evening low clouds. |
| Thu | 16th | 68/56 | Good chance of morning low clouds; Otherwise, mostly sunny remainder of day. Mostly clear evening. |
| Fri | 17th | 75/57 | Amended high temperature…Mostly sunny day with some high clouds. Scattered evening high clouds. |
Synopsis
There are disadvantages of forecasting remotely, one of which is not being able to directly view the weather at UCLA. Cold air instability and a passing upper level disturbance promoted “home grown” showers and thunderstorms in parts of southern California (a notable thunderstorm started west of Simi Valley during the noon hour). Based on the computer model output, I thought relevant showers would not get south of the San Fernando Valley. In my preliminary, morning forecast, I wrote in for a “slight chance of sprinkles”. I came close, but a thunderstorm outflow around Van Nuys (during 1 PM hour) helped trigger a relevant shower cloud over the Sepulveda Pass (this one didn’t form into a brief-lived, thunderstorm, to my knowledge). That passed over the campus area around 2:30 PM. Most nearby (to UCLA) stations did not report any measurable rain, but UCLA and one home station to the west of the campus reported 0.01 inch (enough rain to produce small puddles). Such are the fortunes of forecasting when convective showers are concerned (far more serious, of course, when severe thunderstorms are involved).
And back to weather forecasting for the week…The current, upper level trough causing the showers and cooler than normal weather will exit the state tonight. A return to mundane weather is expected tomorrow. A marginal, weak, off-shore flow is predicted for tomorrow, but high pressure aloft is forecast to be fairly weak. So, only modest, daytime warming is predicted for most areas of southern California (likely no warmer than seasonal normals). An approaching, weak, upper air trough should introduce variable high clouds, but daytime temperatures should be very similar to what occurs tomorrow (perhaps, a bit cooler by the coast).
An “inside slider” type trough is forecast to make a nearby pass on the Southland Thursday evening. Depending on how close the trough gets, there is some chance for marine layer induced, light showers (mostly around/adjacent to the coastal facing mountains). It should promote breezy weather in the interior sections (higher mountains/deserts), but model consensus for breezy weather developing in Santa Ana wind prone areas isn’t great (for now). Should it happen, the valid period should be late Thursday evening through Friday morning (some potential for mountain wind gusts reaching 50 mph).
Surface off-shore flow is predicted for Friday (dying down Saturday. Although high pressure aloft isn’t forecast to intensify greatly, subsidence warming should promote temperatures into the mid/upper 70s on Friday (inland coastal plain and valleys). There is potential for isolated 80 degree readings. Saturday should be a bit warmer most areas (immediate coast likely cooler due to weakening off-shore flow). A general cooling trend should set up starting on Sunday.
Uncertainty looms for the weather for much of next week. A return to cooler than normal weather looks probable, based on recent model consensus. There are some model solutions showing a trough capable of producing wet weather early next week (Monday or Tuesday at latest). It wouldn’t be a significant storm (anywhere in state), and wet weather might not be widespread in areal coverage. Since there are model solutions keeping the Southland essentially dry (trough ends up being an “inside slider”), I have little confidence in a model trend for now. The same applies for weather later next week. Other “inside sliders” are possible later in the week.
Next issued forecast/synopsis should be on Thursday, 16 April.