Weather Synopsis – April 18, 2024

James Murakami

Thu18th68/54Morning low clouds but mostly sunny afternoon. Chance of evening low clouds.
Fri19th67/54Morning low clouds likely but mostly sunny afternoon. Chance of evening low clouds.
Sat20th67/55Morning low clouds likely but mostly sunny afternoon. Mostly clear evening.
Sun21st71/55Chance of early morning low clouds; Otherwise, mostly sunny day. Chance of late evening low clouds.
Mon22nd70/54Chance of morning low clouds; Otherwise, mostly sunny day. Chance of evening low clouds.


A very weak, upper level disturbance brought considerable high clouds to the Southland overnight (low clouds masking the view in the coastal plain for much of the time). It’s now passed, but a larger trough will move through the Southland tomorrow. Its approach should help maintain the healthy, on-shore flow pattern for another day, That should result in more extensive low clouds tomorrow morning. The low clouds may also linger longer than it did this morning. Where low clouds aren’t present, variable mid/high clouds are anticipated tomorrow through Saturday morning. None of computer model forecasts show any shower threat from the approaching trough. However, I wouldn’t be surprised if isolated, sprinkle showers or marine layer induced mist occurs tomorrow morning (too remote a chance to “officially” include in the campus forecast).

High pressure aloft is forecast to rebuild back into the Southwest over the weekend. Some northerly winds should develop late Saturday into Sunday, but it’s not expected to be significant (i.e. no strong winds in Santa Ana wind prone areas expected). The marginal, off-shore flow conditions should promote some warming over the weekend (Sunday being the warmer day in most areas). However, it shouldn’t get any warmer than it did earlier this week. Near the coast, a shallow but defined marine layer might remain in place (indicated by most model forecasts). If so, the warming trend this weekend should be minimal or even absent near the coast.

By Monday, the aforementioned high pressure aloft should weaken and move off to the east. General but weak, upper level troughing is forecast to develop off the state coast. Some model solutions show the trough promoting a marine layer deep enough for areas of drizzle or light rain (valid Tuesday). The trough should weaken some around midweek, but there are a number of model forecasts showing an “inside slider” trough late next week. This predicted trough would be more a wind storm than a wet system (not unusual by mid-spring), but another period with areas of drizzle/light rain would be possible (Thursday and/or Friday). Some of the model solutions have shown the trough developing off the coast. That would foster a more widespread wet event (still nothing significant, precipitation-wise). Regardless of which outcome verifies, it doesn’t look like any warmer than normal weather will prevail next week. Perhaps, a return to seasonable temperatures may occur over the subsequent, final weekend of April.

Next issued forecast/synopsis may occur on Tuesday, 23 April.