Weather Synopsis – April 23, 2024

James Murakami

Tue23rd64/57Possible, partial afternoon-early evening clearing; Otherwise, mostly cloudy through the evening.
Wed24th64/57Possible, partial afternoon-early evening clearing; Otherwise, mostly cloudy through the evening.
Thu25th65/55Mostly cloudy day. Partly to mostly cloudy evening.
Fri26th66/53Partly cloudy day and possibly breezy at times in the afternoon. Mostly clear evening.
Sat27th67/52Mostly sunny day except chance of some morning low clouds. Mostly clear evening.


“May Gray” weather has gotten off to an early start this year. Marine layer clouds cleared from the Westside this afternoon, but many areas west of the mountains were still shrouded with low clouds as if this writing. The computer models predict generally minor changes in the wind flow pattern affecting southern California. A healthy, low level, on-shore flow should continue to support a deep marine layer through this work week. Spotty drizzle was reported early this morning (mostly Inland Empire), and that may re-occur for the next couple of mornings (not necessarily same locales each day though best chances near coastal facing foothills/mountains). Like today, there may also be areas with partial afternoon clearing (again, not necessarily same locales each day though better chances near the coast than farther inland…”reverse clearing pattern”).

A complicating factor to the cloud forecast is the predicted passage of a weak, upper level trough. It may help support more organized areas of drizzle tomorrow (not confined to early morning hours). Areas of San Diego County stand the best shot at this weather (most favored wind flow pattern for wet weather). Still, rainfall should be minor (well under a tenth inch most locales). In addition, the low cloud field could get disrupted at some point tomorrow, and partial clearing could occur in more areas than today (some predicted mid/high clouds may prevent complete clearing though). In any case, temperatures tomorrow should vary little from today.

The aforementioned trough should be east of the region by Thursday. The various models aren’t forecasting much change to the marine layer nor on-shore flow (maybe a bit weaker). I don’t show it in the camps forecast, but I wouldn’t be surprised if no widespread, low cloud overcast occurs that day. On Friday, an “inside slider” type trough will pass through southern California by the evening hours. General northwest wind flow shouldn’t favor widespread overcast Friday morning (at least, not on the Westside due to some subsidence accompanying the northwest winds aloft). Down toward San Diego County (parts of Inland Empire too), more favorable winds could promote persistent low clouds and spotty drizzle (not confined to early morning hours). Also, the “inside slider” should promote breezy weather in the interior sections (possibly spreading to the coast in the afternoon…that is, brisk, afternoon sea breeze).

The various models don’t predict an end to the on-shore flow nor purging of the marine layer. However, both should be less prevalent than it is today. The low cloud pattern this weekend and early next week should be more on the patchy side (expecting a diluted, shallow marine layer). Assuming the on-shore flow weakens sufficiently, a steady, gradual, warming trend should occur in most areas. Best warming will occur for well inland areas (as is common by this time of year…less influence by the sea breeze and accompanying marine layer). At this point, I’m not expecting Southland temperatures will get any warmer early next week than it did a couple days ago.

Most longer range models predict a new, upper level trough developing over the state late next week. If true, a new cooling cycle should begin around the middle of next week, and a new round of persistent marine layer clouds should develop (similar to recent weather). A few model solutions predict conditions favorable for wet weather, but the most likely outcome favors nothing more than marine layer drizzle. Cooler than normal weather could last through the subsequent weekend (1st weekend of May).

Next issued forecast/synopsis may occur on Thursday, 25 April.