Weather Synopsis – February 27, 2024

James Murakami

Tue27th63/50Partly cloudy morning; Mostly sunny afternoon. Mostly clear evening.
Wed28th66/52Chance of some morning low clouds; Otherwise, mostly sunny day. Chance of evening low clouds.
Thu29th64/52Good chance of morning low clouds; Otherwise, generally sunny day. Mostly cloudy evening.
Fri1st (March)62/54Mostly cloudy day with a slight chance of morning drizzle. Mostly cloudy evening with a chance of light showers.
Sat2nd59/48Overnight rain likely tapering to a chance of showers daylight morning; Partly cloudy afternoon and breezy at times. Decreasing clouds in the evening.


The latest storm dropped widespread precipitation in southern California, but storm totals were minor in most areas (generally a tenth inch or less away from foothills/mountains). The highest totals were in the mountains of the Inland Empire where rainfall was between a half inch and one inch (no available snowfall reports though relevant accumulation below 7000 feet unlikely). At UCLA, the auto-gauge recorded 0.16 inch (Official measurement planned Wednesday). That would bring the monthly tally to around 19.30 inches (2nd wettest February in campus history…wettest was 20.51 inches in 1998).

A deep, moist layer (i.e. marine layer) remains west of the mountains today (started out clear in parts of the coastal plain, but clouds developed quickly with some warming of the air mass. The numerical models show high pressure building over the Southland tonight through tomorrow. A marginal, surface off-shore flow is predicted, but it looks to be feeble at most. None of the models show a purge of the current marine layer. Some shrinkage in depth or dilution of the moist air may occur in places, but low clouds should occur tomorrow morning in most areas west of the mountains (not necessarily as a widespread overcast, however). The high pressure aloft should help exert some daytime warming (over today’s readings), but temperatures probably won’t exceed seasonal normals in most locales.

On-shore flow should return in earnest on Thursday. That should promote widespread, morning low clouds west of the mountains. Some model solutions even forecast patchy drizzle from the low clouds (mainly around coastal facing mountains). By Friday, the marine layer may get deep enough for more widespread, drizzle activity. That will depend on how quickly a predicted, Gulf of Alaska trough of low pressure approaches. This should be a major storm for the northern Sierras (potentially dropping several feet of snow in favored locales over a few days period). For southern California, it’s expected to be an “ordinary” storm (typical cold, breezy Southland storm). No tap into an atmospheric river is anticipated, and the best storm dynamics are predicted to remain north of our region.

Despite my description of “ordinary”, most areas should receive more rainfall than yesterday’s system. Storm totals in the lowlands away from the mountains should range in the quarter to half inch range (some scenarios favor up to 0.75 inch). Snow levels should drop to 5000 feet and even a little lower on the north facing slopes of the Tehachapi Mountains (not till late Saturday). Some favored locales may receive up to 10 inches though 3 – 6 inches should be more common). If today’s model consensus holds up, the threat of lingering showers should end by sunrise Sunday (anticipating showers ending in the L.A. County coastal plain by Saturday afternoon).

Most of the longer range models continue to keep the “storm gate” open even after the early weekend storm. A least a couple of more storms should affect the state later next week (possibly as early as Tuesday). These subsequent storms should be weaker than the one expected this weekend. The predicted, wind flow pattern should also promote cooler than normal weather for all of next week. Coldest weather is expected with the passage of the weekend storm. Overnight low temperatures should fall well into the 40s west of the mountains for at least a couple of days (isolated valley locales cooling into the upper 30s briefly Monday).

Next issued forecast/synopsis should be on Thursday, 29 February.