UCLA Weather

from the Department of Atmospheric and Oceanic Sciences.

Thursday - 2:45pm

Fog

73°

High - 75°

Low - 65°

Today: Low clouds clearing late morning to hazy sunshine remainder of the day.. Chance of some low clouds in the evening.

Five Day Forecast

Latest Average Hourly Temperatures

Note: No forecast will be issued on Friday (20 September).

The marine layer deepened overnight, which allowed low clouds to reach many coastal, valley locales early today. However, the low cloud field remained tattered in appearance (as viewed by satellite imagery). Some areas experienced overcast. Other areas were mostly sunny with just scattered low clouds (campus area was closer to the former). An upper level trough, which helped deepen the marine layer, will move east of the state tomorrow. Low clouds are expected tonight, but no widespread overcast is expected. The marine layer should get shallower, and areal coverage of low clouds (whether scattered or overcast in character) should be less tomorrow than it was this morning. A marginal off-shore flow beginning tomorrow and lasting through most of the weekend should then promote just patchy low clouds/fog by the coast (mostly south of L.A. County).

As expected, a little further cooling has occurred in most areas today (compared with yesterday). This should be the last cooler than normal day for several days. The aforementioned off-shore flow is expected to promote a warming trend that lasts through the weekend (computer model forecasts previously showed cooling on Sunday). Although high pressure aloft isn't forecast to get all that strong, a defined, low level, off-shore flow is forecast (relevant winds only in the higher mountains, however). There is now a distinct chance for widespread 90 degree in the inland, coastal plain this weekend (especially if deep layered, easterly wind flow develops). There could even be isolated, triple digit readings in the valleys this weekend. The beaches, of course, will remain the coolest, lowland spot, but temperatures should be warmer than normal unless a shallow but defined, marine layer persists (daytime temperatures should get well into the 70s there).

Astronomically speaking, autumn begins on Monday (12:50 AM). A passing, "inside slider" type trough will promote cooler weather that day. However, it's likely to be slightly warmer than normal over most of the Southland (maybe seasonable in the interior). More weak, off-shore flow is predicted to return Monday night or Tuesday. So, renewed warming is expected for Tuesday and Wednesday. Today's model consensus doesn't show it getting as warm as what's expected this weekend, but it could come close (a couple of model solutions actually show temperatures exceeding this weekend's forecast).

Remarkably, the longer range models agree on a new West Coast trough late next week. That will spell a cooling trend that continues through the subsequent weekend (possibly remainder of the month). Details on the weather, however, vary. One extreme shows the first, autumn storm for the entire state (widespread precipitation that includes southern California). On the other end of the spectrum, there could be a cool, "inside slider" trough (some chance for instability showers in the mountains). That would be followed by the first, significant, Santa Ana wind event of the season (warmer weather last couple days of month). At this point, anything is possible.

UCLA Forecasts and analyses are written by James Murakami

– posted: 2019-09-19

Data and technology is provided by UCLA's Department of Atmospheric and Oceanic Sciences

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Department of Atmospheric and Oceanic Sciences

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