UCLA Weather

from the Department of Atmospheric and Oceanic Sciences.

Tuesday - 1:04pm



High - 80°

Low - 64°

Today: Sunny day. Clear evening.

Five Day Forecast

Latest Average Hourly Temperatures

New synopsis should follow by 2:30 PM.

Previous synopsis: Off-shore flow developed yesterday, which led to noticeable, daytime warming west of the mountains (all the way to the coast in many areas). The off-shore flow strengthened some overnight. It has promoted a little better warming (compared to yesterday). A number of locales (west of the mountains) are expected to reach the low 90s today (just one spot yesterday...Chino). In addition, breezier weather in Santa Ana wind prone areas is occurring today. Gusts in some higher mountains locales are exceeding 35 mph (lowland gusts mostly under 20 mph). Little change in daytime temperatures is expected tomorrow in most areas (perhaps a bit cooler along the coast, especially south of L.A. County where a predicted, coastal eddy may help trigger an earlier ocean breeze).

An upper level disturbance aloft will travel south in the northerly wind flow pattern on the West Coast. The passage of the disturbance through southern California should help enhance the off-shore flow in places overnight into the daytime, morning hours tomorrow. Peak wind gusts in the higher mountains could exceed 50 mph for a time (not widespread in areal coverage though), and even some lowland areas prone to Santa Ana winds may see gusts reach 30 mph. I considered adding "breezy at times" to the campus forecast for tonight/early tomorrow, but today's model output wasn't compelling enough to add in this forecast (hopefully, I don't regret it tomorrow morning). The wind should diminish tomorrow afternoon, but a secondary increase in wind may occur tomorrow night (just less windy than what's expected late tonight).

An upper level, low pressure is forecast to develop around the eastern state border by Wednesday. The low level, off-shore flow should weaken enough to allow earlier and stronger, ocean breezes to develop. That should lead to modest, daytime cooling west of the mountains. High pressure aloft should strengthen some as the aforementioned low pressure moves east after Wednesday. So, a new, warming cycle is anticipated late next week. However, unlike a number of computer model forecasts last week, the latest model consensus doesn't predict a well developed, high pressure. The high pressure also doesn't remain over the Southland for long (breaks down over the weekend). In addition, the low level, wind flow pattern will favor on-shore flow (albeit weak). The resultant weather should be one where the warming trend is modest and most of that happening for well inland areas.

The predicted, wind flow pattern is more reminiscent of late spring than early autumn. A shallow marine layer is forecast to develop by the weekend (possibly as early as Friday).. That could bring back widespread low clouds/fog to the coast. That in turn would cut down on the warming trend in the coastal plain (especially near the coast). Even in the valleys, temperatures might not exceed today's values (earlier thoughts of triple digit heat gone, if the model consensus is right). Campus temperatures may struggle to reach 80 degrees this weekend. Still, temperatures should at least be slightly warmer than normal in most areas (seasonable along the coast, if a well defined, marine layer forms).

It's not a clear majority model solution, but it looks like next week's weather will feature ho-hum, on-shore flow. Widespread, marine layer clouds would occur in the coastal plain for the late night/morning hours (mostly clear elsewhere). Temperatures would be seasonable or slightly cooler than normal, depending on the strength of the on-shore flow. There are a few model solutions still showing a warm, off-shore flow pattern for a part of next week, but it's a minority model solution now (less likely to verify). At least for now, the only threat of wet weather in the state should be this weekend near the Oregon border.

UCLA Forecasts and analyses are written by James Murakami

– posted: 2017-09-26

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

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