UCLA Weather

from the Department of Atmospheric and Oceanic Sciences.

Thursday - 1:10pm



High - 81°

Low - 68°

Today: Sunny remainder of day but some clouds in the distance. Mostly clear evening.

Five Day Forecast

Latest Average Hourly Temperatures

New synopsis should follow around 2:30 PM.

Previous synopsis: Although the surface on-shore flow weakened slightly overnight, the marine layer over the L.A. Basin increased in depth a bit. The presence of a coastal eddy circulation may have supported a deeper marine layer despite the weaker on-shore flow. In any case, areal coverage of early morning low clouds was more than yesterday. Based on today's computer model consensus, a repeat performance of the low cloud pattern is anticipated tomorrow. After tomorrow, however, there should be a trend toward less low clouds in the coastal plain (high pressure aloft building over the Southland to help "squash" the marine layer).

Daytime temperatures in most areas were close to yesterday when looking at noon temperatures (most the same or a bit warmer). Subtle changes to the wind flow pattern may result in minor variations in temperatures tomorrow (some spots a little warmer, some a little cooler, a few remaining unchanged). The same should apply to Friday in the coastal plain, but a slow but general warming trend should occur for more well inland areas by Friday (less influence of the marine layer along with minor warming aloft promoted by high pressure aloft).

"Monsoon" moisture has increased modestly today over the southern mountains/eastern deserts. Cloud build-ups were progressing more quickly out there this morning, and isolated, brief-lived showers and thunderstorms should occur in the afternoon hours. Thunderstorm activity may be more widespread tomorrow in the mountain/desert region tomorrow, but the predicted wind flow aloft should prevent these showers from drifting into the coastal plain (possibly into the coastal side valleys of the Inland Empire, however). Unless some unforeseen disturbance moves into the Southland, no prolonged, heavy rain should accompany the thunderstorms today/tomorrow. A predicted shift in winds aloft should help decrease the "monsoon" moisture in the Southland after tomorrow. If most model solutions are right, there should be no shower threat in the Southland mountain/desert region by Sunday (minor threat eastern most desert Saturday afternoon).

While we're not really expecting "monsoon" moisture to reach the coast, areas west of the mountains should remain a little muggier than usual. Thanks to a warmer than normal ocean, locally, the marine layer currently in place has a higher water vapor content than normal for this time of year (greater evaporation occurring with the "warm" ocean). The marine layer is forecast to become shallower over the weekend, which should support better drying in the valleys relative to areas closer to the coast (like the campus area). However, a shallower marine layer should just serve to concentrate what moisture there is. So, unless some entrainment of drier air from the open Pacific (to our northwest) occurs or dry air from aloft punches through into the marine layer (via subsidence warming from high pressure aloft), the current, somewhat muggy weather should continue for the foreseeable future (at least through most of next week).

Most of the longer range models aren't forecasting major changes in the wind flow pattern affecting the Southwest. Depending on where the center of high pressure resides next week, there could be another, "monsoon" moisture incursion early next week (just for a couple days or so). That would promote isolated, mainly afternoon thunderstorm for some mountain/desert locales (same areas as today/tomorrow). Warmer than normal weather is expected next week, based on the majority model solution, but it shouldn't be much warmer than normal. Some model solutions show cooling back to seasonable levels or slightly more at the end of next week, but that is far from certain.

UCLA Forecasts and analyses are written by James Murakami

– posted: 2018-08-16

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

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