UCLA Weather

from the Department of Atmospheric and Oceanic Sciences.

Monday - 9:07pm

Partly Cloudy

60°

High - 73°

Low - 57°

Today: Mostly cloudy day with high clouds. Becoming partly cloudy in the evening.

Five Day Forecast

Latest Average Hourly Temperatures

Note: A forecast will not be issued on Tuesday, 20 November.

We're in an off-shore flow pattern today, but you wouldn't know it looking outside. The low level, off-shore flow peaked in strength in the early morning hours. Things dried out considerably early today after a marine layer dominated weekend. It got breezy in Santa Ana wind prone areas at higher elevations (2000 feet or higher), but peak gusts were mostly under 30 mph. Without any "muscle" at lower elevations, a sea breeze began to re-humidify the coastal plain in the late morning. The off-shore flow itself should die off this evening

The mostly cloudy weather today comes courtesy of an upper level, low pressure (centered about 450 miles west-southwest of Los Angeles at midday). Showers and some thunderstorms exist in a band near the low pressure center. All the computer models have the low pressure passing by well to our south. It's forecast to weaken considerably too, and most of the current shower activity is expected to dissipate before reaching northern Baja California. Other than the clouds, nothing else is expected over southern California through the evening hours. If it weren't for the low level, off-shore flow, it likely would have been several degrees cooler today (still got warmer than normal, albeit a little cooler most areas west of the mountains than it got yesterday). Lower daytime temperatures should prevail for the next couple of days as a different storm affects the state (temperatures actually becoming cooler than normal...quite a contrast to last year's holiday weather when UCLA had its hottest Thanksgiving Day on record...94 degrees!).

Over the weekend, all the computer models came to agreement on whether widespread precipitation would reach southern California later this week (answer: YES). A storm in the southern Gulf of Alaska will reach northern California by Wednesday. Wet weather should reach San Luis Obispo/western Santa Barbara Counties by the late afternoon hours that day. Unless the storm moves faster than today's model consensus, steady rain shouldn't reach L.A. County till the mid/late evening hours on Wednesday (can''t rule out some hors d'oeuvres showers by sunset, however...mainly west of L.A. County). For the most part, the wet weather should be over in L.A. County by sunrise, Thanksgiving Day (excepting some mountain locales). The threat of lingering showers should end from west to east as the day progresses (generally no worse than partly cloudy for the daytime hours). General clearing is anticipated Thursday night.

How wet the storm will be when it reaches southern California is still uncertain (expected to a good soaker for most of northern California, along with the first good snowfall of the season in the Sierras). Model predictions vary on storm dynamics once it reaches the Southland. Lowland rainfall may be in the one-third to one half inch range (higher near/over the mountains...possibly over an inch in spots though mostly to the west of L.A. County). Some model forecasts show less storm dynamics getting this far south, which would promote less rain (storm totals in the L.A. Basin generally under a quarter inch). Since the usually reliable ECMWF model favors the wetter scenario, I'm leaning in that direction. In either scenario, there is some chance for a brief, heavy rain (a concern for recent burn areas). However, the storm should move quickly enough that such intensities won't pose too great a problem (hopefully). Some snow should fall at the local resorts, but little accumulation is expected (most of the wet weather should be ending when it gets cold enough). In a best case scenario, a couple of inches of "wet" snow may fall down to 6000 feet (a few inches at the highest peaks).

Most of the longer range models show dry weather for the remainder of the holiday weekend. A few model solutions still show a chance for scattered, mainly mountain showers sometime after Thanksgiving Day (as early as Friday evening or as late as Sunday, the 25th). A number of model solutions show off-shore flow developing over the latter part of the weekend. At this point, it doesn't look to get any windier than it did today, and temperatures shouldn't be too much different from today (maybe a couple degrees warmer for most locales). The ECMWF model shows dry weather, but it doesn't warm things up much over the holiday weeken, and it leaves the door open for a potential storm before the end of the month.

UCLA Forecasts and analyses are written byfretter

– posted: 2018-11-19

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

© 2018 UC Regents | University of California, Los Angeles

Department of Atmospheric and Oceanic Sciences

Math Sciences Building 7127 | Los Angeles, CA 90095-1565 | Phone: (310) 825-1217