UCLA Weather

from the Department of Atmospheric and Oceanic Sciences.

Friday - 2:57pm

High Clouds

71°

High - 77°

Low - 61°

Today: Partly cloudy day. Mostly cloudy evening with a slight chance of sprinkles late evening.

Five Day Forecast

Latest Average Hourly Temperatures

Sorry for the lack of a forecast and/or synopsis in recent days. Class obligations and a problem involving the department, weather server took priority.

The most recent off-shore flow event, while not a windy one, was better at producing warmer than normal weather than anticipated (by me). Even today, with variable mid/high clouds, widespread 70 degree weather away from the immediate coast was common (even a few readings into the low 80s). I suspect sub-tropical air aloft was mixing down to the ground to produce the above average warmth (more so than one might expect from the given, wind flow pattern).

An upper level trough of low pressure was located several hundred miles west-southwest of Los Angeles at midday (reason for the abundance of mid/high clouds today). Radar imagery indicated some light showers west of San Luis Obispo/Santa Barbara Counties. I'm unsure whether any rain drops are actually reaching the ground. None of today's computer models show anything developing till the evening hours. At least in L.A. County, nothing worse than some sprinkles should occur before midnight. However, as the upper low pressure moves ashore tomorrow, widespread showers should develop in the County (sufficient moisture, instability, and trigger mechanism). This should be mostly in the early morning hours on the Westside. Shower activity should diminish from west to east as the afternoon progresses. Dry, mostly sunny weather should return on Sunday.

Except around the higher mountains, relevant precipitation isn't expected from this storm. Lowland rainfall away from the mountains should be well under a quarter inch (maybe only trace amounts in some areas due to the expected, showery nature of the storm). Unless isolated thunderstorms occur (slight risk), rainfall around the mountains should remain well under half an inch. Snow levels shouldn't get much below 6000 feet when the core of the storm passes through tomorrow morning. A couple inches of "wet" snow may fall.

Most of the longer range models continue to forecast a dominant high pressure next week (as has been the case for most of this year so far). Off-shore flow early next week should be weak (no widespread, significant wind for lowland areas that are prone to Santa Ana winds). However, like this recent, off-shore flow event, widespread 70 degree weather is likely for much of next week (isolated 80 degree weather possible too). Cooler weather is anticipated for the end of next when upper low pressure should return to the western states.

Some of the various models show a chance of wet weather reaching northern California at the end of the month. Some show wet weather reaching southern California at the beginning of March. However, model solutions vary greatly, and none show much run to run consistency (one run wet, another dry). It's possible that the trough (or troughs) will be "inside sliders". That would result in little precipitation (more wind storm than wet storm). It's still too early to say with any confidence which scenario is most likely to occur.

UCLA Forecasts and analyses are written by James Murakami

– posted: 2020-02-21

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

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