UCLA Weather

from the Department of Atmospheric and Oceanic Sciences.

Monday - 10:36pm

High Clouds

70°

High - 85°

Low - 68°

Today: Mostly sunny day with scattered high clouds. Scattered high clouds in the evening but decreasing late evening.

Five Day Forecast

Latest Average Hourly Temperatures

It sounds redundant, but off-shore flow continues over the Southland. The only relevant change has been a decrease in overall wind speeds associated with the current Santa Ana wind event. Still, it remains breezy in many Santa Ana wind prone areas at higher elevations (gusts exceeding 25 mph). Some of today's computer models show yet another increase in wind speeds tonight (lasting into tomorrow). Peak wind speeds, however, should be under 50 mph at higher elevations. If today's model consensus is right, a marginal, on-shore flow should develop in the second half of the week (may go fully on-shore, albeit weak late Friday through Saturday morning).

Despite the presence of abundant high clouds (associated currently with an upper low pressure over central Baja California)., widespread 80 degree weather occurred yesterday and today (got a bit warmer than I anticipated today at UCLA...85 degrees...thought weaker off-shore flow would prevent that much warming). No significant day to day temperatures changes are expected for a couple days. On the one hand, the models show slight warming aloft tomorrow (lasting through Wednesday) due to the slight increase in off-shore flow strength. However, predicted winds are northerly instead of the recent easterly winds. The former typically leads to less warming for most areas (for a given temperature profile), which is the reason I show slightly cooler weather tomorrow.

Assuming the marginal, on-shore flow develops, a minor cooling trend should occur west of the mountains (best cooling at the coast). At this point, Friday should be the coolest day of this week (possibly Saturday if the next, predicted off-shore flow is slow to develop). Temperatures, however, aren't predicted to fall back to seasonable levels (mid-60s at UCLA) since high pressure aloft never completely leaves the "neighborhood: (at least, as the models predict).

The predicted return of a brief, on-shore flow at the end of the week occurs due to the passage of an "inside slider" type, low pressure trough. It may bring a few light showers as far south as the state border area, but the trough should essentially be a wind storm only in the state. How windy it gets in the Southland (Saturday) is still uncertain, but most model solutions show only a weak off-shore flow (no widespread, significant wind at lower elevations). Even if significant wind occurs, it should be a short-lived event (less than 36 hours in duration). The off-shore flow, however, wouldn't completely go away till Tuesday or Wednesday (next week).

The predicted warming this weekend into early next week shouldn't produce as much warming as with the current event (weaker high pressure aloft predicted). However, the spate of warmer than normal weather would continue well into next week (peak temperatures could approach 80 degree but it shouldn't be widespread in areal coverage).

While most longer range model solutions show dry weather in southern California leading up to Christmas Day, it's not unanimous. A few model solutions do show a weakening storm reaching the Southland sometime after the 20th (only one storm). A minor rain event could occur with this scenario (lowland rainfall under a quarter inch). Northern California would have a better shot at wet weather, but it may be mainly over the northern third of the state. There is definitely a trend toward cooler weather next week, but how much cooling and how long that occurs is still uncertain.

UCLA Forecasts and analyses are written by James Murakami

– posted: 2017-12-11

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

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