Not a whole lot changed with the wind flow pattern over southern California (just as the computer models predicted). Winds aloft associated with the current, off-shore flow were a little stronger, but they haven't yet purged the marine layer in the coastal plain (fog/low clouds actually more extensive along and off the coast than yesterday). Noontime temperatures were running at or behind yesterday's pace near the immediate coast (L.A. County southward). Farther inland, the pace of warming was ahead of yesterday (significantly more in the San Fernando Valley where the air has dried out significantly from the off-shore flow). Today's computer models continue to insist that the existing, shallow marine layer will be pushed off the coast by tomorrow. Hence, I'm sticking with the warming scenario offered by the various, numerical models.for this weekend.
Unless the off-shore flow is unsuccessful in purging the marine layer, deep layered, easterly wind flow should promote widespread 80 degree weather tomorrow/Sunday. The predicted, vertical temperature profile could support readings into the mid/upper 80s although low 80s should be more common (beaches should warm well into the 70s tomorrow and perhaps Sunday too). Off-shore flow should weaken enough on MLK, Jr. Day to promote modest cooling by the coast (earlier onset of the sea breeze) and minor cooling elsewhere west of the mountains. The cooling trend should continue on Tuesday when a storm to our north brushes by the Southland (daytime temperatures should still be above normal though).
With stronger wind aloft, it's occasionally breezy today in many Santa Ana wind prone areas in the higher mountains. The peak winds in the mountains could reach 45 mph for a time early tomorrow. Most lowland areas prone to Santa Ana winds should be breezy at times, but peak wind gusts shouldn't exceed 30 mph (much lower most of the time). Support for significant wind should taper off tomorrow afternoon. No widespread, significant wind is expected by Sunday as wind support aloft dies off. A return to a marginal, on-shore flow is predicted for Tuesday,
As stated earlier, a storm will brush by the Southland on Tuesday. Wet weather is expected over the northwest corner of the state on Monday and spread south with time. However, except for a chance of very light showers over the northern most sections of southern California, no wet weather is likely to occur from this storm. Most likely, the weather down here will be no worse than partly cloudy that day.
High pressure aloft will build back over the Southland Tuesday night and Wednesday. At this point, only a marginal, surface off-shore flow is predicted. So, any warming next week should be minor (warmer than normal but no widespread, 80 degree weather anticipated next week). Cooler weather is expected again on Thursday/Friday of next week (another storm).
Past model solutions for next Friday showed widespread wet weather reaching southern California (consensus for only a minor rain event though). Fewer model solutions today show that happening. Showers are still probable, but they may be confined mainly to the mountains and north of Point Conception. Storm totals may also be under a tenth inch in most areas that get wet weather. Being a week away, the models may still waver back and forth on the projected storm (better chances for widespread, significant precipitation in northern California).
Even if the wet weather scenario verifies, the model consensus shows a moderately strong, off-shore flow for the weekend of the 20th (widespread, breezy weather for a time). Most model solutions show a "cool" Santa Ana wind for this event (temperatures getting only slightly warmer than normal). Other storms may reach the Southland in the days that follow. So, the off-shore flow should be a short-lived event. It's unclear whether widespread precipitation will occur with any storm for the week of the 22nd. Some solutions show a minor rain early on followed by a more significant storm late that week. Of course, with rather varied solutions for that time period, I have little confidence in a weather trend (other than hot weather appears very unlikely).
UCLA Forecasts and analyses are written by James Murakami
– posted: 2018-01-12