Note: No forecast will be issued on Monday, 25 June.
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High pressure aloft continues to promote warmer than normal weather in the interior (110 degrees yesterday in Palm Springs, 104 degrees in Lancaster, and 126 degrees in Death Valley). Had it not been for a coastal eddy helping to prop up the marine layer, things could have been much warmer in the coastal plain this week. It's been quite warm in most coastal valleys (upper 80s to low 90s...even a 100 degree reading in Lake Elsinore), but the marine layer has tempered the warming (could have been several degrees higher). The computer models continue to forecast only minor shifts in the wind flow pattern affecting southern California. This is expected to continue right up the 4th of July (possibly several days after that).
There should be minor cooling/warming cycles over the next several days. I had expected some warming today over yesterday, but so far, most areas have been running the same or slightly behind yesterday's pace of daytime warming. As I've stated in previous synopses, temperature changes in the coastal plain should be almost unnoticeable (no more a three degree rise or fall for a given cycle). Valley temperatures could vary a little more, but no significant heat (for June) is expected anytime soon. The only region remaining much warmer than normal should be the higher mountains and deserts (yesterday warmed into the mid/upper 80s at the 5000-6000 feet elevation). Still, some modest cooling is anticipated there at times (like this weekend).
A minor warming cycle is expected early next week. Another cooling cycle should follow in the second half of next week (may last into the subsequent weekend). At this point, the days leading up to the 4th of July should be near seasonable levels (includes the deserts). One model scenario shows a fair strength, trough of low pressure that could promote cooler than normal weather. However, it's solution is being rejected for now (most of the other model solutions show a much weaker trough).
While the marine layer depth should go up and down periodically (depth about the same as yesterday early today but expected to deepen over the weekend)., these changes should be minor. Areal coverage from one day to the next shouldn't vary a lot. Subtle shifts in the low level winds (sometimes associated with coastal eddies) may result in more persistent low clouds in one locale versus another (variations from one day to the next). One thing that could result in much less low clouds is entrainment of dry air from aloft (above the marine layer). None of the model forecasts show this happening in the next week, but a random event could happen unexpectedly. In this case, not only would the weather turn sunny for those areas, it could wind up several degrees warmer than currently forecast.
UCLA Forecasts and analyses are written by James Murakami
– posted: 2018-06-22