Notice: Swayed by comments about the weather page, I will write campus forecasts and synopses on a limited basis (starting with a once a week edition). However, I'll be on hiatus for the summer till after 11 September.
Whew! Such a busy day replying to emails today and taking care of business...Well, here goes for the final time as a regular, employee of UCLA...
The on-shore flow weakened as expected, and the marine layer became a little shallower this morning. Low clouds cleared away to the coast more completely than yesterday. Temperature-wise today, modest but noticeable warming (over yesterday) has occurred in the coastal valleys. In the coastal plain, temperatures are about the same or slightly lower than it got yesterday (through early afternoon, at least). It seems that a shallower marine layer sometimes results in less vertical air mixing, which then cuts down on daytime heating. Little change to this pattern is anticipated tomorrow, but a new, approaching trough from the north will rapidly increase the on-shore flow from Sunday into Monday. That should promote general cooling, including the desert region (finally relief for a couple of days out there).
In the meantime, a different, weak upper level trough is promoting some instability showers in the southern Sierras. Some building clouds around the Big Bear Lake area may become brief-lived, thunderstorms later in the afternoon. This instability should wane rapidly by sunset. No further shower threat should occur out there after today. The predicted, deepening marine layer on Sunday and Monday, however, could promote spotty, early morning drizzle on Sunday (predicted coastal eddy aiding as a trigger mechanism). Some models continue to show increasing areal coverage late Sunday night into early Monday morning. Potentially, wet weather won't be restricted to areas up against the coastal facing foothills/mountains. Rainfall could amount to a tenth in places (trace amounts being more common).
Based on today's model consensus, there is an increasing chance for the low cloud field getting disrupted Monday evening. However, the shallow marine layer may "repair" itself as the week progresses (i.e. more widespread, low clouds returning to the coastal plain late next week). Still, my confidence in this scenario still on the low side. As stated in previous synopses, the integrity of the marine layer will have bearing on how warm the coastal plain gets late next week. Today's model consensus has back tracked a little on how warm it may get in the interior (high pressure aloft may not expand into southern California as much as earlier forecasts showed). Only time will tell.
Well, I've babbled on long enough. Time to take a summer break (first in a long, long, time).
UCLA Forecasts and analyses are written by James Murakami
– posted: 2020-06-26