21/755 PM.
A weak upper level trough will move northeast out of the area tonight. A warming trend will begin Tuesday and peak on Wednesday, with highs 5 to 10 degrees above normal. The marine layer will shrink during this time, with overnight low clouds and fog limited to near coastal areas.
(Mon-Thu), 21/813 PM.
***UPDATE***
A weak upper level low moved over the area today, producing some mid to upper clouds, a deep marine layer, and cooler daytime highs. Max temperatures today were mostly in the 70s, but with some 80s across the interior sections. The marine layer will shrink overnight as the upper low shifts northeastward, with low clouds and fog expected to be much less extensive, especially south of Point Conception. Gusty northerly winds along SW Santa Barbara County will keep the south coast mostly clear, as well as the Ventura Coast. For LA County low clouds will affect mainly the coastal areas and portions of the coastal valleys, but overall expecting much less coverage with good afternoon clearing.
Temperatures will rebound the next couple of days, likely peaking on Wednesday with 80s to 90s nearly everywhere. This is a result of weak ridging aloft behind today's upper low, and surface pressure gradients trending to weak onshore to very weakly offshore (LAX to Daggett) with weak northerly gradients forecast for LAX to Bakersfield. Max temps will rise 2 to 4 degrees and locally to 6 degrees on Tuesday, with 8 to 12 degrees warmer on Wednesday.
***From Previous Discussion***
Wednesday's temps should mostly end up in the 80s across the csts and in the 90s in the vlys. These max temps are 3 to 6 degrees above normal except for the Central Coast where there will be about 10 degrees over normal. There is a 20 to 25 percent chance that the forecast is not warm enough and max temps will end up high enough to warrant some heat advisories. Pockets of breezy offshore winds of 20 to 30 mph are anticipated across interior mountains and foothills.
A reversal to onshore flow will drive a modest cool down into Thursday, although above normal temperatures may continue for one more day.
(Fri-Mon), 21/203 PM.
Broad troffing will likely cover the state later this week and into the weekend. The GFS does favor a ridge on Sunday but the EC, the EC-AI and many ensembles show the trof hanging on to the coast.
The onshore gradients will be fairly week through the period and there will be some weak offshore flow from the north during the mornings. This and the fact the troffing is not very sharp or dynamic will likely result in only a patchy marine layer stratus pattern.
Max temps will cool a little on most of the days, but most temps will remain a few degrees above normal. Blended ensemble guidance shows 4 to 8 degrees of cooling on Sunday, but this may be over done given the 586 fcst hgts and offshore flow from the north in the morning.
Distant tropical cyclones may send another round of swells and large surf and dangerous rip currents to south or southwest facing coasts by late this weekend. We could see some increasing mid to high clouds well ahead of these systems.
21/2359z.
At 2355Z at KLAX, the marine layer was 3700 ft deep. The top of the inversion was at 5800 feet with a temperature of 15 C.
High confidence in VFR conds for KPMD & KWJF.
Low to moderate confidence in the remaining sites. Arrival of cigs tonight may be off by 3 hours, and confidence is low in min cig heights, where TAFs may be off my one category. There is a chance for no cigs tonight at KOXR/KCMA (40%),KLAX/KLGB/KSMO (20%). There is a 20% chance for brief IFR-MVFR cigs at KSBA and KBUR after 12Z.
KLAX, Low confidence in return cig timing (+/- 3 hours) tonight and min cig height (015-025). There is a 20% chance for no low clouds tonight. Any east wind component is expected to remain less than 6kt.
KBUR, Latest TAF for KBUR trending lower probability for cig return on Tuesday morning (20%).
21/835 PM.
Good confidence in Small Craft Advisory (SCA) west to northwest winds across the outer waters south and west of Point Sal and through the Santa Barbara Channel continuing through late tonight. After a break Tuesday morning, SCA winds are expected to become more widespread in the afternoon into early Wednesday, including across the nearshore Central Coast waters. Winds are expected to decrease some Wednesday with only a 30-40% chance for SCAs (highest across the northern-most outer waters), then SCA northwest winds may return to the outer waters, nearshore central coast waters, and potentially the Santa Barbara Channel as early as late Thursday into the weekend.
Ca, NONE. PZ, Small Craft Advisory in effect from 3 PM Tuesday to 3 AM PDT Wednesday for zones 645-670. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM to 9 PM PDT Tuesday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Wednesday for zones 673-676. (See LAXMWWLOX).
