21/204 PM.
A weak upper level trough will move over the area today, cooling temperatures and increasing marine layer stratus. A warming trend will begin Tuesday and peak on Wednesday, with highs 5 to 10 degrees above normal.
(tdy-Thu), 21/204 PM.
The position of a upper low was near overhead today, supporting a deep marine layer with pockets of slow to burn off low to mid level clouds and temperatures generally in the 70s. An isolated afternoon cumulus cloud has formed over the Ventura County Mountains and there is still a 5-15 percent chance of a shower or thunderstorm through 5 pm.
A small ridge will move into the area Tuesday and Wednesday. Hgts will rise to about 582 dam. More importantly there will be good offshore trends both days. This will lead to only weak onshore flow to the east and actual offshore flow from the north in the mornings. Look for a reduction in the marine layer cloud coverage as well as much earlier and complete clearing. Max temps will rise 2 to 4 locally 6 degrees on Tuesday. Due the weakened onshore flow, Wednesday will see a big 8 to 12 degree jump in temps.
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 chc 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%).
21/207 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 tonight. SCA winds are expected to become more widespread tomorrow afternoon into early Wednesday, including across the nearshore Central Coast waters. Winds are expected to decrease some Wednesday with only a 30-50% chance for SCAs (highest across the northern-most outer waters), then SCA northwest winds will likely return across 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 until 9 PM PDT this evening for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 5 AM PDT Tuesday for zones 673-676. (See LAXMWWLOX).
