12/1256 PM.
Several degrees of cooling are expected through Wednesday as an upper low moves through northern California. Low clouds and fog will move into the coastal valleys with clouds lingering at some coastal areas through today. Gusty winds are expected times across the mountains and deserts. Slight warming is expected Thursday into Friday.
(tdy-Fri), 12/1256 PM.
The marine layer has deepened significantly since yesterday, accounting for nearly all of the cooling trends over this time especially for coastal valleys. Low clouds will likely stick around most of the day for many areas west of the mountains thanks to strong onshore flow and strong inversion. Isolated mid level clouds have started to develop over some interior mountains. This is evidence of the weak moisture intrusion from the southeast that will support about a 5 percent chance of a shower or thunderstorm to interior mountains and valleys, especially northern Ventura into northeast Santa Barbara Counties. Dry lightning fire starts and gusty winds would be the greatest concern if a thunderstorm were to form.
A weak trough passing overhead will boost the marine layer another 1000 feet or so to 3000-4000 feet into Wednesday. Sending the cooling trends experienced today further inland with temperatures near normal for this time of year. The additional deepening may support spotty drizzle especially into foothill to lower mountain locals. One more day of slow to no clearing of low clouds is likely Wednesday, especially into the coastal slopes as a reverse clearing (clearing at the coast before the valleys/foothills) day is likely.
Breezy northwest to southwest winds will is expected afternoon to evening, possibly boosting to near advisory levels for areas prone to northwest winds (southwest Santa Barbara County & I-5 corridor in the mountains) Wednesday evening and again as early as Friday afternoon.
A weak ridging building into the region will likely shrink the marine layer closer to the coast and lead to warming trends Thursday and Friday, but no where near the heat we saw just yesterday.
(Sat-Tue), 12/1256 PM.
Below normal confidence this weekend into early next week as a sharp trough (for May) is poised to pass nearby. An inland track (50 percent chance) would lead to near normal temperatures with breezy winds nearing advisory levels for some interior areas such as the mountains near the I-5 corridor and southwest Santa Barbara County into Saturday or Sunday with the potential for offshore winds with decent warming and drying trends into Monday. A close pass (30 percent chance) would lead to gusty and probably advisory northerly winds for the interior and mostly below normal temperatures.
12/1751z.
At 1725Z at KLAX, the marine layer was 2100 ft deep. The top of the inversion was at 4600 ft with a temperature of 22 C.
High confidence in VFR TAFs for desert airfields (KPMD & KWJF).
Low to moderate confidence in remainder of TAFs. Timing of flight category changes may be off by 3 hours and by one flight category.
KLAX, Moderate confidence in TAF. MVFR CIGs 015-025 expected thru 13/21Z. Periodic IFR CIGs 008 may occur through 13/15Z. 50% chance CIGs persist throughout entire forecast period. No significant east wind component.
KBUR, Moderate confidence in TAF. IFR to MVFR CIGs likely to persist through entire forecast period. 15% chance of LIFR CIGs 004 13/08Z-15Z. No wind issues expected.
12/754 AM.
Winds and seas will remain below Small Craft Advisory (SCA) levels through Wednesday morning.
SCA conditions (winds and seas) are expected to develop across the northern Outer Waters Wednesday afternoon, expanding in coverage to include all Outer Waters by Wednesday night.
These hazardous conditions will persist into the weekend reaching portions of inner waters (along the Central Coast and SB Channel) at times.
GALE Force winds will be possible across the outer waters as early as Thursday afternoon, with highest (30-50 percent) chances on Saturday into Sunday.
Seas will continue to build into the weekend peaking 10-15 ft across the outer waters.
Dense fog will be possible through mid morning Today.
Ca, Wind Advisory in effect until 10 PM PDT this evening for zones 381-383. (See LAXNPWLOX). PZ, NONE.
