06/907 AM.
Night through morning low clouds and fog will be common over coastal areas and the coastal valleys through at least this weekend, with clearing each afternoon. Hazardous heat will occur through this weekend over interior areas. Aside from the chance of a few mountain showers on Sunday, dry conditions will prevail.
(tdy-Sat), 06/945 AM.
***UPDATE***
Little change in the pattern through the short term, with a ridge of high pressure centered near the four corners region. This ridge will remain stationary through Friday and then expand westward so that heights rise over southern California. Saturday is likely to be the warmest day in this stretch of heat as heights aloft rise to 596 dam. Sunday will be slightly cooler but still hot, followed by more significant cooling next week.
At the surface, onshore winds are already gusting 25 to 35 mph through the interior passes and canyons into the Antelope Valley. In general, onshore gradients to the northeast and north (LAX to Daggett and LAX to Bakersfield) will weaken some Friday, then strengthen Saturday and especially Sunday.
Monsoonal moisture will begin to move over the area today with southeast flow aloft, resulting in a non-zero chance of showers and thunderstorms over the eastern San Gabriels and eastern Antelope Valley this afternoon and evening.
Low clouds and fog will continue to affect coastal areas and some of the coastal valleys during the night to morning hours through the short term. This pattern could be disrupted depending on the amount of monsoonal moisture aloft, which could slow or prevent marine layer formation.
***From Previous Discussion***
Due to the position of the upper high there will be SE flow at the upper levels during the period. This flow pattern will usher in some monsoon moisture. PWs will increase each day starting out around an inch over KLAX today and ending up near 1.6 inches on Sunday. This increase in moisture will drive up humidities. There will be a non zero chc of mtn convection in the afternoon starting today but the actual chc of convection will remain at 10-15 percent or less through Saturday. On Sunday at the peak of the monsoon the chc will increase to near 10-20 percent.
There will be slow warming through Saturday as hgts rise aloft. There will only be a degree or two today, but on Friday areas should see a 3 to 5 degree warm up. Saturday will follow with an additional 1 to 2 degrees of warming for most areas. Max temps Friday through Sunday will mostly be 4 to 8 locally 10 degrees above normal. There is lower confidence in the warming trend for the nearshore area as the onshore flow and marine layer could easily defeat any other warming effects.
In addition to the temperature the area will see an increase in humidity each day. This will make the actual temps feel worse than normal. At night the higher moisture content will inhibit cooling resulting in above normal and sticky overnight lows. Heat advisories and warnings are in effect for the lower mtn elevations and the far interior. Even through the coastal vlys are not in any of these advisories residents will need to be mindful of the afternoon heat and take appropriate precautions.
The strong onshore flow in the afternoon will produce stronger than normal sea breezes and gusty afternoon winds in the interior. The gusty winds in the interior in combination with the hot and dry conditions will produce elevated fire weather conditions.
(Sun-Wed), 06/537 AM.
Cooling will finally arrive on Monday.
The ridge will slowly weaken as a series of weak trofs moves through OR and far nrn CA. Hgts will fall to 592 dam. At the same time onshore flow will increase both to the north and the east becoming strongly onshore in both directions in the afternoons. The marine layer will respond to this and low clouds will likely begin to xtnd into the vlys. Look for slower than normal clearing and some west facing beaches may see only limited clearing.
The combination of a deeper marine layer, stronger onshore flow and falling hgts will bring 2 to 3 degrees of cooling each day Monday through Thursday. Max temps will approach normals on Tuesday and then most areas will see blo normal max temps on Wed and Thu. Vly temps on Wed and Thu will only be in the mid 80s to lower 90s.
PWs will remain elevated through the period however. This will make things feel a little stickier than normal and will keep overnight lows a little warmer than normal. This moisture will keep the low chc (10 to 15 percent) of afternoon mtn convection going through the period.
The strong onshore flow to the east will produce gusty near advisory level wind gusts across the western Antelope Vly and the western foothills.
06/0944z.
At 0820Z at KLAX, the marine layer was 1100 feet deep. The top of the inversion was at 4100 feet with a temperature of 28 C.
High confidence in TAFs for KPMD & KWJF.
Good confidence in TAFs for KBUR & KVNY with a 15 percent chc of IFR cigs 13Z-16Z.
Moderate confidence in remaining TAFs. Timing of flight cat restrictions may be off +/- 2 hours, and CIG heights by +/- 200 ft.
KLAX, Moderate confidence in TAF. There is a 30 percent chc that cigs will remain AOA 010. VFR conds could arrive any time between 17Z and 19Z. No significant east wind component expected.
KBUR, Good confidence in TAF. There is only a 15% chance of BKN-OVC006-010 conds 13Z-16Z.
06/906 AM.
Winds and seas are expected to remain below Small Craft Advisory (SCA) criteria into this weekend, with the exception of northwest winds locally gusting to 20-25 knots in typically windy areas around and to the south of Point Conception each afternoon and evening through Saturday.
Dense fog may affect portions of the coastal waters each night through morning into this weekend, especially across the waters north and west of Point Conception.
Ca, Extreme Heat Warning in effect until 8 PM PDT Sunday for zones 38-377-381>383. (See LAXNPWLOX). Heat Advisory in effect until 8 PM PDT Sunday for zones 344-345-353-375-376-378>380. (See LAXNPWLOX). PZ, NONE.
