06/243 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 possibility of a couple mountain showers on Sunday, dry conditions will prevail.
(tdy-Sat), 06/243 AM.
The next 4 days will be very similar to each other and will be defined by dangerous heat/humidity across the vlys areas further inland.
There will not be much synoptic change at all through this weekend. A 599 dam upper high will sit near the four corners region and not move much. Hgts will slowly rise from 594 dam today to 596 dam Friday. The hgts will not change much Saturday and then slowly subside back to 594 dam Sunday. At the sfc there will be mdt-stg onshore flow to the east and weak-mdt onshore flow to the north.
The marine layer will be near 1400 ft and night through morning low clouds and fog will affect not only the csts but also some of the lower coastal vlys each day. Clearing will be slower than normal but the low clouds should clear by noon each day. The only fly in the ointment is the increasing amount of monsoon moisture which could disrupt or slow the marine layer stratus formation.
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 percent or less through Saturday. On Sunday at the peak of the monsoon the chc will increase to near 15 percent.
There will be a slow warming trend through Saturday as the hgts rise and then little change on Sunday. 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), 06/225 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.
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.
06/243 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.
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.
