30/113 PM.
Little change in weather conditions is expected through Thursday with temperatures 4-8 degrees above normal. Areas of morning low clouds and fog are possible near the coast as well. A major and long lasting heat wave will begin Friday and last through all of next week at least with with dangerously hot temperatures.
(Wed-Sat), 30/809 PM.
***UPDATE***
***A VERY DANGEROUS AND LONG LASTING HEAT WAVE FRIDAY THROUGH AT LEAST NEXT WEEK AND LIKELY EXTENDING INTO THE SECOND WEEK IN OCTOBER***
Yesterday's northerly winds backed off today, with gradients shifting back to weakly onshore (LAX to Daggett +1.9 mb). Cooler conditions were observed along the Central and SBA South Coasts, but with plenty of 80s and 90s across Ventura and LA Counties. Slight warming is expected into Thursday, but mainly over LA County with highs up 2-4 degrees compared to today. This is a brief preview of the significant, long-duration heat wave to come for the region starting Friday. Through the short term, the hottest day looks to be Saturday, with 90s to around 105 for most areas, except for the immediate coastline and higher mountains. After that temperatures will back off a few degrees and remain at around 10-15 degrees above normal through at least the coming week.
All this is set to occur as an upper ridge builds over Central to Southern California, and then remains more or less over the area with weak offshore flow at the surface. The very warm ocean surface temperatures will create muggy conditions near the coast during this time, providing limited relief for beach goers. Low clouds will be on the wane due to the offshore trends, and tonight may be the last night of low clouds south of Point Conception. The Central Coast should see stratus tonight and Thursday night, but lower confidence over the weekend.
***From Previous Discussion***
For the most part the short and long term forecasts have not changed and likely won't change much through next week. Models continue to advertise a long duration heat wave starting Friday, peaking Saturday, then leveling off at 10-15 degrees above normal Sunday through all of next week and into the second week of October. While the gradients will technically be 2-4mb offshore and we are entering our typical Santa Ana season, this really is not a Santa Ana event and winds, for the most part, will be relatively light in most areas. This is just a very hot air mass with light offshore flow that will significantly delay the arrival of any cooling effects from our much warmer than normal ocean. And while temperatures will be very hot, there may not be many broken temperature records because heat waves in previous years were accompanied by a stronger offshore flow with stronger subsidence aloft to generate additional heat at the surface. So this heat wave will be most notable for it's length rather than the daily temperatures. On the bright side, with that little offshore flow humidities should remain on the lower side at least through Saturday.
In summary, an Extreme Heat Watch has been issued for all coast and valley areas south of Pt Conception starting on Friday. There will be warming north of Pt Conception but it will take 1-3 more days to reach heat advisory levels there so expect additional heat hazards in the coming days for the Central Coast.
(Sun-Wed), 30/215 PM.
The short term discussion covered most of the long term issues. Models do indicate some increase in PW's Sunday and Monday from newly crowned Hurricane Rachel. Most of this storm is tracking to the west but it will send some moisture and likely ocean swells north early next week. There's even a small (5-15) percent chance of a shower or thunderstorm, mainly in the mountains.
Also, model solutions are showing even higher temperatures around mid week associated with a stronger offshore push and downsloping effects. The latest GFS is indicating 950mb temps in the mid 30s (celcius) so there is at least a 10-20% chance of reaching record temperatures during this heat wave.
01/0102z.
At 2314Z at KLAX, the marine layer was 1100 ft deep. The top of the inversion was near 3500 ft with a maximum temp of 27 C.
High confidence in VFR TAFs for KPRB, KWJF, and KPMD.
Moderate confidence in remaining TAFs. Timing of change groups may be off +/- 2 hours. CIG height accuracy +/- 300 ft of fcst.
Lowest confidence in KBUR & KVNY between 01/10-16Z. There is a 40% chance IFR CIGs do not arrive or last less than an hour.
KLAX, Moderate confidence in TAF. Arrival & clearing times of IFR CIGs 008 (+/- 200 ft) may be off +/- 2 hours. No significant east wind component expected.
KBUR, Low to moderate confidence in TAF. 40% chance IFR CIGs near 007 do not arrive or last less than an hour between 01/10-16Z. No wind issues expected.
30/814 PM.
Lingering swell near 10 feet for the far northern outer waters is expected to trend downwards going forward. Local areas of Small Craft Advisory Level (SCA) gusts are possible each afternoon and evening through at least Saturday, for areas around Point Conception, off the coast of Point Dume, and across the San Pedro Channel. Beside the aforementioned areas, quiet marine conditions are expected for the rest of the coastal waters.
30/801 PM.
Beach Hazards Statement has been allowed to expire.
While we will get a break from the coastal flooding concerns for the rest of the week, another hurricane swell (from Rachel) will likely bring a larger-than-Polo south swell to southern California for the early to middle part of next week. Thankfully tides at that time will not be extreme, but they should be around 6.5 feet which is high enough to cause some concern, but it all depends on how big the surf ends up. Stay tuned for future updates.
Ca, Extreme Heat Watch in effect from Friday morning through Thursday evening for zones 38-87-88-349>358-362-366>375-548-550. (See LAXNPWLOX). PZ, NONE.
