09/521 PM.
Monday will again be very warm and dry, especially across the Los Angeles and Ventura County valleys. A cooling trend will start Tuesday, ahead of the incoming storm system. Rain may start as early as Wednesday night, however the heaviest rainfall and greatest impacts are likely to occur Thursday and Thursday night.
(Sun-Wed), 09/1221 PM.
Upper level wind support wasn't strong enough with this Santa Ana event to push wind and hot temps to the coast today and it may struggle again Monday. However, the valleys are warming up quite a bit with many areas close to 90 as of noon. Meanwhile, most areas below 500 feet elevation are in the 60s to low 70s. Winds haven't been overly impressive with this event either with just a handful of sites over 25 mph. Models are still indicating a slight increase in offshore flow Monday but still with very minimal upper support so for the most part a very similar day as today except likely a few degrees warmer.
A very shallow inversion is holding its own and some beaches are still having periods of dense fog this afternoon. Since there is little upper support again tonight there is a better chance than not that dense fog will be an issue near the coast (and over the coastal waters) and creating impacts for drivers, aviation, and boaters.
A significant cooling trend will begin Tuesday as high pressure weakens ahead of the next low pressure arrival. Gradients will quickly turn onshore and most areas will drop 5-10 degrees both Tuesday and again Wednesday. A deepening marine layer will push low clouds into the valleys by Wednesday morning with highs back down into the 70s.
(Thu-Sun), 09/1248 PM.
Starting to get some improved consensus in the models regarding the storm later in the week. Timing-wise models are zoning in on Thursday being the primary period for rain across the area, but with some early showers arriving Wednesday night along the Central Coast.
Models are also coming into better agreement on the amounts as well with a large percentage of the ensemble solutions showing a heavy, but relatively short period of rain as the main front moves through. Orographics will play a significant roll in the amounts with upslope areas getting twice to 3 times the amounts at sea level. Overall, sticking with the 1-2/2-4 inch range (coast and valleys/mountains), with much of that falling in 5-10 hour period, and hourly amounts between a quarter and half inch, and as much as 0.75 in the upslope areas.
Snow levels will likely remain at or above 8000' for most of the storm, then drop to around 6000 feet as the last of the precip is moving through later Thursday night into Friday morning. At this point it does not appear to be cold enough for snow on the Grapevine, but some light accumulations (2-4") are possible down to around 6000'.
Dry and cool weather expected next weekend with highs mostly in the upper 60s to low 70s.
10/0109z.
At 2331Z at KLAX, the marine layer was 600 feet deep. The top of the inversion was near 1300 feet with a temperature of 29 degrees Celsius.
For the 00Z TAF package, high confidence in desert and valley site, but low confidence in coastal sites except for the Central Coast sites where moderate confidence exists in LIFR-VLIFR conds. Further south along the coast, low confidence exists due to uncertainty in the timing and extent of CIGs. There is a 40% chance of LIFR-VLIFR conds for all coastal TAFs. The timing of low clouds arrival and dissipation could differ +/- 3 hrs from TAF times.
KLAX, Overall, low confidence in the 00Z TAF. There is a 30-40% chance of LIFR/VLIFR conditions overnight, most likely from 06Z to 15Z, but the timing could differ by +/- 3 hrs from TAF times. No significant easterly wind component is expected. KBUR, High confidence in the 00Z TAF.
09/1216 PM.
For the Outer Waters, moderate to high confidence in current forecast. Today through Wednesday, high confidence in winds and seas remaining below Small Craft Advisory (SCA) levels. For Thursday and Friday, high confidence in a combination of SCA level winds and seas. Additionally, there is a 30% chance of Gale force Thursday night across PZZ676.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Today through Wednesday, high confidence in winds and seas remaining below SCA levels. For Thursday and Friday, high confidence in a combination of SCA level winds and seas developing. There is a 30% chance of Gale force winds on Thursday.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Today through Wednesday, high confidence in winds and seas remaining below SCA levels. On Thursday and Friday, there is a 60-80% chance of SCA level winds with a 30-40% chance of Gale force winds.
Ca, NONE. PZ, NONE.
