15/137 PM.
A warming trend will continue through Tuesday as high pressure aloft over northern Mexico builds over the region. Areas of night through morning low clouds and fog will continue near the coast through Wednesday. Moisture from tropical storm Mario will move into the area later Wednesday through Friday leading to a chance of showers and thunderstorms at times, especially on Thursday. Dry weather is expected over the weekend.
(tdy-Thu), 15/224 PM.
Significant warming occurred across inland areas today as onshore flow weakened and high pressure was building aloft. These trends did not make it to the coast where highs were mostly unchanged or slightly cooler, especially along the Central Coast. The marine layer is expected to continue to lower again tonight, keeping most of the valleys clear but still pushing into most coastal areas.
After the typical morning marine layer Tuesday, 2-4 degrees of additional warming is expected, including the coast areas, as the upper high over the desert southwest continues to build into the area and onshore flow continues to weaken. And it now looks like Tuesday will be the warmest day of the week. Warmer valley areas are expected to reach the lower 100s while inland coastal areas will be in the 80s to lower 90s. Highs overall will be 4-8 degrees above normal. While well above normal, heat risk values will remain below advisory levels.
Tropical Storm Mario still remains around 1000 miles south of Los Angeles. It is expected to weaken and become a remnant low over the next 24-48 hours while drifting over cooler waters along the northern Baja coast. High level moisture will begin to enter the area Wednesday and the latest model projections suggest that rain chances locally will hold off until at least later on Wednesday or Wednesday night. The exception could be over the outer portion of the coastal waters where some showers and thunderstorms could develop earlier. PW's will be increasing to between 1.5 and 1.75" Wednesday leading to a very muggy day across the area and it now appears that high temperatures in many areas will actually lower slightly due to the added moisture aloft. However, while temperatures will be slightly cooler, humidities will be increasing and there is still a 20-40 percent chance that a heat advisory will be needed across portions of LA County. Will re- evaluate that on Tuesday.
Wednesday night into Thursday appear to be the most likely period for showers and thunderstorms area-wide as the ensemble solutions show Mario's remnant upper low crossing into the US somewhere near 32n/122w and moving north. PW's will increase to almost 2" and there will be enough instability to generate showers and thunderstorms at times across the area. There is still a fair amount of uncertainty with the timing and rainfall rates and amounts as even a small deviation of the track could make a significant change to the outcome. But a large percentage of the ensemble solutions show at least some rain falling during this period pretty much everywhere across the 4 county area. And there are roughly 10-15% of the solutions showing an inch or more or rain so there is certainly the potential for periods of very heavy rain and flooding.
(Fri-Mon), 15/235 PM.
The threat of showers and thunderstorms is expected to continue into at least the first half of Friday as the last of the moisture moves through the area.
The weekend is now expected to be dry, though there are still a small percentage of the ensemble solutions showing some additional light showers associated with a quick moving upper low from the northwest. Aside from that, the region will be slowly recovering from the warm tropical pattern and it may take several days before any marine layer reforms. Temperatures are expected to near normal Saturday, then warming to slightly above normal Sun/Mon.
15/2357z.
At 2259Z at KLAX, the marine layer was 1100 ft deep. The top of the inversion was at 2400 ft with a temperature of 27 C.
High confidence in VFR TAFs for desert airfields (KWJF & KPMD).
Most uncertain in arrival times of CIGs (+/- 3 hours), & moderate confidence in clearing times (+/-2 hours). Flight minimums may be off one category.
Chances for CIGs tonight into Tuesday at KBUR (15%), KVNY (10%), & KPRB (10%).
Chances for rain are increasing for Thursday, with a chance for thunderstorms.
KLAX, Moderate confidence in 00Z TAF. Arrival and clearing times likely to be accurate within +/- 2 hours from current forecast. There is a 20% chance of lowering to 0VC004 from 10Z to 15Z Tue. No significant east wind component expected through the period.
KBUR, High confidence in VFR through at least 06Z. 20% chance of IFR conds 08Z-15Z Tue.
15/210 PM.
Minimal risks of Small Craft Advisory (SCA) winds through Wednesday Night, except for a 30% chance of low-end SCA winds off the Central Coast Wednesday afternoon and evening.
Tropical Storm Mario was Moisture and energy from the remnants of what is currently Tropical Storm Mario will impact southwest California Wednesday through Thursday or Friday. A period of showers is likely at some time, with Thursday having the highest chances, but confidence is fairly low on timing and amounts. Thunderstorms are also possible at any time in the time window, but again confidence is low on the details. Any thunderstorm will bring a risk of brief but strong winds and frequent lightning. In addition, gusty Santa Ana- like winds are possible on Thursday due to the proximity of the core of the weakened storm. Please monitor the forecast if you have any plans on going out on the water this week, as this will be a low- confidence and evolving situation.
Ca, NONE. PZ, NONE.
