29/1258 PM.
The weather will be dry and warmer across the region through Tuesday with gusty Santa Ana winds at times. The next storm will move into the area from the south Wednesday with periods of rain through at least Saturday, heaviest Wednesday night into New Years Day.
(tdy-Thu), 29/209 PM.
A strong Santa Ana wind event began late Sunday night and is peaking this afternoon with a number of sites reporting wind gusts between 35 and 50 mph in the usual favored areas of LA/Ventura Counties, outside of the LA Basin, with some isolated gusts between 50 and 70 mph, mostly in the mountains. Per usual the winds will start to weaken during the afternoon and evening. Offshore gradients will remain strong Tuesday but weakening upper support and cold advection should keep winds below advisory levels in most areas.
Temperatures have warmed up today at lower elevations with the downslope winds with highs in the low to mid 70s in the warmest areas. Expecting to see some additional warming Tuesday, especially across the interior due to the cold air mass shifting eastward. Elsewhere temperatures will be about the same as today.
A return to wet weather is expected Wednesday as moisture from off the coast of Mexico gets pulled up into southern California. Onset time is still in question, but no later than Wednesday evening. Some light rain is possible as early as Wednesday morning, especially far western areas as the hi res models show the initial trajectory farther to the west over the Channel Islands and Central Coast, but then shifting east during the afternoon and evening. Precipitable waters rise quickly Wednesday night, rising to between 1.25 and 1.5" through New Years Day. This will be the period of heaviest rainfall with this storm, but likely still at least 50% lighter than the last event. Will have a better estimate on specific rainfall rates by Tuesday as the storm moves into the higher res models, but based on the lower res models overall rain rates should peak at around 0.5" per hour, with isolated rates up to 0.75" per hour. The higher rates will again be south of Pt Conception and mostly in the upslope areas. So the chances of a wet New Years Parade, and including the night before when people camp out before the parade, are extremely high, 80-90% at this point. The last wet New Year's parade was in 2006. Given the amount of rain that recently fell, the expected rain rates and amounts with this system will likely generate more runoff than usual and flood watches will be strongly considered over the next 24 hours, particularly in light of the slight risk of excessive rainfall from WPC.
Rain totals through Thursday south of Pt Conception are expected to be 1-2.5" coast and valleys and 2-4" in the mountains. Rain amounts north will be about 50% of that. Convective potential remains low with this event, but not zero. But like the last event, it won't necessarily require a thunderstorm to generate heavy rain. Winds will not be as strong with this event either, but local gusts to 40 mph are possible in the heavier storms. As this system is orginating from the south it is quite warm with snow levels over 9000 feet.
(Fri-Mon), 29/210 PM.
There will be a break in the steady rainfall sometime later Thursday night into Friday with just scattered light showers and minimal rain amounts.
A more traditional cold front coming from the northwest will move into the area Saturday into Saturday night with another increase in rain rates, though likely lighter than Thursday with minimal impacts. Snow level will lower as there is more colder air with this system but still mostly at or above 6500 feet.
Lots of uncertainty with regard to how long this showery regime will continue into the following week. Most of the deterministic models shut the rain door late Sunday but there are more than a few ensemble solutions indicating additional light precip into early next week.
29/1526z.
At 1530Z at KLAX, there was a surface-based inversion. The top of the inversion was 1000 feet with a temperature of 16 degrees Celsius.
For 18Z TAF package, high confidence in VFR conditions for all sites except for KPRB. At KPRB, there is a 40% chance of LIFR/VLIFR conditions 11Z-17Z.
Strong offshore winds will generate moderate turbulence and LLWS across the local mountains and foothills through the period.
KLAX, For 18Z TAF, high confidence in VFR conditions through the period. Moderate confidence in easterly wind around 7 knots in the 14Z-21Z time frame.
KBUR, For 18Z TAF, high confidence in VFR conditions through the period. Moderate confidence in wind forecast as there is a 30-40% chance of stronger N-NE winds through this afternoon.
29/141 PM.
For the Outer Waters, moderate to high confidence in current forecast. This afternoon through Tuesday, high confidence in Small Craft Advisory (SCA) level northeast winds are expected south of the Channel Islands with winds and seas remaining below SCA levels elsewhere. For Wednesday through Thursday, there is a 60-80% chance of SCA level southeasterly winds with a 20% chance of GALE force winds. On Friday, there is a 30-40% chance of SCA level winds continuing. For Saturday, high confidence in winds remaining below SCA levels, but there is a 50% chance of SCA level seas.
For the Inner Waters north of Point Sal, moderate confidence in current forecast. There is a 60-70% chance of SCA level NE winds through Tuesday morning with the strongest winds nearshore from Point Estero to Morro Bay and Irish hills to Oceano Beach. For Wednesday, there is a 30-40% chance of SCA level southeasterly winds. On Thursday, the chance of SCA level southeasterly winds increases to 60-80% with a 30-40% chance of the SCA level winds continuing on Friday. For Saturday, high confidence in winds remaining below SCA levels, but there is a 20-30% chance of SCA level seas.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. High confidence in SCA level northeast winds through Wednesday morning from Point Mugu to Santa Monica with a 20-30% chance of GALE force winds tonight and Tuesday morning. From Wednesday afternoon through Thursday, there is a 50-70% chance of SCA level southeasterly winds. For Friday and Saturday, high confidence in winds and seas remaining below SCA levels.
Ca, Wind Advisory now in effect until 8 PM PST this evening for zones 88-354-355-358-362-370>374-376-380. (See LAXNPWLOX). High Wind Warning remains in effect until 3 PM PST this afternoon for zones 369-375-378-379. (See LAXNPWLOX). Wind Advisory in effect until 8 PM PST this evening for zones 369-375-378-379. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 9 AM PST Tuesday for zones 645-676. (See LAXMWWLOX). Gale Warning in effect until 3 PM PST this afternoon for zones 650-655. (See LAXMWWLOX). Small Craft Advisory in effect until 3 PM PST Tuesday for zones 650-655. (See LAXMWWLOX).
