10/920 AM.
Today will be mostly cloudy and cooler. Light to moderate rain will overspread the area tonight and continue through Wednesday morning. The rain will be accompanied by gusty southerly winds. The rest of Wednesday and Thursday will be partly cloudy with max temps a few degrees under normal. Warmer temperatures are expected Friday and Saturday. Rain will return Sunday, then off and on through next week.
(tdy-Thu), 10/937 AM.
***UPDATE***
A mix of high clouds and marine layer will keep skies pretty overcast most of the day with temperatures returning to normal levels. Our first storm in over a month is rapidly moving our way with light rain arriving along the Central Coast this afternoon and spreading into LA by tonight. Models haven't changed much from the last couple days in terms of intensity and timing. The hi res models are still indicating the potential for rain rates up 3/4" per hour (mainly in the mountains) and even around 5-10% for rates as high as an inch. However, as mentioned before individual cells will likely be moving at a fast clip so that should limit any significant impacts. Certainly can't rule out isolated ponding of water at times, even at lower elevations. Not planning on issuing any flood hazards at this time but expect to see flood advisories as the heavy part of the storm moves through, which still will be mainly during the overnight hours.
***From Previous Discussion***
A cold front will drag across the area tonight. There is a 150kt jet pushing the front along so the front will move through at decent clip. Look for a 2 to 4 hour period of moderate rain with the front. The atmosphere is a little unstable and with all the jet energy convection cannot be ruled out. Peak rainfall rates will be between .25 and .50 inches/hr with .75 inch per hour rates across south facing slopes. Isolated 1 inch per hour rates are possible under any convective cells that develop. From 6pm to 6am most of the csts and vlys will see around a half inch of rain but the coastal slopes and communities just below the slopes could see 1.5 inches with isolated 2 inch amounts across the Santa Ynez range and the southern VTA mtns. Light snow accumulations are possible above 6000 feet. Accumulation's will mostly be 3 inches or less, but up to 6" could fall at higher elevations.
There will be quite a few post frontal showers Wednesday morning and another quarter (isolated half) inch of rain is possible through noon. The winds will continue through the early afternoon and advisory level winds may linger in the eastern San Gabriels and Antelope Vly until late afternoon. Skies will clear through day. All the cold air behind the front will lower max temps by 2 to 4 degrees and max temps will mostly be in the lower 60s across the csts/vlys or about 6 degrees less than normals.
The upper low morphs into an elongated pos tilted upper trof on Thursday. It hardly has any dynamics with it, but a few ensemble members do show light rain across the Central Coast and the hier elevations of the eastern San Gabriels. Skies might start out mostly cloudy in the morning but will clear to partly cloudy or better by afternoon. Dry conditions and a little more sunshine will bring 2 or 3 degrees of warming to most areas with highs reaching the mid 60s for most cst/vly locations.
(Fri-Mon), 10/255 AM.
A fast moving ridge will move into and over the area on Friday. Offshore flow will develop as well and there will be some sub advisory morning NW winds across the coasts and vlys of VTA/LA counties and portions of the Central Coast. Take advantage of the day if you can as the sunny skies will not last for long. Max temps will rise 4 to 6 degrees and max temps will end up in the upper 60s and lower 70s across the csts and vlys.
On Saturday the ridge will move to the east and will be replaced by SW flow ahead of an upper low. There will be enough mid level clouds in the upper flow to make it a partly cloudy day. The lack of offshore flow will result in several degrees of cooling across the csts/vlys.
There are enough ensemble members showing some rain Saturday night but the overall mdl trend has been slower and feel that the chc of rain here is overdone. This trend continues into Sunday where the latest ensemble based solutions show rain overspreading the entire area during the day. Almost all current mdls (esp the AI mdls) show a much later arrival time and would not be surprised if this wet Sunday fcst is dialed back over the next few days.
AI and Ensembles both agree that three storms will affect the area during the week of the 16th to the 21st. Timing and intensity are still somewhat uncertain although early indications say that the biggest system will affect the area mid week. It looks fairly certain that these will be the coldest systems of the year with plenty of snow at lower than normal levels. Stay tuned to this product for daily updates on the evolutions of these systems.
10/1916z.
Around 18Z, the marine layer depth was around 3000 feet deep at KLAX. The top of the inversion up to around 3600 feet with a temperature around 11 degrees Celsius.
Moderate confidence through around 00Z, then low confidence due to rain with low ceilings and visibility. Timing could be off by 2 hours. At least brief IFR or lower cigs/vsbys possible in heavier rain focused between 00-06Z KSBA and 06-12Z to the south including KLAX. There is a 5-10 percent chance of a brief thunderstorm, mostly within those same windows. Weak to moderate LLWS is possible especially along and before the period of moderate to heavy rain. Periods of moderate to occasionally strong turbulence and low-level wind shear are possible after 00Z.
KPMD and KWJF: Peak winds may be off by 5-10 kt due to possible mountain wave activity.
KLAX, Moderate confidence in TAF through 00Z followed by low confidence due to timing of flight category changes and wind shifts which could be off by 2-3 hours. 5-10 kt east wind component likely between 00Z-04Z with a south cross wind gusts of likely at times between 03Z-10Z
KBUR, Moderate confidence in TAF through 00Z followed by low confidence due to timing of flight category changes and wind shifts which could be off by 2-3 hours. Periods of moderate to occasionally strong turbulence and low-level wind shear are possible after 00Z.
10/320 AM.
Moderate confidence in the current forecast. Less confidence exists in the swell forecast. Higher confidence exists in the wind forecast.
For the waters southwest through northwest of the Channel Islands and the nearshore waters along the Central Coast, Small Craft Advisory (SCA) conditions will be imminent (80-100 percent chance) by this evening. SCA conditions due to marginally high seas will linger through midday, then there is a high to likely (50-70 percent) chance of Gale Force southwesterly winds between from this afternoon through late tonight, especially for the waters west through north of Point Conception. Chances for SCA conditions for winds will decrease some on Wednesday and Wednesday night, but there is a high to likely (50-60 percent) chance that SCA conditions due to a mix of wind and seas will linger into Wednesday night. A brief lull in the SCA conditions should develop for the daylight hours on Thursday then SCA level winds and higher seas will develop on Thursday evening and likely persist into the weekend.
Inside the southern California bight, there is a moderate (30-40 percent) chance of SCA level winds this morning, increasing to a likely to imminent (60-90 percent) chance by this evening. Winds will likely fall below SCA levels between Wednesday and the end of the week, but there is a moderate to high (30-50 percent) chance of SCA conditions developing each evening across the western portions.
There is a high chance that marine conditions will be poor for the upcoming weekend with rain, large seas, and gusty winds spreading over the area between Friday and Tuesday. There is a moderate to high (30-50 percent) chance of widespread GALES early next week.
10/244 AM.
Lower confidence in the current forecast. A high surf advisory has been expanded across all beaches this due to higher than modeled west to northwest swells moving across the coastal waters this morning, then a southwest swell will develop tonight as gusty southwest winds develop. Southwest and west facing shores will be particularly vulnerable to developing swell and surf tonight and into Wednesday, especially the Santa Barbara South Coast, Ventura County Line, and Leo Carrillo, and Zuma Beach.
Swell and surf will likely drop below high surf advisory criteria for Thursday, but high surf is likely to develop again from Friday. It is likely that the swell and surf will remain at or above high surf criteria through the upcoming weekend.
The latest swell models continue to highlight a period of very large waves developing for early next week. There is a high to likely (50-60 percent) chance of widespread high surf between Monday night and Wednesday. Sets above 10 feet will be possible at west and northwest shores. There is a 20-40 percent chance of damaging sets developing between Tuesday and Wednesday, highest for northwest-facing shores along the Central Coast.
Ca, Wind Advisory remains in effect until 1 PM PST Wednesday for zones 38-344-345-353-376>383. (See LAXNPWLOX). High Surf Advisory in effect until 9 PM PST Wednesday for zones 87-340-346-354-362-366. (See LAXCFWLOX). Wind Advisory in effect from 3 PM this afternoon to 4 AM PST Wednesday for zones 340>343-346>349. (See LAXNPWLOX). High Surf Advisory in effect from midnight tonight to 9 PM PST Wednesday for zones 349-350. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until noon PST today for zones 645-670-673. (See LAXMWWLOX). Gale Warning in effect until 3 AM PST Wednesday for zones 645-670-673. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PST Wednesday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PST Wednesday for zone 655. (See LAXMWWLOX). Small Craft Advisory in effect until 3 PM PST Wednesday for zone 676. (See LAXMWWLOX).
