27/232 AM.
Gradual cooling will continue through the week, with increasing cloud coverage and a high chance of rain sometime from Friday- Monday, with highest chances Saturday (Halloween) through Sunday. Additionally, coastal flooding issues will continue due to very high tides.
(tdy-Thu), 27/944 AM.
***UPDATE***
Dry and mild conditions will continue through at least Friday with minimal weather impacts locally, limited to some morning stratus. Still monitoring a system headed this direction but models have been trending weaker the last few runs. Still looks like a high chance of rain with the most likely period being Saturday into Sunday but at this time amounts seem to be under an inch.
***From Previous Discussion***
Very quiet weather will continue over the area through Thursday with minimal weather impacts expected aside from the continual coastal flooding threat due to very high tides.
Today through Thursday, the upper level flow will slowly transition from the NW to the SW as a series of upper lows spins out of British Columbia. Hgts will fall from 580 dam to 572 dam. At the sfc flow will be near neutral in the N/S direction through the period. There will be weak onshore flow to the east at the same time.
There will be a little more low clouds south of Pt Concpetion this morning, but the Central Coast will have much less low clouds than on Monday morning. Max temps will fall 2 to 4 degrees with the decreasing hgts. Look for highs in the lower to mid 70s across the csts and mid to upper 70s (isolated lower 80s) in the vlys.
Increased cyclonic turning aloft plus falling hgts will bring a much more robust morning marine cloud pattern to the coasts and some of the vlys. Clearing will be fairly slow. Skies, aside from the low clouds, will be partly cloudy as high clouds drift along with the upper level flow. Max temps will fall another 1 to 3 degrees and max temps will end up mostly 2 to 4 degrees blo normal.
For Thursday, the strongest of the upper lows will move into the PACNW and the troffing over CA will become sharper. This will likely gin up a grip of low clouds that will likely cover the csts and most of the vlys. The day will be a cloudy one as mid and high clouds will bring overcast conditions throughout the day. All the extra cloud cover will bring an additional 1 to 3 degrees of cooling to the area. Max temps across the csts and vlys will only be in the 70s.
(Fri-Mon), 27/225 AM.
The weekend storm begins to set up Friday as moisture entrained in the SW flow aloft begins to move into the area. Odds are Friday will be just a cloudy and cool day as PWATs only reach .8 across the southern edge of LA county. There is a 15 to 25 percent chc of a brief shower through the day, but nothing of significance.
The latest forecast for the weekend storm system is now further south and less wet. There is still a fair amount of mdl disagreement between mdls and the ensembles still exhibit a fair amount of spread. Still the more southerly trend has been pretty consistent across most mdls. There will be an increasing chc of rain Saturday with the best chc of rain occuring Saturday night. At this time it like the chc of rain will decrease Sunday morning and then end during the afternoon. Since this system is coming from the SW and is trending southward SLO county may not see much rain at all and LA county is poised to have the best chc of rain and most rainfall total.
All mdls are trending the amount of rain downward and now the best estimates call for Less than a quarter inch north of Pt Conception and a third to a half inch for most areas south of Pt Conception. The eastern San Gabriels could see an inch of rain.
Only moderate confidence in this forecast and it is not a foregone conclusion that the storm will behave this way, so stay tuned for the latest forecast developments.
Due to the SW origins of this system, snow will not be an issue with the only possible snow occuring at resort levels.
It will be on the cool side with max temps only in the mid to upper 60s across the csts and vlys.
Ridging moves in Monday and will bring sunnier skies and a 4 to 6 degree warming trend.
27/1639z.
At 1630Z at KLAX, the marine layer was 2600 feet deep. The top of the inversion was 5700 feet with a temperature of 14 degrees Celsius.
Moderate to high confidence in 18Z TAF package. For KPRB, there is a 40% chance of CIG/VSBY restrictions not developing. For KSBP, KSMX, KSBA, KOXR and KCMA, there is a 30-40% chance of CIG/VSBY restrictions 08Z-17Z. For KSMO, KLAX, KLGB, KBUR and KVNY, there is a 30-40% chance VFR conditions prevail through the period. For KWJF and KPMD, high confidence in VFR conditions through the period.
KLAX, Moderate confidence in 18Z TAF. There is a 30% chance that MVFR conditions do not develop overnight. No significant easterly wind component is expected.
KBUR, Moderate confidence in 18Z TAF. There is a 40% chance that MVFR conditions do not develop overnight.
27/652 AM.
For the Outer Waters, moderate to high confidence in current forecast. Through Wednesday, high confidence in Small Craft Advisory (SCA) level wind. On Thursday through Saturday, there is a 40-50% chance of SCA level winds continuing.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Today through Saturday, there is a 20-30% chance of SCA level winds each afternoon and evening.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Through Saturday, high confidence in winds and seas remaining below SCA levels for most of the southern Inner Waters. The only exception will be the western half of the Santa Barbara Channel with a 30-40% chance of SCA level winds late this afternoon and evening.
Dense fog is likely to form over portions of the coastal waters over the next 48 hours, but low confidence on exactly when and where.
A significant storm system will impact the area sometime in the late Friday through early next week timeframe. There is a wide range of outcomes, but there is at least a low threat of a 12-24 hour period of strong winds and step seas.
27/652 AM.
Very high tides between 7.5 and 8.0 feet (roughly 1.0-1.5 feet above astronomical predictions) are expected during the morning hours through Thursday over all coastal areas, with the highest towards Los Angeles County. Through Wednesday, the tides may remain near record. In fact, at San Pedro, a new record tide of 8.02 feet was set on Monday morning.
Minor coastal flooding is likely purely based on the high tides. While these tides might be the highest of all-time, similar extreme tides in the past tell us that coastal communities should expect shallow flooding of harbor walkways, beach parking lots and bike paths. With swells and surf on the lower-end during these extreme tides (2-3 feet), the threat of more significance/damaging impacts should be limited to the most vulnerable areas that have little-to-no sandy beach left and have already seen water damage.
With that said, these is a small change for more elevated surf on south-facing shores around Wednesday as waves from a southern Hemisphere storm arrive. The majority of computer projections keep this wave energy on the small side, but a couple are a little larger.
With all of these considerations in play, Coastal Flood Advisories are in effect today through Thursday. There is a low potential for targeted Coastal Flooding Warnings if a larger swell develops and produces elevated surf on top of the very high tides.
Ca, Coastal Flood Advisory in effect until 1 PM PDT Thursday for zones 87-340-346-349-350-354-362-366. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until 3 AM PDT Wednesday for zones 670-673-676. (See LAXMWWLOX).
