24/233 AM.
High temperatures will remain above normal through Saturday. There will be some low clouds and fog each morning. Substantial cooling will arrive Sunday.
(tdy-Sat), 24/917 AM.
***UPDATE***
The marine layer returned more robustly than expected with a depth of 2000 feet and clouds well into the coastal valleys. The original plan was for little change in temperatures today, and that looks reasonable for the Central Coast, but for LA/Ventura Counties, the most likely outcome is for at least a few degrees of cooling due to the marine layer and a 2mb onshore trend in the gradients.
***From Previous Discussion***
Very dull and benign weather likely for the next three days. SW flow will be over the state with a trof to the N and ridge SE. Hgts will be around 585 dam. The marine layer is about 1600 ft deep and there will be some coastal low clouds each morning will local penetration into the vlys. Saturday may see an increase in mid or high level clouds depending on Hurricane Polo's exact track and evolution. Max temps will not change much day to day with perhaps a little better cooling Saturday if the clouds are thick enough. Max temps will mostly be in the 80s across the csts and 90s in the vlys. These max temps are 4 to 8 degrees above normal.
(Sun-Wed), 24/235 AM.
Sunday will feature a noticeable cool down as pretty decent trof moves into the state. The falling hgts and increasing cyclonic flow should produce a widespread mass of marine layer stratus. At one time the mdls showed a substantial amount of mid and high level clouds moving overhead from the blow off from the tropical systems to the south, but now those clouds should stay to the south and it will be a partly cloudy day (save for the morning low clouds). Max temps will fall 4 to 8 degrees and most areas will be 3 to 6 degrees blo normal.
There is much uncertainty in the Monday forecast and it all depends on the exact track of Polo and Odalys. Right now it looks like most of the action will stay to the south of LA county and focus on San Diego and Imperial counties. There are enough ensemble members that keep the tracks a little more to the north and this results in a 20-30 percent chc of rain for SE LA County. Skies will likely be partly to mostly cloudy and temps will cool another 2 to 4 degrees with the exception of the Central Coast which will see sunnier skies and will have 2 to 4 degrees of warming.
The biggest threat from all of the hurricanes will be at the beaches where increasing south swells will arrive Sunday and then peak over Monday and Tuesday. See the beaches discussion below for more details.
Weak offshore flow and building high pressure should arrive Tuesday and warm max temps by 5 to 10 degrees. This warming will bring max temps in the 80s and lower 90s to most of the csts and vlys. The csts will end up about 8 degrees warmer than normal.
Lots of mdl disagreement for the fcst next Wednesday with the best odds favoring a couple more degrees of warming for most areas.
24/1157z.
At 0832Z at KLAX, the marine layer was 1600 ft deep. The top of the inversion was at 3300 feet with a temperature of 28 C.
High confidence in VFR TAFs for KPRB, KPMD, and KWJF.
Fair confidence in TAF for KSMX. VFR conds may arrive as early as 16Z.
Moderate confidence in the remainder of the TAFs. Flight Cat changes could be off by 2 hours and cig hgt off by +/- 300 ft.
KLAX, Moderate confidence in TAF. There is a 30 percent chc that cigs will remain AOA 010. SCT conds may arrive as late as 19Z. No significant east wind component expected.
KBUR, Moderate confidence in TAF. There is a 30 percent chc of BKN010 conds 13Z-17Z.
24/916 AM.
Good confidence in northwest Small Craft Advisory (SCA) winds off and on across the outer waters and nearshore waters along the Central Coast from tonight through Monday of next week. There is a low chance for low end Gales late Friday. Winds are expected to remain below SCA levels elsewhere, except for around a 50% chance for SCA winds to move into the Santa Barbara Channel Sunday and Monday afternoon through evening.
These winds will help a short period and choppy NW swell build into the weekend, but seas are expected remain below SCA levels. Southerly swells from tropical systems Odalys (SW swell) and Polo (SE swell) will build into the waters as soon as late tonight, but Polo's SE swell is likely to not move into the region until late Sunday. The more significant swell from Polo will likely peak Monday and Tuesday, but confidence remains fairly low in the peak magnitude of the swell.
24/916 AM.
Tropical activity to our south will spin up multiple southerly swells and send them towards our coastline over the next week. Hurricane Odalys will send a smaller southwest swell to our waters as soon as tonight. Hurricane Polo will send a larger southeast swell to our coastline late Sunday through Tuesday. Polo's swell will produce elevated surf across exposed south facing coastlines. High tides near 7 feet will peak in the late morning hours Monday and Tuesday. The combination of elevated surf and high tides will present another coastal flooding issue across some south facing beaches.
This swell is likely to have a more southeast direction compared to the Labor Day weekend event and the areas of most concern are Long beach (Peninsula and Belmont shore), Avalon, Malibu, and possibly Santa Barbara Harbor.
The most likely outcome would result in shallow flooding over seawater over low lying walkways, parking lots, and roads as well as significant beach erosion. Very localized damage to structures is possible in the most vulnerable areas. However, there is a low chances for more widespread and significant flooding of seawater and structural damage across vulnerable areas.
There is a high chance for Coastal Flood Advisories to be issued as soon as tomorrow for the Monday-Tuesday timeframe.
Ca, NONE. PZ, Small Craft Advisory in effect from 9 PM this evening to 9 AM PDT Saturday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect from midnight tonight to 9 AM PDT Saturday for zone 673. (See LAXMWWLOX).
