30/221 AM.
Little change in weather conditions is expected through Thursday with temperatures 3-6 degrees above normal. Areas of morning low clouds and fog are possible near the coast as well. A major and long lasting heat wave will begin Friday and last through all of next week at least with with dangerously hot temperatures.
(tdy-Fri), 30/1206 AM.
, A VERY DANGEROUS AND LONG LASTING HEAT WAVE NEXT WEEK AND LIKELY EXTENDING INTO THE SECOND WEEK IN OCTOBER,
High pressure aloft will move into the state from the west and remain overhead through the short term period and beyond. Hgts will reach 588 dam today and then rise to 590 dam for Fri and Sat.
A weak eddy will bring some clouds to LA County this morning and westerly onshore flow will bring low clouds and dense fog to the Central Coast. There is a small chc that the low clouds will not reach the LA cst. Much weaker offshore flow this morning and much stronger onshore flow in the afternoon will bring 2 to 4 degrees of cooling to the csts and vlys with the exception of the SBA south coast and some beaches in SLO county where the return to onshore flow will bring 5 to 10 degrees of cooling. The mtns and far interior will see 3 to 6 degrees of warming due to the hgts rises.
Marine layer clouds will be more extensive Thursday morning as the eddy continues to spin. Offshore flow in the morning should clear these clouds away by mid morning. There is, however, always a risk that the eddy will be stronger than fcst with low clouds remaining longer and high temps cooling. The most likely temperature scenario calls for an additional 2 to 4 degrees of warming in most places. Two exceptions will be the Central Coast where max temps will hardly change at all and the San Gabriel and San Fernando Vlys where 4 to 6 degrees of warming is likely. Max temps will end up mostly in the 80s across the csts and 90s in the vlys. These max temps are all about 8 degrees over normal.
The heat wave really accelerates on Friday with the 590 dam hgts, upper level subsidence, offshore morning flow and only weak onshore flow in the morning. The eddy will be much weaker and there will be much less morning low clouds. Most max temps across the csts and vlys will bump up another 3 to 5 degrees. This will bring triple digit heat the warmest vlys and lower 90s to the interior coastal sections. Even the beaches will have highs in the lower 80s. There is a 30 percent chc that the offshore flow will be a little stronger with max temps ending up 3 degrees higher than fcst. It is very likely heat advisories will be issued for most of the LA/VTA county cst/vlys.
(Sat-Tue), 30/220 AM.
The long term forecast is all about the heat. It continues to look like a 10 to 14 day heat wave is in store for Srn CA. High pressure aloft will likely remain in place (with a few small day to day changes). More importantly an extended period of offshore flow seems more than likely as well.
Currently Saturday is forecast to be the warmest day with coastal highs in the 90s (20 percent chc of isolated 100 to 102 degrees readings) and vlys reaching 100 to 106 degrees. Slight cooling is forecast Sunday with little change on Mon and Tue, but if the offshore push is stronger than forecast this cooling could turn out to be a mirage. These max temps are 10 to 15 degrees above normal. The offshore flow will keep overnight lows above normal as well which will give residents without air conditioning little room for recovery.
All long range mdls both traditional and AI-enabled show this heat wave reaching all the way to at least the 13th of October.
Extreme Heat Warnings are likely starting Saturday for portions of the LA/VTA County csts and vly. Heat advisories are also likely for any portion of the LA/VTA county csts/vlys as well as the SBA south coast and Catalina Island. Heat Advisories may be need for the Central Coast depending on how much offshore flow develops there. If this heat wave is as relentless as it is currently forecast areas with advisories may need an upgrade to warnings due to the toll taken by day after day of heat.
One positive note - since this is more of an offshore driven event the humidities will be lower than the earlier heat events.
30/0946z.
At 0832Z at KLAX, the marine layer was 900 ft deep. The top of the inversion was at 2000 ft with a temps of 26 C.
High confidence in VFR TAFs for KPRB, KWJF, and KPMD.
There is a 10% chance for brief IFR cigs at KSBA 13Z-17Z.
There is a 20 percent chc that vis will remain above 1/2SM at KSBP/KSMX.
There is a 20 percent chc of IFR cigs at KOXR and KCMA 12Z-16Z.
KLAX, Moderate confidence in TAF. There is a 40 percent chc of OVC008 conds through 17Z. There is a 30% chance of an of a 10 kt east wind component 10Z-16Z.
KBUR, Fair confidence in TAF. There is a 15% chance of BKN008 conds 12Z-16Z.
30/245 AM.
Small Craft Advisory (SCA) winds and steep seas affecting all the inner waters (including the nearshore waters along Los Angeles and Orange Counties) should drop off late tongiht, and will drop for the outer waters late tonight.
Southerly swell from Polo (SSE) is decreasing fairly rapidly. These swells will create larger waves and surf nearshore, which could impact some south exposed harbor entrances.
Conditions are likely to improve to below SCA levels today into next weekend, except for occasional northwest SCA winds near Point Conception in the afternoon/evening hours.
30/245 AM.
The surf from Hurricane Polo has peaked and will lower rather quickly through today, but strong rip currents may linger. The high tide came in 1.0 to 1.2 feet above prediction on Tuesday and above 7.0 feet MLLW. While the high tide will be lower on today compared Tuesday, it will lower only a little and will likely still be above 7.0 feet for morning high tide. With all that in mind, the Coastal Flood Advisory and High Surf Advisory have been replaced them with a lower-tier Beach Hazards Statement to cover through 5 PM today for the rip current and tidal overflow potential.
While we will get a break from the coastal flooding concerns for the rest of the week, another hurricane swell (from soon-to-be Hurricane Rachel) will likely bring a larger-than-Polo south swell to southern California for the early to middle part of next week. Thankfully tides at that time will not be extreme, but they should be around 6.5 feet which is high enough to cause some concern, but it all depends on how big the surf ends up.
Ca, Beach Hazards Statement in effect through this afternoon for zones 87-349-350-354-362-366. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until 3 AM PDT early this morning for zones 645-650-655. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PDT this morning for zones 670-673-676. (See LAXMWWLOX).
