22/913 AM.
Hotter than normal conditions will continue through at least early next week, especially starting Thursday. The hot daytime and warm night conditions will bring elevated risks for heat illness. Thursday through Sunday will generally be the hottest of the next seven days. Gusty north winds will affect some areas through Friday.
(tdy-Fri), 22/922 AM.
***UPDATE***
Welcome back marine layer. Low clouds with some fog returned this morning, far more robustly than anticipated. Several areas had trace amounts of drizzle and wet roads. This will certainly dampen the expected heating for the coastal and adjacent valley areas today, with some areas at or below yesterdays temperatures (especially the Central Coast which is trending more than 10 degrees cooler than 24 hours ago). Everything is still pointing to far less marine layer tomorrow and a significant bump up in temperatures. The mountains and interior valleys on the other hand are already trending up and are on track to start the heat today. Decided to not touch the current Heat Advisories and Warnings despite the changes today, but will emphasize the widespread ramp up focused more for tomorrow than today. Gusty Sundowner winds are on track for tonight, with the SBA-SMX surface pressure gradient already over -3 millibars and several projections having it peaking around -5 millibars tonight, which is in the upper tier of gradient strengths. Wind Advisories are in place. Similar winds will affect some mountain areas as well, especially the I-5 Corridor, but they look a touch under Wind Advisory levels.
***From Previous Discussion***
Last evening brought a rapidly expanding fast moving marine layer stratus deck first to the Central Coast, then down through the SBA channel to southern SBA county and the Ventura cst and vlys. The clouds then pushed into LA county just before mid night. This unusual occurrence was brought about by an interesting interaction between the SW flow around the remnant core of Elida and a near 7 mb onshore push to the east.
Today marks the start of a long duration heat wave. A heat advisory is in effect for much of the forecast areas from today through Monday evening. Please see the product LAXNPWLOX for details. Citizens are urged to take precautions to avoid heat related illness during this time.
There will be 1 to 2 mb of offshore trends in the morning and this weakened onshore flow should allow for decently quick and complete clearing leave totally sunny skies by late morning. The sunny afternoon skies, slightly weaker onshore flow and 594 dam hgts (3 dam higher than normal) will all combine to make today a very warm day. Most areas away from the cst will see 3 to 6 degrees of warming (The mega exception to this will be the Central Coast where the return to onshore flow will bring 8 to 10 degrees of cooling). The inland coastal areas will reach the lower 90s, the vlys will sizzle with temps from 95 to 105 and the lower elevation mtns and far interior will all see highs from 100 to 105 degrees. Max temps (even those on the Central Coast) will be 5 to 10 degrees over normal today.
1 or 2 degrees of warming is possible both Thursday and Friday as the upper high pushes to the west and hgts remain at 594 dam. There may be some cooling at random coastal sites depending on how much the onshore flow fluctuates. The warmest vly locations will likely see 107 degree readings with all the rest of the vlys seeing highs no lower than the upper 90s.
Two more items will compound the heat dangers. The overnight lows will be well above normal thru the period and this will not allow people's body's to recover from the days heat in houses without AC. Also due to the tropical systems passing to the west and the above normal sea sfc temperatures there will be higher than normal humidities through period. These higher humidities will stifle the body;s ability to cool through sweating.
There will be a little wind to deal with as well, mainly over southern Santa Barbara County, the I-5 Corridor, and the western Antelope Valley today through Friday Night. Look for northwesterly to north gusts of 30 to 50 mph in those areas. Advisory level gusts are likely across the southwest portion of Santa Barbara County.
(Sat-Tue), 22/252 AM.
The upper high will sit atop of the four corners region through Monday and then is forecast to shift a little to the east on Tuesday. Hgts will remain above normal - between 594 dam and 596 dam. The onshore flow will increase through the period. Not the best confidence in the low cloud forecast as the warm sea sfc temps and mid level monsoon moisture tend to suppress marine layer development. The monsoon push will likely bring some mtn build up in the afternoon over the mtns as well as low but not zero chc of convection. The the onshore flow will bring a slight cooling trend to the csts and some vlys but max and min temps will remain well above normal and the heat advisories will continue through Monday. By Tuesday the shift of the upper high and strong onshore flow to the east should bring enough cooling to allow the advisories to expire.
Long range mdls still suggest another heat event later next week.
22/1005z.
At 0830Z at KLAX, the marine layer was 900 ft deep. The top of the inversion was at 1600 ft with a max temperature of 23 C.
High confidence in VFR TAFs for KPMD and KWJF.
Fair confidence in TAFs for KBUR and KVNY with a 20 percent chc of IFR cig/vis 11Z-16Z.
Moderate confidence the remainder of TAFs VFR conds could arrive +/- 90 min from fcst time and cig hgts could be off by +/- 300 ft.
Low confidence in low cloud fcst for Thursday morning both if there will be clouds and timing of their arrival.
KLAX, Moderate confidence in TAF. VFR conds may arrive as early as 1630Z or as late as 1830Z. Low confidence in TAF aft 23/06Z with low clouds possible at any time from 06Z-12Z. No significant east wind component expected.
KBUR, Fair confidence in TAF. There is a 20 percent chance of 2SM OVC005 conds 11Z-16Z.
22/738 AM.
Widespread Small Craft Advisory (SCA) NW winds will develop this afternoon and will likely continue through the weekend across the Outer Waters. Seas will approach 10 ft starting Thursday. Local gusts may reach 35 kt across the southern portion of the Santa Barbara Channel and PZZ676 this evening. Will be watching trends in observations and guidance this morning - there is a bit of low-mid level support that would suggests more widespread gusts to 35 kt across PZZ676. Thus, a last minute GALE Warning may be needed for this evening. 30% chance of GALE Force winds across the Outer Waters Thursday afternoon/eve.
22/721 AM.
A long period, southern hemisphere swell will arrive later this week and will add to the continuing swell from Hurricane Fausto. This will create hazardous Beach conditions Friday into the weekend. Additional Beach Hazard Statements and/or advisories will likely be needed during this timeframe.
Guidance suggests the Eastern Pacific will likely remain active over the next couple of weeks which could result in additional southerly swells impacting Southern California's coastline.
Ca, Heat Advisory remains in effect until 8 PM PDT Monday for zones 38-88-342>345-348-351>353-355>358-368>382-548. (See LAXNPWLOX). Heat Advisory remains in effect until 8 PM PDT Thursday for zones 349-350. (See LAXNPWLOX). Wind Advisory in effect from 6 PM this evening to 6 AM PDT Thursday for zones 349-351-352. (See LAXNPWLOX). Extreme Heat Warning in effect from 10 AM Thursday to 8 PM PDT Monday for zone 383. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PDT Thursday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM this afternoon to 9 PM PDT this evening for zone 655. (See LAXMWWLOX). Small Craft Advisory in effect from 6 PM this evening to 5 PM PDT Thursday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 5 PM PDT Thursday for zones 673-676. (See LAXMWWLOX).
