04/531 AM.
A major and long lasting heat wave is expected to persist through all of next week with dangerously hot temperatures. Clouds and dense fog are expected over portions of the coastal waters this morning, most likely over the waters off the Central Coast.
(tdy-Tue), 04/942 AM.
***UPDATE***
Day 3 of the heatwave is underway, and temperatures are already off the races with highs in the 90s as of 930 AM for many areas including Downtown Los Angeles and LAX Airport. Offshore winds are light in speed, even so the LAX to DAG surface pressure gradient was 4.2 mb offshore around 8 AM this morning, which is moderate strength. A few calender day temperature records may be broken today.
***From Previous Discussion***
Some low clouds with patchy dense fog has developed off the Central Coast overnight into this morning, but mostly remains off the coast. Overnight lows are struggling to fall, especially over the coasts and valleys of Ventura and Los Angeles Counties and the southern coast of Santa Barbara County where temperatures are currently in the 70s and 80s. Offshore winds have kept the cooler marine airmass off the coast for these regions, and winds limit radiational cooling.
For today, the oppressive heat will continue, with more of the same in store into early this coming week. Expecting fairly widespread highs in the 90s to mid 100s for many valleys and coasts, and temperatures will continue to be within a few degrees of their daily records for a lot of the area. Highs are forecast to be 15 to 27 degrees above normal for our valleys, coastal mountains, and coastal areas, with the most unseasonably hot conditions focused over the LA Basin, and the LA and Ventura County coasts. Highs in the 90s for the interior fall closer to normal (about 10-15 degrees above normal). Overnight lows will remain on the warmer side through Tuesday night.
The forecast through the coming week has really not changed as strong high pressure will maintain its grip over the region. Adding to this is the fairly persistent 2-4 mb offshore gradient, which supports heat all the way to the coast. Guidance is beginning to show the offshore flow could finally weaken by Tuesday evening, meaning we may start seeing some downward trends in temperatures near the coasts Tuesday night.
(Wed-Sat), 04/548 AM.
The hot weather will continue all of this coming week, but as offshore gradients are forecast to weaken slowly through the period. Although most days through Thursday should see offshore winds in the morning hours, the sea breeze may return as soon as Thursday. This translates to a very slow cooling trend, first most evident at the coasts, with perhaps more notable cooling Friday. There is a 20-30% chance that at least some heat advisories will be needed on Friday. More significant and widespread cooling is expected Saturday and continuing into early the next week. Recent model trends are indicating at least a 20-30% chance of some showers for the weekend based on the latest ensemble tracks of Hurricane Rachel. Some increasing swells from Rachel are possible as early as mid week.
04/1756z.
At 1630Z at KLAX, there was no marine layer nor an inversion.
High confidence in VFR TAFs for all sites except for KSBP/KSMX. Chc of V/LIFR conds between 05/08Z-16Z: KSBP (15%) & KSMX (40%).
KLAX, High confidence in VFR TAF. Good confidence that any east wind component will remain below 7-8 kts after 04/19Z.
KBUR, High confidence in VFR TAF. No wind issues expected.
04/531 AM.
Generally quiet conditions expected across the coastal waters through the forecast period. Localized Small Craft Advisory (SCA) gusts may occur each afternoon and evening between Point Conception and San Nicolas Island, off the coast of Point Dume, and across the San Pedro Channel.
04/532 AM.
Quiet conditions are expected through the weekend, aside from the heat. Meanwhile, another hurricane (Rachel) will likely bring a larger- than- Polo southerly swell to southern California for much of the coming work week. The window of most concern is Tuesday through Friday. Elevated surf up to 5-6 ft is likely with a lower chance of high surf 7 ft or higher across exposed south facing beaches. High tides of 6.5-7.0 ft are expected. Unlike previous events, morning and evening tides will be similar in height. Initially, the swell will have a more SE direction (150-160) targeting areas like Long Beach Tuesday and Wednesday. As Rachel moves westward, the swell direction will become more southerly (170-190) Thursday and Friday targeting areas like Zuma. There is a high risk for Beach Hazard Statements and a moderate risk for Coastal Flood Advisories and High Surf Advisories along the LA/VTA coastline. Stay tuned for future updates.
Ca, Extreme Heat Warning in effect until 8 PM PDT Thursday for zones 38-87-88-349>358-362-366>375-548-550. (See LAXNPWLOX). Heat Advisory in effect until 8 PM PDT Wednesday for zones 341>345-347-348. (See LAXNPWLOX). PZ, NONE.
