24/805 AM.
Very hot conditions will dominate the week, with a high risk for heat illness. Patchy night through morning low clouds and locally dense fog will be confined to coastal areas, mainly north of Point Conception.
(tdy-Wed), 24/840 AM.
***UPDATE***
Based on the current forecast today we are on track to tie or break 8 high temperature records in LA and Ventura Counties. There is a a very slight offshore trend this morning, however temperatures are starting off a couple degrees cooler so it's going to be a close call on the records today.
Going forward though it does look like there will be just enough offshore trend through the middle of the week to support the 2-5 degrees of additional warming across the area through at least Thursday, pushing the warmer valleys to 110 or higher and Downtown to around 100. These temperatures certainly justify upgrading most, if not all the heat advisories to Extreme Heat Warnings starting Tuesday.
Here is a list of the current high temperature records today:
Downtown LA. ..96 in 1931 LAX. . . ..85 in 1979 Long Beach. , 95 in 2010 Hawthorne. . 84 in 2010 Santa Monica. .79 in 2010 Burbank. . ..103 in 1985 Van Nuys. . .105 in 2010 Woodland Hills, 116 in 1985 Palmdale. . .107 in 1985 Lancaster. . 108 in 2010 Camarillo. . 87 in 1931 Oxnard. . , 87 in 1931 Santa Barbara. 85 in 1979
***From Previous Discussion***
The story this entire week will be the heat.
A 597 dam upper high will sit, quasi-stationary, over NM through the period. Hgts over Srn CA will be around 593 dam all three days. At the sfc the E/W gradient will oscillate between near very weak onshore flow in the morning to mdt onshore flow in the afternoon. In the N/S direction there will be weak onshore flow each afternoon, but in the mornings there will be increasing offshore flow.
The strong high pressure aloft, weak offshore flow from the north and lack of an eddy will limit the amount of low clouds south of Pt Conception each morning. The Central Coast will have more low clouds but since the marine layer will be squashed to under 800 ft there will be areas of dense fog each morning.
There will not be too much in the way of winds given the lack of strong sfc gradients. The only exception will be the SBA south coast where there will be Sundowners each night. There is a chc that the gusts will reach advisory levels Tuesday night.
But still, everything is about the heat. Today may be a few degrees cooler than it was ydy as the upper high wobbles slightly to the east. Max temps will still end up 6 to 12 degrees above normal. Vly temps will rise to 96 to 106 degrees. Heat advisories are in effect for the vlys, lower mtn elevations and far interior.
The offshore flow from the north increases on Tuesday as does the offshore flow across the Central Coast. This will bring 1 to 3 degrees of warming to most areas, except for the Central Coast which will see a 8 to 12 degrees of warming. Vly Temps will end up between 100 and 110 degrees. Inland coastal areas such as DTLA, LGB and SLO will have max temps in the 90s. Heat advisories may be needed for these inland coastal areas.
Another increase in the offshore flow from the north and across the Central Coast will add another 1 to 3 degrees of warming to most of the area. Triple digit heat will cover almost the entire forecast areas save for the beaches which will still have highs in the 80s and the Central Coast which will see max temps in the upper 80s and 90s. Of note: The EC is still forecasting offshore flow from both the east and north and if this were to happen max temps would be even higher in the vlys and significantly higher across the csts. This scenario seems less likely now, however, as the NAM does show continued onshore flow to the east. It is almost a certainty that all of the heat watches will be converted to warnings and much of the rest of the area will be covered with heat advisories.
One last heat reflated issue, due to the very warm atmosphere and powerful inversion under the upper high, overnight low temps will also be 6 to 12 degrees over normals with some vly areas experiencing 80s for the bulk of the night. These low temps will add to the heat risk as people who lack air conditioning will not be able to cool off overnight.
(Thu-Sun), 24/158 AM.
Not much change in the upper levels on Thursday and Friday. The sfc gradient problem in the E/W direction remains with the EC remaining significantly offshore while the GFS keeps it onshore. Given how the NAM is tracking the gradients it seems the best bet is for onshore gradients, but weaker than the GFS is forecasting. All mdls show offshore flow from the north, but again the EC is much stronger.
Thursdays temps will be very similar to Thursday's with most max temps 10 to 15 degrees above normal. High confidence that all of the heat warnings and advisories will continue.
The current forecast for Friday shows some cooling. This is a low confidence forecast and depends on the gradient forecast. There is a very good chc that temps will be very similar to Thursday's values.
The overnight lows will continue 8 to 12 degrees above normal and this will greatly exacerbate the heat risk as there will be no time for people's body to release the heat stress.
Very hot sundowners across southern SBA county remain a concern as well. A decent N to S gradient will set up over the county each evening and gusty north canyon winds will develop. These hot winds could drive max temps into the 100-105 degree range and could also keep temperatures in the 80s until almost dawn.
Better confidence in a noticeable cooling trend for the weekend. Both the EC and GFS agree that troffing will move into the west coast and force the upper high to the east. Hgts will fall to 590 dam Sat and then to 588 dam on Sun. More importantly both mdls show a return to onshore flow from both the South and West. Look for 2 to 4 degrees of cooling on Saturday and an additional 3 to 6 degrees on Sunday. Even with the cooling, Sunday's max temps will end up 2 to 4 degrees above normal south of Pt Conception. The Central Coast will fall a few degrees blo normal.
24/1650z.
At 1600Z at KLAX, the marine layer was 700 feet deep. The top of the inversion was at 2500 feet with a temperature of 27 degrees Celsius.
For 18Z TAF package:
- High confidence in KPRB, KBUR, KVNY, KPMD, KWJF and KCMA.
- For KSMX and KSBP, timing of flight category changes could be +/- 2 hours of current forecasts with a 30% chance that CIG and VSBY restrictions do not develop.
- For KLAX, KSMO and KLGB, there is a 30% chance of IFR/LIFR CIGs and VSBYs 09Z-17Z.
KLAX, Moderate confidence in 18Z TAF. There is a 50% chance that VFR conditions will prevail through the period. There is a 20-30% chance of IFR/LIFR conditions 09Z-17Z. No significant easterly wind component is expected.
KBUR, High confidence in 18Z TAF with VFR conditions through the period.
24/644 AM.
For the Outer Waters, high confidence in current forecast. Today through Friday, Small Craft Advisory (SCA) winds are expected to continue although the winds will drop briefly across PZZ670 today. Short period SCA level seas (5 to 7 feet at 6-8 seconds) will continue along with the gusty winds. For Wednesday into Thursday, larger seas approaching 7-9 feet are likely.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Today through Monday night, high confidence in winds and seas remaining below SCA levels. For Tuesday through Friday, there is a 50-70% chance of SCA level winds each afternoon and evening.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. For a majority of the southern Inner Waters, high confidence in winds and seas remaining below SCA levels through Friday. The only exception will be the western half of the Santa Barbara Channel where there is a 30-40% chance of SCA level winds late this afternoon and evening, then a 60-80% chance of SCA level winds Tuesday through Friday, mainly in the late afternoon and evening hours.
Ca, Heat Advisory in effect until 10 AM PDT Tuesday for zones 38-87-88-349>358-362-366>376-378>380-548. (See LAXNPWLOX). Extreme Heat Watch in effect from Tuesday morning through Friday evening for zones 38-87-88-349>358-362-366>376-378>383-548. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 4 AM PDT Tuesday for zones 673-676. (See LAXMWWLOX).
