18/843 AM.
Dangerously hot temperatures will continue all week. Coastal areas likely peaked Tuesday, while valley and interior areas peak through Friday. Dense coastal fog may develop as early as Thursday. Temperatures lower significantly over the weekend and into next week, but remain well above normal.
(tdy-Fri), 18/852 AM.
***UPDATE***
Onshore trends on the order of 2-3mb will likely provide some amount of relief to coastal areas today, but how much is difficult to say. The 24 hour temperature change map shows as much as 20 degrees of cooling across eastern Ventura county and western LA County, but elsewhere temps are generally within 5 degrees of yesterday at this time. Most likely outcome for today is highs in the 80s near the coast, and 90s in the valleys and other interior locations. Note that daily temperature records today are significantly cooler than yesterday so records will be easier to reach.
***From Previous Discussion***
Like a broken record, the dangerously hot conditions will continue to impact the region through at least Friday. Can't say too much different in the short term that hasn't been said the past few days. Very strong, record breaking high pressure continues to inch to the east this week. While today will see an increase in onshore trends, which will allow the coastal temperatures to decrease a few degrees (but remaining near the 80s and 90s), valleys and mountains will continue to be around 90-104 degrees through Friday. Additionally, warm overnight lows will provide little relief from the heat, especially in the foothill and mountain locations. The combination of dangerously high temperatures, and continued warm overnight low temperatures over multiple days will continue to bring a HIGH RISK of Heat Illness for just about everyone. Thus, Extreme Heat Warnings and Heat Advisories continue to be in effect through Friday 8pm for the majority of the area. In general, daily records today are quite a bit cooler, so most if not all sites, especially away from the immediate coast, will likely break records today.
While not in the forecast, patches of very dense fog cannot be discounted as early as tonight over the waters and immediate coast, with increasing chances each day going forward as pressure gradients become neutral to weakly onshore. This would bring some relief to the immediate coasts, but would not affect areas inland due to the shallowness of any marine layer.
Record highs for Downtown LA this week are as follows:
Today: 87 in 1997 Thursday: 97 in 1997 Friday: 93 in 1997
(Sat-Tue), 18/243 AM.
Saturday and Sunday, models suggest that the high pressure will start to flatten out, and a shallow short-wave trough will move through the region. As for the heat, temperatures will finally start to decrease again on Saturday. For Saturday, there is a 50% chance that some heat products will need to extended through the evening hours, mainly inland and away from the beaches. However by Sunday, things should cool down rather noticeably. Therefore, no heat products are anticipated. On Monday, high pressure starts to build in again, which will bring a slight warming trend once again through early week, but not to the degree we are seeing this week. Additionally, the marine layer low clouds and fog may return to coastal areas each night as early as Friday night, and more widespread Saturday night.
As for rain chances, the GFS and EC deterministic runs are dry through the 28th, looking at their respective ensembles and ensemble AI projections, rain chances were pushed back to the 29th or 30th of March at the earliest. Even then, projections are still very light in accumulations, and not even close to significant at this time.
18/0946z.
Around 0715Z, there was no marine layer depth at KLAX. There was a surface-based inversion up to around 1300 feet with a temperature around 28 degrees Celsius.
VFR conditions are expected through the period, except for a very low to low chance of VLIFR to LIFR conditions at coastal terminals through 14Z, and a low to moderate chance at coastal terminals after 08Z Thursday.
KLAX, VFR conditions are expected through the period, except for 10 percent chance of VLIFR to LIFR conditions through 14Z, and a 30 percent chance at coastal terminals after 08Z Thursday. Any east winds will likely be less than 7 knots.
KBUR, VFR conditions are expected through the period. No wind impacts are expected through the period.
18/245 AM.
High confidence in the current forecast through Thursday, then moderate confidence thereafter.
Winds will very likely remain below Small Craft Advisory (SCA) levels through at least Thursday. There is a moderate (30-40 percent) chance of SCA level winds each evening across the far northwestern portion of the coastal waters on Thursday evening and Friday evening. Otherwise,
For the waters southwest through northwest of the Channel Islands and the nearshore waters along the Central Coast, there is a high to likely (40-60 percent) chance of SCA level conditions developing over the weekend with a low to moderate (20-30 percent) chance of GALES.
There is a slight chance for dense fog this morning, becoming more likely tonight into Thursday morning as a shallow marine inversion will be in place over the coastal waters through the week.
Ca, Heat Advisory remains in effect until 8 PM PDT Friday for zones 38-87-340-341-343-344-346>350-354-355-362-366-367-549-550. (See LAXNPWLOX). Heat Advisory in effect until 8 PM PDT Friday for zones 38-87-343-344. (See LAXNPWLOX). Extreme Heat Warning in effect until 8 PM PDT Friday for zones 88-342-345-351>353-356>358-368>376-378>380-548. (See LAXNPWLOX). PZ, NONE.
