26/945 AM.
Very hot conditions will dominate the week, with a high risk of heat-related illness. Isolated showers possible Thursday and Friday. Significant cooling is likely over the weekend but it will remain warm.
(tdy-Fri), 26/945 AM.
***UPDATE***
Forecast remains on track in terms of the heat. No changes (cancellations or extensions) planned with the Heat Warnings and Advisories. Significant relief still on target by early next week. The extra clouds expected for Thursday and Friday will likely have little effect on the temperatures because of their tropical origin and likely embedded breaks of sunshine. Not only that, but even if temperatures lower a little, the mugginess feeling will rise.
The evolving piece of the forecast involved the showers and thunderstorm potential. Looking at satellite this morning, two features stand out. First, there is a lot of moisture off of Baja associated with what was Tropical Storm Iselle (ee-SELL). This moisture will push over California later tonight through Friday, with the majority of solutions focused on Central California. Second, an organized cluster of convection over the northern Gulf of California is steadily moving towards the northwest. This convection will likely weaken, but the circulation at its heart will likely continue to move towards us overnight into Thursday. Putting all of this together, it is hard to discount a shower anywhere on Thursday and Friday so 20% PoPs were added. While the most likely outcome is for a few clusters of light big-drop showers scattered around our area, amounting to very little. There is however a small chance of a heavier cell or two and a thunderstorm. The best instability does not line up with the best moisture, but it is hard to say all clear when we are looking at tropical moisture and extreme heat. This is a classic low chance, potentially high impact scenario.
***From Previous Discussion***
Today will be the warmest day of the current heat wave. Strong high pressure aloft will combine with weaker than normal onshore flow to the east and actual (weak) offshore flow from the north. The marine is very shallow and will not make much inland penetration at all. Marine layer stratus will be largely absent from all areas today - even the Central Coast. Most cst/vly temps will end up 10 to 15 degrees over normal with vly temps in the 100 to 112 degree range. This is a dangerous heat event and almost all areas are under either an extreme heat warning or a heat advisory. Please see the product LAXNPWLOX for all details.
Here are some records and today's forecast highs:
Here is a list of the current high temperature records today (August 26th):
Downtown LA. , 98 in 1981 - forecast high = 101 LAX. . . , 94 in 1985 - forecast high = 86 Long Beach. , 100 in 1981 - forecast high = 99 Hawthorne. . .88 in 2015 - forecast high = 93 Santa Monica. ..85 in 2011 - forecast high = 87 Burbank. . ..111 in 1944 - forecast high = 105 Van Nuys. . .105 in 2010 - forecast high = 107 Woodland Hills, 109 in 1981 - forecast high = 111 Palmdale. . .107 in 2011 - forecast high = 105 Lancaster. . 106 in 1950 - forecast high = 105 Camarillo. . .86 in 2015 - forecast high = 105 Oxnard. . . 86 in 2015 - forecast high = 90 Santa Barbara. .86 in 1977 - forecast high = 85 Santa Maria. , 92 in 1925 - forecast high = 86 Paso Robles. ..106 in 2017 - forecast high = 107
Thursday's forecast is an interesting one as a grip of moisture from the remnants of Tropical Storm Iselle will move over the state sometime from late Wednesday through early Friday. The big forecast problem is that there is tremendous disagreement on the location and timing of these clouds. Thursday's highs could be quite a bit cooler than fcst if the thickest clouds move over Srn CA during the late morning to late afternoon hours. Conversely max temps could be a little warmer than fcst if the clouds miss our portion of the state or go overhead in the evening or overnight. There is also a 10 to 15 percent chc of a shower from these clouds. The current forecast calls for a few degrees of cooling and this seems like the best compromise. The cooling may not feel much better as the extra moisture will make things more humid.
On Friday a trof will approach the west coast and will push the upper high away from the state. Hgts will fall a few dam and onshore flow will increase a little bit. Look for a few degrees of cooling in most areas (a few more over SLO county where the affects of the trof will be greatest). That said if Thursday's max temps are suppressed by cloud cover Friday's sunny skies will then bring warming. With max temps still 10 to 15 degrees above normal and overnight lows 8 to 12 degrees warmer the current suite of heat products looks good to continue through the day.
(Sat-Tue), 26/304 AM.
The weekend will bring a much welcomed cooling trend. The trof will swing into the west coast and the upper high will be shunted all the way to Arkansas. Hgts will fall to 587 dam. Onshore flow will increase some and the marine layer along with morning marine layer stratus will make a comeback. Look for 3 to 6 degrees of cooling Saturday followed by an additional 4 to 8 degrees on Sunday. Vly temps in on Sunday will only be in the lower to mid 90s. The Central Coast will see the greatest cooling with highs in the upper 60s to mid 70s. Most highs on Sunday will be a few degrees blo normal.
The trof sharpens some on Monday lowering hgts to about 585 dam. The onshore flow will increase a little as well. This will lead to another 2 to 4 degrees of cooling with most areas coming in 3 to 6 degrees under normal. Look for vlys temps only in the upper 80s and lower 90s.
Little change is forecast for Tuesday as troffing will hold sway over the west coast.
The EC-AI mdl does not show any significant heat in the area through at least September 4th.
26/1638z.
At 1600Z at KLAX, the marine layer was 500 feet deep. The top of the inversion was 2200 feet with a temperature of 32 degrees Celsius.
High confidence in 18Z TAF package. VFR conditions are expected for all sites through the period as increasing high clouds tonight are expected to inhibit any stratus formation.
KLAX, High confidence in 18Z TAF as VFR conditions are expected through the period.
KBUR, High confidence in 18Z TAF as VFR conditions are expected through the period.
26/703 AM.
For the Outer Waters, high confidence in current forecast. Small Craft Advisory (SCA) level winds are expected across all of the Outer Waters through Sunday. Additionally, seas will hover near SCA levels through the week, including hazardous steep seas with building wave heights.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. SCA level winds are expected during most afternoon to evening periods through the weekend. Steep choppy seas are expected through the week.
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 Sunday. The only exception will be the Western half of the Santa Barbara Channel where there is a 30-40% chance of SCA level winds during the afternoon and evening hours today then a 60-80% chance Thursday through Sunday during the same time frame. Choppy short period seas will persist through the weekend.
26/703 AM.
Southerly swell from Tropical Storms Iselle and Julio will move into the coastal waters today and continue through Thursday. Swell heights of 3-5 feet with a period around 14 seconds can be expected. producing elevated surf and dangerous rip currents along south-facing beaches of Ventura and LA counties. Therefore, a BEACH HAZARDS STATEMENT is in effect through 11 PM Thursday.
Ca, Extreme Heat Warning in effect until 8 PM PDT Friday for zones 38-87-88-349>358-362-366>376-378>383-548. (See LAXNPWLOX). Beach Hazards Statement in effect through Thursday evening for zones 87-354-362-366. (See LAXCFWLOX). Heat Advisory in effect until 8 PM PDT Thursday for zones 341-347-348. (See LAXNPWLOX). Heat Advisory in effect until 8 PM PDT Friday for zones 342>345. (See LAXNPWLOX). Red Flag Warning in effect until 3 PM PDT Friday for zones 345-353-375>380. (See LAXRFWLOX). PZ, Small Craft Advisory in effect until 3 AM PDT Thursday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Friday for zones 670-673-676. (See LAXMWWLOX).
