05/1151 PM.
Weak onshore flow will continue to bring limited low cloud cover to the coasts and coastal valleys each night through morning over the next several days as temperatures warm across the region. Interior temperatures will likely reach 100 degrees or higher across some of the interior valleys Tuesday through Thursday. A Heat Advisory is in effect for non-coastal areas starting at 10 AM Tuesday.
(tdy-Wed), 06/948 AM.
***UPDATE***
A very limited marine layer early this morning has mostly burned off from the Santa Barbara coast down to the LA county beaches. This clearing should allow temperatures to warm a degree or two above yesterday readings as high pressure continues to build in aloft.
As this area of high pressure retrogrades further west across southern California over the next couple of days, expect temperatures to climb further, and for potentially dangerous heat to become possible across areas away from the immediate coast. At this point, still no plans to expand the heat advisory for Tuesday, but may need to expand into some of the inland coastal areas/valleys for Wednesday and Thursday when the peak heat associated with the dome of high pressure is expected to be across the local area. Minimal changes necessary to the forecast temperatures this morning, but will re-look at the heat advisory for the Tue-Thu time period around midday.
Additionally, sundowner winds were evident in spots early this morning with Gaviota briefly gusting to 45 MPH around 3 AM. With the pressure gradient across this area expected to intensify over the next couple of evening/overnight periods, will also consider a wind advisory for parts of the Santa Barbara County Southwestern Coast and Santa Ynez Mountains Western Range later today as winds should intensify (gusts 50 MPH+) and become more widespread across this area the next 2 days.
***From Previous Discussion***
The main weather focus through much of the coming week will be temperatures, in combination with gusty winds in some areas, and more widespread elevated to brief critical fire weather concerns due to very warm and dry conditions.
Heights aloft will be rising through Wednesday before leveling off on Thursday, with decreasing onshore winds. Highs will rise a few degrees today, with more significant rises expected Tuesday and Wednesday as heights rise to 592 mb Tuesday, and up to 596 mb by Wednesday and Thursday. A Heat Advisory is in effect for all areas away from the coast from Tuesday morning through Thursday evening, with highs in the valleys and interior in the upper 80s to around 100 degrees Monday, with 90s to lower 100s on Tuesday. By Wednesday, the warmest valleys will be near or over 100 degrees, with 104 or higher over the Antelope Valley. Overnight lows will be unusually warm as well, especially over the foothills and lower mountain slopes where mid 70s will be common. There is still some uncertainty as to how warm the coastal areas will get during the Tuesday through Thursday period, as it largely depends on the afternoon sea breeze and the extent of the marine layer clouds and if they form. However, temperatures will still be near normal for this time period for the coasts.
Onshore winds gusting up to around 35 mph will affect the Antelope Valley and foothills this afternoon and evening. Sundowner winds will affect southwest Santa Barbara County each late afternoon to overnight period through Wednesday, likely strongest Tuesday and Wednesday with gusts between 45 to 50 mph.
As for low clouds, the marine layer should be able to reform overnight, at least for coastal areas. The Santa Barbara South Coast should remain clear due to Sundowner winds, and this will continue each night through midweek as the Sundowners strengthen. Otherwise, low clouds will likely be limited to coastal areas for much of this week under building heights aloft.
(Thu-Sun), 06/251 AM.
Above normal temperatures across the region will continue through the extended period as the high pressure aloft starts to shift northeastward into the northern Rockies Friday night through the weekend. As a result, 500 mb heights will decrease across Southwest California, paired with increasing onshore gradients, and temperatures will start to decrease over the weekend. However, these temperatures will still remain near or above normal, mainly across interior areas.
However, as the high pressure moves northeast, some disturbances start to move into the region and open the door to some southwesterly flow aloft and potential monsoonal moisture as early as this weekend into next week. While the current forecast remains dry, this could eventually justify the mention of some showers and thunderstorms across the higher terrain and deserts by next Monday as both the EC/GFS are indicating some light QPF across these areas.
Additionally, the EC/GFS ensembles and their AI ensembles have been hinting these past few days at yet another, possibly higher, warm up mid- to- late next week.
06/1258z.
At 1227Z at KLAX, the marine layer was 1100 ft deep. The top of the inversion was 2300 ft deep with a temperature of 21 C.
High confidence in VFR TAFs for desert airfields (KWJF & KPMD).
Low to moderate confidence in remaining TAFs. Timing of flight cat may be off +/- 3 hours and CIG heights +/- 300 ft. Confidence in CIG forecast for KOXR, KCMA, KSMO, KLAX, & KLGB is lowest due to disorganized marine layer stratus. CIGs at those locations may arrive briefly, and scatter and reform through 18Z Mon. There is a 30% chance of IFR-MVFR conds at the aforementioned sites after 09Z Sun.
KLAX, Moderate confidence in TAF. Low confidence from through 18Z due to likely disorganized stratus, with a 30% chance that CIGs do not arrive or form briefly at times. No significant easterly wind component expected.
KBUR, High confidence in TAF.
06/112 AM.
High confidence in Small Craft Advisory (SCA) level NW winds persisting through at least Thursday across the Outer Waters. There is a 20-30% chance of GALE Force winds Tuesday afternoon through Thursday. Winds will likely be strongest near Point Conception, Channel Islands, and the far northern outer waters. Short-period, advisory level, choppy seas will gradually increase and reach around 10 ft by mid-week and then subside below advisory levels on Friday into the weekend.
SCA level NW-W winds will reach into the inner waters along the Central Coast and the Santa Barbara Channel during the afternoon and evening hours starting today through Wednesday or Thursday. For the inner waters adjacent to Los Angeles County, winds will increase to SCA levels this afternoon across the western portion, through the Anacapa Passage to near Point Dume, and across the San Pedro Channel this afternoon and evening. Otherwise, local gusts during the late afternoon and evening hours are possible for the aforementioned waters through Tuesday or Wednesday.
Ca, Heat Advisory in effect from 10 AM Tuesday to 8 PM PDT Thursday for zones 38-88-343>345-353-372-373-375>380-548. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from 3 PM this afternoon to midnight PDT tonight for zones 650-655. (See LAXMWWLOX). Small Craft Advisory in effect from 5 PM this afternoon to 5 AM PDT Tuesday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 5 AM PDT Tuesday for zones 673-676. (See LAXMWWLOX).
