09/723 PM.
Moderate heat impacts will continue into next week, though there will be slight cooling over the weekend. Monsoonal showers and thunderstorms will be possible starting Sunday. Temperatures will rise again on Tuesday and may reach Major Heat Risk levels, with the monsoonal moisture adding to the discomfort from the heat.
(tdy-Sat), 09/724 PM.
***UPDATE***
Another warm and sunny afternoon across the majority of the local area. Maximum temperatures this afternoon ranged from the 70s along the coast, to the mid-80s across downtown Los Angeles, and from the mid 90s to around 103 across the interior and desert portions of the local area.
Latest satellite imagery has the marine layer starting to push inland across the Santa Barbara beaches and further south along the Los Angeles beaches, with some clear skies noted in between. Expect the marine layer to mostly fill in the gaps and return to much of the coastline later this evening and overnight, with a similarly warm afternoon expected across the area to finish out the work week. As anticipated, there will be some modest cooling over the weekend and into early next week, but a heat advisory remains in effect through Tuesday morning as temperatures will remain above average through the period with a resurgence in warmth anticipated over the middle of next week.
***From Previous Discussion***
High pressure is currently centered over the area, and will drift towards the four corners region through the weekend. 500 mb heights over SoCal will gradually trend downwards each day but still remain above normal. Temperatures will generally remain warm through the weekend, with today being the warmest day followed by a slight cooling trend through Sunday inline with the 500 mb heights. Highs will top out between 5 to 10 degrees above normal during the short term forecast period. Humidity will increase starting late Saturday which will add to any heat discomfort. Heat Advisories are in effect until Tuesday morning (when the Extreme Heat Watch will go into effect) for many areas away from the coast including Downtown Los Angeles. Moderate HeatRisk is expected for areas in the Advisory, which is a moderate risk of heat-realted illness for those sensitive to heat or working outdoors.
When the center of the high pressure system settles over the Great Basin area, southeasterly flow over SoCal will shuttle monsoonal moisture into the area. PWATs of nearly 1.5 will be possible across Los Angeles County, which is a considerable value. There will be a 10-20 percent chance of thunderstorms in the afternoon and evening on starting Sunday, with the greatest chances for the mountains of Los Angles and Ventura Counties. Hazards with any storm may include lightning (fire starts possible) and brief flash flooding, though predictability at this point for any one location is low.
Marine layer clouds are likely to be more widespread across the coasts and possibly Paso Robles each morning in the short term, and areas of dense fog will be possible especially along the Central Coast. Gusty onshore flow will occur in the afternoons and evening across the Antelope Valley and foothills, and elevated fire weather conditions will continue for this area as well.
(Sun-Wed), 09/311 PM.
High pressure aloft will encompass much of the western half of the CONUS to start the extended periods, centered across the intermountain west. This will result in southeasterly flow across the local area, helping to steer in some monsoonal moisture around the periphery of this high over the course of next week. As this ridge expands to the southwest over the middle of next week, expect heights aloft to rise and for temperatures to climb further, with a potential for extreme heat across parts of the local area. With all this in mind, there have been no changes to the previous headlines with a heat advisory in effect through Tuesday (for moderate heat - a level 2 of 4) and an extreme heat watch for next Tuesday through Thursday when temperatures are expected to warm further.
Regarding the monsoonal moisture, global models paint a fairly consistent picture that there should be some showers and thunderstorms across at least parts of the local area for several days. While the exact location and timing of convective activity several days out is uncertain, the most favored ares will be across the interior mountains and deserts each day from the late afternoon through evening hours, highly dependent on any embedded disturbances that could help force more widespread activity. At this time, we are thinking a 10-20% chance of a storm each day should cover this potential, with additional refinements as we get closer in time/certainty.
Otherwise, the prolonged period of warm weather rounds out the rest of the story, with slightly above normal temperatures and noticeably more humid conditions both Monday and Tuesday, followed by a bump in temps over the middle to latter portion of the week that is currently covered by the aforementioned excessive heat watch.
10/0034z.
At 0001Z at KLAX, the marine layer was 1100 ft deep. The top of the inversion was around 5100 ft deep with a temperature of 27 C.
High confidence in TAFs for the desert sites of LA County, with moderate to high confidence in KPRB, KSBA, KBUR and KVNY with a 30 percent chance of low clouds moving in overnight. LIFR conds possible at KPRB and KSBA, with IFR to MVFR for the LA County valley sites. Timing of CIGs arrival could differ by up to 2 hours from forecast times.
Otherwise moderate confidence the remaining coastal sites, with LIFR conds likely north of Point Conception, IFR for Ventura and LA coastal sites. There is a 30% chance of MVFR conds for the LA coastal sites.
KLAX, Moderate confidence in the 00Z TAF. There is a 40 percent chc of no cigs. Moderate confidence that MVFR/IFR conds will arrive between 0300Z and 0600Z. Otherwise, timing may differ by +/- 2 hrs from TAF times. High confidence that any east wind component will be AOB 6kt.
KBUR, MOderate to high confidence in TAF. with a 30% chance of IFR to MVFR CIGS between 10Z and 16Z.
09/802 PM.
For the outer waters, Small Craft Advisory (SCA) level NW winds are expected to continue subside from south to north late tonight through Saturday. There will be local gusts to 35 knots over the far northern outer waters tonight, otherwise gusts up to 30 knots are expected. Large short period NW seas will continue through tonight at around 9 to 11 feet at 8 seconds, largest over the northern waters. The seas will gradually diminish Friday through early next week.
For the nearshore waters along the Central Coast, SCA winds are expected through late tonight, and again Friday afternoon and evening. Otherwise, mainly light winds are then expected through Tuesday morning, then increasing Tuesday afternoon and evening.
For the inner waters south of Point Conception, conditions are expected to remain below SCA levels through the period.
09/756 PM.
A south to southwest swell will continue to affect the coastal waters through next week. With this longer period swell, the potential for larger surf and a greater risk for rip currents will continue. High tides are expected to increase this weekend going into next week with Monday expected to be the highest tide of 7.0 to 7.6 ft above MLLW. There is the potential for some minor coastal flooding next week with the high tides and south swell. One thing that will need to be watched into next week will be the potential of a greater south to southwest swell from potential tropical development.
Thunderstorms still continue to be possible starting Sunday and going through next week with a 10-20% chance.
Ca, Heat Advisory remains in effect until 10 AM PDT Tuesday for zones 38-88-343>345-353-368-372-373-375>380-548. (See LAXNPWLOX). Extreme Heat Watch in effect from Tuesday morning through Thursday evening for zones 38-88-341>345-347>358-362-366>376-378>383-548. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 3 AM PDT Friday for zones 645-676. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM to 9 PM PDT Friday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 5 PM PDT Saturday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Saturday for zone 673. (See LAXMWWLOX).
