03/130 PM.
Heat relief is coming. Temperatures will slowly lower through Friday, including the abnormally warm overnight temperatures. Monsoonal moisture will remain over the region through Thursday, but the risks for significant impacts have lowered. Slight warming on track Saturday through Monday, then a likely big cool down to follow.
(Wed-Sat), 03/846 PM.
***UPDATE***
Although clouds developed over the mountains today, no showers developed this afternoon and evening, in line with the direction guidance was trending. Temperatures were nearly the same as Tuesday's highs, with 90s common from the warmer valleys to the interior, and 70s to 80s near the coasts. Weakening high pressure should result in slightly cooler temperatures Thursday, with a more significant cool down Friday as an upper level low approaches from the northwest. Tonight, marine layer clouds have formed off the Central Coast, and expecting to see a deepening marine layer with potential for clouds to increase in coverage over the next few days. The current forecast looks on track, however low confidence in showers for the mountains on Thursday.
***From Previous Discussion***
Still keeping the 10 to 20 percent chance of thunderstorms for each afternoon through tomorrow over the Los Angeles and Ventura County Mountains as the convective parameters are still there, but the chance for everything to line up for flash flooding is extremely low. The latest consensus of tracks for the remnants of Tropical Storm Lorena continues to push it further to the east of our area. This is still something to monitor, but still looks like to be any part of our story. As a result, precipitable water values should fall below one inch by Friday, and the thunderstorm threat is below mentionable by then. Not seeing any appreciable monsoonal surge chances through at least the middle of next week.
The high pressure center that brought all the heat stretching back to last week will continue to weaken through Friday or Saturday. Onshore flow and pressure gradients will also trend more and more onshore each day through Saturday. This will all lead to a steady lowering of daytime temperatures. More significantly, with the monsoonal moisture steadily declining each day, night time temperatures and overall mugginess will noticeably improve each day. As such, the current Heat Advisories will be allowed to expire on time at 6pm this evening with no changes or extensions planned.
Other than that, we are looking at a pretty benign rest of the week. The flow aloft will turn from moist southeast today to dry southwest by Saturday. Some gusty Sundowner winds will form each evening, as well as some gusty onshore winds over the interior, but nothing looks to approach Advisory levels.
(Sun-Wed), 03/220 PM.
High pressure aloft will peak on Sunday or Monday (around 590 decameters) with onshore pressure gradients weakening to around +1 millibars. This should allow temperatures to push back up to a few degrees above normal. Thankfully overnight temperatures will change little due to the dry airmass (nothing like the very warm nights we have been having). The risk for Heat Advisories is close to zero.
More and more of the ensemble projections (on the order of 70%) are now on board for a large trough of low pressure quickly dropping over the west coast on Tuesday then moving very slowly for the rest of next week. This surely means an extended period of temperatures much below normal from Tuesday onward and a likely deep and expansive marine layer. Some solutions have the core of the low cutting off and drifting right over southern California on Friday. Such a solution could bring a few showers but we have some time to figure that out.
04/0516z.
Due to a national METAR outage, there will be limited or no amendments until observations are restored.
At 0424Z at KLAX, the marine layer was 700 ft deep. The top of the inversion was at 1400 ft with a temperature of 28 C.
High confidence in VFR TAFs for KPRB, KBUR, KVNY, KPMD, and KWJF.
Low confidence in arrival of low clouds for KOXR and KCMA. There is a 40% chance for low clouds tonight. If low clouds arrive, 40% chance for LIFR conds.
Moderate confidence in remaining TAFs. Dissipation may be off +/- 90 minutes for KSBP and KSMX. There is a 20% chance for vsbys less than 1SM at KSMX and KSBP. There is a 15% chance for IFR conds at KSMO, KLAX, and KLGB between 10Z and 17Z.
KLAX, Moderate confidence in TAF. There is a 15% chance for IFR conditions 10Z to 17Z Thursday. No significant east wind component expected.
KBUR, High confidence in VFR TAF.
03/834 PM.
Moderate to high confidence in current forecast.
For the Outer Waters, Small Craft Advisory (SCA) winds will be present especially during the afternoon and evening hours through the weekend. Seas will peak around 7 feet Thursday into Friday, becoming small over the weekend.
For the Inner Waters along the Central Coast, moderate chances each day during the afternoon & evening timeframe for SCA level wind gusts especially across NW portions and nearshore Port San Luis through the weekend.
Inside the southern California bight, there is a moderate chance of SCA level winds Thursday through Saturday afternoon and evening - especially across western/southern portions of the Santa Barbara Channel, near Point dume, & into the San Pedro Channel. By Sunday, chances for SCA level winds in the Santa Barbara Channel increase as wind speeds and spatial coverage increase. Seas will remain small, but will begin to increase Sunday and Monday across the Santa Barbara Channel.
Ca, NONE. PZ, Small Craft Advisory in effect from noon to 9 PM PDT Thursday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect from noon Thursday to 3 AM PDT Saturday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Thursday for zones 673-676. (See LAXMWWLOX).
