12/1031 AM.
A cooling trend will continue through Thursday, with cooler than normal temperatures expected across the area into the weekend. There is a chance of mountain and occasional lower elevation convection through at least tonight and potentially lingering into Thursday morning. More robust marine layer cloud coverage is likely this week, however, higher clouds may disrupt the formation of the marine layer at times.
(tdy-Fri), 12/815 AM.
***UPDATE***
Current Satellite shows a vorticity lobe with active convection 250 SM WSW of Point Conception. This is expected to move onshore this evening through Tomorrow morning bringing around a 30% chance for showers and thunderstorms across SLO & SB counties.
Our main focus this afternoon is convective chances (40%) over the Lockwood valley area - most likely 12pm-6pm. Lowered the chances some over eastern San Gabriels due to lack of moisture in the mid-levels, but still 30% chance of shower or T-storm.
There is another shortwave dives southward behind on Friday but has less vorticity and is dry in the 700-300 mb layer - not expecting any impacts at this time.
***From Previous Discussion***
Troffing will set up over the west coast today and will continue through Friday. Hgts will fall to 584 dam today and then to 582 dam Thursday. At the sfc there will be mdt-stg onshore flow both to the north and east.
Most of the coast will wake up to low clouds this morning with some patchy dense fog across the Central Coast. Skies otherwise will be partly to mostly cloudy as plenty of mid and high level clouds drift overhead. There will be enough low level moisture to allow for a chc of TSTMs over the mtns esp the northern VTA county ones. A small vort lobe will drift over SBA/SLO counties and will bring a chc of showers/TSTMs to those areas as well. Max temps will drop 4 to 8 locally 10 degrees as the marine layer, onshore flow, cloud cover and lowering hgts all conspire together. Most max temps will end up about 6 degrees under normals.
On Thursday the SW flow from the trof will bring enough drying to eliminate the convective threat. The onshore flow and troffing aloft will gin up a pretty robust marine layer cloud deck that will cover most of the csts and will xtnd into the vlys. Clearing will be slower than normal and some beaches may only see limited clearing. Another 2 to 4 locally 6 degrees of cooling will bring max temps that are 2 to 4 degrees blo normals across the csts and a whopping 5 to 10 degrees across the vlys. Vly highs will only be in the upper 70s to mid 80s.
Not much change is slated for Friday and the day should greatly resemble Thursday.
The onshore push to the east will top out near every afternoon. This strong push will generate gusty winds across the Antelope Valley and its foothills. There will be a 20-30 percent chc of low end wind advisories each afternoon.
(Sat-Tue), 12/246 AM.
Good agreement with all of the medium range mdls. The west coast trof will persist through Saturday with hgts rising to 588 dam. The trof will then be pushed to the west by a powerful upper high that spans most of the southern portion of the CONUS. Srn CA will then be under flat dry SW. Hgts will climb to 592 dam. At the sfc the mdt to stg onshore flow to the east will continue but the onshore push to the north will weaken substantially and might even be offshore by Tuesday or Wednesday.
The weather will be benign through the period. There will be plenty of night through morning low clouds and fog across the csts. Due to the rising hgts the marine layer will be shrunk to under a 1000 ft which should keep it out of the vlys. Skies, otherwise, will be mostly clear. The weakening onshore flow to the north will also lessen the amount of coastal low clouds early next week esp if the offshore flow develops.
Gusty but still sub-advisory levels winds will continue across the Antelope Vly.
Temps will begin to warm on Saturday. Look for 2 to 4 degrees of warming on Saturday and Sunday and 1 to 2 degrees each day Monday and Tuesday. Even with the four days of warming max temps Tuesday will remain 2 to 4 degrees blo normal.
12/1736z.
At 1639Z at KLAX, the marine layer was 1600 feet deep. The top of the inversion was near 2500 feet with a temperature of 21 C.
High confidence in TAFs for desert airfields (KPMD & KWJF).
Moderate confidence in remaining TAFs. Timing of prevailing groups may be off +/- 2 hours and conditions by one category.
KLAX, Moderate confidence in TAF. Arrival and clearing of MVFR CIGs (012-018) may be off +/- 2 hours. No significant east wind component expected.
KBUR, Moderate confidence in TAF. No wind issues expected.
12/815 AM.
High confidence that conditions will remain below Small Craft Advisory (SCA) criteria across all coastal waters through Friday morning. Low to moderate chances for SCA winds across favored areas south of Point Conception this weekend. Increasing chances across all coastal waters heading into next week.
There is a slight chance of a shower or a thunderstorm around and north of Point Conception later this afternoon thru early Thursday morning.
Ca, Coastal Flood Advisory in effect until midnight PDT tonight for zones 349-350-354-362-366. (See LAXCFWLOX). PZ, NONE.
