11/128 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 Wednesday night. More robust marine layer cloud coverage is likely this week, however, higher clouds may disrupt the formation of the marine layer at times.
(tdy-Thu), 11/128 AM.
A large blob of convective debris clouds is wafting over the area this morning. As is so ofter the case, the high clouds are inhibiting low cloud formation. Skies should turn mostly sunny by afternoon. The sunny skies will bring enough differential heating in the mtns that when combined with the 1.25+" PWs will produce a 30 to 50 percent chc of convection. The greatest chc of convection will be over far nrn VTA county and the eastern San Gabriel mtns. Some storms could roll off the mtns and in the Antelope and Cuyama Vlys as well. The other big news is the temps. Hgts will fall to 590 dam and this along with mdt onshore flow in the afternoon will bring 2 to 4 locally 6 degrees of cooling to the area. This cooling will bring most mtn and vly locations to below normal. Max temps today will most be in the upper 70s to mid 80s across the csts and upper 80s to mid 90s in the vlys.
There should be less high clouds tonight and this along with the mdt onshore flow should allow low clouds to form and move across most of the csts.
A trof sets up over the west cst on Wednesday. Hgts fall to about 585 dam. Onshore trends will bring strong onshore flow to both the N and E in the afternoon. The onshore flow, marine layer and lower hgts will all combine and lower max temps another 3 to 6 degrees. This cooling will bring below normal temps to almost the entire forecast area. Vly temps will range from 80 to 90 degrees or 5 to 10 degrees under normal. The other issue Wednesday will the convective chcs. The upper level trough along the coast could bring in some additional moisture. This moisture combined with elevated instability will bring a 30 to 40 percent chc of convection to nrn VTA county and the eastern San Gabriels as well as a 10-15% chance of afternoon thunderstorms across much of SLO and Santa Barbara Counties. That said the latest hi rez convective allowing mdls are much less bullish on any convection and if this trend continues the convective chc's for Wednesday will be trended downward.
The strong onshore flow will continue into Thursday. The troffing aloft and strong onshore flow at the sfc will likely produce a pretty robust marine cloudy layer extending into the vlys. Clearing will likely be on the slow side with some beaches remaining cloudy all day. Max temps will tumble another 3 to 5 degrees and its unlikely that any station will reach 90 degrees. Max temps in the vlys will likely end up 6 to 12 degrees blo normals.
The onshore push to the east will top out near 8mb both Wed and Thu afternoon. This strong push will generate gusty winds across the Antelope Valley and its foothills. There will be a 30 percent chc of low end wind advisories each afternoon.
(Fri-Mon), 11/251 AM.
Good agreement with all of the medium range mdls, which show broad troffing with dry SW flow over the state. Hgts do climb through the period as an impressively large upper high expands and nudges hgts up from 586 dam on Friday to 590 dam on Saturday and then up to 592 dam for Sun and Mon. At the sfc the mdt to stg onshore flow to the east will continue but the onshore push to the north will weaken substantially.
The weather should be pretty dull. There will be plenty of night through morning low clouds and fog across the csts. The vlys will see less and less stratus and marine influence as the north push decreases and the hgts increase (smooshing the marine layer to under 1000 ft).
Gusty but still under advisory levels winds will continue across the Antelope Vly.
Blo normal max temps will continue Friday where max temps will be very similar to Thursday's cool values. Look for 2 to 5 degrees of warming on Saturday followed by 1 to 3 degrees on Sunday. The vlys will see the greatest amount of warming as the marine influence wanes. Despite the 2 days of warming, Sunday's max temps will remain 4 to 8 degrees blo normal. Monday's max temps will greatly resemble Sunday's.
11/1148z.
At 0822Z at KLAX, the marine layer was 800 feet deep. The top of the inversion was at 2400 feet with a temperature of 27 C.
High confidence in TAFs for the valleys and deserts.
Fair confidence in TAF for KLGB with a 20 percent chc of OVC012 conds 13Z-17Z.
Low confidence in TAFs for KLAX and KSMO with a 40 percent chc of no low clouds.
Moderate confidence in TAFs for remaining sites VFR conds may arrive +/- 90 minutes or fcst time. Lower confidence in the timing of return of low clouds this evening with timing errors up to 3 hours possible.
There is a 30% chc of -TSRA at KWJF KPMD through 03Z 22Z-02Z.
KLAX, Low confidence in the TAF. There is a 40 percent chc of no low clouds. If low clouds do arrive, VFR conds could arrive as early as 15Z or as late as 1730Z. Low confidence in low cloud return this evening as low clouds could arrive as early as 04Z. High confidence in minimal or no east wind component. KBUR, High confidence in TAF. There is a 5% chance of -TSRA 22Z-02Z.
11/128 AM.
High confidence that conditions will remain below Small Craft Advisory (SCA) across all of the southwestern California coastal waters through at least Friday night. Patchy dense fog are possible on the Central Coast each morning. There is also a 5-10% chance of a thunderstorm over the coastal waters Tuesday through Wednesday.
Ca, Coastal Flood Advisory in effect until midnight PDT Wednesday night for zones 349-350-354-362-366. (See LAXCFWLOX). PZ, NONE.
