19/239 AM.
A significant cool down is expected across southwest California through the middle part of the week. Widespread rain is likely Tuesday night or Wednesday through Thursday with a slight chance of thunderstorms.
(tdy-Wed), 19/1002 AM.
***UPDATE***
High temps will continue their downward trajectory today as offshore flow continues to weaken. Overall a quite weather day with highs near normal levels, except along the Central Coast where highs will be 4-8 degrees cooler due to the presence of the marine layer.
Still looking at a good chance of our first traditional storm system of the season Wednesday and Thursday. Timing still an issue but for now it looks like Wednesday will primarily be light rain, then transitioning to more of a convective/showery system overnight into Thursday.
***From Previous Discussion***
Pretty benign weather day as the set up for the first storm of the season begins. A 548 dam upper low will begin to spin down the coast off of the PAC NW. The upper flow over Srn CA will turn to the SW and become cyclonic. There will be one last gasp of offshore (weak) flow this morning and it will turn onshore in the afternoon. Low clouds have developed across the Central Coast and there is some patchy low clouds across the cst of VTA county. The main story today will be the cooling. The csts/vlys south of Pt Conception will cool 3 to 6 degrees while the Central Coast cools 5 to 10 degrees. Central Coast temps will be about 6 degrees blo normal but the csts/vlys south of Pt Conception will still be 2 or 3 degrees over normal.
Continued onshore flow, lowering hgts and increasing cyclonic turning aloft will create marine stratus over the Central Coast, The LA Coast and portions of the VTA cst.
By the afternoon the upper low will have moved to the west of the Bay Area. Hgts will fall to about 572 dam. Aside from the morning low clouds, there will be enough mid and high clouds to make it a partly cloudy day. The Central Coast will not cool much more after today's big cool down, but the rest of the area will see 4 to 8 degrees of cooling. Almost all max temps across the csts/vlys south of Pt Conception will be in the 70s or 3 to 6 degrees under normal.
The upper low will move south just to the west of Monterey CA Tuesday night where it will likely sit and spin through Wednesday afternoon. At this moment the mdl consensus is for a chc of rain to overspread the area with a greater than 80 percent chc of rain developing across the Central Coast after midnight. That said the mdl trend is slower and would not be surprised if the chc of rain is lowered during this time period over the next 24 to 36 hours.
There is still a great deal of uncertainty in the timing of the system on Wed and Thu. There is good confidence that the upper low will move to the east and open up into trof. It will bring about 12 hours of rain along with a slight chc of tstms. Storm total rainfall should fall between .75" and 1.00 inch. Foothills/cstl slopes could see up to 2 inches. There is a 25 percent chc that these numbers could end up higher. Right now it does not look like rainfall rates will not be that hazardous unless a TSTM develops. The rain should taper off to nothing Thursday evening or shortly after midnight.
Needless to say both days will be cloudy and cool with highs only in the mid 60s to lower 70s.
(Thu-Sun), 19/245 AM.
The trof axis will be to the east of the area Friday morning. There will be rising hgts and clearing skies. Breezy NW to N winds will develop as well as offshore flow from the north develops at the sfc and is reinforced by the upper level support. Most max temps will rise 3 to 6 degrees. Even with the warming cst/vly temps will only reach the lower to mid 70s or 3 to 6 locally 8 degrees blo normal.
As is so often the case with the passage of an upper low/trof offshore flow will develop. Right now it looks like a two day low to medium event and nothing like last Friday's. Max temps will warm 3 to 6 degrees Saturday and then change little on Sunday.
19/0940z.
At 083Z at KLAX, the marine layer was 600 ft deep. The top of the inversion was at 1500 ft with a temp of 24 deg C.
Moderate confidence in TAF for KPRB, KOXR and KCMA (30 percent chc of IFR conds 12Z-15Z) and KSMO, KLAX and KLGB (30 percent chc of MVFR Vis 12Z-17Z)
Good confidence in remainder of TAFs
KLAX, Moderate confidence in TAF. However, there is a 30 percent chance of 5SM HZ 12Z-16Z. Any east wind component is expected to be 6 kt or less thru the period.
KBUR, High confidence in TAF.
19/806 AM.
Small Craft Advisory (SCA) northwest winds will be common across portions of the outer waters through tonight, with localized SCA wind gusts into the western portion of the Santa Barbara Channel.
Tuesday will feature relatively quiet conditions, then a storm system will move into the coastal waters as early as late Tuesday evening. This system will impact the area into Thursday, impacting the northern waters first. While at this point it doesn't appear as though this system will bring significant winds, there will likely be some enhanced southerly flow Wednesday, which may require SCAs to be issued. In addition to the enhanced southerly flow, boaters can expect rain and a slight chance of thunderstorms. With any thunderstorm there is the threat of lightning, gusty and erratic winds, and choppy seas.
As the system leaves the area Thursday, fairly widespread west to northwest SCA winds will impact much of the coastal waters, creating steep, choppy wind waves.
Then a weak to locally moderate Santa Ana Wind event is likely this weekend, with some localized SCA level gusts possible nearshore in favored areas nearshore adjacent to Ventura and LA Counties.
19/222 AM.
The combination of a west to northwest swell and a 3-ft southerly swell will bring elevated surf of 3 to 6 feet mainly to south and southwest-facing beaches of Ventura and Los Angeles Counties through Tuesday morning.
In addition to the elevated surf, dangerous rip currents can be expected. Minor beach erosion and tidal overflows cannot be ruled out for low-lying beach areas around the times of high tides.
Ca, Beach Hazards Statement in effect through Tuesday morning for zones 354-362-366. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until noon PDT today for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Tuesday for zones 673-676. (See LAXMWWLOX).
