20/227 AM.
It will be cooler today. Widespread rain will develop Wednesday and continue into Thursday with a chance of thunderstorms. A weak Santa Ana will develop in the storms wake.
(tdy-Thu), 20/227 AM.
Not too much excitement today as all eyes are on the approach of the first non tropical storm of the rainy season. Today will see an upper low that is about 300 miles off the coast of OR slide south ending up west of Monterey Bay late this afternoon. Flow aloft will become more and more cyclonic. SW winds over Srn CA will increase. Hgts will fall to about 572 dam. The marine layer is somewhat disrupted and there will only be patchy coastal low clouds. During the day there will be an increase in high level clouds assoc with the low. Most max temps will fall 3 to 6 degrees which will bring most below normal temps to most areas (the LA coast and San Gabriel Vly will be the exception).
The southward progression of the low will slow on Wednesday and by late afternoon it will be west of Pt Conception. Fairly strong SSW flow will set up over Srn CA. PWATs will increase to a little over an inch across the csts and vlys. Fairly decent lift and dynamics will overspread the area. Skies will turn cloudy. Steady rain will develop over the Central Coast in the morning with a chc of rain as far south as VTA county. Rain is a near certainty across SLO. SBA and VTA counties in the afternoon with a 60 to 70 percent chc that it will fall over LA county as well. The instability and lift ahead of the low will bring a slight chc of TSTMs to SLO and SBA counties as well.
Lots of action is likely for the entire forecast area Wednesday night into Thursday morning as the upper low will slowly track to the east bringing maximum low level jet dynamics, a good omega field and decent instability. Rain and slgt chc of TSTMs will cover the area with the greatest threat of TSTM near the lows core over SBA county. At this time low level south sfc flow will bring enhanced rainfall rates and totals to the south facing coastal slopes.
The rain showers and slgt chc of TSTMs will continue into Thursday morning. The best chc of TSTMs will follow the upper low and will shift to VTA/LA counties. There will be a diminishing chc of rain esp over SLO and SBA counties in the afternoon. Most precip activity should end during the evening as the low pulls out of the area to the east.
Snow levels will remain above 8000 ft and snow will not be an issue with this system.
Most cst and vly areas should see close to an inch of rain with 2 inches probably across favored south slopes (esp the Santa Ynez range). There may be locally higher amounts over areas where cell train or TSTMs form. Max rainfall rates .75"/hr are likely with this system esp across upslope areas or under TSTMs. Flood watches will be discussed during the day shift after an inspection of the 12Z mdls.
Clouds and rain will limit warming and max temps on Wednesday will be in the mid 60s to lower 70s with only 60s forecast for Thursday.
(Fri-Mon), 20/227 AM.
As it often happens east Pac ridging will follow on the heals of the upper low. Dry NNW flow will move into the state on Friday. In addition offshore flow from north will develop at the sfc. This will lead to some close to advisory wind gusts through the northerly oriented passes and canyons. Skies will turn sunny and this along with rising hgts will bring 3 to 6 degrees of warming to the area.
A low level Santa Ana will develop Saturday and continue through Monday. There will only be 2 to 4 mb offshore flow and marginal upper level support so winds may even stay under advisory level - it will certainly be nothing like last Friday's wind event. Look for another 3 to 6 degrees of warming on Saturday with little change on Sunday and Monday. Even with the warming almost all max temps across the csts and vly will only reach into the 70s.
20/0928z.
At 0832Z at KLAX, the marine layer was 800 ft deep. The top of the inversion was at 1800 ft with a temperature of 22 C.
High confidence in VFR TAFs at KBUR, KVNY, KPMD, and KWJF.
Moderate confidence in IFR-MVFR conds at KSMX, KSMO, KLAX, & KLGB. Timing may be off +/- 3 hours with CIG height +/- 200 ft of TAF. There is a 25% chance for no low clouds.
Good confidence in TAFs for KSBP, KSBA, KOXR, and KCMA. There is a 15% chance for brief IFR-MVFR conds 20/12Z-17Z.
KLAX, Moderate confidence in TAF. There is a 25% chance for no low clouds. There is a 30% chc of lower cigs of OVC008. Low clouds may arrive as early as 11Z. No significant east wind component expected.
KBUR, High confidence in TAF. Less than 10% chance for brief BKN008 conds 20/13Z-17Z.
20/216 AM.
Relatively quiet conditions are expected across the waters today, then a storm system will move into the coastal waters as early as late this evening. This system will impact the area through Thursday. While at this point it doesn't appear as though it will bring significant winds, there will likely be some enhanced southerly flow Wednesday, which may require SCAs to be issued (including nearshore). In addition to the enhanced southerly flow, boaters can expect rain and a chance of thunderstorms and isolated waterspouts. With any thunderstorm there is the threat of lightning, gusty and erratic winds, small hail, 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.
Ca, Beach Hazards Statement in effect through late Thursday night for zones 354-362-366. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until 3 AM PDT early this morning for zones 673-676. (See LAXMWWLOX).
