13/108 AM.
Cooler than normal temperatures and widespread marine layer clouds will continue through the weekend. There is a low chance of showers/thunderstorms through this afternoon.
(tdy-Sat), 13/104 AM.
The trough along the coast has finally settled in. Mid-level clouds are streaming in from the southwest, temperatures will continue to cool, and there remains a small chance for convective activity today.
The low chance of showers/thunderstorms continues through this afternoon across the area, with highest chances (15% chance) across the Central Coast as well as the northern Ventura/interior Santa Barbara County mountains. While high resolution CAMs really don't show much in the way of reflectivity, there is fairly widespread elevated instability associated with this trough across Santa Barbara and SLO Counties, as well as some left over monsoonal moisture to play with through later this morning. A small lobe of vorticity is projected to swing across the northern part of our CWA now through this morning. This could be the best opportunity for storm initiation through the day, although afternoon heating and orographics could be the best source across the interior areas. At lower elevations, the more significant impacts could be gusty winds and dry lightning, while higher terrain would potentially see higher rainfall rates--although not expecting storms of the same magnitude as Tuesday's storms. Very low chances for showers/thunderstorms exist into the weekend as the trough remains almost stationary along the coast. However, the environment will become rather mositure starved, so not expecting much in the way of rainfall if any storms get going.
Aside from the small chance for storms to develop, the most significant aspect of the forecast is the continued cooler than (mid-August) normal temperatures region-wide. Thanks the the lower 500 mb heights brought along by the trough as well as moderate to strong onshore flow, a very long stretch of above normal temperatures has ceased. Friday's max temps are forecast to be very similar to today, around 8-15 degrees above normal in many places. We are expecting a couple degrees of warming on Saturday, but still well below seasonal normals.
A very deep marine has already expanded to many valleys. Fairly similar coverage is expected Friday, with slightly less coverage Saturday due to a shrinking marine layer depth. The marine layer will burn off in the late morning to early afternoon, although some west facing beaches may not see much in the way of clearing as the onshore flow will try to keep the clouds in place. Additionally, there is a chance for some patchy drizzle this morning and again Friday morning. There is potential for mid level clouds to disrupt the radiative cooling processes that help the marine layer form. This could create more of a patchy marine layer, with highest potential for this across LA and Ventura Counties.
Enhanced onshore flow means fairly gusty west to southwest winds will be common across the interior, with winds likely the strongest across the Antelope Valley and foothills. While some advisory level wind gusts may occur, not expecting these winds to be widespread enough to warrant an advisory at this time.
(Sun-Wed), 13/104 AM.
The extended period will generally feature rather benign sensible weather relative to the time of year. The upper level ridge of high pressure over the southern United States will push the trough to the west. 500 mb heights will increase to around 592-594 dam with dry southwest flow aloft. 500 mb heights are projected to peak Tuesday/Wednesday. Additionally, onshore flow is expected to weaken some to some, with the LAX-BFL pressure gradient even forecast to become negative by next week.
Marine layer clouds will shrink each day with increasing 500 mb heights and weakening onshore flow, likely retreating to just the coastal areas by early next week. By Tuesday, increasing northwest flow will likely wipe out the marine layer from southern Santa Barbara County and potentially Ventura County.
With 500 mb heights increasing, onshore flow weakening, and marine layer coverage shrinking, temperatures will climb to near normal for mid-August. The more noticeable increase in temperatures will be across the valleys and interior since most coastal areas will still be under marine influences.
Increasing northwest flow next week will likely bringing gusty winds in the afternoon through late evening hours to Southwestern Santa Barbara County as well as the interior mountains, especially along the I-5 through the Grapevine.
13/1049z.
At 0922Z at KLAX, the marine layer was 2700 feet deep. The top of the inversion was near 5000 feet with a temperature of 20 C.
High confidence in VFR TAFs for KPMD & KWJF.
Moderate to low confidence in remaining TAFs. Timing of arrival/clearing of cigs may be off +/- 3 hours, with lower confidence in clearing times. There is a low to moderate chance for cigs to linger through the period at all immediate coastal sites. High/mid level clouds may disrupt the marine layer at times tonight, leading to conds becoming VFR at times, especially for Ventura and LA County sites.
KLAX, Moderate confidence in TAF. Mid/high clouds may disrupt marine layer tonight, leading to VFR conds at times. Clearing time may be off +/- 3 hours, arrival tomorrow night may be off +/- 4 hours. There is a low to moderate chance for no clearing. No significant east wind component expected.
KBUR, Moderate confidence in TAF. Clearing time expected to be 16Z-19Z. High/mid level clouds may disrupt the marine layer at times tonight, leading to conds becoming VFR at times. Arrival of cigs tonight may be off +/- 4 hours.
13/111 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 very small chance of a shower or a thunderstorm around and north of Point Conception later through this morning.
Ca, NONE. PZ, NONE.
