27/217 PM.
Hot and muggy conditions will continue through Friday with a high risk for heat-related illness. Scattered showers and thunderstorms are possible through Friday, with risks of lightning, fire starts, and erratic winds. Temperature and moisture relief will start over the weekend, but will increase again starting Tuesday, with a chance for showers and convection.
(Thu-Sun), 27/830 PM.
***UPDATE***
Highs today came in about 5 to 12 degrees colder today for Ventura and Los Angeles Counties, likely due to some additional clouds and some sporadic showers. Pressure gradients were pretty weak, with very minimal onshore flow. Further north, the difference was far more significant, with areas away from the coast seeing a large 15 to 25 degrees drop. More showers along with much thicker clouds likely played a role. Looking at temperatures for tomorrow, expecting clouds to break up in the afternoon hours, so thinking things will be warmer than today, and temperatures were decreased 2 to 5 degrees from Santa Barbara to San Luis Obispo County to account for the ongoing shower/thunderstorm chances and additional clouds.
This evening, showers have grown isolated but chances are ongoing into Friday. Gusty sundowner winds have developed as well, and guidance failed to pick up on a SBA-BFL offshore gradient of 5 mb, helping to drive these winds. A short-duration wind advisory was issued for the Santa Ynez Range and southwestern Santa Barbara Coast to cover wind gusts up to 45 mph, although this may need to be canceled early if winds fail to sustain/increase their speeds. The current forecast looks on track, with no other significant changes.
***From Previous Discussion***
What a difficult forecast thanks to the remnants of Tropical Storm Iselle (ee-SELL) which are now upon us. There are so many potential impacts and outcomes over the next 36 hours.
Lets start off with the shower and thunderstorm piece. For the rest of today, scattered light showers will continue to impact portions of all four of our counties. Any rain amounts should stay under 0.10 inches. We had 8 lightning strikes around Vandenberg this morning, but not much since then. There is still a small chance anywhere today, with the highest chances on the Central Coast and any of our mountains and deserts. All indications suggest a shift northward and decrease in activity overall tonight, but with the moisture still in place, cannot completely rule out an isolated shower or two. For tomorrow, a trough to the northwest will interact with this tropical moisture and enhance the chance for showers and thunderstorms, mainly for areas north of Santa Ynez. As a possible glimpse into the future, this interaction is currently taking place about 400 miles southwest of Point Conception. The current IR satellite over there shows rapidly cooling cloud tops (an indicator of convection) with the lightning-cast algorithm showing a 50% chance of thunderstorms. This all adds up to a 10-30% chance of showers and thunderstorms, with the highest chances over San Luis Obispo County, decreasing to the south. The main threat will continue to be cloud-to-ground lightning and erratic winds, which pose a significant risk for fire starts and growth. The risk for isolated heavy rain and flooding is not zero but it is low. The moisture is on track to exit the region overnight on Friday and be gone by Saturday.
Next up, the temperature bit. The clouds wreaked havoc on the temperatures today. Much of Los Angeles and Ventura Counties are down 5-10 degrees compared to yesterday, and much of Santa Barbara and San Luis Obispo Counties are down 15-25 degrees (except for 5-10 degrees of warming over SW Santa Barbara County). Despite the numeric cool down, most will agree that it still feels hot as dewpoints are around 70 degrees for much of our region, which is similar to Florida right now. With the new tropical airmass, overnight lows last night were sweltering. While some areas will be different, cannot see a reason for the majority of the region to experience something similar again tonight. Daytime temperatures on Friday are a muddled mess. Fairly confidence that Los Angeles and Ventura Counties will see less cloud cover and therefore should be noticeably warmer than today. For Santa Barbara and San Luis Obispo County, the trends could be up 10 or down 10 depending on how that moisture plume and any convection sets up. Because of all of these complexities and uncertainties, we will NOT be changing any of the Heat Warnings or Advisories today, but might need to make some adjustments tomorrow. At this point, the chance of extending any heat seeing any need to extend anything beyond tomorrow.
That gets us through Friday Night. For the weekend, the airmass will dry out and cool down, especially by Sunday when temperatures will drop enough to cross under normal. The marine layer clouds will likely make a return, but exact coverage is always a tough call. Sundowner winds will peak Saturday Night with a Wind Advisory more favorable than not.
(Mon-Thu), 27/215 PM.
Monday looks pretty benign with below normal temperatures, coastal low clouds, and typically breezy mountain winds. After that, anything goes. A disturbance currently forming off the Baja coast will likely form into a Tropical Storm as it moves toward the west to northwest. Another trough will likely form to the north and interact with that tropical moisture in the Tuesday through Thursday timeframe. About half of the projections result in some of this moisture streaming over southwest California, with about 10 percent of the solutions resulting in rain. About 5% of the earlier projections showed heavy rain with the bulk of the moisture moving over, but that signal is largely gone in the latest projections. With all that stated, the most likely outcome is for some increased mugginess and warmer conditions and that is about it, with intel about the rest of the risks in a clear wait and see holding pattern.
28/0518z.
At 0510Z at KLAX, the marine layer was 600 feet deep. The top of the inversion was 2500 feet with a temperature of 32 C.
Overall, moderate confidence in 06Z TAF Package. For most of the period expecting BKN/OVC150.
KLAX, Moderate confidence in TAF. BKN/OVC deck above 10KFT thru at least 28/18Z. Any east wind component is expected to remain below 7 kts.
KBUR, Moderate confidence in TAF. BKN/OVC deck above 10KFT thru at least 28/18Z.
27/744 PM.
Through this weekend, high confidence in small craft advisory (SCA) level winds across the outer waters with short-period choppy seas. These hazardous conditions will reach into the nearshore waters along the Central and into the Santa Barbara Channel at times (especially afternoon/eve). Local gusts may approach 35 kt near Point Conception Saturday evening.
Isolated to scattered showers are expected to continue across the coastal waters mainly north and west of Point Conception. There is a 10% chance of thunderstorms which could bring the threat of erratic winds, localized rough seas and cloud-to-surface lightning. For next week, most waters are likely to fall below SCA levels Monday and Tuesday. Increasing chances for SCA conditions later in the week but signal isn't strong, moderate at best.
Ca, Extreme Heat Warning in effect until 8 PM PDT Friday for zones 38-87-88-349>358-362-366>376-378>383-548. (See LAXNPWLOX). Beach Hazards Statement in effect until 11 PM PDT this evening for zones 87-354-362-366. (See LAXCFWLOX). Heat Advisory in effect until 8 PM PDT Friday for zones 341>345-347-348. (See LAXNPWLOX). Wind Advisory in effect until 1 AM PDT Friday for zones 349-351-352. (See LAXNPWLOX). Red Flag Warning in effect from 5 AM to 3 PM PDT Friday for zones 340>345. (See LAXRFWLOX). Red Flag Warning in effect until 3 PM PDT Friday for zones 353-375>380. (See LAXRFWLOX). PZ, Small Craft Advisory in effect from 3 PM Friday to 3 AM PDT Saturday for zones 645-650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 PM PDT Saturday for zones 670-673-676. (See LAXMWWLOX).
