25/1202 PM.
An upper low and frontal system will bring rain to the area Saturday with snow above 5000 feet. Highs will be 10 to 25 degrees below normal. Dry and warmer weather is expected Sunday through next week though temperatures are expected to remain below normal in most areas.
(Fri-Mon), 25/841 PM.
***UPDATE***
Falling hgts and interior cloudiness brought max temps down by 8 to 12 degrees across the mtns, deserts and interior vlys today. The coasts and vlys did not change much. Most high temps today ended up 8 to 12 degrees blo normal. Currently, most of the csts/vlys are mostly clear while clouds continue over the interior.
All eyes on a late season storm which will sweep a cold front into and through the area Saturday morning. Rain will move in form the WSW and will move into SLO and SBA counties around 5am and then VTA and LA counties from 7am to 9am. The rain will taper off in the afternoon leaving only scattered showers in its wake. The cold core of the upper low does pass over SLO county and will bring enough instability for a slight chc of TSTMS. Current rainfall fcst (.25 to .50 locally .80 foothills) looks good.
It sure will be cold tomorrow with max temps barely scraping to 60 degrees or 10 to 15 locally 20 degrees blo normal.
Forecast was updated for slight adjustments to clouds and pops.
***From Previous Discussion***
An unseasonably cold upper low will move into the area later tonight and Saturday. Most of the model solutions have the low moving onshore near Lompoc Saturday morning, then following the Transverse Range east before exiting LA County Saturday evening. As the upper low approaches tonight the cold front will pivot and take on a northwest to southeast orientation. This will result in the rain arriving at a similar time, roughly between 4 and 7am from SLO County down through Ventura County. Then moving into LA County between 8 and 10am. Rain totals have been nudged upward slightly with amounts up to around .80" in the foothills and mountains and between a quarter and half inch elsewhere. Most of the morning rain is expected to be on the lighter side, generally a tenth of an inch per hour or less. However, as the upper low moves inland and colder air moves into the region Saturday afternoon, the steady light rain in the morning will change to a showery pattern as the air mass destabilizes. While some areas may receive minimal additional rain in the afternoon, the instability aloft will create stronger uplift and a possibility of some heavier showers and possibly even an thunderstorm. Hi res models continue to indicate peak rain rates around a quarter inch per hour, so at this time there is no concern for any burn area debris flows with this storm. While thunderstorms can't be ruled out anywhere, the most unstable air will be across the interior, from the mountains and north and east.
With the uptick in rain amounts, especially in the mountains, a Winter Weather Advisory has been issued above 5000 feet through Saturday evening with snow totals up to 6 inches. At this time snow is not expected to accumulate on the Grapevine over Interstate 5, however it is possible that convective showers with strong updrafts could result in snow reaching the surface with temperatures above freezing as low as 3500-4000 feet.
Rain and snow is expected to taper off by Saturday evening (if not before) with dry weather Sunday into early next week. Gusty west to northwest winds expected Sunday afternoon, especially near the coast. Temperatures will trend warmer both days, but more so inland, though will still be at least 3-6 degrees below normal.
(Tue-Fri), 25/1253 PM.
The warming trend will continue through Tuesday with some warmer valleys getting into the lower 80s while coastal areas are in the upper 60s to mid 70s. Models show onshore increasing Wednesday through Friday leading to cooler temperatures and a likely return of the marine layer.
26/0029z.
At 2305Z at KLAX, the marine layer was around 4900 ft deep. The top of the inversion was at 5500 ft with a temperature of 4 C.
Good confidence in TAFs for KPMD and KWJF
Moderate confidence in the remainder of TAFs There is 30 percent chc of no cigs overnight at any given site and a 15 percent chc of MVFR cigs as well.
Rain onset and ending may be off by as much as 2 hours and rain may produce MVFR cigs and vis at times. Brief showers may occur a few hours after the main rainband has exited the site.
KLAX, Moderate confidence in TAF. There is a 30 percent chc of SCT060 conds lasting until 15Z and a 15 percent chc of BKN025 conds 09Z-15Z. Rain could start as early as 14Z or as late as 16Z. Cig and Vis may vary between BKN025 and BKN035 and 3SM and 6SM during rain.There is a 30 percent chance of an 8 kt east wind component 12Z to 18Z.
KBUR, Moderate confidence in TAF. There is a 30 percent chc of SCT060 conds lasting until 15Z. Cig and Vis may vary between BKN025 and BKN035 and 3SM and 6SM during rain.
25/759 PM.
Moderate confidence in forecast.
For the Outer Waters, there is a 20% chance of SCA level wind gusts for western portions of PZZ676 during afternoon/eve hours on Sat. Widespread chances for SCA conds increase (60-90%) Sun afternoon thru Tues night.
For the Inner Waters north of Point Sal, conditions are expected to remain below SCA Criteria through Sat. Potential for widespread SCA winds during the afternoon/eve hours Sun thru Tues (50-70% chance).
For the Inner Waters south of Point Conception, conditions are expected to remain below SCA levels through tonight. There is a 30% chance of SCA level winds across the Santa Barbara Channel during the afternoon/eve hours on Sat. Thereafter, chances increase to 60% across the SBA Channel and southern Inner Waters off the LA and OC coasts on Sunday, including nearshore. There is a 20-30% chance of SCA level winds for western portions of SBA Channel Mon afternoon/eve. Much lower chances Tue through Wed.
Across the waters, rain is forecast to begin as early as tonight and impact the waters through at least Sat night. There is a low chance of thunderstorms (10%) Sat over the Inner and Outer Waters along the Central Coast. Any thunderstorm could produce gusty, erratic winds, lightning, and small hail.
Ca, Winter Weather Advisory in effect from 7 AM to 11 PM PDT Saturday for zones 353-376-377. (See LAXWSWLOX). Winter Weather Advisory in effect from 9 AM to 11 PM PDT Saturday for zones 378>380. (See LAXWSWLOX). PZ, NONE.
