18/928 PM.
The remnants of Tropical Storm Mario will continue to affect the region through Friday, bringing humid conditions, showers, and isolated thunderstorms. Temperatures may be cooler due to cloudy skies and showers, but areas that receive any sunshine during the day will heat up rapidly. Some drying will take place over the weekend, but there is slight chance of showers as additional moisture from the south arrives. Temperatures will be near normal and the muggy weather will continue into early next week.
(Thu-Sun), 18/924 PM.
***UPDATE***
Plenty of showers moved through the area early this morning, but with a thick layer of clouds covering San Luis Obispo to Ventura County, stronger thunderstorm activity was limited to the areas that saw better heating, mostly over LA County. Luckily, heavier showers were more isolated in nature. The Flood Watch for northern Ventura County and northern portions of Los Angeles County has been expired as more intense thunderstorm and shower activity has ended this evening.
So far, rainfall totals have amounted to anywhere from 0.05 inches to 0.20 to 0.50 inches over the past 48 hours, with isolated higher amounts. Some showers are expected overnight into Friday morning, focused on interior San Luis Obispo County, eastern Santa Barbara County, along with Ventura and interior Los Angeles County. The current forecast looks on track, but may need to cut back on coverage of showers and thunderstorms if guidance continues to back off on rainfall.
***From Previous Discussion***
Synoptically, the area is under an upper-level trough that extends the length of California. Moisture remnants of Tropical Storm Mario are fueling widespread showers in SoCal. While the moisture will remain in the area for a couple of days, a ridge will begin to push in from the south later Friday and through the weekend. On Monday a low pressure area that was hovering to the west will move over SoCal for a returning change of rain Monday through Wednesday. By next Thursday the ridge begins to rebuild.
Showers and isolated thunderstorms continue to move north across southern California as moisture and instability with the remnants of former Tropical Storm Mario tracks north. A very moist air mass is in place already with precipitable water values approaching 2 inches this morning, or about 200 to 250 percent normal. Most areas across the Southland have seen light amounts today with some isolated heavier cells occasionally. Rainfall amounts are generally a tenth of an inch or less with local amounts up to 0.25 inch. Eastern LA County, especially in the mountains, will be a focus for lightning strikes as daytime heating will increase instability With the very moist air mass in the place and the threat of thunderstorms developing, heavy rainfall is possible with any thunderstorms in addition to dangerous lightning, and gusty and erratic winds. A Flood Watch remains in effect through early Friday morning, mostly for the mountains and Antelope Valley.
Showers will continue on and off through late tonight and into Friday, then convective activity should become confined to the the higher terrain. With more sunlight and daytime heating, brief heavy rainfall cannot be ruled out again Friday afternoon as less cloudiness could promote a more unstable lapse rate to develop.
A slightly warmer and drier pattern should develop Saturday and Sunday with downtown LA getting into the low 80s.
(Mon-Thu), 18/143 PM.
There is a moderate chance that another moisture surge from the south could bring some showers and thunderstorms with locally heavy rain between Monday and Tuesday. An upper low meandering down the West Coast could ingest some subtropical moisture with a shortwave trough off Cabo San Lucas and bring it northward. This could happen as early as Sunday afternoon, but more likely not until Monday afternoon. Confidence is remains low at this point, but there are low chances of showers in the forecast for early next week.
The latter part of next week looks warm and dry. There is a moderate chance that a heatwave could develop for the latter half of next week, but the spread across the model solution is pretty wide at this point.
18/1627z.
At 1615Z at KLAX, there was no marine layer. However, there was a moist layer up to 10000 feet.
Overall, low to moderate confidence in 18Z TAF package. Through this evening, VFR conditions are expected at all sites although brief periods of MVFR conditions will be possible with any showers or thunderstorms.
For tonight/Friday morning, low confidence in return of MVFR conditions to coastal/valley sites as well as low confidence in timing of potential return of CIG/VSBY restrictions.
KLAX, Overall, moderate confidence in 18Z TAF. There is a 20-30% chance of brief MVFR conditions through 03Z with any shower activity. There is a 20% chance of tstms 18Z-03Z. For tonight, there is a 50% chance that CIG/VSBY restrictions do not develop. No significant easterly wind component is expected.
KBUR, Overall, moderate confidence in 18Z TAF. There is a 20-30% chance of brief MVFR conditions through 03Z with any shower activity. There is a 20% chance of tstms 18Z-03Z. For tonight, there is a 50% chance that CIG/VSBY restrictions do not develop.
18/920 PM.
For the Outer Waters, moderate to high confidence in current forecast. Currently, local Small Craft Advisory (SCA) level seas are affecting the extreme northern waters, as well as local SCA level gusts just south of Point Conception. Expecting these conditions to calm down overnight and drop below advisory levels by mid-morning and remain below advisory levels through Friday. Saturday through Monday, there is a 50-70% chance of SCA level winds across the outer waters.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Today through Saturday, high confidence in winds and seas remaining below SCA levels. For Sunday and Monday, there is a 30-40% chance of SCA level winds in the afternoon and evening hours.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. For the western half of the Santa Barbara Channel, there is a 40-50% chance of SCA level winds in the late afternoon and evening hours Saturday through Monday. Otherwise across the southern Inner Waters, high confidence in winds and seas remaining below SCA levels through Monday.
The remnants of former Tropical Storm Mario will affect the Southern California coastal waters through Friday. Showers with can be expected through tonight.
Ca, NONE. PZ, NONE.
