Marine Weather and Tide Forecast for Pasadena, CA

.SHORT TERM (TDY-THU)...13/248 PM.

A rare and very potent storm system remains on track to affect the area tonight through tomorrow, with lingering showers possible into early Wednesday. All areas will see rain. Some areas will see short bursts of heavy rain, although it remains difficult to predict exactly where. South-facing slopes and foothills have the highest chance of seeing those heavy bursts, but they can happen anywhere.

Rainfall totals remain on target, with 0.75 and 1.50 inches common, except 2.00 to 4.00 inches in the favorable south facing slopes and anywhere those heavy bursts form. An isolated reading of 5 inches is on the table, especially over the San Gabriels where computer projections show the highest totals. Peak rainfall rates of 0.33 to 0.66 inches per hour will be common, which should be enough to cause plenty of minor road issues and heavy traffic for the Tuesday morning commute - as well as shallow debris flows impacting a few roads near a burn scar. A few lanes or offramps could be flooded. Rockslides in canyon roads are nearly certain. Isolated rates to around 1.00 inches per hour are also likely, but again not exactly sure where. Wherever those occur, impacts will be locally amplified. If they occur in an urban area, several lanes of a freeway could flood. If they occur over a burn scar, a deeper more significant debris flow would form which could cover and close a road and or threaten structures.
That is a real possibility, with the Palisades, Eaton, and southern Bridge burn scars having the highest threat.

In addition to the hydro risks, there is a significant threat for severe thunderstorms capable of producing very localized but damaging winds and or a tornado. Still seeing several signatures (the trajectory of the low, the diffluence aloft, the high shear environment) for supercell thunderstorms with several high resolution models resolving finer scale parameters conducive of isolated strong downdraft winds and/or weak tornadoes (updraft helicity being one of them).

What should people do? For tonight through Tuesday: Avoid outdoor activities and stay indoors as much as possible, especially if you hear thunder, see lightning, or experience sudden wind shifts. Avoid parking near tall trees. Be ready for sudden power outages. Avoid the roads as much as possible, and if you have to drive, allow extra time as traffic will be increased due to slippery roads, low visibility, and localized flooding. If you are near a burn scar, there is a risk of significant debris flows.
Heed the advice of local officials, and expect at the very least mud and debris on some roads. Boaters, please stay in safe harbor.
For everyone, stay tuned to your local news outlet and weather.gov for any updates.

In addition, there will be a period of gusty southwest winds focused over the interior areas. Snow levels remain high (above 7,000 feet) for the majority of the precipitation, but they lower to 5,500 to 6,000 feet after the main rain later on Tuesday. So while this is not a big snow maker of a storm, any post frontal showers could be some light accumulations down to 6,000 foot elevations.

By Wednesday afternoon or evening, any linger showers should end.
Drying and warming northwest to north winds will quickly follow Wednesday Night and turn northeasterly on Thursday. Gusts in the 20 to 35 mph range are the most likely outcome. Temperatures will increase as a result, along with a warming airmass, with highs in the 70s common by Thursday.

.LONG TERM (FRI-MON)...13/249 PM.

Some models are showing the northeast flow that forms on Thursday increasing some more on Friday then decreasing through Saturday.
Meanwhile high pressure will be building over the southwest.
Temperatures will continue to rise as a result, with highs in the mid 70s to mid 80s common Friday through the weekend.

AVIATION
13/1805Z.

At 1715Z at KLAX, the marine layer was 5000 ft deep. The top of the inversion was near 5800 ft with a temperature of 8 deg C.

Low confidence overall in the 18Z TAFs.

Expecting SHRA after 00Z Tue along Central Coast and after about 03Z-05Z for VTU/L.A. Counties with MVFR conditions at times.
Around a 40% chance of TSRA during this timeframe for KPRB, KSBP, KSMX, & KSBA, with a 20%-30% chance elsewhere later this evening thru late tonight. Expect visibility reductions under heavy rainfall. Brief IFR conditions cannot be ruled out.

LLWS and turbulence is possible as front approaches and near any thunderstorms that develops.

Low to moderate confidence in wind forecasts. Wind gusts may be off 5 to 10 knots and/or direction by 30 degrees, especially for coast and valley sites after 00Z Tuesday - as front approaches.

KLAX...Low to moderate confidence in the 18Z TAF. MVFR CIGs 015- 025 common thru much of the period. Reduced visibility due to heavy rainfall likely as strong storms arrive with front.
Conditions may fall to IFR at times with the front later tonight.
There is a 20%-30% chance of a thunderstorm from 05Z to 13Z Tue.
There is a 90% chance of an east wind component reaching up to 15 knots thru 21Z today, and a 40% chance of an east wind component of 10-15 knots at times 05Z-18Z.

KBUR...Low to moderate confidence in 18Z TAF. Reduced visibility due to heavy rainfall likely as strong storms arrive with front.
Conditions may fall to IFR at times from 06Z to 15Z Tuesday.
20%-30% chance of a thunderstorm 06Z-12Z tonight.

MARINE
13/104 PM.

This afternoon through Tuesday afternoon, a storm system and associated cold front will move across the region. This will bring a 20-40% chance of thunderstorms across all the coastal waters during that timeframe. Any thunderstorms that form may be capable of frequent cloud to surface lightning, gusty and erratic winds, small hail, and even a waterspout. Please see the latest Marine Weather Statement (LAXMWSLOX) for further details.

For the outer waters and inner waters N of Point Sal, Small Craft Advisory (SCA) level winds are expected (60%-70% chance) with the cold front tonight into Tuesday morning, then decreasing from the west behind the front Tuesday afternoon through Tuesday night.
Wednesday through Thursday increasing NW winds will likely reach SCA levels once again. Best chances south of Point Conception.
Conds should then be below SCA levels Friday through Saturday night.

For the inner waters south of Point Conception, S to SW winds increasing to SCA levels are expected across the area mainly tonight into Tuesday morning as the front approaches and moves through the region. There is also a 50% chance of Gale Force winds over these waters later tonight into early Tuesday. Conds should then be below SCA levels Tuesday night through Saturday night.

LOX WATCHES/WARNINGS/ADVISORIES
CA...Wind Advisory in effect until 8 AM PDT Tuesday for zones 38-342>345-351>353. (See LAXNPWLOX).
Flood Watch remains in effect from 8 PM PDT this evening through Tuesday afternoon for zones 38-88-342-344-345-348-353-355-358-362-368>375-377>380-548. (See LAXFFALOX).
Wind Advisory in effect until 2 PM PDT Tuesday for zones 376>383. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 AM PDT Tuesday for zone 645. (See LAXMWWLOX).
Gale Warning in effect until 3 AM PDT Tuesday for zones 650-655. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 AM PDT Tuesday for zone 670. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 PM PDT Tuesday for zones 673-676. (See LAXMWWLOX).