Marine Weather and Tide Forecast for Rossmoor, CA

.SHORT TERM (TDY-MON)...28/314 AM.

Another very warm day region-wide will close out February. Skies will feature high clouds through much of the day and the ridge responsible for several broken temperatures yesterday will begin to flatten out. Offshore flow will be weaker, then winds will quickly turn onshore. As a result, highs at the coasts will cool by several degrees, with highs topping out in the mid 70’s to low 80’s. Slightly less cooling will occur across the coastal valleys, and downsloping onshore flow will warm the interior by several degrees. There are a handful of locations across the forecast area that will flirt with record high temperatures, namely in the San Fernando and Antelope Valleys.

There is very good agreement amongst ensembles that a weak trough will approach northern California Sunday and move through the state through the beginning of the week. In response, significant cooling will take place Sunday with additional cooling on Monday, bringing us back to near normal temperatures with most of the region topping out in the 60’s and 70’s. Any widespread precipitation will remain well north of us, however, upslope winds may generate some light rain across the northern slopes late Sunday into Monday.

As previously mentioned, offshore flow will be weaker this morning, then a reversal to onshore flow will bring widespread gusty west to southwest winds to the area today and Sunday. There is a moderate chance for wind advisories to be needed Sunday.
Windiest locations will be the Antelope Valley, AV Foothills, the northern Ventura County Mountains, and the western San Gabriels.
Sundowner winds will return late tonight and increase in strength Sunday, reaching near advisory levels into Monday morning across southern Santa Barbara County. The overall wind pattern will turn more northwest Monday as the upper level trough exits California to the east. Chances for additional wind advisories on Monday are similar to Sunday’s probabilities.

Dense fog may become an issue at immediate coastal sites along the Central Coast and southern Los Angeles County late tonight into Sunday morning, but confidence is low.

.LONG TERM (TUE-FRI)...28/314 AM.

A pop up ridge will elevate temperatures a few degrees Tuesday, with little change Wednesday. The real focus in the extended is the potential for a fairly sharp trough (inside slider) to swing down across the western CONUS southwest into southern California sometime from the middle to late next week.

There is quite a bit of disagreement in terms of timing and placement of this trough. The EC, ECAI, AIGFS and their respective ensembles (plus the GEFS) keep the placement of the trough more to the east than the GFS 00Z run, which barrels the trough through SoCal, then cuts off just off the coast of Southern California and northern Baja California. While the majority of solutions are dry, the cut off nature shown by GFS 00Z would likely result in rain and mountain snow as early as next Friday, March 6th. Healthy K Indices and Mid Level Lapse Rates would support the potential for convection in this cutoff low scenario.

It’s worth noting again that the GFS is the OUTLIER amongst models at the moment, but this is certainly worth following.

What appears to be likely regardless of the scenario that comes to fruition is a period of widespread advisory level winds across the region, with a low to moderate chance for high wind warnings to be needed across the mountains, as there is a good amount of upper level support in each scenario. Keeping the uncertainty in the timing and placement of the upper level trough in mind, winds appear to begin increasing sometime Wednesday and will continue at least into the weekend. Stay tuned to the forecast for future details.

AVIATION
28/1117Z.

Around 0745Z, there was no marine layer depth at KLAX. There was a surface based inversion up to around 1700 feet with a temperature around 27 degrees Celsius. There was another inversion above up to near 2500 feet.

Moderate to high confidence in the current forecast. Higher confidence exists in valley and desert terminals. Less confidence exist in coastal terminals. VFR conditions are expected through the period, except for a low to moderate chance of VLIFR to LIFR conditions at coastal terminals through 16Z, and a moderate to high chance of VLIFR to LIFR conditions at coastal terminals after 03Z Sunday.

KLAX...VFR conditions are expected through the period, except for a 10 percent chance of VLIFR to LIFR conditions through 16Z, and a 50 percent chance of VLIFR to LIFR conditions after 04Z Sunday.
There is a 10 percent chance of conditions starting out as LIFR to IFR conditions and moving in with a stronger sea breeze between 23Z and 02Z. Any easterly winds will remain less than 7 knots.

KBUR...VFR conditions are expected through the period. No wind impacts are expected at this time.

MARINE
28/304 AM.

Moderate to high confidence in the current forecast. High confidence in the sea forecast through Monday, then moderate confidence thereafter. Moderate to high confidence in the wind forecast through period with higher confidence in the winds for southern waters versus the northern waters through Monday.

For the waters from near Point Sal south to San Nicolas Island and west of the Channel Islands, there is a moderate (30-40 percent)
chance of Small Craft Advisory (SCA) level winds through this evening, then there is a high to likely (50-60 percent) chance of SCA level winds developing between this evening and Sunday afternoon. By Sunday evening, widespread SCA level winds are expected into early Tuesday. There is a moderate (30 percent)
chance of GALES on Monday and Monday night. Winds will diminish some between Tuesday and Wednesday afternoon, then there is a likely (55-65 percent) chance of widespread SCA conditions with a moderate (30-40 percent) chance of GALES between Wednesday night and Friday.

For the waters northwest of Point Sal and the nearshore waters along the Central Coast, there is a low to moderate (20-40 percent) chance of Small Craft Advisory (SCA) level winds through early Monday, highest across the southern portion. Then, there is a moderate to high (40-50 percent) chance of SCA level winds developing between Monday and Tuesday. Winds will likely diminish below SCA levels between Tuesday and Wednesday afternoon, then there is a likely (65-75 percent) chance of widespread SCA conditions with a moderate to high (40-50 percent) chance of GALES between Wednesday night and Friday.

Inside the southern California bight, there is a low to moderate (20-40 percent) chance of Small Craft Advisory (SCA) level winds through Sunday morning, highest across the western portions. Then, there is a likely (55-65 percent) chance of SCA level winds developing between Sunday afternoon and Monday night. Winds will likely diminish below SCA levels between Tuesday and Wednesday afternoon, then there is a likely (55-65 percent) chance of widespread SCA conditions with a moderate (30-40 percent) chance of GALES between Wednesday night and Friday.

LOX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...Small Craft Advisory in effect from noon Sunday to 3 AM PST Monday for zone 650. (See LAXMWWLOX).
Small Craft Advisory in effect from 3 PM Sunday to 3 AM PST Monday for zone 655. (See LAXMWWLOX).
Small Craft Advisory in effect from 9 PM this evening to 3 AM PST Monday for zones 673-676. (See LAXMWWLOX).