Marine Weather and Tide Forecast for San Luis Obispo, CA

.SHORT TERM (TDY-SUN)...12/228 PM.

Light offshore flow is expected to develop overnight and peak in the morning hours. LAX-DAG around -1 mb and LAX BFL near -4 mb.
Along with no upper-level support, wind speeds will remain below advisory levels. Radiation FG will likely redevelop late overnight into the morning hours across the southern Salinas Valley. Weak ridging will also aid in modest (3-6F) of warming across the area tomorrow with coast/valley upper 60s to low 70s and 50s to 60s across the interior and mountain locations. Max Temperatures will be slightly above climate normals. Onshore flow will return on Saturday cooling coast/valley locations 3-6F with slightly warming across the far interior. 500mb Heights will decrease and cloud cover is expected to increase starting Saturday as the system starts to approach towards our CWA Temps will cool a bit more on Sunday and chances for rain will start to increase.

.LONG TERM (MON-THU)...12/219 PM.

The general consensus among guidance is that there is likely to be three storm systems to impact Southwest California next week.
Although timing is not set in stone, it appears that the system could arrive to the Central Coast sometime late Sunday night, with fairly good confidence of widespread impacts on Monday. Details will be ironed out with time.

This first system appears the most robust in terms of rainfall amounts and rain rates. One caveat that could dampen hydrologic concerns a bit would be the storm's fast motion. However, this system will take more time to move through the region compared to the last storm system. PWAT values are expected to average around 1" on Monday with 10% of ensembles indicating closer to 1.2". This would be over the 95th percentile. Still with the same general thoughts of 1-2" for coast/valley and 2x that for the mountains on Monday. There is still quite the range with respect to amounts.

Quite a bit of uncertainty regarding the convective potential.
There is a handful of models such as the UKMET and ICON that are less favorable synoptically for severe storms. There is a slight chance for thunderstorms as the front moves through on Monday.

There appears to be less discontinuity in guidance between Monday and Tuesday's storm - likely continuing through Wednesday. There could be another shortwave diving southward embedded in NW flow on Thursday but uncertain in how much moisture will be present.

Snow levels will begin near 6000 ft for the first storm and will decrease to 3000-3500 ft by Wed. Significant snow accumulation is possible to likely through this timeframe. Details will be ironed out with time. ECMWF 500mb temps drop to -33 C over the Central Coast by late Wednesday morning with 700-500mb (7-8 C) lapse rates indicating favorable mid-level instability. Despite less low-level moisture compared to Monday, these values will likely be enough to compensate and support thunderstorm potential.

Please continue to monitor the latest information from the National Weather Service in Los Angeles/Oxnard, California, as forecast details become refined over the coming days.

AVIATION
12/1753Z.

At 1625Z, there was a moist layer to around 2000 ft, and a very weak inversion to 3000 ft with a temperature of 11 degrees C.

High confidence in VFR TAFs except for KPRB, where there is a 45% chance for VLIFR conds and a 20% chance for VLIFR to LIFR conds at coastal sites after 06Z. after 12Z. Moderate confidence in winds over the period. There is a 15% chance for north winds 5-10 kt at KSBA 07Z-16Z. For all sites, wind gusts up to 10 kt higher at possible this afternoon through early evening.

KLAX...High confidence in VFR conds through at least 12Z. Then a 15% chance for VV002 and 1/2SM conds 12Z-18Z, although light (less than 4 kt) north winds overnight will likely limit any stratus formation. 30% chance for west wind gusts reaching 20 kt between 22Z and 03Z. No significant east wind component expected.

KBUR...There is a 30 percent chance of VLIFR to LIFR conditions in ground fog through 16Z, otherwise VFR conditions are expected.
No wind impacts are expected at this time.

MARINE
12/212 PM.

A series of storm systems will move over the coastal waters early next week and continuing through the rest of the week, bringing hazardous winds and seas along with rain and a slight chance of thunderstorms. Confidence is growing in dangerous marine conditions across the coastal waters building Sunday night, thus it is encouraged to think about altering plans for next week.

Near Term: Small Craft Advisory (SCA) winds and seas will be common across much of the waters through late Friday night or early Saturday morning then a relative lull is forecast during most of Saturday. For the inner waters south of Point Conception, there is a 30-40% chance for winds to reach SCA levels again Friday afternoon and evening. The Catalina Eddy is forecast to spin up again on Saturday morning, bringing a 30% chance of SCA level southeast winds to the inner waters south of Point Conception Saturday morning to early afternoon. Southerly winds will begin to reach the Outer Waters by late Saturday, then spread across the remainder of the waters through Sunday night.

Outlook: All eyes shift to late Sunday through at least Wednesday when moderate to strong southerly to southwesterly flow will impact the entirety of the coastal waters, and there is a moderate to high chance for widespread Gale Force winds, especially Monday through Tuesday night. Seas will also build and become large and hazardous, including across the nearshore waters.

Hazardous marine conditions are forecast to continue through the end of the week.

BEACHES
12/214 PM.

Surf and swell will build again at area beaches through late Friday night, and a High Surf Advisory was issued for the Central Coast.
Local sets to 7 feet are possible at Ventura County Beaches.

A period of very large waves continues to be advertised by the latest swell model guidance early next week. There is a high to likely (50-70 percent) chance of widespread high surf between Monday and Thursday as a combination of southwesterly and west- northwesterly swells arrive along the California coastline. Sets above 10 feet will be possible across all beaches, but there is a higher chances for west to northwest facing shores. There is a 20-30 percent chance of damaging sets developing between Tuesday night and Wednesday night, highest for northwest-facing shores along the Central Coast.

Elevated high tides as the new moon cycle approaches will coincide with the arrival of the higher surf and swell with storm system early next week. This will bring an elevated chance of coastal flooding, or at the very least, minor tidal overflows during times of the highest high tides each evening. A coastal flood advisory may be needed should swell guidance indicate similar surf and swell and locally wind-driven swell affect the beaches and coastline.

LOX WATCHES/WARNINGS/ADVISORIES
CA...High Surf Advisory in effect from 9 AM Friday to 2 AM PST Saturday for zones 340-346. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect from 9 AM to 9 PM PST Friday for zone 645. (See LAXMWWLOX).
Small Craft Advisory in effect until midnight PST tonight for zones 650-655. (See LAXMWWLOX).
Small Craft Advisory in effect from 9 PM this evening to 9 AM PST Saturday for zone 670. (See LAXMWWLOX).
Small Craft Advisory in effect until 9 AM PST Saturday for zones 673-676. (See LAXMWWLOX).