Marine Weather and Tide Forecast for Scotia, CA

DISCUSSION
An upper level remains just off the coast this morning. This is expected to become an open wave trough and move onshore bringing additional thunderstorms to the area on Friday.
These are expected to pick up again, but the models are struggling on the timing. The HRRR shows them increasing in coverage and intensity before sunrise while a bigger percentage of the models show the increase later in the morning and into the afternoon. These are expected to not be as strong as on Thursday.
Deep shear is also lower than Thursday with only around 25 to 30 kt. Upper level lapse rates are quite a bit lower, only around 6.5 to 7c/km. The biggest change is more showers and thunderstorms are expected to be in Mendocino and Lake counties than on Thursday.

Friday night the next upper level low rapidly approaches the west coast. The models are coming into better agreement on this low dropping to near or just south of the area before it reaches the coast. An associated occluded front is expected to bring a round of heavier rain and snow to much of the area through the day on Saturday. A fairly widespread area of a around 0.75 to 1 inch is expected with local amounts around 2 inches in the mountains. Snow levels are generally expected to be around 5000 to 6000 feet as the main front moves through. This brings only a 25 percent chance of seeing more than 2 inches at Scott Mountain pass which is at 5500 feet in northern Trinity county. This low on Saturday is also expected to bring a fairly brief period of stronger winds to southern Mendocino and Lake counties. For now it looks like these will mainly be over the higher terrain with gusts to 40 mph. There may be a few locally higher gusts over the highest peaks.

Saturday night and Sunday the upper low finally moves onshore.
The ensemble clusters show this somewhere between SF Bay and Cape Mendocino. There is also some uncertainty on how cold this system will be. Currently the forecast rainfall amounts range from a quarter inch in the north to over a half inch in the south of additional rain. Snow levels are generally expected to drop as low as 4,000 feet Sunday morning before rising above 5,000 feet again in the afternoon. This could bring a few inches of snow as low as 4,000 feet. MKK

Long term
Much colder temperatures are likely during and and behind this frontal passage. Near-freezing to sub-freezing temperatures are forecast, especially Sunday, Monday, and Tuesday mornings. Frost advisories and/or freeze warnings might be needed. Looking towards next week, about half of ensemble members show at least weak ridging developing by mid next week, with the other half showing the continuation of the troughing (wet)
pattern. Stay tuned! JB

AVIATION
Conditions continue to vary widely as showers pass through the aviation sites. When there are breaks in the showers this allows low clouds and fog to develop. Shower coverage is expected to increase later this morning and afternoon. There will also be the potential for thunderstorms once again. The highest chance will be over the inland areas including KUKI. They may also make it out to the coast, but confidence is lower on this so have held off on adding them to the forecast. Tonight showers are expected to diminish in coverage, but this may allow more low clouds to form. MKK

MARINE
The approach of a cutoff low brought dangerous lightning, hail and erratic gusty winds to area waters through Thursday early evening. Most of the severe weather was inland but a Marine Weather Statement was issued for the southern outer waters Thursday morning to warn of the hazard. Model data also strongly suggests that Friday morning will bring another round of showers and thunderstorms with a similar threat of lightning, small hail and erratic wind gusts. All area waters from Point St. George down to Point Arena are susceptible to hazardous marine conditions through the early evening on Saturday. Otherwise, there are NW swells around 15 seconds with wave heights 3- 5ft but conditions between the pressure systems will be fairly benign.

Saturday an area of low pressure is expected to approach the coast from the northwest and move through the waters off the Mendocino coast. Confidence is low on the strength and track of the low which could lead to stronger than expected winds. /EYS/MKK



EKA WATCHES/WARNINGS/ADVISORIES
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
None.