textproduct: Eureka

KEY MESSAGES

* Light rain likely for Saturday.

* Additional light rain early next week

* Heavier rain possible with stronger Pacific storm systems remain in the week two extended forecast

SYNOPSIS

More isolated areas of frost and freezing temperatures Friday night. A cold front will bring light rainfall with some possible isolated embedded thunderstorms Saturday through Saturday night. Additional light rainfall at times next week, some chances for heavier rainfall in the extended forecast.

DISCUSSION

Rain chances increase Saturday morning as a NE Pacific trough moves in. Rainfall totals will be on the low side with the trough. The trough will turn negatively titled on approach and will contain some instability, so locally heavier rainfall amounts and perhaps some isolated thunderstorms are possible given the associated dynamics. This cold trough will lower snow levels and may bring small accumulations near 0.5 inch over Scott Mountain pass.

The increasing cloudcover will limit coverage of frost and subfreezing temperatures where the growing season remains active, but areas of frost are expected through Mendocino and Lake counties.

A transient ridge will pass through Monday ahead of another trough, brining slightly warmer and drier conditions. Chances for light rainfall arrive late Monday and increase Tuesday. There is only a 30 to 40% chance for rainfall over 0.1 inch for the area with that trough. A deeper low with a stronger front is modeled for late next week. This could bring some higher rainfall amounts and round of gusty southerly winds, but it does look to weaken as it nears the N CA coast. Rainfall chances for over 0.5 inch are currently only 25% for that system.

For the extended forecast, the longer term guidance continues to outline a stretch of more active weather and atmospheric river potential over week two, somewhere near or after the 9th. Models guidance can overestimate storm strength in the extended through the transition into the wet season, but the signal seems to be becoming more consistent and bears watching. JJW

AVIATION

VFR conditions continue across much of the area this afternoon. These are expected to continue through the evening. Towards morning a frontal boundary is expected to start approaching the area. This is expected to start lowering ceilings and will likely bring some showers to the area Saturday morning. Currently the models are showing fairly low probabilities of CIGS lowering very much. This may be underdone and cigs will drop lower in the rain. MKK

MARINE

The waves remain fairly small with mainly just a couple of swells. One out of the northwest at 11 seconds around 4 feet and is expected to diminish tonight. The other one is out of the south around 2 feet at 14 seconds. Northerly winds have increased briefly in the southern to around 10 to 15 kt. Late tonight and Saturday winds will be less than ten kt. Some of these may be southerly as a weak front moves through on Saturday.

Saturday night into Sunday northerly winds are expected to return again as high pressure builds in briefly. The most recent models are showing this to be fairly short lived and the northerly winds may not be very strong on the northern waters. Fairly light winds are expected on Monday with southerly winds starting as early as Tuesday.

Also of a note, a very long period northwest swell is expected to start moving into the waters Sunday late in the afternoon. Initial waves are expected to be around 2 feet at 21 seconds. This will likely bring some fairly big sets of larger waves interspersed with smaller waves overnight and into Monday. This may show up on the shoals near harbor entrances. MKK

BEACH HAZARDS

A very long period northwest swell is expected to start moving into the waters Sunday late in the afternoon. Initial waves are expected to be around 2 feet at 21 seconds. This is expected to start bringing a sneaker wave threat Sunday evening. These are expected to build to around around 6 feet at 17 seconds Monday morning. The be large enough to bring some fairly big sets of larger waves interspersed with smaller waves Monday morning. This is a fairly classic sneaker wave scenario with fairly limited waves besides this one. A beach hazard statement may be needed as it gets closer. MKK

EKA WATCHES/WARNINGS/ADVISORIES

CA... Frost Advisory from 8 PM this evening to 10 AM PDT Saturday for CAZ110-111-114.

NORTHWEST CALIFORNIA COASTAL WATERS... None.