textproduct: Eureka

KEY MESSAGES

* Cold front most likely to cross the area Monday into Tuesday. 10-20% chance of wetting rain for the coastal areas.

* Cooler temperatures with a slight chance of lingering very light showers through the week.

SYNOPSIS

A cold front arrive tomorrow keeping temperatures limited for the inland valleys. Coastal areas can expect minimal warming as well through the remainder of the weekend. There is a chance for rain Monday night into Tuesday morning, yet any meaning accumulations are unlikely at this time.

DISCUSSION

The effects of a building cold front are beginning to be felt today across the forecast area. A hefty coastal stratus bank has filled into the North Coast creating a stark boundary between blue skies and fog along the coast. High clouds can be seen flowing over the interior areas signaling the arrival of this incoming frontal system tomorrow. Expect cooling conditions Sunday through Monday. Temperatures tomorrow will struggle to reach the low to mid 80s and by Monday, expect further cooling with Ukiah barely reaching the high 60s.

The trajectory of this low pressure system remains to be just on the outside of the forecast area making the future rain forecast difficult to pin down at this time. What is known at the moment is that the most likely time for rain remain to be Monday afternoon through the night before sharply decreasing by Tuesday morning. The NBM probabilities for any rain (>0.01") remains around 15-30%, yet wetting rain chances are under 20% while also only being restricted to the direct coastline.

Throughout the coming work week, cooler conditions are expected as this low pressure system flows to the south and then east of the area. Temperatures are expected to remain in the 70s to low 80s during this time. The current forecasted trajectory will also allow for continued light, non-wetting rain to develop across the southern then eastern portions of the forecast area. A secondary frontal system is possibly impacting the area by as soon as Thursday evening, yet any meaningful precipitation for next weekend looks unlikely. DS

AVIATION...18Z UPDATE

A stubborn surge of coastal stratus remains along the Del Norte and N. Humboldt coastline bringing continued LIFR conditions through early midday. Southerly winds suggest that this layer will more likely to remain than to clear. Periods of extremely brief clearing are possible, yet overall unlikely through the afternoon. Fog is forecast to return again with extremely low ceilings and visibilities at or under 1/4SM for North Coast terminals. The probability of LIFR returning is around 65-80% after 03Z. Inland terminals are expected to have VFR conditions with NW winds funneling through channels or gaps in the terrain through the afternoon. DS

MARINE

Marine winds have increased in the outer waters while lighter winds remain for the inner waters. Short period seas will continue to build downwind of Cape Blanco and Cape Mendocino through the afternoon. These short period seas will mix with an ongoing and building, mid-period NW swell and a small, mid- to long-period S swell. Winds remain elevated in the outer waters through the weekend before a frontal system arrive early Monday morning, disrupting the pressure gradient allowing for winds to weaken. Light to moderate breezes are expected through midweek as the sea state becomes dominated by an incoming NW swell. Swell heights are currently forecasted to be around 14-15feet, yet during peak arrival (overnight Mon into Tues) these heights could be as tall as 16-18 feet. This mid-period NW swell will lower Tuesday into Wednesday. DS

FIRE WEATHER

Inland conditions are beginning to feel the effect of the incoming cold front with a slightly unstable atmosphere allowing for wind gusts up to 15-20mph this afternoon. A fairly significant cooling is expected tomorrow as this frontal system passes overhead. Widespread RH recoveries will increase with increased chances of valley fog along coastal river valleys as the marine layer deepens. Rain chances for this system remain low with only a 40-50% chance of any rain (>0.01"), and only a 10-20% of wetting rain (>0.10"). The timing for the chance of rain is most likely Monday afternoon until early Tuesday morning. Conditions remain unsettled and cooler next week with lingering chances of very light, non- wetting rain through midweek. DS

BEACH HAZARDS

An incoming mid to long period swell is forecasted to arrive Monday evening into Tuesday night. While the swell is not the usual signal of a sneaker wave threat due to its mid-period characteristic (15-16sec). That said, an increased threat of sneaker waves is possible due to minimal short period seas in the waters. These conditions could allow for a larger signal of set behavior allowing for long breaks in wave groups that could rush up the coastline. DS

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 PM PDT Sunday for PZZ470.

Small Craft Advisory until 3 PM PDT Sunday for PZZ475.