textproduct: Eureka

SYNOPSIS

Cloudy and misty conditions for Del Norte and Humboldt counties tonight. Generally dry weather conditions and a warming trend are expected to prevail across NW CA this coming week, with periods of light rain/drizzle for the North Coast.

DISCUSSION

A stubborn high pressure center off the CA/Mexican coast is keeping the synoptic storm track pointed at the northern PacNW of CONUS. As these storms impact OR and WA, the moisture will occasionally clip the North Coast, specifically Del Norte & northern Humbodlt counties. The increased atmospheric moisture will create fog and low clouds along the coast and in the inland valleys overnight. The inland cloud coverage is forecasted to burn off quickly in the valleys.

A warm frontal passage forced between ~0.1-0.2" of precipitation to fall in northern Del Norte Co. yesterday. The next frontal passage is forecasted to be late tonight into Tuesday. The warm front from yesterday will interact with an incoming cold front creating a stationary boundary over the CA/OR boarder. Most of the forcing for this next system will remain to the north with stratiform light rain/drizzle possible through Tuesday. Del Norte will likely experience at least a handful of hundredths of an inch of precipitation through this event, and Even less precipitation is expected for Humboldt north of the Bay.

The previously mentioned ridge of persistent high pressure responsible for blocking stronger weather systems will strengthen and expand eastward through the week. With this synoptic shift, expect significant warming inland. The current forecast yields high interior temperatures reaching 10-20 degrees above climatological normal midweek through the weekend as the warming high pressure expands overhead. NBM data shows high probabilities of ~70-80% & 80- 90 for the warmer interior valleys to exceed 70F Thursday and especially Friday, respectively. When looking at NBM probabilities for 75F, the Ukiah area shows probabilities of ~20% and ~30% for Thursday and Friday, respectively. This would likely break the high temperature record of 72F from 1958 for Ukiah on Friday if the forecast holds.

Some ensembles are indicating a weather pattern change next weekend. There is still a great deal of variability, due to the uncertainty in how quick the ridge weakens, but some (~15%) of the ensemble members show the possibility for >1" of 24 hour rainfall by Sunday/ Monday next week. As of right now, next weekend is still quite far into the future for any true meaning to be applied to the forecast. DS

AVIATION...(06Z TAFS)

General overcast skies will continue for coastal terminals. In general, MVFR ceilings will continue around the Del Norte coast with the possibility of IFR/LIFR conditions by early to mid Monday. Some light drizzle/rain could still be a possibility for mostly the Del Norte Coast into early Monday, as well. Coastal terminals in the vicinity of Humboldt Bay are forecast to remain in the IFR/LIFR range into late Monday morning. Some interior valleys could see stratus and fog into early Monday morning, but confidence is low on UKI seeing any. There is a possibility for general lifting or slight clearing of ceilings for coastal terminals; however, IFR/LIFR conditions are expected again by Monday evening. /JLW

MARINE

Generally light winds are forecast through at least the middle of this week, with south winds forecast north of Cape Mendocino and west-northwest winds forecast south of the Cape. A mid period northwest swell has peaked and continues to decay. Seas subside into early Monday as this swell decays. Another mid-period northwest swell will fill in Monday afternoon and evening, peaking at 7-9 ft at 13 seconds by Tuesday. Combined seas may briefly reach or exceed 10 ft Tuesday. Additional mid-period northwest swells will continue to fill in through the week. JB

BEACH HAZARDS

A low to moderate threat of sneaker waves is expected for the Del Norte, Humboldt, and Mendocino coastlines late this week. A mid-period westerly swell generated by a storm currently ~500mi south of the Aleutian Islands will enter the coastal waters early Thursday morning. A lack of local wind waves will allow this swell to dominate the sea state, creating beach conditions that could look deceivingly calm. Forecast confidence will grow in time as NDBC data becomes available for observations closer to NW CA as the swell passes midweek. Remember to never turn your back to the ocean, and to avoid steep beaches, jetties, outcroppings, and rocks during these events. DS

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... None.