textproduct: Eureka

SYNOPSIS

A few more days of mild weather continue before a colder spell towards the end of the weekend. Precipitation chances have retreated for most areas. Coastal flooding is possible Saturday with the high tide and low end anomaly.

DISCUSSION

Quiet weather conditions prevail across NW California as an upper-level blocking flow pattern promotes dry and mild weather conditions. Daytime temperatures have been generally in the upper 50s to mid 60s, with similar effects through Saturday. We will see a cooler pattern emerging Sunday as the offshore low approaches the CWA. Increasing high- level moisture is expected as weak shortwave embedded in the southwest- westerly flow moves toward OR/WA. Otherwise, dry and mild weather conditions prevailing over NW California as the main ridge gradually amplifies over the West Coast into the weekend. Some moderate southerly breezes are expected to developed over the interior higher terrain. Overnight temperatures are forecast to be in the upper 30s to mid 40s along the interior valleys. Patchy fog and low clouds will likely form again in the valleys Friday morning, especially in Trinity, Humboldt and interior Mendocino. Friday and Saturday afternoon temperatures are expected to be slightly warmer similar compared with today, with highs mainly in the 60s, especially on Saturday.

Over the weekend, an broad upper level trough approaches the Pacific Northwest, and the high pressure shift eastward. A shortwave trough and cold front embedded to the trough will approaches the area Saturday night through Sunday. A cold front will traverse the northern portion of the area from west-northwest on Sunday. A faster scenario suggests rain arriving earlier, Saturday night. Multi- model ensemble (NBM QMD) continues to indicate a 40-65% chance for 0.25 inches or more in 24 hours ending 4 PM or 10 PM Sunday for mainly the northern zones, especially Del Norte and Humboldt counties. There is up to 15% chance for 1" in 24 hours over Del Norte mountains and SW Humboldt (King Range) for the same 24 hour time periods. Generally lighter amounts of rain are forecast for eastern valleys of Trinity and northern Mendocino where chances for 0.10 inches in 24 hours are around 20-45% ending 10 PM Sunday. Snow levels appear quite high when most of the precip arrives, generally above 6kt on Sunday, lowering to 5kft in the cooler air after frontal passage by Monday morning.

Lingering showers will be possible on Monday before a ridge aloft amplifies and northerly to northeasterly surface flow develops and we stay dry for a day or two and perhaps most of next week. /ZVS /EYS

AVIATION

Light offshore flow has continued to promote VFR conditions all across the area this evening with broken clouds around 15 kft being the only notable feature. There is again very slight potential (20% chance) of fog around Ukiah near sunrise, but overall probability is low. Otherwise, VFR conditions will persist through the day Friday. /JHW

MARINE

Currently gentle southerly winds throughout the waters will persist until Saturday with only very isolated gusts over 20 kts in the far outer waters. That said, a persistent series of long period westerly swells will maintain a steep sea state. Combined seas will most likely barely drop below 10 feet Friday, but another westerly swell will build in and keep seas no shorter than about 8 feet into the weekend. Sea will most likely very briefly calm Saturday night into Sunday, but a weak front crossing the area Sunday will rebuild steep short period seas at least for the northern waters. Yet another round of steep, long period swells will build behind the front Sunday once again building over 10 feet into early next week. /JHW

COASTAL FLOODING

A high astronomical tide accompanied with a slight anomaly, will bring the threat of flooding to low lying areas around Humboldt bay on Saturday January 31st. A CF.Y (Coastal Flood Advisory) has been hoisted for Saturday from 8am to noon, with the peak expected around 10am. Friday forecasts for tide and anomaly are just under the criteria for a Coastal Flood Advisory.

EKA WATCHES/WARNINGS/ADVISORIES

CA... Coastal Flood Advisory from 8 AM to noon PST Saturday for CAZ103.

NORTHWEST CALIFORNIA COASTAL WATERS... Coastal Flood Advisory from 8 AM to noon PST Saturday for PZZ415.

Small Craft Advisory until 3 AM PST early this morning for PZZ450-455-475.

Small Craft Advisory until 9 PM PST this evening for PZZ470.