textproduct: Eureka

SYNOPSIS

Light rain showers are expected in the early morning hours for the northernmost areas of the CWA. Most precip will diminish by the late afternoon. Otherwise, dry and stable weather is expected to continue through most of next week.

DISCUSSION

KBHX radar began receiving 30dbZ returns just before 07z, indicating moderate rain bands offshore of the Del Norte/Northern Humboldt coast. Satellite imagery also confirms moisture plumes streaming up from the southwest at the mid to upper level. HRRR and other convective allowance models are in similar agreement for location and timing, with most of the precipitous activity ending around 00z Monday/16:00 PST Sunday. At the time of this discussion there were not any ground stations reporting accumulation via automated tipping buckets or other surface observation stations. The hydro-meteors may not be making it to the ground just yet or precipitating where there are no data collection platforms and/or possibly virga not reaching the ground.

Precipitation accumulation is being forecasted in the range of 0.15 to 0.4 inches for Del Norte County, while a few hundredths are expected for Humboldt County. Light sprinkles or drizzle is possible for Trinity and northern Mendocino counties. Very low to zero probabilities for wetting rain in southern Mendocino and Lake counties. Chances for precipitation diminish throughout the day on Sunday as a dry air mass encroaches over the area in the wake of the front, promoting a gradual clearing of skies.

High pressure aloft will spring back up by Monday and then dominate most all next week resulting in multiple days of dry and stable weather. A shallow moist air push behind the front and N-NW surface flow may result in fog and low clouds overnight Sunday into Monday morning in the interior valleys. Otherwise, a general warming trend is forecast for much of the area early to mid next week. Highs are forecast to warm up into the lower to mid 70's in the interior next week. South facing exposures and higher terrain stand the best chance for highs in the 70's, while valleys trapped under the nocturnal inversion with night and morning fog may not warm up even into the lower 60s, especially in Trinity and northern Humboldt. Overnight low temperatures will remain on the chilly side with subfreezing minimums highly probable for valleys in Trinity and perhaps portions Humboldt, Lake and northern Mendocino. Global Ensembles and WPC cluster guidance are suggesting a break- through in the westerlies or undercutting of the blocking ridge late next week and next weekend. This may have the potential to bring increasing chances of precipitation and a cooling trend. Stand by for more details as the situation develops. /ZVS /EYS

AVIATION

An approaching weak cold front has gradually begun to impact the area overnight with midlevel clouds streaming over the area. Wind and rain will build along the front near sunrise, brining MVFR and periods of borderline IFR conditions through the morning hours Sunday. Instability and drier air behind the front will most likely promote clearer skies and VFr conditions by late Sunday afternoon and evening, though there is some potential (30% chance) for IFR conditions to hang around isolated areas such as Humboldt Bay. Light ground fog could bring some IFR conditions late SUnday night into Monday in areas with recent rain. /JHW

MARINE

Combined seas are currently below 10 feet across the waters, mainly driven by persistent westerly swells. A weak front will cross the waters early Sunday morning. This will bring very brief, moderate southerly winds and steep short period seas, isolated mostly to the northern outer waters. Then, after a very brief lull, a fresh, long period westerly swell will build steep seas near 13 feet Sunday evening and through he day Monday before finally subsiding around midweek. There is moderate confidence in at least a 24 hour period of calmer seas around midweek but another set of swells is likely to steepen seas again late in the week. Wind, however, will remain gentle. /JHW

BEACH HAZARDS

Two long period (>16 seconds) westerly swell groups will spread into the coastal this weekend. The first one is expected to arrive late this afternoon and build to around 3 to 4 ft. Spectral density plots so far showed all the energy in the 11 second band. Another long period westerly swell train arrives on Sunday with heights eventually building to 12 to 14 feet with periods near 16 seconds by Sunday. This swell may be too large for sneaker waves, though it could still pose a threat to beachgoers. Breakers up to 16 feet for west and northwest facing beaches are forecast based on average beach slope profiles. Beachgoers venturing near or in the surf zone Sunday night or early Monday morning should remain vigilant. Avoid rocks, jetties and steep beaches.

COASTAL FLOODING

High astronomical tides are predicted to continue on Sunday. High tides are forecast to be at 8.22 feet at the North Spit tide gauge at around 10:42 AM local time on Sunday. High tides combine with surge and tidal anomaly will result in water level at or near 8.8 feet. Minor coastal flooding around Humboldt Bay, including King Salmon and Jackson Ranch Road in the Arcata Bottoms, will be likely between 9AM and 12PM. A Coastal Flooding Advisory will be in effect from 9AM to 2PM Monday. High tides are predicted to be at 7.98 feet @ 11:31 PM on Monday. At this moment, combine with surge and anomaly is expected to remain below advisory for Monday. /ZVS

EKA WATCHES/WARNINGS/ADVISORIES

CA... Coastal Flood Advisory from 9 AM this morning to noon PST today for CAZ103.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 8 AM this morning to 4 PM PST Monday for PZZ450-455.

Small Craft Advisory until 4 PM PST Monday for PZZ470-475.