Gale Watch 4, NWS Eureka, CA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
509 AM PST Sat Jan 20 2024

.SYNOPSIS...Low pressure approaching the coast has brought southeast
winds gusting in excess of 45 mph that will continue to impact the
coast though the early afternoon. Periods of moderate rain showers
will build behind the wind with the heaviest rain rates and risk of
urban and small stream flooding through this afternoon. Wet weather
will continue through at least Monday.

&&

.DISCUSSION...A center of low pressure is well resolved on radar
just offshore of Eureka. Convective rain bands wrapping around this
systems have started to move onshore bring periods of moderate rain
to much of the northcoast, particularly south of the King Range. A
strong rain shadow effect is evident around Humboldt Bay, even on
radar, with only a couple tenths of an inch observed at most. More
rain has been observed further south with 0.3 to 0.6 inches in much
of Mendocino County.

Meanwhile, gusty south to southeast winds swirling around the low
are impacting the area. A low level jet is evident on radar with
speeds in excess of 60 kts. These speeds have been realized at the
surface in the King Range with gusts up to 35 mph observed so far
around Humboldt Bay. Wind will continue to increase this morning as
mixing deepens and low pressure makes landfall. High resolution
models are suggesting peak gusts in excess of 45 mph even at low
elevations along the coast. NBM now agrees with a 50 to 70% chance
of gusts over 45 mph in Eureka. These speeds agree with buoy
observations gusting over 40 mph. With this in mind, short fused
wind advisory has been issued for the North Coast through the early
afternoon.

Though periods of moderate rain are expected with showers this
morning, the bulk of precipitation. is expected this afternoon as
narrow band of moisture (now visible near Sonoma County) moves north
along the coast. Model guidance this morning places the focus of
precipitation significantly further north than yesterday with
Humboldt and Del Norte now forecast to receive some of the heaviest
rain rates later this afternoon. This shift is due to changes in the
lows track slightly further north. As we head into the afternoon,
most likely rainfall is 1.5 to 3.5 inches stretching from northern
Mendocino County up to Del Norte. The whole are is solidly in the
warm sector of the system, ensuring snow levels stay above 5000 feet
even in Trinity County. As moisture sweeps north, HRRR and NBM are
showing peak rain rates of 0.3 to 0.5 in / hour. Generally offshore
flow will limit peak rain rates in contrast to last weekends strong
onshore flow.

A brief lull is expected late tonight into early Sunday before a more
classic shortwave and associated cold front impacts the coast late
Sunday into Monday. This system looks less dynamic with only
moderate winds gusting to 30 mph. Additional rainfall is expected,
with pretty even 0.5 to 2.0 inches across the area. The general
lack of instability or upper level support with this system will
limit rain rates and flooding concerns relative to today, though
mainstem rivers will continue to rise (see hydrology section).

Cluster ensemble members generally show unsettled weather continue
through most of the early week with periods increasingly weak rain
and gusty wind. No single system looks particularly strong with this
weekend most likely posing the most hazardous weather. Agreement is
also good that ridging and more quiet weather will build in by next
Friday though the amplitude of the ridge is more uncertain. The
exact evolution if this ridge is highly uncertain headed into next
weekend. /JHW

&&

.AVIATION...Rain and wind will be impactful to all terminals today.
MVFR conditions are expected at all terminals, with some IFR
conditions possible during heavier rain showers. Gusty winds along
the coast are expected to persist through the day, but are forecast
to subside by tomorrow evening in UKI. The low level wind shear
threat remains at the coastal locations for the next 24 hours. A
brief lull in the LLWS is possible this afternoon, but will increase
again by tonight.

&&

.MARINE...Strong gale force gusts of up to 45 kts will peak
early this morning and will gradually subside through the day. Gales
are expected to subside in the southern waters late this morning,
then subside in the northern waters this afternoon. Very steep and
elevated seas will peak at 12-16 feet this afternoon, then gradually
subside below 10 feet Sunday afternoon. Even as widespread gales
ease, winds will remain elevated, especially around Cape Mendocino.
After a brief lull Sunday morning, winds will increase again ahead
of another system that arrives early Monday.

&&

.HYDROLOGY...Periods of moderate rain have already helped saturate
soils this morning. As mentioned above. rain rates will be strongest
early this afternoon as low pressure moves onshore and offshore flow
weakens. High resolution models show rain rates of 0.5 in/hr
extending form northern Mendocino County all the way up to Del
Norte. While not as impressive as lest weekend, such rain rates will
bring concerns of urban and small stream flooding all along the
coast this afternoon. Though weaker rain rates Sunday into Monday
will bring lesser areal flood concerns, mainstem rivers will
continue to rise, especially along the north Coast with the general
northward shift of the forecast. At the moment, the Eel and Mad
rivers are both forecast by the CNRFC to reach monitor stage on
Sunday. The Russian RIver at Hopland also remains on track to graze
a couple feet above flood stage on Sunday. Scotts Creek near
Lakeport, the Navarro River, and the Garcia River near Pt. Arena all
remain points of concern, though less so with the recent northward
shift of the forecast precipitation. /JHW

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Wind Advisory until noon PST today for CAZ101>106.

     Flood Watch through this evening for CAZ101>106-108>115.

     Coastal Flood Advisory until 8 AM PST this morning for
     CAZ103.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Coastal Flood Advisory until 8 AM PST this morning for
     PZZ415.

     Gale Warning until 3 PM PST this afternoon for PZZ450-470.

     Gale Warning until 9 AM PST this morning for PZZ455-475.

&&

Visit us at https://www.weather.gov/eureka

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For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png

Preliminary Local Storm Report
National Weather Service Eureka CA
1138 AM PST Sat Jan 20 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1127 AM     Flood            3 NNE Samoa             40.86N 124.16W
01/20/2024                   Humboldt           CA   Law Enforcement

            Flooding on roadway at 79 Young Ln (off
            SR255) in the SB lane.

&&

JLW

Preliminary Local Storm Report
National Weather Service Eureka CA
1202 PM PST Sat Jan 20 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1154 AM     Flood            3 NNE Loleta            40.67N 124.20W
01/20/2024                   Humboldt           CA   Law Enforcement

            Roadway flooding at the junction of Hookton
            Rd and Eel River Dr. Potential for closing
            the off-ramp from US101.

&&

JLW

Preliminary Local Storm Report
National Weather Service Eureka CA
1239 PM PST Sat Jan 20 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1154 AM     Flood            3 NNE Loleta            40.67N 124.20W
01/20/2024                   Humboldt           CA   Law Enforcement

            Corrects previous flood report from 3 NNE
            Loleta. Roadway flooding at the junction of
            Hookton Rd and Eel River Dr. US101
            Southbound off-ramp at Hookton Rd closed due
            to flooding.

&&

JLW

Preliminary Local Storm Report
National Weather Service Eureka CA
115 PM PST Sat Jan 20 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0106 PM     Flood            3 WNW Comptche          39.28N 123.65W
01/20/2024                   Mendocino          CA   Law Enforcement

            Roadway flooded at 0 Comptche Ukiah Rd.

&&

JLW

Preliminary Local Storm Report
National Weather Service Eureka CA
135 PM PST Sat Jan 20 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0128 PM     Landslide        Helena                  40.77N 123.13W
01/20/2024                   Trinity            CA   Law Enforcement

            Slide in WB lane on SR299.

&&

JLW

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