275
FXUS66 KEKA 022245
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
245 PM PST Sun Nov 2 2025

.SYNOPSIS...Dry weather expected today. Wet weather returns on
Monday. Strong storm to bring potentially damaging winds, heavy
rain and increased risk for urban and small stream flooding
Tuesday night and Wednesday. Rain and potential flooding impacts
to continue on Thursday before rain tapers off on Friday.


&&

.KEY MESSAGES...

- Periods of moderate to heavy rainfall and gusty south winds
  returns on Monday.

- Strong Atmospheric River to bring strong and damaging winds,
  heavy rainfall and a risk for urban and small stream flooding
  Tuesday night and Wednesday.

- Higher than normal tides next week with storm surge, promoting
  coastal flooding expected in Humboldt Bay-North Spit and
  Crescent City.

- Rain and potential flooding impacts to continue Thursday into
  Friday.


.DISCUSSION...A surface high pressure building quickly over the
area is promoting drying and warming conditions today. Despite
some high cirrus clouds (CI) streaming southeast, mostly sunny
skies. Breezy northwesterly winds have been developing over the
coastal headlands this afternoon. Max temperatures observed have
been running generally 5 to 10 degrees warmer across much of the
interior, while coastal areas have been running cooler with the
marine sea breezes.

Wet and unsettled weather returns on Monday as the next of a
series of front along high IVT plume impacts the area with rain
and gusty south winds. The system on Monday will be driven by a
compact surface low swinging northeastward toward the Oregon Coast
Monday afternoon. Southerly winds is expected to increase along
the North Coaost ahead of the frontal boundary Monday morning.
Strong southerly winds are forecast develop over the coastal
headlands and exposed ridges in Del Norte and Humboldt counties
Tuesday afternoon through early evening. Gusts from 35 to 45 mph
is expected, especially in Del Norte County. High-resolution
models suggest a period of moderate to heavy rainfall arriving
late afternoon for Del Norte and early evening for Humboldt.
Models then vary showing the upper-level low moving with the
system, resulting in a split front. The front should push
southward during the evening and overnight hours Monday and
provide modest amounts of rain to Mendocino and Lake Counties as
well. The next shortwave trough will rapidly approach on Tuesday
and precipitation will once again increase throughout from south
to north by morning and afternoon on Tuesday.

A second, stronger system will intensify Tuesday night into Wednesday
as a potent upstream trough deepens and a surface cyclone spins
up offshore in response. Ensemble means and deterministic GFS and
ECMWF remain in a good agreement with the deep trough becoming
negatively tilted by 12Z Wednesday. This will send a plume of
high PWATS and high IVT into NW CA. Ensemble means indicate a
moderate AR while control runs indicate a stronger atmospheric
river event. Heavy rainfall is probable.

Strong damaging south winds are also probable (60-90% chance) as
surface pressure gradient tighten Tuesday night and a low level
jet at 925mb up to 70 kts develops along the coast. The 12Z ECMWF
Extreme Forects Index highlight widespre 90-99th percentile, with
localize 100th percentile, across Northwest California on Wednesday.
A well- mixed boundary layer near or along the surface front will
allow for higher momentum air to mix down to the surface. There
is a 40-60% chance of gusts greater than 40 mph for the lowest
elevations widespread. For higher elevations and coastal
headlands, NBM indicates a 60-90% chance for wind gusts greater
than 55 mph in Del Norte and Humboldt counties. ECMWF ensemble
mean 6 hourly wind gusts are over 50 mph for the Del Norte Coast,
specifically CEC and over 40 mph for the greater Humboldt Bay
area, ACV, EKA and FOT. There are more extreme members from 55-70
mph in the ECMWF distribution. Stronger wind gusts over 60 mph are
highly probable over the coastal mountains. A wind advisory will
be necessary while a high wind warning remains less certain (less
than 50% chance). Gusts over 55 mph is a sure thing for many of
our wind prone ridges and venturi-effect RAWS, specifically in the
King Range.

Regarding precipitation, substantial rain is expected for much of
the area Tuesday through Thursday, with the heaviest rates likely
Tuesday night into Wednesday. The probability of 6 hours
precipitation greater than 1 inch is 40-70% for Del Norte and
Humboldt counties from 10 PM Tue to 10 AM Wednesday. While 25-40%
for Mendocino and Trinity counties, and limited to 10-15% chance
for Lake County. Colder temperatures aloft behind the frontal
passage could support greater instability with heavy rain showers
and possibly thunderstorms continuing Wednesday afternoon and
evening or into Thursday. There is a fairly large spread in
precipitation estimates. Comparing the low end and high end
amounts (25th and 75th percentile) for 48 hour precipitation (4 AM
Tuesday to 4 AM Thursday). The high-end amounts from NBM (75th
percentile) for 48 hr of precipitation (4 AM Tuesday to 4 AM
Thursday) indicates 2.5 to 4.0 inches in Del Norte, Humboldt and
Trinity counties, with locally up to 4.5 inches over exposed
ridges. While 1.5 to 2.5 inches for Mendocino and Lake counties,
with heaviest along the coast. The low end precipitation (25th
percentile) suggest 1.0 to 2.50 inches, with locally up to 3.0
inches over the southwest windward facing terrain. Details will
become clearer in the coming days. This an unusually strong
AR event for early November and will need to be watched for
the possibility of urban and small stream flooding.

Another plume of moisture will take aim on the Pacific NW Thu-Fri
and bring another round of moderate to locally heavy rain to NW CA.
There are considerable timing difference with large spreads in 12-24
hour rain amounts. Once again urban and small stream flooding
will be possible as well as rock and mudslides in steep terrain.
A break in the parade of storms is forecast later on Friday into
Saturday as the flow amplifies in advance of another trough that
is forecast to dig over the central Pacific. This next trough may
bring more light to moderate rain as early as Sat. The frontal
boundary may stall offshore and take til Sun to arrive. /ZVS


&&

.AVIATION...18Z TAFs...Poorly modeled quickly clearing skies and
surface moisture from light rain/drizzle aided in fog development
Sunday morning. The bulk of the lingering terrain locked stratus
faded midday Sunday afternoon. Diurnal drying, and increasing
southerly winds will greatly reduce chances for fog outside of the
wind protected interior valleys tonight. Shallow stratus and
potentially brief fog visibility is forecast to increase along the
coast overnight as southerly winds strengthen.

Southeast winds begin a slow strengthening trend overnight. These
winds will be initially stronger over Del Norte, where there is the
lowest probability for IFR or lower CIGS/VIS. The winds will be
slower to increase farther south along the North Coast, where much
higher chances for LIFR exist (60%). Current thinking is the winds
will increase enough early Monday morning to mostly prevent lasting
fog formation at ACV.

There is growing indications a shallow band of stratus advects up
the Russian River Valley and into UKI early Monday morning from the
southerly flow. Have introduced a scattered layer in the 18Z TAFs,
and this will be reevaluated for potential greater coverage in the
coming 0/6Z TAF issuance. JJW


&&

.MARINE...A large, long period WNW swell will slowly subside over
the next few days. Northerly winds will trend much lower this
afternoon. Combined sea heights from the short period seas and
fading WNW swell will remain near 14 ft into Sunday night.

An area of low pressure will clip the waters Monday. This system has
trended farther south, increasing the magnitude of southerly winds
for our waters. Winds are expected to gust to Gale strength Monday
afternoon and evening for the northern outer zone 470 as the low
clips the waters. A Gale Warning has been applied to this zone for
Monday.

A strong frontal system will begin moving in Tuesday when
southerly winds quickly strengthen. Strong Gale conditions are
forecast, with Storm force gusts over 50 kts Tuesday night and
Wednesday morning. Short period seas will build to 15 to 17 ft
Wednesday in response to the Storm force winds. A large post frontal
westerly swell will then build in Thursday as southerly winds
increase again from a secondary trough. Gale criteria may be met
from this second system. JJW



&&

.COASTAL FLOODING...Starting on Tuesday, astronomical high tides
will near or exceed 8 ft at the North Spit tide gauge. The highest
tides, at around 8.5 ft will in occur in the late mornings through
midday on Thursday and Friday. Moderate to strong southerly winds
are forecast through this timeframe and will further contribute to a
positive tidal anomaly. Water levels may reach 10 ft at North Spit
when high tides align with the strong southerly winds. Currently,
the strongest southerly winds are forecast Wednesday morning, but a
slightly higher tide is forecast Thursday. Expect Coastal Flood
Advisory issuance, with the possibility of a Coastal Flood Warning
around Humboldt Bay if confidence increase of the southerly wind
anomaly. The high tides, heavy rainfall, and tidal anomaly may
require an expansion of an advisory along much of the coast
Wednesday and Thursday. JJW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 7 PM PST Monday for PZZ450.

     Gale Watch from Tuesday morning through Wednesday morning
     for PZZ450-455.

     Small Craft Advisory until 3 PM PST Monday for PZZ455-475.

     Small Craft Advisory until 1 PM PST Monday for PZZ470.

     Gale Warning from 1 PM to 9 PM PST Monday for PZZ470.

     Storm Watch from Tuesday afternoon through late Tuesday
     night for PZZ470-475.

&&

$$

NOTE: The full forecast discussion is now regularly issued between
10 am/pm and 1 pm/am. Additional updates will be issued as needed.

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