Mad River, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

911
FXUS66 KEKA 192049
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1249 PM PST Fri Dec 19 2025

.SYNOPSIS...Moderate to heavy rainfall will taper off to the south
into the afternoon. More heavy rainfall returns Saturday night into
Sunday. An active storm track will bring additional heavy rainfall
and a flooding threat, strong winds, and lowering snow levels much
of next week.

&&

.KEY MESSAGES...

- Pacific storm track remains active with additional heavy rainfall
and chances for strong southerly winds this weekend and through much
of next week.

- Flooding risk trends higher into this weekend and early next
  week as more rounds of heavy rainfall occur over saturated
  grounds.

- Snow levels gradually drop by early next week, and could be as low
as 3500 to 4500 ft by Tuesday.

&&

.DISCUSSION...The frontal passage moving through today is gradually
moving to the south and will exit the area by this afternoon.
Generally, 2-5 inches have been reported outside the lower
elevations along the coast, where 1-2 inches have been reported.
Minor flooding from creeks and streams will ease this afternoon as
moderate to heavy stratiform rain transitions to light to locally
moderate showers.

This lull will be short lived as another round of rain arrives to
the area Saturday afternoon and evening. This round of rain is more
focused on the southern half of the area, Mendocino and Lake
Counties. CAMs are showing mostly light to locally moderate rain to
start with in the afternoon and evening hours with precipitation
enhancing overnight into early Sunday. Probabilities of rain rates
over 0.25 inches an hour are above 70% for the higher elevations of
Mendocino and Lake Counties. Chances for rates above 0.5 inches an
hour are also high in the highest terrain of Mendocino and Lake
Counties. These will elevate creeks and streams further as soils are
already saturated. As a result, a Flood Watch has been issued for
Mendocino and Lake Counties. Areas north of Cape Mendocino will also
see rain, however impacts are expected to be more limited. Total
amounts from Saturday afternoon to Monday afternoon south of Cape
Mendocino range from 3-6 inches with locally higher amounts in
higher elevations. North of Cape Mendocino, 1-2 additional inches of
rain are forecast for the same time period.

Going into early next week, ensemble guidance continues to keep the
storm door open, but the position of the systems are uncertain. Some
ensembles keep the bullseye to the south of the area towards the Bay
and some keep the bullseye in Mendocino and Lake Counties. A potent
shortwave trough or perhaps a compact closed low with heavy rainfall
and strong winds has been modeled to arrive around Tuesday or into
Wednesday. NBM is showing near 50% probabilities for peak gusts over
40 mph for much of Mendocino and Lake Counties. The exact location
and timing of this feature yields the ensemble uncertainty. There is
then the potential for a strong Pacific cyclone to impact the area
late next week. Eventually, main stem river flooding is possible
with additional storm systems. See the Hydrology section below for
more information.

Snow levels remain high (above 7000 ft) through the weekend. Snow
levels will gradually fall going into early to mid next week. Monday
night to Tuesday morning and again Tuesday night and Wednesday
morning, snow levels may drop for the northern portions of the area
to 3500-4500 ft. Depending on precipitation amounts, these may bring
us our first impactful snowfall of the season to the high mountain
passes.

Outside a few brief lulls in the next week, precipitation is
forecast somewhere in northwest California each day through at least
Friday of next week. NBM probabilities drop to below 20% for a 1/2
inch of rain or more in 24 hours by Saturday. CPC does maintain our
area as being more likely to receive above normal precipitation in
their 8-14 day outlook, which goes through January 1st.


&&

.AVIATION...(18Z TAFs)...Rapidly evolving conditions immanent for
all terminals. Degraded visibilities and rainshowers with IFR/LIFR
ceilings are forming midday along the North Coast. The last bit of
the surface front is also bringing gusty northerlies to terminals
along the coast. After this passage, clearing to scattered MVFR/VFR
skies is expected this afternoon with calm winds. Inland terminals
can expect continued cloud coverage as a orographic lift cloud
coverage with MVFR ceilings with IFR conditions under rainshowers.
Westerly winds aloft can create some Low Level Turbulence and a
continues mountain wave threat, especially in the wake of the
frontal boundary. TOnight into tomorrow conditions are to remain
MVFR and above along the coast whereas inland areas could
experience valley fog due to increased moisture in the area. DS


&&

.MARINE...Winds are quickly become northwesterly behind the frontal
passage from early this morning. The wind waves have already been
recorded as dropping steadily in the areas where the front has past
through, leaving a swell dominated sea state. A west to northwest
swell is has been building today, and is forecasted to reach around
10 feet at 11 seconds. This will slowly diminish tomorrow.

Another weather system is expected on Sunday yet there is wide
variability in the model solutions. The models are currently
struggling to resolve the location of a strong area of low pressure
and where it will exactly track. The locations of this storm will
dramatically impact the strength of the coastal winds, so looking at
multiple models can give a better idea of the potential winds
formation. The NAM is now showing weaker winds more like the GFS,
yet the ECMWF seems to capture the influence of the coastal terrain
the best so a 2:1 blend has been made with the previous forecast.
This yielded winds of around 20 kt. This seems reasonable for now,
as confidence remains low, yet there is still the potential for a
stronger winds with only a slight variation in the
forecasted strength and/or track of the low.

Monday and Tuesday the winds look to generally remain fairly light
with the next storm system likely to bring gales on Wednesday or
Thursday. MKK


&&

.HYDROLOGY...Creeks and streams are responding to today`s pulse of
heavy rain. In Del Norte, the Smith River at Dr. Fine Bridge came
just a couple inches short of reaching monitor stage before starting
to recede. Minor flood impacts will ease this afternoon as rain
moves to the south of the area and creeks and streams peak and
recede.

Additional rain starting Saturday night and continuing into early
next week has the potential to be more impactful. There is still
some uncertainty on the positioning and how long the heaviest rain
will last, but the heaviest rain will start around Cape Mendocino
and southward. This will again pose a threat for quick rises in
streams and creeks along with rock and mudslides. Risk for rock and
mudslides will again increase and could impact travel on area
highways.

At this time, none of the main stem rivers are forecast to exceed
action/monitor stages. Ensembles are showing slightly higher
probabilities for main stem rivers to reach flood stage within the
next 10 days. The highest chances are mid to late next week, but
some potential is there Sunday-Tuesday. Over the next ten days the
RFC gives the Russian River at Hopland a 47% chance to reach minor
flood stage. The Navarro River at Navarro has a 40% chance to reach
minor flood stage and an 18% chance to reach moderate flood stage.
The Eel River at Fernbridge has a 31% chance to reach minor flood
stage and a 60% chance to reach action/monitor stage. The Mad River
at Arcata has a 56% chance to reach action/monitor stage with only a
4% chance to reach minor flood stage. No other rivers have more than
a 10% chance to reach flood stage at this time. This can change if
the narrow bands of moisture deviate from the forecast, so these
probabilities are likely to change.



&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Flood Watch from Saturday afternoon through Monday
     afternoon for CAZ109>115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 PM PST this evening for PZZ450-
     475.

     Small Craft Advisory until 3 AM PST Saturday for PZZ470.

&&

$$

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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