Sherwood Valley Rancheria, California Weather Forecast Discussion

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FXUS66 KEKA 272200
AFDEKA
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
300 PM PDT Sat Sep 27 2025
.SYNOPSIS...The ridging pattern that helped warm dry weather
persist, is breaking down over next few days as we transition into
a wet weather pattern. Rain chances arrive late Sunday, with
increasing probability for widespread rainfall and periods of
breezy winds through early next week. The opportunity for
additional rainfall may continue through mid-week.
&&
KEY MESSAGES: This coming week, a succession of storm systems
will bring a wet pattern with periods of moderate to heavy
rainfall along with breezy to strong southerly winds.
.DISCUSSION...Winds will continue to increase into the evening as
the pressure gradient squeezes between the ridge and the cutoff
low as it exits south. Air quality has been greatly reduced after
offshore winds pulled smoke plumes from the Moon Complex, north of
our CWA. It looks like the incoming frontal barrage will help
clean the heavy particulates out of the area by Sunday late
afternoon.
The ridge continues to quickly breakdown going into the weekend as a
NE Pacific trough develops and moves towards California.
Temperatures will trend lower by Sunday with the arrival of
cloud cover and chances for light rainfall as the trough nears.
The trough and associated cold front will then move in by late
Sunday and into Monday. The system will contain a band of high
precipital water values and likely a relatively strong southerly
jet. That said, the IVT (integrated water vapor transport) values
will be 350 up to 500 kg m-1 s-1, supporting a weak atmospheric
river type system. This will allow for some periods of heavier
rainfall rates. The US Drought Monitor now has a good portion of
Humboldt and Trinity County in the `Abnormally Dry` category, with
Del Norte entering `Moderate Drought`, so this rainfall will be
welcomed and beneficial.
An upper level southerly jet, at 925mb, could have winds up to 40 kt
and some instability with this first trough. Breezy southerly winds
will be possible with 20-30 mph gusts, and locally 40 mph gusts on
the higher ridges. Ensembles still show a large spread in rainfall
totals. NBM holds a general 60% chance for 24 hour totals over 1
inch for Del Norte, most of Humboldt and other higher terrain areas
of NWCA. Greater precipitation totals would be likely over the
higher more southerly to southwest oriented terrain.
A cyclone and associated cold front will then form in the NE Pacific
region. Models continue to struggle with the depth and southern
track of the of the low. The GFS model suite depict a much deeper
low, down to 976 mb, and on a more southern track before swinging
north into the Pacific Northwest. The system will also bring chances
for moderate to heavy rainfall with probability for IVT values over
250 70-80%. Chances for 24 hour rainfall totals over an inch are
around 55%, and greater precipitation totals would again be likely
over the higher more southerly to southwest oriented terrain.
The dynamics of this system will be more favorable for stronger
southerly winds, but the strength will be dependent on the depth and
track of the low. NBM 90% shows a larger percentage of the area to
see the 30 to 35 mph winds, with locally 40 mph gusts, but if models
trend closer to the deterministic GFS, these winds may be much
stronger. A small percentage of the ensemble members show gusts of
40 to 45 mph for some coastal regions, so this aspect of the
forecast will be watched closely. Unsettled weather with additional
light rainfall will be possible mid to late next week. JJW
&&
.AVIATION...(18Z TAFs)...Stratus has largely lifted early this
afternoon, though some patches are still visible on satellite. Aside
from smoke from southern Oregon and a few high clouds, skies will be
clear into the evening and winds are forecast to be light. Weakening
offshore flow tonight is expected to allow stratus to form at the
coastal terminals. A deeper marine layer is expected as high
pressure weakens, keeping ceilings IFR to MVFR. Brief LIFR impacts
are possible, but generally ceilings are forecast to lift through
the night. Southerly winds in the Russian River Valley may bring
stratus from the Bay Area early Sunday morning. Any stratus is
forecast to lift after sunrise. JB
&&
.MARINE...Northerly winds continue to weaken as high pressure moves
eastward. Seas remain steep, especially in the outer waters, but
have started to ease as winds have eased. By Sunday winds will turn
southerly as a cold front approaches the waters. Strong southerly
winds with near gale force wind gusts will occur just in advance of
the front Sunday night into early Monday morning. Small craft
advisories for all the coastal zones are likely with the potential
for gales likely reserved to waters outside of 10 nautical miles
north of Cape Mendocino. Winds will decrease behind this front on
Monday, only to quickly increase again Tuesday morning as another
front approaches the waters. This front will approach within a more
unstable atmosphere, potentially allowing for better mixing of winds
to the surface and a greater chance of gales. Additionally, the most
recent wave guidance is indicating this second front could also
usher in a larger northwesterly swell. Winds will decrease behind
the frontal passage Tuesday night into Wednesday but seas will
likely remain elevated if the larger swell moves into the waters.
RPA/JB
&&
.FIRE WEATHER...Tonight into Sunday, RH is expected to increase
ahead of a strong cold front. At the same time southerly winds are
expected to increase. The tricky part will be which one increases
first. There could be some periods and locations of increased
fire danger if the winds come up before the RH does. Confidence is
fairly high that most areas will see a wetting rain starting late
Sunday evening in the north and spreading south into Lake county
before midday Monday. Rainfall amounts are expected to range from
a 0.75 inch to 1.5 inches with the heaviest amounts in the north
and in the higher terrain. Additional moderate to heavy rain is
expected on Tuesday with light showers continuing through mid
week. Southerly winds may be stronger with the second front
Tuesday.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 PM PDT this afternoon for
     PZZ450.
Small Craft Advisory until 11 PM PDT this evening for
     PZZ455-470.
Gale Watch from Sunday evening through Monday morning for
     PZZ470.
Small Craft Advisory until 3 AM PDT Sunday for PZZ475.
&&
$$
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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NWS EKA Office Area Forecast Discussion