802
FXUS66 KEKA 222247
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
247 PM PST Fri Nov 22 2024

.SYNOPSIS...A strong atmospheric river has finally began to move out
of the area. Isolated showers and coastal thunderstorms are possible
this evening through Saturday morning. Another weaker system is
possible Sunday into Monday, bringing more rain and gusty wind.


&&

.DISCUSSION...The strong atmospheric river affecting us for the last
few days has finally started to make it`s way out of our area. Some
rain is still being seen in interior Humboldt county and southern
Lake county, but the worst is officially over. Colder air aloft will
continue to spread across the West Coast this afternoon and evening.
As result, instability will increase to around 100-300 J/kg of CAPE.
Instability could allow for low-topped thunderstorms (15 to 40%
chance) over the waters and right along shore. Another round of
periods of moderate to locally heavy rainfall are anticipated. HRRR
model indicates max hourly rain rates around 0.15 to 0.30 inches.
Additional rainfall amounts from this system are forecast to range
from 0.75 to 2.0 inches from today through late Saturday afternoon.
The highest amounts are expected across the southwest windward
facing terrain with total rainfall up to 3 inches.

Snow levels in NE Trinity are expected to lower between 5000 to 4000
feet this evening into Saturday morning. 3-5 inches will be possible
above 4000 feet and could impact travel on Highway 3 at Scott
Mountain Pass late this afternoon through Saturday afternoon. More
significant snowfall is expected for the Trinty Alps. A Winter Storm
Advisory is now in effect from 4 PM this afternoon to 4 PM Saturday
for elevations above 4000 feet in portions of NE Trinity County.

A brief break will be possible over the weekend, before another
series of fronts impacts the area Sunday through Tuesday. These
fronts will be progressive and have less moisture. 6-hourly rainfall
and snowfall rates and storm total rain and snow amounts are
forecast to be much less than our current storm with less potential
for major impacts. Storm total precipitation is highest over the
King Range and Del Norte County, with 2-4 additional inches possible
there. Elsewhere, 1-2 inches are possible. Gusty winds are also
possible with this system; NBM has a 40-80% chance of southerly
gusts greater than 40 mph along the coast of Humboldt and Del Norte,
with higher probabilities along ridges and coastal headlands of
Humboldt and Del Norte. Snow levels start around 4000 ft Sunday,
and are forecast to gradually rise to about 5000 ft through the
day Sunday into Monday. A Winter Storm Watch has been issued
starting Sunday morning for elevations above 4000 ft in NE Trinity
County, which includes Scott Mountain Pass on Highway 3.

Upper ridging is forecast to restore more peaceful and dry weather
mid to late next week, though after multiple days of rain, valleys
will no doubt fog up during the night and morning hours. JB/ZVS


&&

.AVIATION...Flying conditions have improved to mostly VFR with
occasional MVFR ceilings and vsbys in showers.  Satellite and radar
data indicated showers and isolated thunderstorms over the coastal
waters. This activity will spread toward the coastal terminals this
evening and overnight. Brief IFR in locally heavy showers and gusty
winds and moderate turbulence may impact coastal terminals overnight
into Saturday. Ukiah will also have occasion rain and MVFR
conditions overnight. Some fog and low clouds may also form in the
valley after multiple days of rain, but the atmosphere will probably
remain too well mixed for that. DB


&&

.MARINE...Showers and isolated thunderstorm will spread into the
waters tonight through Saturday night. Brief wind gusts to 30 kt
will be possible with stronger showers and isolated thunderstorms as
cold and unstable air spread over the waters. Seas remained elevated
today due primarily to a combination of a short period SW wave group
and a short period NW wave group. These wave groups will continue to
combine through Saturday and keep seas elevated around 10 ft into
Saturday. Southerly and southeasterly winds will increase Saturday
night into Sunday as another surface low and frontal boundary
approaches the outer waters. Brief gale gusts are possible (50%
chance) - mostly around Cape Mendocino and over the northern outer
waters in advance of the occlusion. Greater uncertainty arises early
next week as additional frontal systems or troughs pin-wheel around
a nearly stationary surface low that will weeble-wobble around over
the NE Pacific into early next week. DB


&&

.HYDROLOGY...The rise on most of the main stem rivers has slowed or
started to slowly recede this afternoon. Flooding impacts from
main stem rivers will continue into tonight and tomorrow. The Eel
River at Fernbridge is forecast to fall below flood stage (20 ft)
by 8 AM Saturday. The Navarro River near Navarro and the Russian
River at Hopland is forecast to fall below flood stage (23 ft and
15 ft, respectively) is forecast to fall below flood stage (23 ft)
by 8 PM tonight. Rain showers tonight into tomorrow are expected
to be intermittent, and are not expected to make any impacts to
main stem rivers. Although, a heavy shower could bring localized
small stream impacts given soils are completely saturated. More
rain Sunday through Tuesday could cause the rivers to rise, but
main stem river flood impacts are not currently expected. JB


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Winter Weather Advisory until 4 PM PST Saturday for CAZ107.

     Winter Storm Watch from Sunday morning through late Monday
     night for CAZ107.

     Flood Watch until 10 PM PST this evening for CAZ114-115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 AM PST Saturday for PZZ450-455-
     470-475.

&&

$$

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