Smith River, California Weather Forecast Discussion

273
FXUS66 KEKA 232032
AFDEKA
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
132 PM PDT Tue Sep 23 2025
.SYNOPSIS...Isolated light showers will be possible for southern
Lake and southern Mendocino Counties Wednesday. Otherwise, dry
and stable weather with an increase in coastal fog and stratus is
expected for the rest of this week. Additional troughs may yield
some rain over the weekend, primarily Sunday.
&&
.DISCUSSION...A closed low pressure system is forecast to approach
central and southern California tonight and then track slightly
northward over the coastal waters on Wednesday. Model guidance
continues to indicate there is less than a 10 percent chance for
wetting rain across Northwest California as this low moves through
to the south. However, there could still be a few light showers
or isolated thunderstorm along or near the border of southern
Lake County Wed evening. HRRR depicts a band of mid level
moisture and possible elevated convection advancing northward
Wednesday afternoon and evening. Latest HREF and NBM probabilistic
guidance continues to indicate low potential (5% or less) for
thunderstorms along the border with Nape and Sonoma County Wed
evening. Real-time observations such as radar, lightning detection
network and satellite data will give us a much better idea on
this threat. We added isolated light showers or sprinkles to the
forecast for southern Lake per the NBM guidance, NAM and ICON
models.
Generally above normal temperatures and greater cloud cover are
forecast for Wed. Also, the low will still pull up moisture form
the south, but the general northeast flow around the low will not
be favorable for widespread wetting rain. Showers that do form
will most likely be around the rim of southern Lake County where
the wind best aligns with topography as orographic lift will
mostly be a storm catalyst. The low ejects into the Great Basin
on Thu as ridging aloft rebuild over NW California. Temps should
warm back up in the interior. Northerlies ramp up offshore over
the coastal waters and stratus and fog may once again dominate
coastal weather for a day or two before clearing out.
Wetter weather conditions will be possible as we head into the
latter portion of the weekend (Sunday) and early next week (Monday
and Tuesday). A series of troughs may break down a dominant ridge
parked over Northwest Cal. Models typically do poorly this time
of year and tend to bring precip (rain) in too fast. Other than
some patches of coastal drizzle/fog, Sunday may turn out to be
dry with mild temperatures too.
&&
.AVIATION...(18Z TAFs)...Outside patchy ground fog, skies remained
clear for the night. Satellite is currently showing clear skies
across the area, and this is likely to continue through the day.
Offshore flow aloft is weaker tonight, but most models are in
agreement in it likely being enough to keep skies mostly clear
again. Some LIFR stratus or fog is not out of the question around
sunrise Wednesday, but chances aren`t high. A southerly wind
reversal tonight into the morning hours will likely bring stratus
north from the Mendocino coast. At ACV and CEC, stratus would likely
arrive sometime in the afternoon Wednesday. Any daytime heating will
likely keep this stratus elevated and off the coast until the
evening, but this depends on when it arrives. Inland areas are
likely to remain VFR with generally light winds for the next 24
hours. JB
&&
.MARINE...Northerly winds continue to diminish and move further
offshore. Steep seas are also starting to subside as these winds
diminish. Southerly winds nearshore increase tonight, and may be
breezy around Cape Mendocino, and will carry stratus northward. High
pressure will then nose back from the west in Thursday,
strengthening the pressure gradient against a cutoff upper low over
Central CA. Northerly winds will strengthen Thursday through Friday
in response. Gale conditions are looking more likely in the outer
zones. NBM now holds a 40 to 60% chance for gales late Thursday and
Friday. Steep seas are currently forecast to build to 10-12 ft in
the outer waters through that period.
&&
.FIRE WEATHER...Above normal high temperatures and low daytime
RH`s are expected through Friday and perhaps into the weekend.
Winds have been generally favoring east to northeast directions
over the exposed ridges. Not too big of a concern with localized
peak gusts to 25 mph or so over exposed ridges. Southerlies and
upslope breezes should generally prevail as we head into Wed as
surface low pressure develops over the northern interior. RH`s
should increase slightly with the southerlies in some areas near
the coast and areas susceptible to marine air intrusions from the
south and eventually the west.
Northerlies ramp up over the coastal ranges toward the end of the
week, Thu- Fri, after a cut-off low moves across central California
on Wednesday. Potential for lightning and deep moist convection
with this low is looking quite low (5%) for our southern interior,
particularly southern Lake on the border with Napa and Sonoma. A
band of mid level moisture is forecast to advance northward through
the day on Wed. A few high based showers or sprinkles will be
possible for southern Lake and far southern Mendocino in the
afternoon and evening. Most if not all model sounding depict a
very dry lower atmosphere and any drops from mid level clouds will
probably evaporate. There is slim chance for stronger west-southwest
gusts if evaporatively cooled downdrafts couple with surface
winds, especially in southern Lake County. Only one model (HRRR)
from the HREF shows convective cells >40dBZ. Right now it appears
the consensus is for the band to dissipate upon moving into a dry
and stable air mass.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
None.
&&
$$
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