Glenhaven, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

233
FXUS66 KEKA 250835
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1235 AM PST Thu Dec 25 2025

.SYNOPSIS...Another strong storm system will bring additional
moderate to heavy rain, mountain snow, and strong winds Thursday
into Friday. Shower and isolated thunderstorm activity will
gradually to diminish through the day on Friday. Drier and colder
weather is forecast for the weekend and should last into early
next week.

&&

.KEY MESSAGES...

* Strong southerly winds, periods of moderate to heavy rain, and
  embedded thunderstorms expected through Thursday.

* Gusty winds, showers and isolated thunderstorms with locally
  heavy rain expected on Friday.

* Flood Watch remains in effect through Friday evening for
  Humboldt, Trinity, Mendocino and Lake counties.

* Winter Storm Warning for elevations above 4000 ft through
  Friday evening for Trinity County.

* Hazardous marine and coastal conditions expected through
  Thursday.

&&


.DISCUSSION...A deepening surface low (978-982mb) inside 130W
north of Cape Mendo will impact NW California with strong and
gusty winds, moderate to heavy rain and high mountain snow (above
4000 feet) on Thu and Fri. There will probably be some isolated
to scattered thunderstorms as cooling aloft and low level moist
air transport creates greater instability. We have already had
multiple lightning strikes detected offshore associated with
transient shortwave trough. A coastal barrier jet best represented
by the 925mb surface is forecast to develop Wed evening and early
Thu morning with top speeds around 65 to 70 kts. The atmosphere
is much more unstable and well mixed and the chance of downward
momentum transport is greater compared to the last storm. It appears
the window of greatest threat for strong and damaging wind gusts
down to the coastal plain (mean sea level) will be with the
passage of the frontal occlusion by early Thu morning. It is a
sure bet, winds will gusts to 70 mph or more over the ridges. The
surface low will deepen slightly offshore Del Norte and S-SE winds
will remain strong into at least mid or late morning. Del Norte
coast stands the best chance of gusts to 60 mph more on Thu.
Rate of pressure falls may not support winds that strong for the
Humbodlt Bay area and Eel delta. Another secondary spoke of
energy or trough line will pin-wheel around the low in the
afternoon and head toward the Mendocino coast Thu afternoon. This
line will likely be convective and may have a few strong thunderstorms
over the waters. The surface low will slowly meander offshore and
eastward toward the coast Thu night into Friday morning with
additional rounds of gusty winds. Winds look to be borderline for
an advisory. Expect more showers, isolated thunderstorms with
locally heavy rain into at least the morning hours on Friday.

Cold air moving in from the deep trough will support lower snow
levels late tonight into Thursday. Snow levels should drop to
4000-4500 ft tonight and then to 3500-4000 ft Thu night and Fri.
48-hour total snow amounts of 2-3 feet are expected through
midday Friday. 6-hourly rates fall off during the afternoon and
evening, but travel over Scott Mtn Pass will be very difficult or
impossible if roads are now plowed. Even south Fork Mtn Summit on
highway 36 (around 4000 ft) may get a dumping of snow with NBM
chances for 4" in 48 hours around 70%.

The models remain in general agreement that the upper trough
complex responsible for multiple days of rain will finally
head eastward into the Great Basin as high pressure rebuilds
offshore and toward the West coast.

High pressure is expected to start to move over the area bringing
a break in the prolonged wet spell. Northerly may be a bit breezy
and gusty over ridges this weekend weekend. The valleys will likely
see widespread fog and low clouds each night and morning. Frost
and freezing temperatures will also be possible for the North
Coast, especially Sunday morning. Cooler and drier weather should
last into early next week. This may be too optimistic this time
of year. Chances for more than 4 to 5 days in a row of no
possibility of precip is not high. In fact CPC 8-14 day outlook
already has us back in a slight risk for heavy rain and high
mountain snow.

&&

.AVIATION... Latest METARs show -RA and VFR/nearly MVFR conditions
as a powerful frontal system approaches. High confidence exists
for the arrival of a 60-70 kt LLJ at 925mb after 08Z, resulting in
severe Low-Level Wind Shear (LLWS) and high-end mechanical turbulence
at all terminals. Surface wind gusts are expected to peak between
40-50 kt at KACV and KCEC between 09Z and 12Z. Despite the heavy
rain and embedded thunderstorms, ceilings at the coastal terminals
are forecast to hold in the MVFR range at OVC035, while visibilities
drop to 2-3SM in heavier convective cores.

At KUKI, the primary concern is strong southerly flow channeled
through the Russian River Valley, resulting in gusts up to 45 kt
through late Thursday morning. TAF ceilings for the inland terminal
remain in the MVFR category, holding at OVC025-OVC030. HRRR and NBM
guidance suggest that while deep moisture and mechanical lift will
persist, cloud decks should remain above IFR thresholds through the
24-hour period. Conditions will trend toward VFR ceilings (OVC050)
late in the period as the region transitions to post-frontal
showers. /MH

&&

.MARINE...Storm Warnings remain in effect for all coastal waters.
Observations and high-resolution models indicate the LLJ will
produce frequent storm-force gusts to 55 kt through Thursday
morning. These winds will build extremely steep, life-threatening
seas peaking between 20-24 ft, particularly for the waters from Pt
St George to Cape Mendocino.

The environment will remain highly unstable, with frequent
thunderstorms and the potential for waterspouts across all zones
through Thursday afternoon. While the pressure gradient will slowly
relax on Friday, chaotic and hazardous seas will persist before a
moderate northerly flow develops over the weekend. /MH

&&

.HYDROLOGY...Once again rivers and streams have been receding
through this evening after a period mostly moderate rain. This
will likely begin to reverse overnight into Thursday as the next
surge of moderate to locally heavy rain spreads into the area
overnight into Thu morning. Period of highest rain rates over
0.25in/hr occurs after midnight and during the morning on Thu.
HREF banded maxima over 0.50in/hr is forecast over SW and SRN
Humboldt, much of Mendocino and Lake, and into the higher terrain
of NE Trinity where it should be all snow.  Minor flooding of
smaller rivers, creeks and streams with poor drainage will be
possible with grounds saturated and all the water going into
run-off. Mad River at Arcata and Eel River at Fernbridge could
touch Monitor Stages Thu-Fri. Hopland could also touch or exceed
slightly minor flood stage (15% chance) Thu-Fri. Otherwise, all
main stem river stages are forecast to remain below Monitor or
Action stages through Friday. Another period of organized and
widespread rain arrive Thu night into Friday morning. Duration
and moisture flux will drop off and the convection will be
shallow and short-lived.

&&


.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Flood Watch through Friday evening for CAZ101>115.

     High Wind Warning until 8 PM PST this evening for CAZ101.

     Wind Advisory until 8 PM PST this evening for CAZ102.

     Wind Advisory until 2 PM PST this afternoon for CAZ103.

     High Wind Warning until 2 PM PST this afternoon for
     CAZ104>106.

     Winter Storm Warning until 10 PM PST Friday for CAZ107-108.

     High Wind Warning until 10 AM PST Friday for CAZ109.

     Wind Advisory until 10 AM PST this morning for CAZ110>115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Storm Warning until 3 PM PST this afternoon for PZZ450-455-
     475.

     Storm Warning until 11 PM PST this evening 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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