982
FXUS66 KEKA 032151
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
251 PM PDT Thu Apr 3 2025

.SYNOPSIS...Warm, dry, and calm weather will build through Saturday.
Another quick round of light to moderate rain is expected around
Sunday.


&&

.DISCUSSION...

KEY MESSAGES:

-Warm, calm, and dry weather through Saturday: interior highs in the
upper 70s. Cool temperatures at night: isolated interior frost.

-Moderate south wind and rain return around Sunday: minimal impacts
expected.

WEATHER PATTERN OVERVIEW: A narrow but slow moving ridge has started
to drape across the area today and will continue through Saturday.
The front edge of the ridge  moving onshore has allowed for
continued drying and clearing conditions all across the area with
interior highs increasing into the 60s. Along shore, surface high
pressure aligning with the coast has sustained moderate northerly
winds gusting up to 25 kts in exposed areas. Clear skies may allow
for patchy interior frost tonight. Though lows will likely be higher
than lass night, less fog and cloud cover will likely allow for more
efficient cooling. NBM places a 60 to 80% chance of lows at least as
low as 36 throughout northeast Mendocino Country and eastern
Humboldt.

WArm, calm, and dry conditions will continue to build through
Saturday. By Saturday, the warmest interior valleys will most likely
see highs between 75 and 79 with little chance (10%) of highs
reaching above 80). Along the coast, northerly wind will decrease
but gentle onshore flow and an enhanced inversion will likely allow
for a sporadic, diurnally driven marine layer to form just along
shore.

There is high model confidence that an upper level shortwave will
sweep past the area around Sunday. This wave will most likely bring
a short lived period of moderate southerly wind and rain. Rain will
be mostly focused in Humboldt and Del Norte. 0.5 to 2.0 inches of
rain is most likely over 24 hours, dependent upon elevation, with
minimal expected impacts. Snow levels most likely above 4500 feet
will greatly limit any winter weather impacts. Wind will most likely
be similarly moderate with gusts 20 to 30 mph. Warmer and dryer
weather is most likely to quickly return after the rain.


FORECAST CONFIDENCE AND DEVIATIONS:

There is relatively high forecast confidence for the next 7 days. In
the short term, the greatest uncertainty is related to nighttime
frost. The extent of frost will largely be determined by very
localized changes in moisture and exposure. In either case, the
chances of frost wills steadily decrease into the weekend.

There is some uncertainty regarding this weekend`s rain system, and
model guidance has steadily gotten wetter over the past few runs.
That said, there is little potential for much more than a moderate
event. There is a contingent of model members (about 15%) which show
higher rain potential around 3.0 inches, but the vast majority
suggest a lower end rain event. Essentially now ensemble members
show wind gusts over 45 mph. /JHW


&&

.AVIATION...Gusty N-NW winds expected this afternoon as high
pressure ridge builds into the eastern Pacific, tightening the
coastal pressure gradient. So far winds have been laminar with
sustained speeds around 15 kt. Turbulence and boundary layer mixing
increases later this afternoon or early evening and should yield
more gustiness with peaks around 25 to 30 kts. Highest HREF
probabilities for gusts to 35 kt are at KCEC by 5 or 6 PM; about a
20% chance. Also, the downscaled ECMWF ensemble mean indicates peak
gusts just under 40 mph for KCEC while KACV is just shy of 30 mph.
North winds will decouple and shift E-NE by late evening as a
thermal trough pushes offshore. Some misty air conditions may
develop at coastal terminals before drying easterly winds develop
overnight. Gusty NE and E winds are expected over the ridges and
channeled terrain overnight. HREF probabilities for low level wind
shear over the terminals is 20% at most, but much higher over Lake,
northern Mendocino, southern Humboldt and much Trinity. Shallow
mountain wave turbulence may occur as the strong east to northeast
winds intersect the NW-SE oriented ridges early Friday morning.
Otherwise, VFR is expected except for shallow fog and low clouds in
valleys where winds go calm. DB


&&

.MARINE...Fresh to moderate northerly breezes will persist through
this evening. Strongest north winds (20-25kt) are forecast to
continue just outside 10NM, but will extend into portions of the
inner waters this evening in response to land mass heating. A couple
of weak expansion fans, one around and just downwind of Pt St George
and another in the lee of Cape Mendocino, will yield a 30 to 50%
chance for gale force gusts to 35 kt this afternoon and evening. The
persistent northerlies will continue to produce short period waves
from 6 to 8 ft tonight, highest in the outer waters. Thus, small
craft advisories appear to be on track and no modifications were
necessary. Lingering steep waves from 5-7 ft and lingering N-NE
gusts to 20 kt are on the fringes for an advisory Friday morning and
an extensions did not seem necessary at this time.

Overall lighter winds are expected for Friday except for perhaps
localized afternoon gusts near 20 kt right along the land-ocean
interface once the thermal trough shifts inland. Calmer conditions
with much lower seas are anticipated for Saturday. NBM guidance
continues to indicate low chances for even gust to 20kt late on
Saturday as southerlies begin to develop and short period SW waves
increase during the overnight hours. On Sunday NBM continues to
indicate low chances (less than 25%) for wind gust to 25 kt or more.
Deterministic models, including the NAM-nest, GFS, ECMWF and ICON
continue to trend stronger with southerlies on Sunday. Edged wind
forecast higher over NBM on Sunday into Monday. ECMWF, NAM12, GFS
and ICON models indicate potential for gusts to 35kt. So stay tuned
as the southerly winds in advance of the front may be much stronger.
Also, steep southerly waves are forecast to build to 6 to 8 ft while
a large long period westerly builds to 10 to 13 feet.

There may be window for a sneaker wave threat Sunday morning into
early afternoon before southerly winds and short period waves
increase. Stay tuned as this longer period swell may pose a risk for
sneaker waves on Sunday.

A secondary trough may bring another increase in south-southwest
winds by Monday, but confidence on the wind strength is low with NBM
chances for gusts to 25 kt less than 20%. Seas do look to remain
elevated and hazardous into Monday due to a combined westerly swell
and steep SW wind waves fromt 10-12 ft. DB


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Frost Advisory from 2 AM to 9 AM PDT Friday for CAZ110-111-
     113>115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 PM PDT this evening for PZZ450-
     455.

     Small Craft Advisory until 3 AM PDT Friday for PZZ470-475.

&&

$$

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