Potter Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

790
FXUS66 KEKA 172301
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
301 PM PST Fri Jan 17 2025

.SYNOPSIS...Dry weather is expected to continue for the next 7
days. Chilly nights and mornings with areas of frost and patchy
fog are also expected.

&&

.DISCUSSION...Quite weather is expected to continue through the
weekend into all of next with below normal low temperatures. Patches
of low clouds and fog are also expected both along the coast and
in the river valleys. Offshore flow should increase over the
latter portion of this weekend with less potential for coastal
low clouds and patchy fog. NAM12 BUFKIT profiles continue to show
high boundary layer humidities while HREF and individual CAMS
continue to indicate a weak southerly wind reversal over the
weekend. The weak offshore wind flow could also keep the bulk of
stratus and fog offshore too. River valley fog and low clouds will
form for sure (a 100% chance) each night and morning.

Large scale flow pattern continues to resemble an omega block with
no pronounced signal for rain through all next week. A dry offshore
flow regime is forecast to continue next week, increasing the probability
for near or below freezing minimum temperatures for coastal areas
and adjacent valleys. Sub-freezing temperatures are a sure thing
in the interior valleys, especially Trinity and northern Mendocino.
Freezing and sub-freezing morning temperatures are not unusual
for this time of year for NW California valleys.

Now some ensemble members and deterministic outliers indicate
shortwave troughs busting down or breaking through the block late
next week or next weekend. NBM probabilities for > 0.05 of an inch
in 24 hours increases next weekend to 20% for SE Lake and 50% for
Del Norte. So perhaps our long stretch of anomalously dry weather
with below normal low temperatures may finally come to an end.

CW3E atmospheric river landfall hovmoller diagrams from both the
GFS and ECWMF ensembles do not look very promising for any significant
rainfall for the next 10 days, however. GEFS does shows a 20%
chance for IVT over 250kg/m/s skirting the ORCA border near 42N
around days 7-8 or Fri-Sat. In fact, ensemble cluster means reveal
potential for a much drier scenario with a reinforcing cold air
surge (an inside slider) and robust offshore winds, drier air and
below normal minimum temperatures the following weekend. DB

&&

.AVIATION...A slightly deeper and more extensive marine layer
continued to impact the North Coast from Cape Mendocino to
Crescent City today...but especially all of Humboldt. Also, From
Ft Bragg southward. Cig conditions were mostly IFR until mid-
morning; then raised above 1000 Feet (MVFR). Late morning pilot
reports (pireps) from ACV reported bases 1300-1600 and tops
1900-2000 feet. By mid- afternoon there was significant erosion
over Humboldt with a few binovc areas. Fog was very extensive over
many inland valleys. However, UKI escaped any restrictive Cig/Vis
today. Model guidance seems to be in somewhat agreement about the
lack of low clouds Saturday morning at the coast; but there is
plenty of skepticism... so the 18z TAFS included MVFR Cigs
Saturday morning. Most guidances are suggesting another round of
interior valley fog overnight... including at UKI. /TA

&&

.MARINE...High pressure is strengthening over the area and the
northerly winds are increasing. A northwest swell is the main wave
group at around 5 feet at 13 seconds. The short period waves are
starting to increase as well in response to the winds. Winds and
waves are expected to peak this afternoon and evening around 20 to
25 kt in the outer waters. Closer to the coast winds are only
expected to be around 5 to 15 kt with the strongest winds near
Cape Mendocino. Saturday winds are expected to mainly be 5 to 10
kt with a few areas of 20 kt beyond 30 NM. This pattern is
expected to continue through Sunday.

Saturday afternoon a very long period swell is expected to start to
build into the waters. These waves were formed by a strong low
pressure just south of the Aleutians. This will allow them to have
long periods and set behavior. This set behavior will allow periods
of calmer waters up to 20 or 30 minutes between them. This will
increase the threat of shoaling. These waves are expected to build
to around 8 feet at 19 seconds.

Sunday night into Monday northerly winds are expected to increase
again with the 15 to 20 kt winds getting closer to the coast again,
although they are expected to remain beyond 15 NM. This will be
shortlived and generally 5 to 10 kt winds are expected through early
Wednesday there is short increase of the northerly winds. This long
period swell is expected to gradually diminish through the week. MKK

&&

.BEACH HAZARDS...Saturday afternoon through Sunday night a swell
initially around 21 seconds is expected to bring the potential for
sneaker waves. These long periods will allow the waves to be in sets
with up to 20 or 30 minutes between the larger waves. There is some
wave energy lingering in a 10 second swell that may mitigate the
gaps in the sets of the longer period waves. Still a moderate threat
of sneaker waves is likely. The beach hazard statement looks to be
on track. MKK

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Beach Hazards Statement through Wednesday afternoon for
     CAZ101-103-104-109.

NORTHWEST CALIFORNIA COASTAL WATERS...
None.
&&

$$

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