248
FXUS66 KEKA 241205
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
435 AM PDT Fri May 24 2024

.SYNOPSIS...Cooler than normal temperatures are forecast through
Saturday. Possibility for light coastal drizzle will increase this
evening and overnight, followed by a return of modest northwesterly
breezes on Saturday.

&&

.DISCUSSION...Much more extensive coastal stratus is expected
today. River valleys should clear out with daytime heating and
mixing, while clouds persist through much of the day over the
North Coast or Humboldt Bay region. Skies have been clear with
only wispy cirrus even along the Del Norte coast and coastal areas
of SW Humboldt. Temperatures overnight have been warmer for the
most part with the usual colder RAWS around 38-42F as of 4 AM. Not
confident that a frost advisory is necessary with the minimum
duration of 2 hours for 36F or less rapidly closing in.

Otherwise, daytime temperatures will remain below normal today
and Saturday as a weak upper trough remains over the area. Normal
high temperatures are about 80F for Willow Creek, Weaverville and
Ukiah. A shortwave trough in NW flow aloft will bring an influx
of shallow moist air to the North Coast this evening and drizzle
and fog are highly probable. Moderate northwesterly breezes are
forecast to return to coastal areas on Saturday as surface high
pressure rebuilds offshore behind the front. The onshore breezes
are not forecast to be quite as strong as the last couple of
days, but should scour out the stratus. Unfortunately, the stratus
will probably reform around Humboldt Bay Saturday night, but the
potential for low visibility in fog right now is not looking all
that high, less than 14% chance, Saturday evening. High resolution
ensemble forecast, HREF, should shed more light on the potential
for actual fog with vsbys less than 1/2SM for the remainder of
the weekend and early next week.

Broad and flat ridging aloft will build back on Sunday and hold
into early next week. Above normal 500mb heights and warmer 850mb
temperatures will result in above normal interior temperatures
through the end of next week. Rate and progression of the warming
remains uncertain. NBM GUIDANCE remains firm and continues to
support the idea of above normal max temps (>80F) in the interior.
By the latter portion of the week, highs around 90F for the warmest
inland valleys are forecast. Coastal gloom with gray skies may be
the norm next week under a warmer airmass and onshore wind flow.
Some signs for stronger offshore flow around the end of the week
with possible warming for coastal areas or this could just turn into
another wind reversal with a shallow marine airmass pooling up
nearshore again. DB

&&

.AVIATION...12Z TAF
ACV/CEC...Coastal stratus formed along the coast overnight with
increasing low level moisture associated with a passing shortwave
trough. Early morning profiler data reveals a deepened marine layer
from the trough. Sounding data and ensemble guidance points to IFR
to LIFR ceilings and patchy fog through the morning hours, but the
deepened state and subsidence behind the shortwave is currently
hindering these lower cloud levels. Light offshore flow has held the
stratus just south of CEC, but it should make further progress into
the terminal.

The deepened state of the marine layer, the arrival of ample mid to
high level clouds, and onshore flow will likely lock in the stratus
over the terminals much of the day, with a chance for afternoon
scattering. An additional shortwave trough will move through
tonight. This will further deepen the marine layer, and induce light
drizzle. There are high probabilities for ceilings below 1000 ft (70
to 80%) over the terminals, through there does seem to be
variability in ceiling heights and visibility towards the end of the
TAF period.

UKI...VFR conditions will prevail through this period as mid to
upper cloud cover increase ahead of another shortwave trough. WNW to
NW winds will generate some gusts this afternoon in the 20 kt area.
A further deepening marine layer will increase chances for stratus
to spill over from the west late tonight, but confidence is too low
for TAF inclusion.

&&

.MARINE...A passing shortwave trough is passing through, and this
is allowing for the northerly winds and seas to ease. As winds drop
to around 12 kts in the northern zones, the southern waters will
continue to see winds up to 20kts around and south of Cape Mendocino
today. Seas will drop to 3 to 5 ft this afternoon, consisting of a
small NW at 8 seconds, and a small 2 ft SW swell at 15 seconds. The
northerlies will slighlty increase tonight behind the trough. There
will be more of the same through the weekend and into next week,
with northerly winds focused more south of Cape Mendocino. Coverage
of 21 kt or greater winds looks to warrant additional Advisories
through the weekend in the southern zones.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Frost Advisory until 8 AM PDT this morning for CAZ108.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 AM PDT this morning for PZZ455-
     475.

&&

$$

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