401
FXUS66 KEKA 092245
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
245 PM PST Sat Nov 9 2024

.SYNOPSIS...A weak front will continue to pull clouds and cooler
air across the area this evening with possible very light coastal
drizzle. Stronger rain and gusty south wind will arrive late Sunday
into Monday with unsettled weather through the week.


&&

.DISCUSSION...The first of several cold fronts has started to impact
the area today. So far, the only effects of this first front has
been widespread midlevel clouds and gentle southerly wind. The front
itself will cross on shore late tonight. This will help push marine
influence further inland, but the general lack of moisture and
instability will will only support very light coastal drizzle at the
most with a less than 10% chance of even a 0.1 inch anywhere.

Moisture transport and southerly wind will gradually increase Sunday
as a much stronger, second cold front and upper level trough
approaches the area. Southerly wind will reach its peak late Sunday
night into early Monday morning with most likely gusts of 25 to 35
mph. There is a 30 to 50% chance of gusts over 40 mph along high
ridges in Humboldt County with more isolated gusts briefly possible
(50% chance) to 50 mph on the very highest peaks of the King Range
and Del Norte County.

Rain with this second front will mostly begin around sunrise early
morning, behind the strongest wind (especially for lower
elevations). Rain will be strongest for the northern half of the
area though wetting rain should be expected throughout the entire
area, and NBM is placing 70% chance of 0.5 inches of rain as far
south as Lake County. In terrain favored areas, 1.5 to 2.5 inches is
most likely with around 1.0 inch of rain for lower elevation areas.
More rain shadowed areas such as Humboldt Bay could see even less.
Though not too much rain, the progressive nature of the front will
cause most of the rain to fall over a short period of time (around 6
hours) meaning some rain rates of 0.2 to 0.4 in/hr are possible.
Though not hazardous, such rates will certainly increase the risk of
extra debris on area roads.

Rain showers and possible isolated thunderstorms (15% chance) will
continue to impact coastal areas through the day and evening on
Monday. An thunderstorms will be weak and isolated. After a lull
around Tuesday, there is high model agreement in another and ,most
likely slightly stronger system later in the week but timing remains
the most uncertain factor. Most models have generally moved the
timing forward compared to yesterday with the start of the storm
most likely either late Wednesday or during the day Thursday. Exact
precipitation spread remains large with most likely precipitation of
0.5 to 1.5 inches for upper elevations, though a solid 10 to 20% of
models show amounts up to 2.5 inches possible even for lower
elevation locations. Ensemble wind speeds are generally higher for
this late week front which may prompt a need for wind advisories.

In the far extended forecast, very cool air will build behind the
late week system. ROughly 80 percent of model ensemble show a brief
dry period around November 15th with a likely return to unsettled
weather (50 percent chance) after that. /JHW


&&

.AVIATION...An approaching frontal boundary is forcing middle/high
clouds to soar across the area. The day cloud satellite is showing
some hints of low clouds, yet as of right now, they seem to be
restrained to over the ocean away from the coast. The HREF is
showing very low probabilities of stratus on the coast through the
day. However, as the front approaches this may push some
broken/overcast low clouds towards the coast. This front is expected
to bring some light rain later tonight, yet it is not expected to
make it into Mendocino county. This rain could bring some periods of
MVFR conditions towards Sunday morning, but confidence is low on
this. Sunday shows southerlies persisting with multiple cloud layers
a possible mist degrading visibilities slightly, yet confidence on
category changes due to the mist is very low at the current
moment.


&&

.MARINE...An approaching stationary frontal boundary is bringing
south to southeast winds which have been increasing through the day
and will be peaking late tonight as the frontal system finally
passes through our area. Most models show these peaking at 10-20kt.
The current swell moving through the waters of 8ft@14s is expected
to persist through the evening. The small craft advisory
highlighting these winds and waves was pushed back a few hours.
Sunday morning is expected to see a brief lull in the winds between
systems with winds of only 10-15kt.

Sunday afternoon southerly winds start to increase again ahead of
the next front. These are expected to peak Sunday night into Monday
morning with strong to gale force winds. These will be the strongest
in the waters north of Cape Mendocino. The NBM is showing a 30-60%
probability of gale force wind gusts north of Cape Mendocino. To
highlight this we have issued a gale watch for the northern outer
waters. Winds are expected to diminish to around 10-15kt and the
northwest swell is also expected to diminish to around 4-6 feet at
12 seconds on Monday.

Late Monday afternoon through Tuesday morning the models are showing
a large swell generated by a strong low currently near the
Aleutians. Both the ECMWF and the GFS are in good agreement on this
low deepening to around 965 to 970MB as it moves into the Gulf of
Alaska over the next several days. The ECMWF and GFS wave models as
well as the NBM wave heights are in good agreement on this 18-20ft
wave group reaching the waters off the coast of NW CA by early
Tuesday morning. It is important to keep in mind that a small shift
in the track of the low could result in a substantial difference in
wave height. Wednesday models are coming into better agreement on
another front moving into the area potentially bring near gale to
gale force gusts again. MKK


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 PM PST Sunday for PZZ470.

     Gale Watch from Sunday evening through late Sunday night
     for PZZ470.

     Small Craft Advisory until 9 PM PST Sunday for PZZ475.

&&

$$

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For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png