Island Mountain, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

859
FXUS66 KEKA 091323
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
523 AM PST Sat Nov 9 2024

.SYNOPSIS...After a weak frontal passage Saturday, a more active
weather pattern will begin to develop starting late Sunday with
breezy southerly winds and widespread rainfall. The unsettled
pattern will likely carry through next week.


&&

.DISCUSSION...Some thin, high clouds are pushing in from the west
early this morning ahead of a weakening surface front. Surface
temperatures are chilly this morning after effective overnight
radiational cooling brought frosty and some freezing temperatures.
Only light to trace amounts of rainfall is expected through this
evening with this first front. Precipitation chances will remain
behind the front with some lingering showers possible, and will then
increase again late Sunday into early morning with the arrival of a
stronger front. There will be some IVT values up 500 with this
front, but it will be progressive, passing through relatively
quickly and with moderate southerly winds.

NBM holds an 80% chance for 2.5 inches of rainfall in 24 hours for
interior Del Norte and over the portions of the King Range and Cape
Mendocino. Amounts at lower elevations (like Humboldt Bay) will most
likely be around 1.0 inch with the southern half of the area seeing
0.25 to 0.6 inches.

The overall set up does not seem conducive to convective enhancement
with only moderate southerly wind aloft and very little instability.
Southerly winds will still quickly increase late Sunday with this
front. NBM currently has 50 to 70% chance of southerly wind gusts
over 40 mph along high terrain in Humboldt and Trinity with even an
increased chance of 60% of 55 mph gusts in the mountains of Del
Norte and portions of the King Range. These locations will likely
see some heavy rainfall rates due to their orientation to the
moisture driving winds. Though likely brief, Crescent City now has a
60% chance of reaching maximum wind gusts of 45 mph, and that aligns
with ECMWF ensemble mean and the NBM 90th percentile. There remains
up to 10% chance of some isolated thunderstorms in the post-frontal
instability Monday through Monday night, mainly over the northern
coastal waters and coast.

Ensemble-based guidance is highlighting precipitation and wind to
be potentially impactful for a second storm system mid to late
next week. Confidence is growing on this outcome looking at
probability for stronger wind gusts and instability. JJW


&&

.AVIATION...An approaching frontal boundary is spreading high clouds
across the area. The night satellite is showing some hints of
stratus. The HREF is showing very low probabilities of stratus on
the coast through the day. However, as the front approaches this may
push some stratus onto the coast. This front is expected to bring
some light rain later tonight, but 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.
MKK


&&

.MARINE...An approaching frontal boundary is bringing south to
southeast winds to the area this morning and these are expected to
increase through the day peaking late tonight as the front finally
passes through. Most models show these peaking around 10 to 20 kt.
The current swell moving through the waters is around 8 feet at 14
seconds and 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 to 15 kt.

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 to
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 to 15 kt on
Monday. The northwest swell is also expected to diminish to around 4
to 6 feet at 12 seconds.

Late Monday afternoon through Tuesday morning the models are showing
a large swell moving into the waters peaking around 18 to 20 feet at
16 seconds. This swell is 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 all in good agreement on this 18
to 20 feet wave reaching the waters off the coast of NW CA by early
Tuesday morning. Still a small shift in the track of the low could
result in a big 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


&&

.BEACH HAZARDS...The swell of 18 to 20 feet is expected to move into
the waters Monday night and Tuesday morning. This could bring
breakers of 20 to 24 feet to much of the coastline. Confidence is
growing on this and a high surf advisory may be needed to highlight
this as it gets closer. MKK


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Frost Advisory until 8 AM PST this morning for CAZ104-106-
     109-113-115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from noon today to 6 AM PST Sunday for
     PZZ470.

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

     Small Craft Advisory from 3 PM this afternoon to 6 AM PST
     Sunday for PZZ475.

&&

$$

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