186
FXUS66 KEKA 271250
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
550 AM PDT Sat Apr 27 2024

.SYNOPSIS...Light rain in the northern half of the forecast area
is expected this morning through Sunday. Cold temperatures could
cause frost at lower elevations as cold air advection sets in. Drier
weather weather is expected early next week.


&&

.DISCUSSION...Synoptic scale views of 500mb heights show a
persistent eastern Pacific high pressure system near the 140W - 150W
longitude and the 30N latitude. A PWAT heavy moisture plume will
wrap around the top of this high pressure system, aided by an upper
level low positioned over the Aleutian islands. The upper level jet
streaks between these two pressure cogs with the moisture plume
following geostrophic flow. A surface shortwave feature over the
coast will bring precipitation to bear on the PNW as the cold front
arrives a few hours after day break. Most of the precipitation will
accumulate north of Cape Mendocino. The probability of a rainfall
total greater than 0.15 inches is 50% through Sunday morning in Del
Norte and N Humboldt, when rain is expected to cease.

A cold core upper level low spinning off the coast of Alaska will
aide in cold air advection, at least until the previously mentioned
eastern Pacific high dominates our CWA with ridging and warmer air
by early next week. A frost advisory has been hoisted for morning
for elevations below 3000 feet, between 33 and 36 degrees. This has
been isolated to valleys of Trinity, and Northern Mendocino counties.

Otherwise, broad and flat ridging is forecast to build offshore as a
series of shortwave troughs brush the northern portion of the area,
mostly Del Norte county, with periodic precipitation chances into
mid week. Low-amplitude westerly flow will most likely keep
temperatures on the mild side and near seasonal normals through
early next week. Greater uncertainty arises mid to late week with
potential for flow amplification over the NE Pacific and above
normal interior temperatures. /EYS


&&

.Aviation...Low clouds are in place in many of the interior valleys
and along some of the coast. These are expected to lift later this
morning as a weak front approaches the area bringing southerly winds
of 10 to 20 kt today to the northern areas. This afternoon this
front will bring some light rain to KCEC and KACV. This will
gradually bring some lower ceilings late this afternoon and evening
along the Humboldt and Del Norte county areas. KUKI is only expected
to see some high clouds and breezy northwest winds. In the north the
ceilings will drop to IFR later tonight. Sunday clouds are expected
to clear in the morning in most areas. MKK


&&

.Marine...10 to 20 kt northerly winds will diminish this morning as
a weak front brings southerly winds up to 20 kt to areas north of
Cape Mendocino later this morning and into the afternoon. The short
period wind driven waves will diminish through the day as well. The
main swell moving into the waters this morning is around 5 feet at 9
seconds. A new swell hast started to move into the waters and
currently it is around 2 feet at 14 seconds.

Sunday the northwest winds will return across the area as high
pressure builds in. These will be slow to increase through Monday
lingering around 10 to 20 Kt.  These are expected to increase to
around 20 to 25 kt on Tuesday and persist through Thursday. The wind
driven waves associated with these winds are expected to peak around
6 to 9 feet by the middle of the week. In addition to the wind
driven waves the two swells are expected to generally merge on
Sunday. These will be around 8 feet at 12 seconds. These are
expected to diminish slightly, but will generally persist through
the week. MKK


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Frost Advisory until 8 AM PDT this morning for CAZ107-108-
     110-111-114.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 6 PM PDT this evening for PZZ455-
     475.

&&

$$

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