Alton, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

149
FXUS66 KEKA 240000
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
400 PM PST Sat Nov 23 2024

.SYNOPSIS...Series of fronts will bring periods of rain, mountain
snow and gusty southerly winds Sunday through Monday. Drier weather
and colder temperatures are anticipated for mid to late next.

&&

.DISCUSSION...Radar reflectivity imagery showed light showers
moving across the area this afternoon. A brief break in the rain
is expected this evening before precipitation increases again by
early Sunday morning.

The next round of moderate to locally heavy precipitation rates
is expected to arrive Sunday as a surface cyclone approaches the
west coast. Periods of light to moderate and brief locally heavy
precip is expected to continue Monday as another shortwave trough
progresses across the area. These fronts will be progressive and
have less moisture flux compared to our long duration AR Tue-Fri.
6-hourly rainfall and snowfall rates and storm total rain and snow
amounts are forecast to be much less with limited potential for
major impacts. We posted a weather story graphic of 2-3 day
rainfall totals on our web page and facebook page. Highest 2-3
day totals are expected over the King Range and Del Norte County
(2-4 inches of storm total rain). The precip is forecast to wind
down through the day on Tuesday as the northeastern Pacific trough
complex shifts eastward across the area and above normal 500mb
heights builds toward the west coast.

An occluded frontal boundary will approach the North Coast late
tonight into Sunday morning. The surface pressure gradient is
forecast to tighten by midday Sunday as a low level jet (925mb)
around 50 kts develops over the North Coast. A well-mixed boundary
layer near or along the surface front will allow for higher
momentum air to mix down to the surface. Gusts to 40-55 mph are
probable over the coastal headlands and higher terrain of interior
Del Norte and Humboldt. NBM and HREF ensemble means indicated
gusts of 25-35 mph for the lower elevations, while the ECMWF
ensemble indicated mean gusts near 50 mph for Crescent City and
near 40 mph for Humboldt Bay and Eel delta. Even below advisory
gusts could cause trees to uproot due to saturated soil.

Isolated low-topped thunderstorms will also be possible mostly
over the coastal waters and near the coast in response to mid
level cooling and southerly flow at the surface late Sunday into
Monday. The greatest risk for storms appears to be south of Cape
Mendo initially on Sunday. Convective activity is expected to
shift northward Sunday night into Monday. Some small hail is
possible. Freezing levels look to high for any accumulations. The
main threat will be lightning strikes and perhaps very brief
heavy downpours. Swift storm motions will preclude any major
concerns for flash flooding or debris flow.

Snow levels start around 3000-4000 feet Sunday, and are forecast
to gradually rise to about 4500-5000 ft through the day Sunday
into Monday. Up to 1 feet of snowfall is expected above 4500 feet
in NE Trinity County from Sunday afternoon into Monday afternoon.
A Winter Storm Warning is in effect from late Sunday morning for
elevations above 4500 ft in NE Trinity County, which includes
Scott Mountain Pass on Highway 3. Lighter snow accumulations
around 1 inch are possible for Buckhorn Summit and Trinity Center
before levels rise in the afternoon. Precip rates are much lighter
over lower elevations and the potential for low snow levels is
much lower compared to the heavy snow event we had on Wednesday
in NE Trinity.

Upper ridging is forecast to builds into the West Coast downstream
the mid-upper level trough Tuesday night and Wednesday. This will
restore more peaceful and dry weather mid to late next week,
though after multiple days of rain, valleys will no doubt fog up
during the night and morning hours. Chilly morning are expected
Wednesday and Thursday morning with low temperatures ranging from
mid 20`s to mid 30s. DB

&&

.AVIATION...Intermittent MVFR has plagued the Redwood Coast today as
scattered showers move over the coastal terminals. Shower activity
is forecast to decay tonight as a another front approaches the
coast. VFR is expected overnight, and south winds are forecast to
sharply increase Sunday morning. Winds increase through the day
tomorrow, and gusts of 30 to 40 kts are possible along the Redwood
Coast tomorrow afternoon. MVFR ceilings should redevelop by around
midday as this feature approaches, and intermittent IFR cigs and vis
from rain and mist are likely as it moves overhead. /TDJ

&&

.MARINE...Seas weaken through this afternoon as short period SW and
NW waves decay. Southerly and southeasterly winds will increase
tonight into Sunday as another surface low and cold front approaches
the coast. This front looks dynamic and unstable, with 40 to 50 kt
winds present just above the surface. Convective showers should
intermittently mix down these stronger winds across all zones,
especially as the boundary of the front sweeps overhead. Have
hoisted a gale warning in response. Greater uncertainty arises early
next week as additional frontal systems or troughs pin-wheel around
a nearly stationary surface low that will wobble around over the NE
Pacific, however winds generally look lighter with these waves.
Northerlies, at least for the outer zones, may return mid to late
next week as a rex blocking pattern develops offshore...with the
associated low centered to our south and offshore of the Central CA
Coast. This may bring a prolonged period of relatively light winds
and low seas late next week. MH/TDJ

&&

.HYDROLOGY...All main stem rivers continued to recede today. Eel
River at Fernbridge is forecast to recede below monitor stage late
this afternoon. Additional rainfall is expected to arrive Sunday
through Monday, with 6 hourly rain rates of 0.50in in the King
Range and windward slopes of Del Norte. Receding trends will
flatten out or trend up with minor rises, especially in the Smith
basin by the end of the 3 day period. Smaller streams and creeks
may be more responsive to short duration to modest rain rates and
minor impacts are possible due to saturated grounds. DB

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Wind Advisory from 6 AM to 4 PM PST Sunday for CAZ101-102-
     104>106.

     Winter Weather Advisory until 4 PM PST this afternoon for
     CAZ107.

     Winter Storm Warning from 10 AM Sunday to 4 PM PST Monday
     for CAZ107.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Gale Warning from 5 AM to 5 PM PST Sunday for PZZ450-455.

     Gale Warning from 2 AM to 5 PM PST Sunday for PZZ470-475.

&&

$$

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