Smith River, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

367
FXUS66 KEKA 241327
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
527 AM PST Sun Nov 24 2024

.SYNOPSIS...Series of fronts will bring periods of rain, mountain
snow and gusty southerly winds Sunday through Monday. There is a
slight chance (10-20%) of isolated thunderstorms along the coast
this evening into Tuesday morning. Drier weather and colder
temperatures are anticipated for mid to late next.


&&

.DISCUSSION...Satellite imagery showed an area of cyclonic
circulation positioned over the NEPAC overnight. This feature
will gradually drift southward throughout the day today, while an
embedded shortwave trough approaches and swing northeastward
toward Northwest California and the Pacific Northwest this morning
and afternoon. Doppler Radar depict showers and isolated thunderstorms
moving across the local waters, with some occasional intrusions
of showers inland over Cape Mendocino. Moisture will continue to
increase through this afternoon. A low- level jet in advance of
the approaching front will bring warm air advection in from the
west- southwest and aiding in snow levels rise, resultant in
stratiform precipitation. Moderate to locally heavy precipitation
rates is forecast to arrive this afternoon as a surface cyclone
approaches the west coast. Periods of light to moderate and brief
locally heavy precipitation 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. ECMWF Extreme Forecast Index (EFI)
highlight Monday in the 50th- 60th percentile above normal
precipitation along the North Coast, especially for Del Norte
County and northern Humboldt. Post-frontal showers are forecast to
wind down through Tuesday morning. Total rainfall amounts from
this system are forecast to range from 0.50 to 1.5 inches from
this afternoon through late Monday night. The highest amounts are
expected across the interior Del Norte and the King Range with
total rainfall of 2 to 3 inches. The lowest amounts are forecast
for southern Mendocino and Lake counties with total rainfall from
0.30 to 0.70 inches.


The surface pressure gradient is forecast to tighten by midday
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 around 40 mph for Humboldt Bay and Eel
delta. Even below advisory gusts could cause trees to uproot due
to saturated soil. A Wind Advisory is in effect through 4 PM PST
this afternoon for Del NOrte and Humboldt counties interior
mountains.


A colder air aloft will subsequently spread across the West Coast
this evening into Monday. As result, instability will increase to
around 100- 200 J/kg of CAPE this evening and tonight.
Instability could allow for some isolated low-topped thunderstorms
(10 to 20% chance) over the waters and right along shore, but any
storms will be weak and short lived. The greatest risk for storms
appears to be south of Cape Mendo initially late this afternoon.
Convective activity is expected to shift northward tonight 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/ZVS




&&

.AVIATION...Largest concerns will be wind gusts in advance of an
approaching cold front. At least a 50% chance of 24 hour max wind
gusts reaching 40 KTS at KCEC today (and 33 KTS at KACV), so
prevailing gusts this afternoon of 29 KTS at KCEC and 22KTS are not
only appropriate, but perhaps not quite high enough. Strongest gust
should occur in the 17Z to 01Z time frame this late morning to late
afternoon. AT KUKI, probabilities for MVFR ceilings or lower
decrease from near 70% at forecast issuance this morning to near 30%
by 20Z this morning over time at KUKI, only to increase to 50-50%
after 07Z. Chance of MVFR ceilings or low increase to 50-60% for
coastal terminals by 01-03Z. Low-level wind shear may be a problem
for a short window either side of 00Z today along coastal terminals,
and perhaps briefly at UKI at a few hours after 00Z with a low-level
jet axis between 900 and 850 mb crossing the area this
afternoon/evening. /MH


&&

.MARINE...Biggest issue will be south winds ahead of an approaching
cold front. Roughly at least a 50% chance of getting 24 hour wind
gust maxes top out in the 50-55 KT range, so locally higher gusts to
near 55 KTS are certainly in the realm of expectations near and north
of Cape Mendocino, as well as near stronger convective
showers/storms. The gale warning running through today will almost
certainly need to be replaced by a small craft advisory for at least
the northern waters for both steep seas and wind speeds. GFS model
indicates potential longwave swell by perhaps the Tuesday/Tuesday
night time frame, but there is rather high uncertainty of the timing
of the swell. /MH

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Wind Advisory until 4 PM PST this afternoon for CAZ101-102-
     104>106.

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

NORTHWEST CALIFORNIA COASTAL WATERS...
     Gale Warning until 5 PM PST this afternoon for PZZ450-455.

     Gale Warning until 5 PM PST this afternoon for PZZ470-475.

&&

$$

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