Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 032256

National Weather Service Eureka CA
256 PM PST Sun Dec 3 2023

.SYNOPSIS...Heavy rainfall continues to impact northern Humboldt and
Del Norte counties this afternoon through late tonight. Gusty
ridgetop winds are also accompanying the heavy rain. Additional
light to moderate rainfall is expected early next week, with a
stronger system with the potential of heavy rainfall to occur during
mid week.


.DISCUSSION...Moisture flux associated with a moderately strong
atmospheric river has dropped southward toward Del Norte county
today to bring another round of moderate to heavy rain, mostly for
northern Humboldt and Del Norte Counties. Gusty southerly winds
from 25 to 40 mph are being recorded over the more prominent
coastal headlands and higher terrain across the northern portion
of the region. Late morning RAP mesoanalysis verified anomalous
PWAT values at 1-1.25 inches along the Far North Coast. Additional
rainfall amounts will be 1 to 2 inches for Del Norte and far
northern Humboldt counties from today through late tonight, with
locally higher amounts over higher terrain in Del Norte.
Maintained the Flood Watch for urban/small streams across Del
Norte and the northern portion of Humboldt counties, though it may
require trimming from the southern portion. Elsewhere, lighter
total amounts will range from few hundredths to half of an inch.

Moist onshore flow then continues into early next week and will aid
in additional shower activity. PWATS will remain anomalously high on
Monday, but the highest moisture flux will be north of the CWA, and
there will be more of an easterly component to the low level
winds. This will limit the potential for heavier precipitation
rates on Monday, but the soils will remain nearly saturated to
saturated over the Far North Coast. A stronger frontal system is
forecast to advance east across the NERN PAC as well, with hydro
hazards generally focused over WA/OR Monday night into Tuesday.
The front is then forecast to slide south toward NWRN CA Tuesday
night into Wednesday. A midlevel shortwave impulse may interact
with the front and yield an increase in precipitation rates as the
front moves onshore across the EKA CWA. After Wednesday, a
progressive upper flow regime is forecast to persist and aid in
additional rainfall, along with colder temperatures and some
mountain snow. ZVS/JJW


.AVIATION...Conditions have stayed mostly VFR/MVFR today. There were sporadic
bouts of rain, especially over Del Norte where weather had a "yo yo"
effect: up and down from VFR-IFR. Impactful weather can be expected
for ACV and CEC through afternoon/evening as model data continues a
trend of rain for the northern areas; lesser amounts over Mendocino
and Lake Counties. Added the possibility of mostly directional low
level wind shear (LLWS) at CEC...which may be more concerning for
general aviation. Also, gusty southerly winds will continue at CEC
due a pronounced pressure gradient flow. Precipitation should remain
simply "RA", but a few embedded "SHRA" not out of the question
today. /TA


.MARINE...Southerly winds gusting up to 30 kts will continue
through tonight, mainly focused in the northern zones. The southerly
winds will increase on Monday when gusts with near gale strength in
isolated northern areas. The southerlies will strengthen again
early Tuesday along a dynamic frontal system. A northwest swell
peaked this afternoon in the 12 to 15 foot range at 14 seconds.
The first of two long period west- northwest swells will build
tonight and through Monday, to the mid teens at 18 seconds. A
second larger, long period swell will then begin filling in on
Tuesday, peaking early Wednesday in the upper teens at 18 to 19


.HYDROLOGY...Additional moderate to heavy rainfall with a
moderately-strong atmospheric river will continue to impact the
northern portion of the CWA today. 24 hours total rainfall amounts
are forecast to range from 1 to 2 inches in Del Norte and far
northern Humboldt counties. More flash flooding impacts are
likely today mainly across Del Norte County due to additional rain
falling in a short amount of time. CREST soil moisture profile
continues to show the terrain to be saturated. As result, the
additional rainfall today will more quickly develop urban and
small stream flooding, or even flash flooding. In addition, small
rock and mud slides are possible in areas of steep terrain that
are already saturated. Reference the latest flood hazard products
for more information. /ZVS


.BEACH HAZARDS...A long period northwesterly swell will begin to
build in through the coastal waters tonight, and will continue to
build into Monday to around 14 feet at 18 seconds. This swell will
be sufficiently powerful enough for sneaker waves from significant
set behavior and beach runup. Large, unexpected waves can sweep
across the beach without warning, sweeping people into the sea from
rocks, jetties, and beaches. These sneaker waves can also move large
objects such as logs, crushing anyone caught underneath. A second
larger, long period swell will then begin filling in on Tuesday,
peaking early Wednesday in the upper teens at 18 to 19 seconds. This
will generate High Surf Advisory level surf breakers up to 25 feet
Tuesday afternoon through Wednesday.


     Flood Watch through late tonight for CAZ101>103-105-106.

     Beach Hazards Statement from Monday morning through Monday
     afternoon for CAZ104-109.

     Small Craft Advisory until 9 PM PST this evening for PZZ450.

     Small Craft Advisory until 3 AM PST Monday for PZZ455-475.

     Small Craft Advisory until 9 PM PST Monday for PZZ470.



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