Cold Weather Advisory 5, NWS Eureka, CA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
248 PM PST Sun Dec 29 2024

.SYNOPSIS...Widespread rain has eased this afternoon and will
continue to do so into the early evening. Dry conditions will return
for most of Monday and Tuesday as ridging builds over the west
coast. Rain chances return Tuesday night into mid week.

&&

.DISCUSSION...After a 24 hour-plus period of rainfall, an
anticipated flooding response has manifested on major stem rivers
as well as streams and creeks. Ponding will begin to flow back out
of storm drains as the tide ebbs this afternoon. Watershed response
to the steady and sometimes heavy down pours, are causing minor
flood stages to be breached or approached. The Smith, Eel, Russian
and Mad rivers have all been issued Flood Watches or Warnings. Most
of which will expire tonight. Particular attention is being focused
on Mad River - Arcata and Eel river at Fernbridge. These major stems
are in a Flood Watch presently and could be upgraded to a Warning at
any moment. The effects are not forecasted to be major but caution
will need to be observed as flooding at low lying points are
possible. The Russian River at Hopland did rise sharply, exceeding
the peak stage by measure and timing. The Flood Warning for Hopland
will last through the evening and into the early morning hours. Be
especially careful at night as unseen flooded areas abound.

Widespread rain has come to an end this afternoon leaving scattered
showers and isolated thunderstorms into tonight, primarily in Del
Norte and Humboldt counties, though some chances will spread south
into Mendocino County through Monday morning. Drier conditions are
likely Monday through most of Tuesday as ridging builds back over
the west coast. The next chance of rain will return late Tuesday
into mid week when a storm impacting Oregon will likely sag south
into Northwest California. Rain chances will be highest in Del Norte
and Humbodlt counties, with possibly no rain reaching the southern
areas of Mendocino and Lake Counties. Depending on where this front
stalls, another system following on its heals could bring more rain
to the region late in the week as well. This is a change over what
was in the models even only two days ago. So stay tuned for updates
on how the conditions will be for the remainder of the winter
holiday period. /RPA /EYS

&&

.AVIATION...Conditions have improved this afternoon in the wake a
cold frontal passage this morning. Brief periods of MVFR
ceilings/viz with passing showers are still being observed with
post frontal showers. A colder, drier air mass will filter out any
remaining showers overnight into Monday as high pressure begins
to build into the PNW. With the ground very saturated and
temperatures in the 30's and low 40's possible along the coast -
and lower in interior valleys - persistent low level ceilings and
ground fog are possible across all terminals tonight. Westerly
flow is still dominant but will gradually ease this evening and
turn offshore. This may keep visibility's out of IFR, as both HREF
probabilities and model soundings show ceilings remaining around
2000 feet through Monday morning. HREF shows a slightly stronger
signal for reduced viz at UKI, especially below 2000 feet.

&&

.MARINE...Conditions are easing considerably as winds diminish
and the energy from a westerly swell gradually decays. Small craft
conditions will linger through early Monday morning as seas
finally fall below advisory levels. High pressure will begin to
build into the north coast early this week, enhancing northerly
winds south of Cape Mendocino Monday into Tuesday. Winds and seas
are not expected to exceed 5 to 8 feet until midweek, when a weak
upper shortwave dips down into the PNW and generates stronger
southerly flow alongside a 10 to 12 ft mid-period westerly swell.
There is still considerable uncertainty surrounding the strength
of this system, especially regarding winds. Otherwise, wave
heights are forecast to remain above 10 feet as this swell energy
persists into the weekend.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Flood Watch until 6 PM PST this evening for CAZ101>103-105-
     106.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 AM PST Monday for PZZ450-455-
     470-475.

&&

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