Area Forecast Discussion
Issued by NWS Eureka, CA
FXUS66 KEKA 190014
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
414 PM PST Wed Jan 18 2017
.SYNOPSIS...Heavy rain and strong winds are winding down tonight,
and will be replaced by showers and occasional thunderstorms near
the coast. Light snow can be expected above 2500 to 3000 feet.
Additional storm systems can be expected through the week,
including more heavy rain, strong winds, mountain snow and very
large surf and hazardous marine conditions.
.DISCUSSION...Heavy rain and strong winds are winding down
throughout the area this afternoon as a sharp cold front pushes
inland. Rain totals throughout the region have been very close to
predicted values, with widespread totals ranging from around 1.5 to
4 inches across Northwest California over the past 24 hours.
Strong wind gusts were commonplace this morning, including along
the immediate coast and near Humboldt Bay where gusts of around 40
to 50 mph were recorded. Fortunately these winds are expected to
rapidly diminish late this afternoon as the cold front pushes
farther inland. Behind the cold front, heavy rain will transition
to showers, allowing overall rain rates to diminish. However, some
stronger showers will be capable of producing heavy bursts of
rain along with small hail, occasional lightning strikes and gusty
winds along the immediate coast overnight and Thursday morning.
Farther east, much colder air has persisted across the Trinity
Horn today thanks to a combination of trapped cold air and upslope
flow, resulting in persistent snow. Several inches of snow has
already fallen along the Highway 3 corridor, even all the way to
the Trinity Lake level. This snow will continue for the next few
hours, but should diminish in intensity overnight. Some light
snow/graupel will be possible to even lower elevations, but is not
expected to accumulate.
Scattered showers will continue through the day tomorrow, with
snow levels falling to around 3000 to 3500 feet area-wide. The
next storm system will move into the area overnight tomorrow,
bringing with it more widespread precipitation and gusty winds,
although neither is expected to be quite as heavy/strong as
todays system, particularly along the coast. Still, some wind
gusts can be expected to reach close to 45 or 50 mph up along the
typical windy ridges and peaks. Snow levels will be lower
throughout the area with this system though, likely ranging from
2500 to 3500 feet across the region. Several inches of snow can be
expected above these elevations Thursday night through Friday
morning especially, as this is when temperatures are expected to
be lowest and precipitation rates the highest. Light snow may
continue through the day Friday as well as showers move in behind
yet another cold front. A Winter Storm Watch may need to be
considered as current headlines expire, as several inches of new
snow will be possible in many areas with this next system.
Showers will continue through early Saturday, with continued
light snow around 2000 to 3000 feet and chilly temperatures. The
biggest concern during this time frame may actually be along the
beach, where a very large swell will result in high surf and
dangerous conditions. More details can be found in the marine
All eyes then turn to the final system in this series, which is
expected to impact the region late Saturday through early Monday.
This system has the potential to be the strongest of the three
systems, with notably strong winds, periods of heavy rain and
snow all legitimate concerns. This remains several days away, so
stay tuned for more updates regarding the weekend storm as we get
a bit closer to the event. /BRC
.HYDROLOGY...While heavy rains are beginning to diminish, main
stem rivers will continue to rise through the night and into
tomorrow morning. River levels are not expected to crest to nearly
the same levels as last week. However, several rivers are forecast
to reach monitor stage, with the exception of the Navarro which is
expected to crest above flood stage yet again overnight tonight.
The last of the rivers to crest will be the Eel river at
Fernbridge, which is expected to crest tomorrow afternoon just
below it`s flood stage of 20 feet. Rivers will recede through the
day tomorrow. Additional steady rain will cause rivers to rise
again Friday, but lighter rain rates will keep levels below what
is expected today and tomorrow. Heavy rain and river rises are
expected again over the weekend, however, the magnitude of
potential river stages remains highly uncertain at this early
stage. Urban and small stream flooding will recede through the
night tonight. /BRC
.AVIATION...A mixed-bag of flight hazards occurred across
regional airports and airfields throughout the day as a
significant storm system continued to impact Northwest California.
LLWS (low level wind shear)was added to the ACV & CEC Tafs
(Terminal Aerodrome Forecast Sites)from morning to mid afternoon.
Throughout the day CIGS and VIS were mostly MVFR-VFR but
frequently down to IFR across the region especially during periods
of moderate to heavy rains. Winds have also remained robust over
the area. Some higher elevation airfields had snow. The associated
coldfront will moved across the North Coast by late
afternoon/early evening...then move inland. Tonight/ Overnight,
conditions are expected to turn a little unstable... therefore
changing steady rain to showers with the possibility of a few
thunderstorms developing. TA
.MARINE...A strong area of low pressure, about 150 miles west of
Olympia, Washington, continues to churn northeastward. It`s
associated trailing cold front is approaching our coastal waters
as we speak. Ahead of this feature, a stronger than forecast low-
level jet has allowed winds to become quite strong, with gusts
near/slightly over 40 knots having been observed at Crescent City
and Eureka, and the offshore buoys at 17 miles southwest of Eureka
(46022) hitting 54 knots, and the buoy 19 miles north of Point
Arena showing 49 knots.
Although brief periods of reaching Storm Force conditions are in
progress, the cold front crossing the region will allow winds to
rapidly decrease this evening as the low-level jet axis slides east.
Additionally, the Gale Warning does have gusts to 50 mph in the
forecast, so we`re leaving the current headlines in place as is.
The next forecast challenge will be with the storm for the end of
the work week. The latest model data continues to show that a strong
dynamic fetch setup will develop, with model forecasts showing waves
topping the 25 to 35 feet range. For now, we`ll continue to take a
middle of the road approach, with waves around 28 feet expected.
These waves will be accompanied by periods around 18 seconds (at
current forecast). These parameters will fall solidly within
hazardous seas conditions, and a watch and eventual upgrade to a
warning is a distinct possibility. /PD
CA...Wind Advisory until 4 PM PST this afternoon for CAZ101>106.
Winter Storm Warning until 4 AM PST Thursday for CAZ107.
NORTHWEST CALIFORNIA COASTAL WATERS...Gale Warning until 6 PM PST this evening for PZZ450-455-470-475.
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