Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 231246
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
446 AM PST Fri Feb 23 2018

.SYNOPSIS...Temperatures will remain slightly below normal during
the next 7 days as a series of storm systems move south across the
region. Showers will be likely with each system, and mountain snow
may accumulate at highway pass level Sunday night into Monday.

&&

.DISCUSSION...Friday morning surface observations show winds
weakening in the vicinity of Eureka/Arcata, which is allowing
temperatures to fall toward hard freeze values. Similar conditions
were observed near Crescent City north to Smith River. Elsewhere,
interior valley temperatures were in the teens and 20s. After
sunrise, abundant sunshine will aid in temperatures moderating
into the 40s and 50s.

The next upper disturbance to impact the region is forecast to
arrive on Saturday. This feature will aid in generating showers,
first across the coast during Saturday morning, and then interior
areas during midday into early afternoon. The greatest precip
amounts from 0.05-0.3 inches, will occur from central Humboldt
northward across Del Norte county. Elsewhere, precip totals will
be less than 0.05 inch. In addition, snow levels are forecast to
rise to around 2500 feet by afternoon. Thus, impactful snow
accumulations are not expected due to the combination of light QPF
and rising freezing levels.

A stronger storm system, characterized by 700 mb temperatures
near -17C, and 500 mb temperatures at or below -30C, will dig
south across NRN CA Sunday night into Monday. Snow levels near
2000 feet will be probable as a result, and could fall as low as
1000 feet. In addition, model guidance shows the digging trough
yielding a substantial amount of deep-layer upward vertical
motion augmented by a convective environment and westerly upslope
flow. Thus, the potential for impactful snowfall affecting
mountain travel corridors exists. In addition, forecast soundings
and model hail guidance supports small hail along the coast.

Beyond Monday...multi-model consensus supports continued troughing
over the WRN CONUS. However, timing/position differences in trough
evolution become large by Friday/Day 7, which yields low forecast
confidence.

&&

.AVIATION...Skies are clear at the major terminals this morning.
There are some lingering low clouds over portions of the interior.
More low clouds are evident in the strong N flow over the outer
coastal waters. Winds through Thursday evening remained fairly
strong, but they have dropped off and decoupled over the past
several hours. Winds will continue to gradually subside in the
lower levels, and low-level wind shear was not included in the
latest TAF package. Clouds will begin to enter the area from the
NW late in the afternoon and during the evening as the next front
approaches the area. Have included light rain in the forecast for
KCEC and KACV by late evening. VFR conditions are expected to
continue at KUKI. /SEC

&&

.MARINE...N winds will continue to diminish today, but advisory
level winds will continue over the S waters through the day. After
a period of sub-advisory winds this weekend (albeit just barely
in some areas), N winds are forecast to increase again on Monday
with gales possible over the S outer waters by Monday night.
Combined seas will build up to 17 feet in the outer waters during
this time period.

A small NW swell at around an 18 second period this morning will
gradually decay through the day on Sunday. A more substantial NW
swell will impact the area through the forecast timeframe, with
periods 8 to 10 seconds through Saturday, then 12 to 14 seconds on
Sunday into next week. /SEC

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...Hard Freeze Warning until 9 AM PST this morning for CAZ101-103-
     109.

NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 9
     AM PST this morning for PZZ450-470.

     Hazardous Seas Warning until 6 AM PST early this morning for
     PZZ450-455.

     Small Craft Advisory until 6 PM PST this evening for PZZ455.

     Gale Warning until 6 AM PST early this morning for PZZ475.

&&

$$

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