Area Forecast Discussion
Issued by NWS Eureka, CA

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885
FXUS66 KEKA 242306
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
306 PM PST Sat Feb 24 2018

.SYNOPSIS...A storm system will bring rain on Sunday with mountain
snow and small hail possible Monday morning. Otherwise a broad
trough over the region will prolong an active weather pattern and
unseasonably cool temperatures through next week.

&&

.DISCUSSION...Showers will diminish into the afternoon as dry air
moves in behind the passing weak front. There will be a brief break
from shower activity tonight as the next storm system approaches
northwest California. Rain will first impact Del Norte County Sunday
morning and spread southward towards Mendocino County by later
Sunday night. Rainfall totals will not be significant with broad-
brush totals ranging from 0.75 to 1.25 inch to the north and 0.25
to 0.50 inches possible across Trinity and Mendocino Counties.
Snow levels will fall behind the main precipitation band to 1500
to 2000 feet by early Monday morning. Snow accumulations will be
possible across highway passes, however, the heavier precipitation
will occur when snow levels are around 3000 to 4000 feet. Expect
any snow accumulations to be associated with shower activity early
Monday morning. Showers should cease by Monday afternoon with
ridging resulting in mostly dry conditions through Tuesday. In
addition, there will be a marginal threat for coastal hail showers
Monday morning.

Broad troughing across the western United States will not only bring
unseasonably cool temperatures through next week but will also
prolong a generally active pattern. The next storm system is
forecast to materialize during the Wednesday through Friday time
frame. Model output indicates this system will impact the region in
two phases. The frontal phase will occur late Wednesday afternoon
into the evening, with strong southerly winds veering to westerly
with the frontal passage, potentially yielding strong gusts for
exposed coastal and ridgetop locations. In addition, heavy
precipitation appears probable along/ahead of the front. The second
phase will occur Thursday afternoon into Friday as very cold
temperatures aloft spread across the region with an occluded upper
low. This environment will result in a steep lapse rate/convective
regime accompanied by low freezing levels. Heavy mountain snow and
coastal hail will be possible as a result. JG/KML

&&

.AVIATION...Coastal airports/airfields came under the influence of
a weak low pressure trough today. This weather system was
accompanied by mostly light rain (some snow over higher terrain
airfields), reduced CIGS/VIS and breezy winds. Both ACV and CEC
air terminals frequently reported CIGS in MVFR...and briefly IFR.
Scattered showers should linger across the area through middle
afternoon before high pressure briefly rebuilds over the region
through evening. Weather should again worsen Sunday morning and
continue to decline through the remainder of the period as another
disturbance approaches NW Calif. Over Interior Mendocino today,
prevailing conditions were VFR except for some late morning/early
afternoon MVFR reports...especially at UKI.

&&

.MARINE...For the most part winds will remain sub-advisory today
through Sun. North winds are forecast to increase again on Mon with
gales possible over the southern waters by Mon night.

A NW swell will build to around 10 ft tonight and fluctuate from 8
to 10 ft through Sun, which combined with other short period swells
leads to 9 to 12 foot waves. Ended up hoisting a Small Craft
Advisory for the northern and southern outer waters on Sunday
because of the combined sea state and increasing winds late in the
day. A more substantial short period NW swell should build Sun night
into Mon. This swell will combine forces with shorter period wind
waves to produce seas around 17 feet south of the Cape by Mon night.
/DB/KR


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory from 4 AM Sunday to 9 AM PST Monday for
     PZZ470.

     Small Craft Advisory from 9 AM Sunday to 9 AM PST Monday for
     PZZ475.

&&

$$

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