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000
FXUS66 KEKA 152142
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
242 PM PDT Mon Apr 15 2024

.SYNOPSIS...Gusty northerly winds are forecast through mid-week as
high pressure builds into Northwest California. Increasing
temperatures beneath the clearing skies will allow interior valleys
to reach into the upper 70s to possibly lower 80s by the middle to
end of the week. Marine stratus is forecast to return by the latter
half of the week as northerly winds subside.


&&

.DISCUSSION...An inverted ridge of high pressure will continue to
build into Northwest California as an upper cutoff low continues
its trek east. Low stratus and scattered high cirrus from this
morning continue to clear. Northerly winds will continue to
increase along the tightening pressure gradient between the
building ridge and departing low. Gusts 25 to 30 mph are likely
this afternoon along exposed headlands and coastlines from
Crescent City down to Point Arena. Gusts to 35 mph have already
been recorded on Cape Mendocino at the Mattole Road PG&E weather
station.

Warm air advection ahead of the building Pacific High promises a
return to summer-like conditions for the start of this week.
Temperatures are expected to steadily climb beneath mostly clear
skies, with highs likely to reach into the mid 70s in interior
valleys by Wednesday. Nightly offshore flow will also help to dry
out the interior as RH values decrease. Meanwhile, a recurring
pattern of strong northerlies will remain prevalent offshore
through midweek - this should prevent marine stratus from
completely inundating the coastline and encourage diurnal heating.
NBM indicates a high probability of coastal temperatures reaching
60 degrees by Wednesday afternoon.

As northerlies subside and shift to a westerly onshore flow late
this week, the marine layer will likely be able to deepen and spread
further inland beneath broad high pressure subsidence. This will, in
turn, dampen daytime warming for areas closer to the coast. Model
soundings and long-range deterministic models indicate strong low to
mid level warming and drying Thursday and Friday. Interior RH values
are forecast to decrease below 50%. Most interior valleys are
expected to have temperatures in the mid to upper 70s. NBM indicates
a high chance for temperatures above 80 for many interior valleys of
southern Mendocino and Lake counties. The warmest valleys of
interior Humboldt, Trinity, and northern Mendocino counties have a
slightly lower chance of temperatures above 80. However,
temperatures will most likely remain in the low 80s for these areas.

Long range model clusters begin to show the Pacific ridge eroding
into more of a zonal flow by this coming weekend. Currently, no
major storm systems are forecast for the next 7-10 days.


&&

.AVIATION...18Z TAF period: Coastal stratus has eroded this
afternoon. A strengthening low level inversion and wind-driven
terrain influence is holding stratus in some interior locations.
Northerlies are breezy to gusty this afternoon. Overnight weakness
in northerly winds and a small Humboldt Bay wind eddy may allow for
stratus advection northward into ACV (40 to 50%). Soundings resolve
this ceiling to be around 1000 ft AGL with a small chance for a
slightly lower level into IFR (20%). The eddy will not have
influence into CEC where northerlies will remain more resilient.
Northerlies will increase again Tuesday afternoon. UKI will remain
VFR with lighter winds and the occasional gust. Steep wind-driven
seas are on the increase, and will peak 12 to 14 feet Tuesday
through Wednesday. JJW


&&

.MARINE...Northerlies are strengthening this afternoon across the
waters. Gale strength winds will develop this evening, and will
spread south into Tuesday morning. The primary focus will be in the
outer zones. Expansion fans south of Cape Mendocino and Point Saint
George will bring areas of gale (<50% coverage) into the inners,
mainly into the afternoons and evenings through Wednesday. Ensemble
guidance model an at least partial collapse of the expansive ridge
of high pressure contributing to the northerlies late this week.
JJW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 AM PDT Wednesday for PZZ450-
     455.

     Small Craft Advisory until 9 PM PDT this evening for PZZ470.

     Gale Warning from 9 PM this evening to 5 PM PDT Wednesday
     for PZZ470.

     Small Craft Advisory until 9 AM PDT Tuesday for PZZ475.

     Gale Warning from 9 AM Tuesday to 5 PM PDT Wednesday for
     PZZ475.

&&

$$

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