292
FXUS66 KEKA 032215
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
315 PM PDT Mon Jun 3 2024

.SYNOPSIS...Hot, dry weather will rapidly build by mid week with
high heat risk for many interior valleys, especially Lake County,
Wednesday and Thursday. Breezy north to northwesterly winds will
return Wednesday and Thursday, with the strongest gusts over the
coastal headlands and exposed ridges. Isolated thunderstorms are
forecast for the northern Trinity mountain on Thursday during the
late afternoon and evening.

&&

.DISCUSSION...Shallow moisture in the wake of a late season cold
front will linger across the area tonight into Tuesday morning.
The shallow humidity along with recent rainfall will most likely
lead to fog and low clouds in the interior valleys. Coastal areas
north of Cape Mendocino may fair better in terms of low stratus
formation as a decaying post frontal trough approaches from the NW.

Broad and flat upper level ridging and above normal 500mb heights
will build quickly over NW California tonight into Tuesday.
Interior temperatures are forecast to increase into the mid 80s to
mid 90s in the interior valleys on Tuesday except in southern Lake
county where highs in the upper 90s are expected. Interior heat
will build on Wednesday and then peak on Thursday. High temps in
the hottest valleys are expected to range from 100-105F degrees.
The heat risk is forecast to be minor to moderate over the area
Tuesday, but a major heat risk is expected to occur over portions
of Lake County Wed and Thu. The heat will have impacts on anyone
without effective cooling and/or adequate hydration. As a result,
a Heat Advisory remains in effect for Lake County from Wednesday
morning through Thursday night. A heat advisory may also be
necessary for Trinity, interior portion of Mendocino and NE
Humboldt where temperatures are forecast to peak to 100F or
hotter. Temperatures along the coast are expected to warm up as
well, but marine air and stratus will most likely return by
midweek as northerlies increase offshore. This will put a damper
on the warming potential for the North Coast. Highs in the mid to
upper 70s in the lee of Cape Mendocino, across coastal SW
Humboldt or around Shelter Cove is likely, however.

Additionally, a thermal trough is expected to develop near the
coast Wednesday. This will promote breezy north-northwesterly
winds each afternoon Wednesday and Thursday over the exposed
ridges and coastal headlands, with gusts from 25 to 35 mph at
times...locally higher gusts possible over the King Range. NBM
probabilities show a 60% to 80% for gusts of 40 MPH or more in
the King Range, and 45% chances for Pt St George.

Some moist inflow from the south will bring the potential for
late afternoon and evening thunderstorms on Thursday for northern
Trinity county. There may even be overnight thunderstorms. GFS
and NAM model sounding guidances are suggesting elevated instability
and steep lapse rates over northern Trinity County. At this point,
we have a slight chance of thunderstorm over the Trinity Horn
Thursday evening, where thunderstorms development looks possible.

Friday and into the weekend, the ridge starts to shift eastward
and the flow aloft becomes more westerly. A deeper marine layer
should bring cooler-damp air to the coastal counties, mostly
north Cape Mendocino. Trinity, eastern Mendocino and Lake counties
are not expected to see much change on Friday. Interior temperatures
will moderate over the weekend, but most likely remain above
normal, An upper trough may create sufficient instability for
thunderstorms over the interior mountains on Sunday, primarily
Trinity County. There is still a great deal uncertainty at this
point and for now will hold off on adding storms to the forecast.
ZVS/DB

&&

.AVIATION...Satellite imagery shows broken mid to low level ceilings
still lingering around the coastal terminals this afternoon, with
ACV dipping in and out of IFR conditions as ceilings scatter out.
Otherwise, light post-frontal WNW winds and scattered cirrus are
will lend to VFR conditions across the region. A thermal trough
developing out of the central valley is producing strong northerly
gusts at UKI this afternoon beneath mostly clear skies. Winds
expected to remain northerly while diminishing overnight. HREF
indicates MVFR/IFR ceilings returning to the north coast tonight
into early Tuesday morning as high pressure builds into the area,
deepening the marine layer. Stratus will likely linger north of Cape
Mendocino, reinforced by a light southerly wind reversal along the
coastline. Hi-res models suggest IFR ceilings with decreasing
visibility`s in the hours leading up to sunrise. JMM


&&

.MARINE...A moderate mid-period swell 6-8 feet at 8-10 seconds is
dominating the sea state amidst post-frontal northwesterly winds,
with stronger winds observed in the southern waters. As the axis of
an offshore ridge extends into NorCal, a trailing cold front
associated with an upper shortwave over the PNW will produce a split
flow regime in the northern waters. Northerly flow is expected to
continue increasing in the southern waters while weak southerlies
develop north of Cape Mendocino. As the area of high pressure builds
into the west coast, northerly flow will intensify across the waters
late Tuesday into Wednesday. Expansion fans extending lee of
southern OR and Cape Mendo are forecast to produce near-gale force
winds Wednesday afternoon into Thursday, beginning in the southern
waters before expanding into the northern outer waters.

At the same time, a fairly compact low churning in eastern portion
of the Gulf of Alaska will produce a large long period NW swell late
Tuesday afternoon. This swell is expected to arrive Wednesday
alongside the elevated gale force gusts to produce a chaotic sea
state. Combined wave heights have the potential to exceed 14 feet at
14 seconds Wednesday afternoon into early Thursday in the southern
and northern outer waters. The northern inner waters will likely be
slightly sheltered from the strongest wind gusts, while all zones
are expected to subside to sub-10 foot wave heights as the swell
decays. JMM

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Heat Advisory from 8 AM Wednesday to 8 PM PDT Thursday for
     CAZ114-115.

NORTHWEST CALIFORNIA COASTAL WATERS...
 Gale Watch from Wednesday morning through Thursday morning
     for PZZ475.

&&

$$

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