946
FXUS66 KEKA 041257
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
557 AM PDT Tue Jun 4 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...A broad upper level ridging and above normal 500mb
heights will continue to build over NW California today. IR
satellite imagery shows this ridging "flatten" as a shortwave move
into WA. This is bringing a few high-level clouds streaming
across the northern portion of the forecast area. Otherwise,
mostly clear skies with patchy fog due to the radiational cooling
this morning. Interior temperatures are forecast to increase into
the mid 80s to mid 90s in the interior valleys, except in southern
Lake county where highs in the upper 90s are expected. Mainly
minor heat risk is expected for much of area today, with a
moderate heat risk for Lake County.

The warming trend will continue through Thursday. Interior heat
will build on Wednesday and then peak on Thursday. Model guidance
has been very consistent supporting 850 mb temperatures of 24 to
28C or so over much of the interior. High temperatures 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, but
a major heat risk is expected to occur over portions of Lake
County Wednesday and Thursday. The hottest day for Lake County
continues to look like Wednesday. 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
tonight into Wednesday morning 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 20 to 30 mph at
times...locally higher gusts possible over the King Range.

The interior heat coupled with higher upper level humidity may
yield an isolated thunderstorm with gusty outflow winds Thursday
afternoon/evening, primarily over the mountains of northeast
Trinity county. GFS and NAM model sounding guidances are
suggesting elevated instability and steep lapse rates over
northern Trinity County. SREF model guidances is also suggesting
the thunderstorm potential.

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.

Ensemble members and deterministic model guidances are showing an
upper- level trough moving over the area on Sunday. Dry weather
most likely persist with about 85% of the ensemble cluster
analysis with not precipitation over the region. However, this
trough may create sufficient instability for thunderstorms over
the interior mountains, 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

&&

.AVIATION...Residual moisture closest to the boundary layer has kept
mist and fog effects in play this morning despite the greater trend
being subsidence and drier air as clearing is expected with VFR at
most of the terminals through the day. KCEC and KACV could see a
return of IFR conditions overnight into Wednesday morning according
to MOS guidance but not all models are in agreement as high pressure
will likely keep things clear with anticyclonic motion. A return of
gusty northerlies at KUKI is likely this afternoon with soundings
showing winds mixing down with drier air all the way to the flight
deck. /EYS


&&

.MARINE...Combined wave groups this morning around 8 to 10 feet at
11 to 12 seconds will occasionally meet small craft criteria but
most of the concern will be for late tonight into Wednesday morning.
A combination of Gale force gusts and a long period swell from the
NW with 10 to 12 ft wave heights and periods around 16 seconds, will
produce hazardous seas in the northern waters and Gales in the
southern waters. Of particular concern is the threat for beach
hazards in the form of rough surf, and sneaker waves as weather will
be warm and inviting for beachgoers from Wednesday into Thursday. Do
not turn your back on the ocean! Also be cautious around inland
rivers with cold water and swift currents! /EYS


&&

.BEACH HAZARDS...A large long period NW swell will build early
Wednesday with significant swell heights up to 11 feet at 16-17
seconds during the morning. This high energy swell has the
potential to bring a moderate risk of sneaker waves. Shorter
period NW swell of 7-9 feet at 7-9 seconds may mitigate the risk
for the Mendocino coast. However, the risk remain with the
increasing of beachgoers as temperatures across the interior will
be hot. A beach hazard statement has been hoisted for the entire
coast. /ZVS


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Beach Hazards Statement from late tonight through Thursday
     morning for CAZ101-103-104-109.

     Heat Advisory from 8 AM Wednesday to 8 PM PDT Thursday for
     CAZ114-115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Hazardous Seas Warning from 6 AM Wednesday to 3 PM PDT
     Thursday for PZZ450-470.

     Gale Warning from 8 AM Wednesday to 9 AM PDT Thursday for
     PZZ455-475.

&&

$$

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