931
FXUS66 KEKA 312148
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
223 PM PDT Thu Jul 31 2025

.SYNOPSIS...Chance of thunderstorms over the interior of Northwest
California through Friday. Storms may produce gusty outflow winds,
heavy rain and hail. Interior thunderstorms will be possible over
the weekend, primarily on Sunday.

&&

.DISCUSSION...

A mid-level cyclonic circulation was located to the NE of our
forecast area today with wrap around convection developing over the
peripheries of Del Norte and Trinity Counties. So far deep moist
convection and thunderstorms have been just outside the borders with
Siskiyou, Shasta and Tehama Counties with generally SW and W storm
motions. CAPE, high EL`s and inverted-V profiles remain sufficient
for pulsed type storms again today across Trinty County. Convective
allowing models from the HREF continue to show clustering of 45 to
50dBz paint-balls over Trinity County. A few members from the HREF
continues to indicate heavy precip rates over 0.40in/hr over
northern Trinity late today into early evening. Short-fused warnings
for hail, heavy rain and outflow winds may be necessary again today.
Deep moist convection will probably wane quickly after 8 PM this
evening with loss of daytime heating.

Friday will also feature another round of thunderstorms, confined
to mostly the northern Trinity mountains and eastern fringes of Del
Norte and NE Humboldt along the Siskiyou county border. Potential
for thunderstorms decreases substantially on Saturday with drier
westerly flow spreading across the area and higher 500mb heights.
A colder trough will approach on Sunday bringing yet another round
of showers and thunderstorms to the interior mountains. Otherwise,
this trough will bring cooler temps and gusty westerly and
northwesterly winds Sun into Mon.

Interior temperatures will likely begin to warm by mid next week.
How warm remains uncertain. 500mb heights pump up to 588DM or
more by late next week and suspect some of the typically hot
valley locations will reach or exceed 100F. The risk for a long
duration heat wave may be mitigated by persistent and frequent
troughs busting down on the ridge from the NW. Deterministic
models are starting to indicate a flow pattern favorable for more
interior convection and thunderstorms late next week with a closed
500mb circulation offshore the California coast and ESE winds aloft.

&&

.AVIATION...

With probabilities of ceilings lifting out of IFR this afternoon,
you can expect improving flight categories well into the evening.
This is also being verified with observations at the airports of
KACV and KCEC. Overcasts skies around 1000 feet will break and
scatter out, further improving visual and optical conditions
through at least 3-4z. Northerly winds dominate through the TAF
period at or below 10kts with gusts a few kts higher than the
sustained winds. Expect IFR conditions to return tonight(3-4z)
with almost a 60% chance of ceilings <500 feet at KCEC and KACV
likely dropping ceilings sooner.

&&

.MARINE...

Northerly winds will remain enhanced today through Friday in the southern
waters. Northern waters will slightly decrease today, mostly below
21 kts. Locally stronger winds with gale force gusts are expected
in areas downwind of Cape Mendocino. Short period wind waves will
persist over 7 feet in windy areas today. Stronger than normal tidal
currents and lingering surges from the tsunami may continue in harbors
and channel inlets today, especially in Crescent City.

&&

.FIRE WEATHER...Isolated to scattered thunderstorms are expected
again this afternoon and early evening, mostly over Trinty County
(fire weather zone 283). Isolated strikes are possible on the
eastern periphery of Del Norte and Humboldt Counties, but SW flow
aloft and westerly storm motion will likely keep the lightning
activity isolated at best. Storms have been producing precipitation,
rain and hail. Rain gauges and other reports revealed mostly below
one tenth of an inch, but there have been much higher amounts on
the order of 1" or more. There have been some isolated new fire
starts too with drier strikes. Thus we will continue to include a
headline in the fire weather forecast for isolated to scattered
thunderstorms and possible new ignitions. Another trough will
approach on Friday in the SW flow aloft. This should maintain the
threat for storms and isolated dry strikes for the Klamath
Mountain, mostly in Trinity County. Temperatures aloft and
stability will likely increase on Saturday and result in a
significant reduction in thunderstorms probabilities for our
forecast area. A short wavelength trough will approach on Sunday
and then progress across the area Sunday night. Granted the
trough may slow down and arrive as late as Monday. This trough
will bring another round of showers and thunderstorms for the
Klamath Mountains. This trough on Sunday will likely induce
stronger westerly to northwest winds for our typically dry and
windy areas; Lake, southern Mendocino and eastern Trinity.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 PM PDT Friday for PZZ455-475.

&&

$$

NOTE: The full forecast discussion is now regularly issued between
10 am/pm and 1 pm/am. Additional updates will be issued as needed.

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