660
FXUS66 KEKA 151952
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1252 PM PDT Sun Jun 15 2025

.SYNOPSIS...A few brief showers and a very low chance for a
thunderstorm development this afternoon and tonight with little
to no precipitation expected at the surface. Increasing afternoon
breezes and some fire weather concerns in southern Mendocino and
Lake County next week. Warmer temperatures and minor HeatRisk
concerns mid next week.


&&

.DISCUSSION...In the near term, afternoon satellite imagery reveals a
cumulus field and colder cloud tops over Humboldt and Del Norte
counties. An approaching shortwave trough is bringing some weak
elevated instability and moisture this afternoon. Moisture is
lacking, but a low chance (up to 5%) exits for isolated dry
thunderstorms this afternoon and evening for mainly Humboldt and Del
Norte counties as this feature interacts with the higher terrain. Colder
cloud tops and a cumulus field are observed on satellite over
Humboldt and Del Norte counties this afternoon. There are some
weak radar returns over the ocean well offshore and over the
interior. Some light showers with virga (precipitation
evaporating before reaching the surface) are also confirmed on the
cams. A secondary shortwave trough axis and front will swing
through Monday afternoon, slightly lowering daytime high
temperatures and bringing similar low- chances for a couple
showers or lone thunderstorm over far NE Trinity County.

Weak ridging will begin building in behind the trough. Inland valley
temperatures will warm into the low to mid 90s, with some upper 90
in Lake County on Wednesday. Temperatures will trend lower next
Thursday will another weak shortwave trough passing. Initial
analysis of this trough does not show much chances for convective
impacts, but features as this always bear watching this time of
year. A seasonally anomalously strong trough is then forecast to
dive south into the region next Friday. There is currently a low
chance for some light showers with a cold upper low and front. There
is the potential some of this precipitation may be in the form of
thundertorms with steep lapse rates and elevated instability. The
clusters unanimously bring down a cold trough, but show differences
in the heights and depth of the low. Much cooler temperatures may be
in the forecast, but there is time to work out the details. JJW


&&

.AVIATION...(18Z TAFs)A layer of coastal stratus from a deepened
marine layer due to an overhead shortwave trof is beginning to give
way to daytime VFR conditions. Breezy northerly winds are expected
with elevated FEW/SCT clouds. Sounding data shows ample daytime
mixing inland, potential resulting in gusts at or around 20kts this
afternoon. Tonight, a return of coastal stratus is forecasted after
sunset. This layer will be elevated due to the passing trough and
should linger tomorrow through the morning.

Confidence: High resolution models show high confidence (>90%) for
clearing out later this morning along the coast by 19Z. Low winds
and increased atmospheric moisture shows a likely probability (for a
return to IFR-MVFR conditions at KACV. Model data shows the
shortwave trof overhead most likely deepening the marine layer deep
enough to keep terminals out of LIFR categories (<10%) with ample
visibilities over 5SM (<20%) through tonight at KACV.


&&

.MARINE...Strong to near gale force gusts are forecast to continue
through the weekend, with the strongest winds across the outer
waters and southern inner waters. Locally gale force gusts downwind
of Cape Mendocino and Cape Blanco. The sea state will be largely
dominated by steep short period wind waves. Winds are forecast to
gradually decrease and retreat to the southern waters early next
week. Next week as the winds die down, a small mid-period NW swell
enters the water early Tuesday morning.



&&

.FIRE WEATHER...An approaching shortwave trough is bringing some
weak elevated instability and moisture this afternoon. Moisture is
lacking, but a low chance (up to 5%) exits for isolated dry
thunderstorms this afternoon and tonight for mainly Humboldt and
Del Norte counties as this feature interacts with the higher
terrain. Colder cloud tops and a cumulus field are observed on
satellite over Humboldt and Del Norte counties this afternoon.
There are some weak radar returns over the ocean well offshore and
over the interior. Some light showers with virga are also
confirmed on the cams. this will be watched closely through
tonight as the axis of concentrated forcing progresses from the SW
to NE through Humboldt- Del Norte. Trinity County has a brief
chance this afternoon and a second chance in far NE portions of
the county Monday afternoon for an isolated shower or thunderstorm
as the trough axis passes.

Northerly winds are increasing in southern Mendocino and Lake
County this afternoon. These winds will further increase Monday
afternoon over the interior ridges, mainly in southern Mendocino
and Lake counties. These mainly diurnally driven afternoon winds
will trend slightly lower Tuesday, but will increase again late
next week with a stronger trough and front. Minimum RH values will
trend lower early to mid next week, with some values in the mid
to upper teens Wednesday. Locally elevated to some brief critical
fire weather conditions will develop with these afternoon wind
pulses and lowering RH. JJW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 11 PM PDT this evening for
     PZZ450-470.

     Small Craft Advisory until 10 PM PDT Monday 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