Alton, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

941
FXUS66 KEKA 200730
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1230 AM PDT Sun Jul 20 2025

.SYNOPSIS...Another warm day is expected in the interior today with
stratus and fog likely along the coast. Cooler conditions expected
Monday and Tuesday, with a low chance of rain for the area.


&&

.DISCUSSION...High pressure remains in place today, bringing another
warm day to the interior. High temperatures are forecast to be a few
degrees cooler than Saturday, with most interior valleys seeing high
80`s to 90`s. An approaching upper trough will help to tighten the
coastal pressure gradient today into Monday, bringing gusty
northerlies of up to 20 to 30 mph, especially in Trinity and Lake
Counties. This will pose a slight fire weather concern as daytime
RH`s are still largely in the 20`s.

High pressure begins to break down Monday as a positively tilted
upper trough over WA/OR begins to extend into NorCal. Temperatures
are expected to cool off significantly with highs in the upper 70`s
to mid 80`s through midweek. Only a few areas in Trinity and NE
Humboldt may break 90. The main cold front moving in Monday does
bring a chance for a rain shower to the area. NBM is showing around
a 25% chance for any measurable precipitation, while CAMs are
showing more rain to the northeast. Wetting rain (>0.1") chances are
generally limited to eastern Trinity County and are low (15-20%).
The most likely outcome is a few sprinkles and more widespread
coastal drizzle.

Mid-level moisture and cooler upper temperatures could present some
thunderstorm potential each afternoon starting Monday in the Klamath
Mountains. Instability currently looks meager Monday through
Wednesday, so confidence is low (5-10%). Temperatures start to
rebound later in the week as the main trough moves to the east. An
upper-low looks likely to form off the coast of California by the
end of the week, however. This could support a better environment
for thunderstorms, but confidence remains low at this time.


&&

.AVIATION...High pressure is compressing the marine layer and the
increased winds partially cleared skies out Saturday evening. After
sundown the stratus has begun to expand once again and this is
expected to continue to expand overnight. Sunday skies are expected
to clear back to the coast again. The marine layer remains fairly
shallow, but the winds are expected to be lighter. Clearing is
expected to be more limited Sunday afternoon than it was Saturday
afternoon as an upper level trough starts to approach the area. This
will likely increase ceiling heights as well and they may be IFR or
MVFR. MKK


&&

.MARINE...Northerly winds of 15 to 20 kt are expected to continue
through Sunday evening. The stronger winds will generally be beyond
10 miles from shore with winds of 10 to 15 kt closer to shore. Waves
will mainly be steep and wind driven, although there is a small
southerly swell around 2 to 3 feet at 15 seconds.

Starting on Monday lighter winds are expected. These start to
diminish in the north first and then in the southern waters Monday
night and Tuesday.  Wednesday through late in the week the forecast
becomes a little more uncertain. The upper level trough that brought
the lighter winds starts to become a cutoff low and there is quite a
bit of uncertainty on where this will go exactly. Winds are
generally expected to remain light, but exactly how light is more
the question. Waves are generally expected to be wind driven
combined with a small northwest swell. MKK


&&

.FIRE WEATHER...Temperatures remain warm today with afternoon RH in
the 20`s and 30`s with generally good RH recoveries outside the
highest elevations. Breezy west-northwesterly winds are forecast
both today and Monday for the interior areas, with the strongest
winds likely in eastern Trinity and Lake counties. In southern Lake
County, winds are still breezy but mainly from the west-southwest.
Peak gusts of 20-30 mph are possible, bringing locally elevated fire
weather conditions.

Poor air quality persists for interior Humboldt and northern Trinity
County due to the Butler Fire. Some improvement in air quality is
possible in the afternoon with greater mixing except immediately
downwind of the fire.

An approaching trough is expected to deepen the marine layer Monday.
A weak cold front will bring the low chance for light rain to the
area, with the highest chances in Del Norte and eastern Trinity
County. Wetting rain is unlikely, but if there is any, the highest
chances are in eastern Trinity county. A few showers are possible
Monday afternoon in the Trinity Horn, but thunderstorm chances
remain low at around 5-10%. Tuesday and Wednesday afternoons have
similar confidences, with higher probabilities in Siskiyou county.
Thunderstorm chances increase later in the week, but still
confidence remains low.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 11 PM PDT this evening for
     PZZ455-475.

     Small Craft Advisory until 5 PM PDT this afternoon for
     PZZ470.

&&

$$

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