Alton, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

344
FXUS66 KEKA 190702
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1202 AM PDT Sat Jul 19 2025

.SYNOPSIS...Hot conditions continue for the interior areas this
weekend. Overnight fog and stratus continues along the coastal
areas. Temperatures trend downward early next week.


&&

.DISCUSSION...Ridging has started to build, bringing a shallower
marine layer and starting a short warming trend for the interior.
Already warm temperatures will continue to increase into the mid-
90`s across interior valleys this weekend. NBM probabilities for
highs >90 degrees are >80% as far as Redway and Laytonville as warm
temperatures chip away at the marine layer. Triple digit
temperatures are possible (30% chance) in Trinity and northeast
Humboldt. This heat brings minor to moderate HeatRisk, which
indicates heat will be hazardous to those who are especially
sensitive. Along the coast, the shallower marine layer and afternoon
breezes could allow for stratus to scatter, or at least erode to the
coastline. High temperatures remain fairly similar to previous days:
high 50`s to low 60`s.

An approaching upper trough will help to tighten the coastal
pressure gradient Sunday into Monday. Gusty northerlies south of
Cape Mendocino are expected, including Lake County (SW flow in
higher elevations of eastern Lake County). This will pose a slight
fire weather concern as daytime RH`s are still 25 to 30%. High
pressure will begin to break down beginning early next week 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 (with isolated valleys
potentially reaching 90) through midweek. Long range models show
anomalously low heights sitting over the eastern Pacific/PNW through
at least Wednesday. Depending on the position and the moisture
available from the trough, light rain is not out of the question,
with NBM probabilities of at least 0.05" of rain at around 10-20%.
There are some hints of thunderstorms in Trinity County Tuesday and
Wednesday afternoons as mid-level moisture is available and upper-
level temperatures are relatively cool. Uncertainty remains high as
subtle changes in the position of the low could affect thunder
chances considerably.


&&

.AVIATION...High pressure is compressing the marine layer and this
has allowed fog to develop along the coast and LIFR conditions. This
is expected to keep the low clouds more confined to the coast and
not as far up the river valleys. This may also keep it out of Ukiah
this morning. This afternoon the northwesterly winds and the
shallower marine layer may allow the clouds and fog to clear even at
the immediate coast, although this may be brief. Tonight low clouds
and fog are expected to quickly return once again. MKK


&&

.MARINE...Winds and seas are fairly light this morning. There is a
modest northwest swell around 6 feet at 9 seconds. Northerly winds
have started to increase and are expected to continue to increase
and this will generate steep short period waves that will combine
with the existing swell. Northerly winds of 15 to 20 kt are expected
by midday Saturday and these are expected 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.

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


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 11 PM this evening to 5 PM PDT
     Sunday for PZZ470.

     Small Craft Advisory from 3 PM this afternoon to 11 PM PDT
     Sunday for PZZ475.

&&

$$

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