571
FXUS66 KEKA 141140
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
440 AM PDT Mon Apr 14 2025

.SYNOPSIS...Warm and calm weather will continue today with Monday
likely the warmest day of the week. A gradual cooling trended is
expected Tuesday through Thursday. There is a slight chance for
thunderstorms over the interior mountains Tuesday and Wednesday
mainly in the afternoons. Thursday breezy north winds are
expected. A rebound in the temperatures expected for Friday and
Saturday.

&&

.DISCUSSION...

KEY MESSAGES:
-Warm, calm, and dry conditions persist today with the potential
 for interior highs over 85 and coastal highs near 70.

-Tuesday and Wednesday there is the potential for isolated
 Thunderstorms over high terrain Tuesday and Wednesday afternoons.

-Cool and gusty onshore winds return for the coast Wednesday and
 Thursday.

WEATHER PATTERN OVERVIEW:
An upper level low off the coast of southern CA is remaining
nearly stationary, but strengthening slightly as it absorbs some
more energy dropping down into it from the north. Today this will
generally keep offshore flow in place and warm temperatures
throughout the area. Highs near 70 are possibly close to the coast
with low to mid 80s in the inland valleys. This evening and
tonight the coastal stratus and fog is expected to return. The
HREF shows widespread low clouds or fog by 12Z Tuesday at the
immediate coast. Tuesday afternoon any marine clouds are expected
to clear back to all but the most immediate coastal areas. However
this is still expected to keep temperatures in much Del Norte,
Humboldt and Mendocino counties 5 to 10 degrees cooler while
Trinity and Lake counties will be nearly the same as Monday.
Tuesday afternoon the southerly flow due to the upper low off
southern CA will bring some moisture north into the area and this
may bring some thunderstorms late in the afternoon to the interior
mountains. Wednesday there is more uncertainty in the forecast,
however it seems like temperatures will continue to cool in most
areas due to the deepening marine layer aside from eastern
Trinity County. There is the potential for a few inland showers or
thunderstorms, but still quite a bit of uncertainty on this.
Thursday a weather system moving down from the north, but
remaining east of the area will bring cooler temperatures and
breezy conditions. Friday and Saturday this system moves south of
the area and high pressure starts to build in again.

FORECAST CONFIDENCE AND DEVIATIONS:
Skies remain clear across the area this morning setting things up
for the warmest day of the week. Confidence is fairly high in
these temperatures in the inland areas, but closer to the coast
confidence is lower. Kept the forecast 3 to 5 degrees above the
deterministic NBM, but more inline with the NBM mean. If skies
remain clear this forecast looks on track, but if stratus forms
this morning, temperatures at the coast could be more closer to 60
degrees than 70 in the forecast. Tonight the HREF is showing
stratus moving onto the coast late tonight. Tuesday this stratus
and associated marine influence is expected to keep temperatures 5
to 10 degrees cooler at the coast and the near coastal areas such
as Ukiah, Garberville and Gasquet. A pattern change like this
brings lower confidence to the temperatures as the bias
correction doesn`t work as well. Trinity and Lake counties may
also see a couple degrees of cooling.

The upper level low off the southern CA coast is bringing some
moisture north into the area with the south to southeast flow.
This generates some fairly strong instability over the mountains
of eastern Trinity and northeastern Mendocino county. This may
also include northern Lake county. Even the GFS is showing 300 to
500 j/kg of CAPE. Lapse rates aloft are steep, but shear is weak.
So there may be a few stronger storms, but any hail should be
limited given the lack of wind shear needed to sustain storms.

Wednesday the models start to diverge in their solutions. Some of
the models show an upper level low moving down from the north as
an inside slider. This would effectively cut off the moisture and
keep most thunderstorms east of the area. The NAM is slower and
farther east with this system keeping more instability and
potential thunderstorms over the area. So this will need to
watched as it gets closer.

Thursday and Friday cooler temperatures are expected. Thursday is
expected to see the strongest winds as the system moves by to
the east of the area. Slightly warmer temperatures are expected
Friday with more warming on Saturday. Sunday the ensemble clusters
are in reasonable agreement on cooler temperatures, but generally
dry weather continues. MKK

&&

.AVIATION...Prevailing VFR are expected at all TAF terminals
through tonight as high pressure remain over the area promoting
clear skies and dry weather. Surface winds from E-SE up to 5 kts,
becoming WNW 5-10 kts after 17Z. Short-term guidance shows a shallow
marine layer along the coast tonight. After 15/06Z, there is a 40-
60% chance of low ceilings developing along the coastal terminals.
Meanwhile, light southerly winds will push stratus northward from
Santa Rosa toward UKI into Tuesday morning.

&&

.MARINE...Northerly winds continue to ease across the coastal
waters this morning. Gentle to moderate breezes across the outer
waters today, while generally light to gentle breezes for the
inner waters. Seas will continue subside throughout the day today.
Winds are expected to increase again late tonight and strengthen
through Wednesday as the pressure gradient tightens near the north
coast. Strong to gale force gusts are likely in the outer waters
on Wednesday, with the strongest north of Cape Mendocino. Strong
winds are expected to expanded into the northern inner waters
Wednesday afternoon, before back off Wednesday night into
Thursday. Seas will respond with 11-15 ft significant wave heights
possible in the outer waters, while steep seas of 7-12 ft are
likely along the northern inner waters.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 AM PDT Tuesday for PZZ470-475.

     Gale Watch from Tuesday morning through late Tuesday night
     for PZZ470.

&&

$$

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