Arcata, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

422
FXUS66 KEKA 142058
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
158 PM PDT Mon Jul 14 2025

.SYNOPSIS...Hot temperatures continue this afternoon and there is
a slight chance for thunderstorms this afternoon in northern
Trinity county. Temperatures are expected to start cooling on
Tuesday and Wednesday, especially closer to the coast. Highs are
expected to generally in the 90s through the end of the week and
into the weekend.

&&

.DISCUSSION...An upper level trough is moving into the Pacific
Northwest. The southern extent of it is lowering heights aloft.
This generating some instability over Trinity and Siskiyou
counties this afternoons. Lapse rates aloft are steep, but it
still looks like there will be some inhibition around 500 mb. So
have left the slight chance of thunderstorms in the forecast, but
confidence is low on anything developing. Tonight the marine
layer is expected to bring clouds back to the coastal areas. This
may reach slightly farther inland and gradually deepen with the
approaching trough. A shortwave is expected to move through
overnight and this may bring some drizzle to portions of the
coast. The pattern looks similar on Tuesday and as heights
continue to gradually fall this will bring lower temperatures
across the area. This will be enhanced in the near coastal areas
that see influence from the deeper marine layer. With this the
surface temperatures expected to be cooler and lapse rates aloft
are not as steep so this makes it less likely we will see
thunderstorms, although there is still a small potential.

The pattern remains fairly similar through much of the week. Most
of the ensemble clusters keep the ridge axis just east of the
area. This is generally expected to keep high temperatures in the
90s and the marine layer moderately deep with marine clouds
around. The probability of exceeding 100 degrees for much of the
rest of the week is only around 5 to 10 percent for most of the
warmer areas. Some areas along the Trinity river, especially near
Big Bar have higher probabilities of exceeding 100 degrees. For
now there are no days with an obvious through for thunder,
although that will continue to monitored. MKK

&&

.AVIATION...Stratus is being scoured out from the coastal terminals as
northerly winds increase just offshore. A persistent southerly
reversal has kept LIFR ceilings over CEC, but NW wind gusts
exceeding 30 knots are expected this afternoon as a tight pressure
gradient drives the strongest winds towards the coastline. ACV will
be slightly more sheltered with gusts 10 to 15 knots. Afternoon
terrain driven winds will once again bring gusty southerlies to UKI
this afternoon. IFR ceilings are expected to return to ACV late this
evening after 06Z (HREF 50 to 70%). Models show potential for
drizzle in and around Humboldt Bay by Tuesday morning with the
return of the marine stratus layer. Northerly winds will likely
remain gusty at CEC overnight - combined with interior offshore
flow, stratus will struggle to redevelop until after sunrise when
winds turn southerly and diminish. Winds expected to remain lighter
and southerly on Tuesday, allowing the resurgence of a widespread
marine layer Tuesday evening.


&&

.MARINE...Gale force winds in the northern outer waters will expand
southward in coverage today, with gusts exceeding 40 to 45 knots
likely in NW PZZ470. As these winds push towards the coast, near-
gale to gale gusts are possible nearshore of Point Saint George and
Cape Mendocino this afternoon. Seas 9 to 11 feet are already being
observed on buoys as waves propagate into the inner waters. Steep
wind driven seas 12 to 17 feet are expected through Tuesday
afternoon, with the strongest winds and waves expected late this
afternoon and overnight in the outer waters. High pressure will
begin to break down Tuesday afternoon, diminishing hazardous
conditions by midweek.

&&

.FIRE WEATHER...Overnight offshore winds remain breezy in Del Norte
and northern Humboldt counties. This is keeping RH recoveries poor
to moderate in the high elevations, while recoveries are moderate to
good in the lower elevations. High pressure moves eastward Tuesday
and Wednesday. The marine layer will gradually deepen, improving RH
in the near-coastal areas and lowering high temperatures 5-10
degrees. Offshore flow will begin to weaken, as well.

Upper-level moisture from the east along with elevated instability
does bring a 10-15% chance for isolated dry thunderstorms in
northern Trinity County. Today looks like it has the higher
potential, but it is possible Tuesday as well. There is also a
small chance for nocturnal lightning tonight. There is some
elevated instability overnight, but the shortwave doesn`t look
strong enough to spark any thing off. Moisture and instability
decreases by Wednesday into later in the week, along with
thunderstorm chances. JB

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Extreme Heat Warning until 11 PM PDT this evening for
     CAZ102-105-107-108.

     Heat Advisory until 11 PM PDT this evening for CAZ106-110-
     111-113>115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Hazardous Seas Warning until 11 AM PDT Tuesday for PZZ450.

     Small Craft Advisory from 5 PM this afternoon to 11 AM PDT
     Tuesday for PZZ455.

     Gale Warning until 11 AM PDT Tuesday for PZZ470.

     Small Craft Advisory until 9 PM PDT this evening for PZZ475.

     Gale Warning from 9 PM this evening to 9 AM PDT Tuesday 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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