688
FXUS66 KEKA 182139
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
239 PM PDT Wed Jun 18 2025

.SYNOPSIS...Gusty and locally strong coastal northerlies through
Thursday. Stronger west and northwest winds expected for the
interior Thursday through Friday. Much cooler with below normal
temperatures for the interior Friday and Saturday.

&&

.KEY MESSAGES:

* Elevated to locally critical fire weather conditions Thursday
  and Friday fore Lake, eastern Mendocino and eastern Trinity
  Counties due to low RH`s and stronger west and northwest winds.

* Gusty and locally strong coastal northerlies today and again on
  Thursday.

* Much cooler Friday and Saturday in the interior, followed by a
  warming and drying trend early to mid next week.

&&

.DISCUSSION...Interior high temperatures forecast to trend down
on Thursday, but it will still be hot with highs in the 80s.
Interior temperatures are forecast to drop well below seasonal
averages (by 15-20F degrees) Friday and Saturday, and then recover
slightly on Sunday.

Coastal stratus has been slowly dissipating this afternoon but
will most likely (80% chance) reform and then expand over the
coastal plain overnight. Northerlies have also been stronger
today with the usual wind-prone RAWS in SW Humboldt gusting to
35-40 mph. So far gusts for coastal sites near sea level have been
gusting only around 25 mph. High resolution mesoscale model
ensemble (HREF) continues to indicate a 90-100% chance for gusts
to 40 mph over the coastal headlands (Cape Mendo and Pt St George)
late this afternoon into this evening. Downscaled ECMWF ensemble
distribution was not as high as the HREF with an average near
30-35 mph for Pt St George or KCEC today. Thursday is looking very
similar except for higher chances for gusts to 30-40 mph along
the Mendo coast, SW Mendo and higher elevations (above 1500-2500
ft) in Lake County during the afternoon and evening. NBM remains
much lower with zero chances for gusts to 40 mph except for the
ridges of SW Humbodlt.

Prime concern heading into Thursday and Friday will be stronger
west and northwest winds across the interior. Gusts to 20-30 mph
are probable (60-70% chance). Higher terrain and ridges may even
gusts 35-50 mph as an unseasonably cold 500mb low drops down from
the Gulf of AK on Friday. Friday looks to be the strongest wind
day. Humidity generally increases as we head into Friday. Portions
of Lake, eastern Mendocino and eastern Trinty will likely have
lower humidity - around 20-25% on Friday. With the trough
enhancing diurnally westerly and northwesterlies breeze on Friday,
elevated to locally critical fire weather conditions are
forecast. Risk for small and fast spreading grass or brush fires
will increase. Winds may not line up exactly with low RH`s for
8 hours or more for a red flag warning. Now a few windier higher
elevations will probably reach or exceed 8 hours with these
stronger winds on Friday even with slightly higher humidities.

This upper trough/surface front will probably generate some light
rain for the northern most zones; Del Norte and northern Humboldt
Friday afternoon and evening. Generally around 0.10 to 0.25
inches of rain are forecast for Del Norte County with a few
hundredths for northern Humboldt. Model soundings continue to
show some buoyant energy along the far northern portion of our
coastal waters and Del Norte county as 500mb temps dip down to
minus 25C or less. Soundings show low EL`s (equilibrium levels)
and very narrow CAPE with WNW flow through the column. Thus not
convinced there will be any thunder in our area. Calibrated
guidance show higher chances north of the ORCA border with
passages of a shorter wavelength trough. Not very much rain
overall is expected, but just enough to have impacts on any
outdoor activities and projects Friday afternoon and evening.

Additional perturbations in N-NW flow on the backside of an upper
level trough may generate isolated showers over the weekend,
primarily for Del Norte and Trinity. Otherwise, dry and cooler
weather is forecast to prevail into the weekend. If skies clear
out and winds go calm, patchy early morning frost will be possible
(45% chance) for interior valleys; primarily Trinity County
(Hayfork) and NE Mendo (Covelo). A warming trend is forecast early
to mid next week with highs in the lower to mid 90`s by Wed. A
warmer scenario is possible if 500mb heights pump up to 588DM.
This warmer outcome would propel max temps to 100F in valleys of
Lake, interior Mendo, NE Humboldt and Trinity. Big Bar RAWS for
sure will hit 100-105F by Wed next week. Otherwise, no clear
signs for a major heat wave (highs temps to 110F or more).

&&

.AVIATION...

18Z TAF: Persistent marine stratus with mid-level ceilings keeps
ACV MVFR this afternoon. Gusty northerly winds have already helped
to scour out ceilings at CEC; ACV will likely struggle to scatter
until late afternoon. Gusts 20 to 30 knots expected to continue
through this afternoon at all terminals including UKI with a
strengthening coastal pressure gradient. HREF indicates 50 to 60%
chance of stratus returning to northern Humboldt (especially
around Humboldt Bay) after 06Z tonight. Winds will be slow to
diminish but remain elevated just offshore, perhaps lingering at
CEC into the late evening. Greater probabilities for widespread
VFR conditions tomorrow as a low pressure system approaches the
region and disrupts the high pressure ridge.

&&

.MARINE...

Observed winds are continuing to increase this afternoon as
the coastal pressure gradient strengthens. Fresh to strong breezes
producing steep and hazardous wind waves expected through Thursday,
with gales likely and isolated gusts approaching 40 knots possible
in the southern outer waters and downwind and nearshore of Cape
Mendocino. Strongest winds are expected to develop overnight into
early Thursday morning. Near gale to gale force gusts may push
further into portions of the inner waters Thursday afternoon. A
small mid-period NW swell 4-5 ft at 14 seconds will contribute to
the sea state Thursday afternoon, producing combined seas 8 to 10
feet. The sea state will begin to diminish on Friday as low pressure
system approaches the region, disrupting the wind pattern. Gentle to
moderate breezes expected early this weekend before increasing again
in the southern waters.

&&

.FIRE WEATHER...

Stronger westerly and northwesterly winds are expected Thursday
through Friday as an unseasonably cold upper trough moves across
the Pacific NW (Washington and Oregon). With minimum RH`s around
20-25% on Friday and gusty afternoon and evening winds, elevated
to locally critical fire weather conditions are anticipated for
eastern Trinity, eastern Mendocino and Lake Counties. Duration of
these red flag conditions are not forecast to be long-lived for
most of the area. Some higher elevation exposed ridges will likely
remain very dry and windy with over 8 hours of red flag
conditions.

A couple of northerly speed maximums over the Sacramento valley
may graze Lake County Saturday and again Sunday. Low overnight
humidity over the higher terrain of Lake County may yield locally
elevated fire weather conditions. Otherwise, daytime minimum
humidities are forecast to trend drier over the weekend into mid
next week as temperatures increase each day.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 5 PM this afternoon to 9 PM PDT
     Thursday for PZZ450-470.

     Small Craft Advisory until 9 PM PDT Thursday for PZZ455.

     Small Craft Advisory until 3 PM PDT this afternoon for
     PZZ475.

     Gale Warning until 3 PM PDT Thursday 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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see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png