659
FXUS66 KEKA 192127
AFDEKA
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
227 PM PDT Thu Jun 19 2025
.SYNOPSIS...Gusty and locally strong coastal northerlies through
this evening. Stronger west and northwest winds expected for the
interior through Friday. Much cooler with below normal temperatures
for the interior Friday and Saturday.
&&
KEY MESSAGES:
* Elevated to locally critical fire weather conditions through
Friday evening for Lake, eastern Mendocino and eastern Trinity
Counties due to low RH`s and stronger west and northwest winds.
* Gusty and locally strong coastal northerlies this evening.
* Much cooler Friday and Saturday in the interior, followed by a
warming and drying trend early to mid next week.
* Light rain possible for Del Norte and northern Humbodlt Friday
afternoon and evening.
&&
.DISCUSSION...
Prime concern tonight through Friday evening will be strong and
gusty west and northwest winds across the interior. Gusts to
20-30 mph are probable (60-70% chance). Higher terrain and ridges
may even gusts 35-45 mph as an unseasonably cold 500mb low drops
down from the Gulf of AK on Friday. Friday looks to be the
strongest wind day while humidity generally increases. Portions of
Lake, eastern Mendocino and eastern Trinty will likely have low
humidity around 20-25% on Friday. With the trough enhancing
diurnally westerly and northwesterlies breezes 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. We will message this
fire weather threat in weather story graphic and social post.
This upper trough/surface front will probably generate some light
rain for Del Norte and northern Humboldt Friday afternoon and
evening. Around 0.10 to 0.25 inches of rain are forecast for Del
Norte County with a few hundredths for northern Humboldt. This
is not very much rain, but just enough to have impacts on outdoor
activities and projects Friday afternoon and evening. We will message
this low impact light rain episode in a weather story graphic and
social media post. GFS and ECMWF deterministic models continue to
differ substantially with rain amounts. GFS has barely a tenth to
only a few hundredths of an inch while the ECMWF has 0.50 to 1.0
inches over 24 hours from 11 AM Fri to 11 AM Sat. NBM 24 hour
interquartile spreads are on the order of 0.30in for Crescent City
and 0.04in for Eureka with means around 0.25in and 0.04in, respectively.
Model soundings continue to show low CAPE along the far northern
portion of our coastal waters and Del Norte county as 500mb temps
dip down to minus 25C or less. Soundings continue to 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 (HREF and SREF) continues to show much
higher chances north of the ORCA border with passages of a shorter
wavelength trough 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 Trinity County (Hayfork and
Ruth) and NE Mendo (Covelo) Friday and again on Sunday. With
temperatures falling to 36F or less for a few hours right before
sunrise, we will message the potential for frost in a weather
story graphic and social media post.
A warming trend is forecast early to mid next week with highs in
the lower to mid 90`s by Wed. Also of note is the possibility
(10% chance or less) for thunderstorms over the interior
mountains Sunday and Monday as perturbations pin-wheel around the
upper trough or the trough develops into a sem-closed circulation.
GFS indicate inverted V profiles which suggests high based storms.
There is considerable run-to-run and model-to- model variability
and no clear signs of moisture import into the area. At this
point, there is no compelling reason to deviate from the National
Blend of Models (NBM) thunder chances.
&&
.AVIATION...
19/18Z TAFs...VFR conditions at all TAFs terminals with mid-high
level clouds streaming across the northern portion of the weather
forecast area. Increasing NNW winds up to 15-20 kts with higher
gusts until around 20/04Z, decreasing to around 10 kts after.
Winds are expected to remain breezy at CEC through late tonight.
Stratus will gradually to redeveloped after 02Z around Humboldt
Bay, promoting MVFR to IFR ceilings at ACV with a deepen marine
layer. VFR conditions should prevail at CEC and UKI. After 15Z,
SHRA likely at CEC.
&&
.MARINE...
Strong to gale force gusts winds across the outer waters and
southern inner waters today, with the strongest winds south of
Cape Mendocino. Meanwhile, gentle to moderate breezes over the
northern inner waters. Waves will be mainly steep and wind driven.
Winds and seas will ease on Friday as a low pressure system
approaches the Pacific NW region, becoming gentle to moderate
west- northwest breezes. Winds shift back to northerlies Friday
night, before increasing to moderate to strong breeze this
weekend...with the strongest over the southern waters.
&&
.FIRE WEATHER...
Stronger westerly and northwesterly winds are forecast through
Friday across the interior 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. A few higher elevation
exposed ridges will likely remain very dry and windy with 8 hours
or longer of red flag conditions.
A low level northerly speed max (925mb) will likely develop over
the Sacramento valley and clip the eastern peripheries of Mendocino
and Lake Counties this weekend. Lower overnight humidity and gusty
N-NE winds are likely over the higher terrain of Lake and eastern
Mendocino (fire weather zones 264 and 277). Once again we may be
flirting with locally cortical fire weather conditions. Our
neighboring NWS office in Sacramento has a fire weather watch out
for cured grassy fuels for elevations below 1000 feet. Otherwise,
daytime minimum humidities are forecast to trend drier over the
latter portion of the weekend (Sunday) into early next week as
temperatures increase each day.
Also of note is the possibility (10% chance or less) for thunderstorms
over the interior mountains Sunday and Monday as perturbations
pin-wheel around the upper trough. There is considerable run-to-
run and model-to-model variability. At this point, there is no
compelling reason to deviate from the National Blend of Models
(NBM).
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 3 AM PDT Friday for PZZ450-470.
Gale Warning until 9 PM PDT this evening for PZZ455.
Gale Warning until 3 PM PDT this afternoon 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