983
FXUS66 KEKA 172100
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
200 PM PDT Tue Jun 17 2025

.SYNOPSIS...Interior warming with generally minor HeatRisk through
Thursday. Stronger coastal northerlies expected on Wednesday and
Thursday. Cooler temperatures with strong west and northwest winds
expected for interior valleys and ridges Thursday through Saturday.

&&

.KEY MESSAGES:

* Minor HeatRisk interior valleys through Thursday. Areas of
  moderate HeatRisk on Wednesday northeast Trinity and Lake.

* Gusty coastal northerlies expected Wednesday and Thursday.

* Strong westerly and northwest breezes and substantial cooling
  for interior valleys and ridges Thursday through Saturday.

* 10% chance of thunderstorms northern coastal waters and near Del
  Norte County Friday afternoon and evening.

* Interior warming and drying trend Sunday into early next week.

&&

.DISCUSSION...Hot weather to continue with daytime temperatures
generally peaking into the lower to mid 90s on Wednesday in
Trinity, Lake and SE-NE interior Mendocino. Minor HeatRisk is
forecast through Thursday except for areas of moderate HeatRisk
in NE Trinity and portions of Lake on Wed where temps peak into
the upper 90s. Temperatures are forecast to drop well below
seasonal averages (by 15-20F degrees) Friday and Saturday, and
then recover slightly on Sunday. Hot and drier weather with highs
in the 80`s forecast to return in the interior Monday and
Tuesday next week.

Broad flat ridge with above normal 500mb heights will continue
to result in modest interior warming through Wed. Extensive field
of stratus 60 miles offshore has been eroding leaving all of the
coast clear and free of stratus today. High resolution model
averages (HREF), BUFKIT profiles and statistical guidance all
indicate low clouds developing and expanding tonight as
northerlies ramp up over the coastal waters in the wake of
a decaying surface front. Strengthening northerlies offshore
should scour out the stratus on Wed with daytime heating and
mixing. In fact HREF indicates a 70-90% chance of northerly peak
gusts around 35-40 mph around Cape Mendocino and Pt St George late
in the day into the evening Wed. And the King Range range too
will probably have strong gusts to 40 mph or more by Wed evening.
ECMWF ensemble has a much wider distribution with an average
around 30-35 mph for the coastal headlands. ECMWF ensemble
distribution is pegging Thu with stronger gusts near 40 mph for
headlands, particularly Pt St George. NBM indicates much lower or
near zero chances for gusts > 40 MPH.

Prime concern heading into the latter portion of the week (Thu-Fri)
will be stronger west-northwest winds across the interior valleys
and interior ridges. Gusts to 20-30 mph are probable. A few of
venturi-effect ridges may even gusts 40-50 mph or so as an
unseasonably cold 500mb low drops down from the Gulf of AK.
Humidity generally increases as we head into Fri and Sat, however
portions of southern Lake and eastern Trinty may have much lower
RH`s - around 20-25%. With the trough enhancing diurnally
westerly and northwesterlies, locally critical fire weather
conditions will be possible. Risk for small fast spreading
grass or brush fires will increase.

This upper trough/surface front will probably generate some light
rain for the northern most zones; Del Norte, northern Humboldt
and perhaps northern higher terrain of Trinity. NBM indicates a
30% chance for 0.25 inches of rain or more in Del Norte County in
24 hours late Friday into early Saturday. There may even by some
isolated thunder too, mostly over the northern waters with 500mb
temps plunging to -25C. Overall not much rain, but just enough to
have impacts on outdoor activities and projects. So stay tuned
for more details. Depending on how quickly clouds clear out and if
winds die down and decouple over the weekend, there is even a
chance of early morning frost in the valleys of mostly Trinity
County this weekend. It will be considerably colder in the
mountains too, so those venturing to the high mountains should be
prepared for near or subfreezing temperatures in the mornings.

Considerable variability arises with the models over the weekend
into early next week. Upper level trough lingers over the area
or just to the east over the Great Basin this weekend. Trend is
for the trough to lift out and fill, so interior temperatures
should warm each day Sun-Tue. There is still an outside chance
for some showers with perturbations pin-wheeling around the
backside of the trough. Overall no clear signs for thunder or a
major warm up at this time.

&&

.AVIATION...

18Z TAF: VFR conditions prevail this afternoon with light NW
winds and intermittent scattered stratus at ACV. NW gusts 15 to 20
knots possible at UKI around 00Z. The stratus shield sitting
offshore is expected to return between 02 and 06Z this evening as
a weak frontal boundary approaches the coast beneath moderate
upper level ridging. HREF probability`s >80% for <1000 ft ceilings
for the coastal terminals, less certain regarding visibility (40%
probability) as the marine layer stays fairly shallow; 1 to 1.5K
feet. Still, stratus is expected to flow several miles inland
through coastal river valleys. UKI forecast to remain VFR through
the TAF period. Stratus will struggle to scatter out Wednesday
afternoon, especially around the northern Humboldt coast.

&&

.MARINE...

Winds have diminished to gentle to moderate breezes for the northern
waters while stronger NW winds prevail south of the Cape. Winds
will increase beginning early Wednesday as the coastal pressure
gradient tightens. Fresh to strong breezes producing steep and
hazardous wind waves expected through Thursday, with gales likely
and gusts approaching 40 knots possible in the southern outer
waters and downwind and nearshore of Cape Mendocino. Near gale to
gale force gusts may push further into portions of the inner
waters during the afternoon, especially Thursday. 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.

&&

.FIRE WEATHER...Northwesterly afternoon winds remain breezy in the
interior today and Wednesday, particularly in southern Mendocino and
Lake. High temperatures are forecast to rise a few degrees,
continuing the warm and dry trend. RH recoveries remain good, but
afternoon RHs dip into the teens or low 20s, which does present a
localized elevated fire weather threat in the afternoons and
evenings. Winds spike up Thursday and Friday with stronger, gusty
winds possible in the eastern portions of the area in the
afternoons. Min RHs are forecast to be slightly higher, but remain
low. A cold upper low is forecast to dive south into the region late
this week and into the weekend. This will bring cooler temperatures
and a chance for light rain to the area.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 9 PM this evening to 3 PM PDT
     Thursday for PZZ455.

     Small Craft Advisory from 9 PM this evening to 3 PM PDT
     Wednesday for PZZ475.

     Gale Warning from 3 PM Wednesday to 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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