Trinity Center, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

478
FXUS66 KEKA 181228
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
528 AM PDT Wed Jun 18 2025

...New AVIATION...

.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... /issued 1026 PM PDT Tue Jun 17 2025/

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

* Gusty coastal northerlies expected Wednesday and Thursday
  afternoons.

* 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... /issued 1026 PM PDT Tue Jun 17 2025/ 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. 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...(12Z TAFs) A fairly shallow marine layer is bringing
low clouds and patchy fog which is producing IFR to LIFR
conditions this morning. Gusty NNW winds building in the mid-
late morning are forecasted to lift and likely dissipate most of
the stratus by 2100Z. These winds will be strongest on ridges,
river valleys, and coastal headlands. VFR conditions are expected
to hold with light, variable winds in the inland areas this
morning. This evening and tonight the HREF is showing a return of
stratus to the Humboldt coast. Confidence is low to moderate on
this. Later tonight it make it north into KCEC but confidence is
lower on this. MKK

.MARINE.../issued 1026 PM PDT Tue Jun 17 2025/ The calmer
conditions of Tuesday will be short lived as stronger winds
return to the southern waters Wednesday and Thursday. Small craft
advisories have been issued for the southern water through
Wednesday morning. Winds will build through the day Wednesday
bringing gale force gusts to the southern outer waters downwind of
Cape Mendocino. Near gale to gale force gusts may push further
into portions of the inner waters during the afternoon, especially
Thursday. A gale warning remains in place for the southern outer
waters. 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. This late season cold front is expected to bring gentle-
to-moderate breezes and a small mid- period NW swell to the
coastal waters.

.FIRE WEATHER...Northwesterly afternoon winds remain breezy in
the interior through 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 higher each day. 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 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 from 3 PM this afternoon 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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