Mad River, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

891
FXUS66 KEKA 200704
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1204 AM PDT Thu Aug 20 2026

.KEY MESSAGES...
* Thick smoke remains stuck around the Hoopa Valley stretching from
  as far north as to Orleans as far south as Burnt Ranch. Weak
  transport winds will keep smoke here through the week.

* Interior areas will remain warm Thursday, although some of the
  near coastal areas will start to see some cooling as the marine
  layer expands.

* Another trough is expected to bring below normal temperatures and
  very slight potential for a isolated thunderstorms Friday.

&&

.SYNOPSIS...An approaching trough will start to deepen the marine
layer Thursday. Friday this will bring a slight chance for
thunderstorms and cooler temperatures. The coolest day is expected
to be Saturday highs mainly in the 80s across the interior. High
pressure starts to build back into the area warming temperatures
again Sunday and Monday.

&&

.DISCUSSION...The upper level ridge is starting to get pushed out
of the area as an upper level low approaches the area. This is
expected to deepen the marine layer and start cooling off some of
the near coastal areas. Typical afternoon west to southwest
breezes are expected.

Thunderstorms are possible as early as Thursday night into Friday
the upper level is expected to move closer to the coast. The
models are showing some of the ingredients for storms. The
ensembles show fairly high confidence that there will be some
increase moisture aloft. There is some vorticity from the low and
there is an upper level jet moving overhead. For now it looks like
instability will be the limiting factor. The NAM is showing 100 to
300 j/KG of MU CAPE at times Thursday night and Friday. However
this does seem to be an outlier with the other hi-res models not
showing it. Went ahead and added a slight chance of thunderstorms
to northern Trinity county Friday afternoon and evening. If the
instability does materialize, the forecast may change quickly.
This low will also continue to deepen the marine layer and bring
cooler temperatures to the inland areas. Highs may be in the upper
80s to low 90s.

Saturday the upper level low starts to move out of the area.
Temperatures are expected to remain slightly below seasonal
normals in the mid to upper 80s to around 90. Sunday and Monday
temperatures are expected to warm back into the 90s in most areas.
This may briefly help to bring some offshore that would help clear
out the coast. Mid to late next week cooler temperatures are
expected as zonal flow takes over the ridge gets squashed down.
MKK

&&

.AVIATION...The stratus is bringing LIFR conditions to the coastal
areas this morning. Conditions are expected to lift this afternoon
as clouds push back towards the coast, however it is not looking
like there will be any significant clearing in the afternoon.
Clouds may lift to IFR conditions. Tonight the stratus is
expected to persist, although CIGS may not be quite as low as this
morning. The approaching trough may help to lift them slightly.
MKK

&&

.MARINE...Winds and seas are expected continue to diminish
Thursday and be exceptionally low on Friday. These are expected to
continue to be low Friday night. The waves are also slowly
diminishing, but are taking their time in the northern waters.
Saturday it looks like the northerly winds will start to increase
again. This will start in the southern waters and spread north
Saturday night into Sunday.

There are currently two swells moving through the waters. One is
around 2 or 3 feet at 11 seconds out of the northwest and the
other is around 2 or 3 feet as well, but out of the south at
around 14 seconds. These generally expected to persist for the
next several days. MKK

&&

.FIRE WEATHER...Hot and dry weather held on for one more day longer
than initially forecast with the hottest valleys reaching near 100 F
and some RH values in the upper teens. Thermal belts, however, are
expected to begin weakening tonight, slightly improving poor mid and
upper slope recoveries. Winds remain weak and terrain driven.
Conditions will generally ease through the end of the week with
increasing marine influence. Weak transport wind will continue to
allow smoke accumulation around the MP18 fire in Hoop and up the
Trinity River Valley, creating some extra, localized moderation of
conditions. There is also a small chance for thunderstorms on
Friday, for details see the main discussion. MKK/JHW

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 5 AM PDT Thursday for PZZ455.

     Small Craft Advisory until noon 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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For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png