755
FXUS66 KEKA 170705
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1205 AM PDT Thu Sep 17 2026

.KEY MESSAGES...

* A frontal system brought thunderstorms, hail, and showers
  Wednesday and could return Thursday.

* There is a slight chance for thunderstorms in mainly in Trinity,
  Humboldt and Del Norte counties on Thursday.

* Warmer temperatures and dry conditions return end of the week.

&&

.SYNOPSIS...An upper level low brought instability and channeled
flow up the interior valley and through terrain, using orographic
lift to dynamically charge the atmosphere with lightning and hail
embedded thunderstorms causing a slight outbreak Wednesday evening.
cooler temperatures and a chance for showers and Thursday are
possible. Warmer and drier conditions are expected Friday and into
the weekend.


&&

.DISCUSSION...An upper level low that has moved south over the
PACNW is expected to continue impacting the area Thursday. This is
expected to bring some showers and possible thunderstorms to the
area Thursday afternoon and evening. Low pressure will continue to
meander eastward on Thursday. This will pull some more marine
influence near shore with weak southerly wind. Southerly wind may
also help pull in some marine fog and clouds closer to the Lost
Coast and into the upper Russian River. The chance (10%) of
thunderstorms will continue, but the core of instability and
thunderstorm chances will shift further east, more focused around
the Trinity Alps. The potential near the coast will reduce.

A high pressure ridge will gradually rebuild Friday and into the
weekend. This pattern will allow for interior temperatures to dry
back out and warm back into the 90s. Moderate north winds will
return near shore, helping form a shallow but persistent marine
layer especially north of Cape Mendocino. High pressure will most
likely persist through next week. Most models show weak to moderate
high pressure, but about 20% of ensemble members show unusually
strong high pressure around next Tuesday that could push interior
highs closer to 100. Aside from isolated showers today and tomorrow
There is near 0% chance of wetting rain for the next 10 days. /JHW
/EYS


&&

.AVIATION...With variable wind patterns and localized formation of
stratus, the terminals will differ overnight into Thursday morning.
KCEC will stay clear longer than KACV tonight but expect stratus to
fill in by 13z with ceilings below 500ft and possibly 300-400ft a
few hours before dawn. Southerlies are likely to dominate the from
groups at KCEC into Thursday morning. KACV will likely have
southerly winds veering to easterly/offshore by 11-13z with IFR
conditions, ceilings around 300-400ft. Northwest and westerly winds
prevail by Thursday afternoon at KACV with a return of LIFR flight
conditions Thursday night.


&&

.MARINE...Low pressure moving inland has weakened northerly wind and
pushed strong winds further offshore. Seas have fallen in the inner
waters along with the wind and will continue to fall in the outer
waters overnight with seas generally below 6 feet by mid Thursday
morning. Southerly winds will form along shore in the inner waters
early Thursday with gentle gusts staying below 15 kts. Moderate to
strong northerly winds will gradually return to the southern waters
by Friday and gradually spread north through the weekend, though
winds will most likely remain much calmer closer to shore. Short
period wind waves will dominate the marine environment with only a
very minor southwest mid period swell up to 2 feet to speak of.
/JHW


&&

.FIRE WEATHER...Storm potential will remain Thursday, but shift
focus towards the Trinity Alps area. Any storms will be weak with
light rain. Aside from storms, winds are mostly gentle and terrain
driven with generally high RH over 30 percent and good overnight
recoveries. Any new starts are not expected to spread rapidly.
Conditions will significantly dry and warm over the weekend with
thermal belts contributing to much worse RH recovery. There is
little to no chance of wetting rain for the next 10 days. /JHW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 AM PDT Thursday for PZZ470-475.

&&

$$

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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