559
FXUS66 KEKA 182226
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
326 PM PDT Tue Aug 18 2026

.KEY MESSAGES...

* Thick smoke remains stuck around the Hoopa Valley stretching from
  as far north as to Orleans as far south as the middle Eel River
  Valley. Weak transport winds will keep smoke here through the
  week.

* Interior temperatures peaking Tuesday will ease through the week
  with persistent marine influence along shore.

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


&&

.SYNOPSIS...Warm temperatures will ease through the week tanks to
increasing marine influence. Marine clouds will persistent along
shore with some slightly better clearing chances late week.


&&

.DISCUSSION...High pressure has peaked across the area today,
allowing many interior locations to reach into the upper 90s.
Besides a thin and slow to recede marine layer near shore, clear
skies and gentle west winds have persisted. Smoke has continued to
sock in valleys around the MP18 fire in Hoopa with smoke pushing up
the Trinity River with afternoon terrain winds.

An elongated trough will gradually approach shore through the end of
the week. This will help push marine influence further inland and
weaken high pressure, allowing interior highs to pull back into the
upper 80s by late in the week. Increasing marine influence will most
likely help strengthen and deepen the marine layer along shore, a
deeper and slightly more unstable marine layer may allow for better
scattering in the late afternoons. The trough will certainly bring a
string of high clouds across the area around Friday, helping
reinforce cooler temperatures. There is potential for very isolated,
weak thunderstorms along the trough Friday, but instability appears
lacking in all models. Although there will be gusty southerly winds
aloft, no model shows them mixing to the surface where weak north
and west winds will persist. Most long range models show high
pressure at least briefly rebuilding this weekend. /JHW


&&

.AVIATION...A thin but persistent marine layer has brought sporadic
IFR conditions to coastal terminals throughout the day today. Some
sporadic VFR clearing will remain through the early evening, with
fog an stratus resurging around sunset. LIFR conditions are most
likely (70% chance) by midnight before very slowly lifting again
during the day Wednesday. Otherwise, VFR conditions have persisted
across the interior except where thick smoke has socked in valleys
around the MP18 fire in Hoopa. /JHW

&

.MARINE...Fresh north winds gusting up to 28kts have persisted
across the outer waters today with steep seas up to 10 feet. Winds
have been much calmer closer to shore, with gusts only around 12
kts with some seas up to 5 feet pushing in from the outer waters.
Some stronger north winds will briefly push into the southern outer
waters Tuesday evening and early Wednesday, mostly downwind of Cape
Mendocino. Beyond short period seas, a very minor 2 foot, mid period
southerly swell is augmenting the sea state. North winds gradually
ease through the week with particularly calm conditions int he
northern waters by Friday. /JHW


&&

.FIRE WEATHER...Hot and dry weather has peaked today with the
hottest valleys reaching near 100 F and some RH values in the upper
teens. Thermal belt strength will peak Wednesday morning with poor RH
recovery as low as 30 percent along mid and upper slopes. 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.

The greatest forecast challenge remains thunderstorm potential
around Friday. There is high ensemble confidence that a strong stream
of midlevel tropical moisture will push across the area from the
southwest early Friday morning and through the day. At the same
time, a strong southerly jet forming offshore and aligning with
topography could provide and lift and enhance instability to allow
for thunderstorms. Even with this dynamic forcing, however, no model
is consistently showing any amount of instability. Similar events
have generated high clouds and virga, but little to no lightning.
There remains a very slight (5%) chance of lightning in northern
Trinity and Humboldt Counties Friday morning and afternoon, but
coverage would be sporadic and very isolated. Any lightning that
does occur will be dry, increasing fire risk. This forecast could
quickly change if a source of instability materializes. /JHW



&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 AM PDT Wednesday for PZZ455.

     Small Craft Advisory until 9 PM PDT Wednesday for PZZ470.

     Small Craft Advisory until 9 AM 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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see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png