949
FXUS66 KEKA 132144
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
244 PM PDT Mon Jul 13 2026

.KEY MESSAGES...

* Interior Heat: Above normal temperatures continue for the interior
  through Tuesday. High temperatures in the 90s to around 100 likely.

* Slight chance thunderstorms. A 10 percent chance for thunderstorms
  early Tuesday morning. Chances increase to 20 percent in Trinity
  County Tuesday afternoon. Dry lightning and gusty winds will
  elevate fire risk.

* Coastal flooding: Minor coastal flooding around Humboldt Bay
  possible at the evening high tide through Wednesday night.

&&

.SYNOPSIS...Hot temperatures return to much of the interior today.
Monsoonal moisture will bring cloud cover and moisture through
Tuesday. Isolated thunderstorms or showers are possible today and
Tuesday in the interior.


&&

.DISCUSSION...An upper level trough in British Columbia continues to
inch eastward while an upper ridge over the Rockies continues to
expand westward. This ridge will bring above normal temperatures to
the interior with 90s likely for most valleys and the warmest areas
possibly exceeding 100. Minor to locally moderate HeatRisk is
expected. Monsoonal moisture from the south has started to stream
over the area in the form of high clouds. So far, none of this
moisture has resulted in showers with measurable precipitation. CAMs
do show some potential shower activity today in the eastern and
southern portions of the area. Instability remains low, but a stray
sprinkle from a shower is possible.

Tonight and early Tuesday, additional moisture arrives to the area
bringing additional shower and low-end thunderstorm chances.
Convection is already being observed off the coast and this moisture
arrives sometime Tuesday morning. High-resolution models are showing
an increase in instability at this time (100-200 J/kg of CAPE).
There is still large model variability on where this moisture plume
is Tuesday. However, Trinity County is the most likely to see
convection by mid morning into the afternoon. Model soundings show
inverted-V profiles with very dry low level conditions. Downdraft
CAPE of nearly 1000 J/kg is being observed on some model soundings
and PWATs of nearly 0.9 inches support precipitation loading. All
this points to a strong wind threat around any storms that develop.
Should thunderstorms develop, wind gusts could reach or exceed 55
mph within stronger storms. The HRRR among other models show
instability remaining into the evening and overnight hours, but
chances decrease to around 10-15% with the highest in Trinity County.

Drier air returns midweek as the Pacific Northwest trough
moves southwestward. A deeper marine layer will likely bring
interior temperatures down by a few degrees, while bringing more
widespread, and possibly persistent, coastal stratus. High pressure
returns late week, returning warmer interior temperatures. Next
Sunday and Monday, more monsoonal moisture is expected to stream
north over the area. The NBM is showing over 1 inch PWATS and some
low end instability. This will need to be watched as it gets closer
as the NBM already has some 10 to 20 percent chances for thunder. At
this point these look like they may be on the wetter side. /JB/MKK


&&

.AVIATION...18Z TAFS..A strengthened low level inversion has held a
shallow band of stratus along the North Coast. Afternoon heating
allowed for some scattering from the immediate coast, but duration
was limited. The stratus, while remaining shallow will fill back in
Monday evening. Areas fog, potentially dense at times is expected
through Tuesday morning. There should be improvement in ceilings and
visibility going into 18Z Tuesday.

An unstable environment associated with an approaching disturbance
may disrupt the inversion and stratus later Tuesday morning, but the
instability will be aloft above the inversion. Interior
thunderstorms are forecast over mainly Trinty County Tuesday and
Tuesday night from the passing disturbance. The storms will be
capable of strong downdraft winds or even microbursts and may expand
into interior Humboldt and Del Norte Counties, especially overnight
Tuesday.


&&

.MARINE...Northerly winds will continue over the waters, strongest
over the southern zones, particularly around Cape Mendocino.
Afternoon and evening wind pulses will create gale conditions along
and south of Cape Mendocino, with gusts nearing 40kts at times in a
confined expansion fan around the cape. Steep seas up to 9ft will be
generated in response. These seas will likely propagate into inner
coastal waters and coast south of the cape where lighter winds are.

The northern zones north of the cape will see lighter winds and
seas, especially inside of 10 nm. Steep seas up up to 6 ft will
periodically make in into the northern inner zones from the stronger
offshore winds however.

A trough of low pressure will establish itself well offshore the N.
CA coast Friday. This will greatly ease the winds and seas
throughout the day Friday. This feature looks remain around through
the weekend to continue much calmer conditions.


&&

.COASTAL FLOODING...High astronomical tides and the basin wide warmth
in the ocean is creating higher than normal water levels despite
light northerly winds. The water levels were 0.6 feet over the
astronomical tide Sunday evening resulting in a high tide of 8.8
feet. This will likely put water levels around 8.9 feet at the North
Spit in Humbodlt causing and cause minor flooding again this
evening. This may continue Tuesday night as well before astronomical
tides start to diminish Wednesday night/Thursday morning. MKK


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Coastal Flood Advisory from 10 PM this evening to 1 AM PDT
     Tuesday for CAZ103.

     Red Flag Warning from 1 PM Tuesday to 2 AM PDT Wednesday
     for CAZ403-409>412.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 5 AM PDT Friday for PZZ455-475.

     Small Craft Advisory until 5 PM PDT this afternoon for
     PZZ470.

&&

$$

NOTE: The full forecast discussion is now regularly issued between
10 am/pm and 1 pm/am. Additional updates will be issued as needed.

Visit us at https://www.weather.gov/eureka

Follow us on Facebook and Twitter at:
https://www.facebook.com/NWSEureka
https://www.twitter.com/NWSEureka

For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png