148
FXUS66 KEKA 220801
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
101 AM PDT Fri Aug 22 2025

.SYNOPSIS...Hot and very dry weather will begin to peak today with
a strengthening, shallow marine layer near shore. There is slight
potential for thunderstorms over the interior late this weekend into
early next week.


&&

.DISCUSSION...High pressure arching over from the 4
corners region will begin to peak today with highs most likely
between 104 and 108 in the hottest interior valleys this afternoon.
Hot day time conditions combined with enhanced overnight lows in the
mid 60s will combine to generate generally moderate to localized
major HeatRisk. Conditions will be most dangerous along the Trinity
River Valley and around Clear Lake. Temperatures will very slightly
ease Sunday into early next week, though also slightly increase
humidity will help maintain a very similar overall HeatRisk through
at least Tuesday.

High pressure will generally promote a shallow but more resilient
marine layer along the coast, likely encouraging a stronger deck of
marine stratus into the weekend, especially with more persistent
onshore flow. Most recent model runs have generally suggested more
consistent onshore flow which will most likely prevent any warm
conditions from reaching the coast.

Most model ensembles show high pressure slowly weakening early next
week but especially by Wednesday. As high pressure pushes back east,
southerly flow up the Sacramento Valley will help pull up some
midlevel monsoon moisture. This moisture, combined with enhanced
instability from the heat, will produce a slight chance (10 to 20%)
of isolated, mostly dry, thundertorms over high terrain early next
week. ANy storms around Monday will be mostly dry but the chances of
wetting showers will increasingly increase through the week. /JHW


&&

.AVIATION...22/06Z TAFs...Satellite imagery depicts coastal stratus
redeveloping along the Mendocino Coast and around Humboldt Bay and
vicinity. Light southerly wind reversal nearshore will aided coastal
stratus to moves northward toward Del Norte Coast overnight. IFR to
LIFR conditions with low ceilings and vsby in mist/fog are likely
for the coastal terminals. There is a 50-70% chance for visibility
at 1/2SM or less for CEC by Friday morning, while 30-60% chance for
ACV. Low clouds are expected to gradually erode back to the coast,
but stratus will be stubborn to scatter nearshore and at the coastal
terminals with lighter winds and an strengthening low-level
inversion. Surface winds will persist from S at around 5 kts.


For inland areas: VFR conditions persist at UKI through the period.
Surface winds very light and variable, after 21Z becoming SSE at
around 5-10kts with higher occasional gusts./ZVS


&&

.MARINE...Northerly winds has begun to diminish across the
waters. Moderate to strong northerly winds will continue across the
outer waters and around Cape Mendocino through Friday, with light to
gentle winds for the inner waters. A gradual improvement in winds
will continue into the weekend. However, conditions will remain
hazardous for small crafts through at least Saturday afternoon.

Steep short-period seas around 6-9 ft will continue to accompany the
strongest winds. Seas are expected to gradually subside through the
weekend. A small southwest wave around 15 seconds is currently
moving across the waters and will linger into the weekend. /ZVS


&&

.FIRE WEATHER...Heat will begin to peak today with highs reach over
r100 for the hottest interior valleys. RH will drop to some of the
lowest of the season so far with some single digit minimum RH
possible in the far eastern interior today and Saturday. Thankfully,
high pressure will generally suppress wind with only moderate
terrain winds during the afternoon.

Beyond hot and dry weather, the main concerns will be for potential
thunderstorms this weekend and into early next week. Heat will
greatly increase surface instability, but moisture will generally be
lacking to generate thunderstorms. By around Sunday, there is some
indication of monsoon moisture wrapping around and up into the
Central Valley, but the general pattern will be more conducive to
storms over the NE California rather than NW California (only 5%
thunder chance here). A few models show a shortwave that may help
kick off convection Sunday, but this possibility is very uncertain
(10% chance) There is potential for a more concerning pattern around
next Monday and Tuesday with moisture wrapping back around (20%
chance of some storms). Storms this weekend are more likely to be
dry than storms next than next week, so even with more coverage any
storms this weekend may be more impactful from an initial attack
perspective.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Heat Advisory from 11 AM this morning to 11 PM PDT Saturday
     for CAZ105-106-110-113.

     Heat Advisory until 11 PM PDT Saturday for CAZ107-108-111-
     114-115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 5 AM PDT early this morning for
     PZZ450.

     Small Craft Advisory until 11 AM PDT this morning for
     PZZ455.

     Small Craft Advisory until 11 AM PDT Saturday 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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see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png