Hayfork, California Weather Forecast Discussion

611
FXUS66 KEKA 210716
AFDEKA
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1216 AM PDT Sun Sep 21 2025
.SYNOPSIS...Warmer and drier weather will gradually build in Sunday
through Tuesday. A wetter pattern could emerge by mid week.
&&
.DISCUSSION...Lingering cloud cover will generally promote
subdued conditions through the day Sunday. Building northwest flow
will help push out mid and upper level clouds for the interior
Sunday, but will also likely reinforce a gloomy marine layer along
the coast for at least one more day.
There is high confidence that high pressure will at least briefly
arch over the area Monday and Tuesday, allowing interior highs to
crest back into the 90s. The marine layer onshore will likely become
more diurnal with better clearing in the afternoon but shallow fog
and stratus overnight, especially in wind protected areas such as
Humboldt Bay.
There remains decent forecast uncertainty by mid next week. The
majority of models show a cutoff low meandering into southern
California. The impacts of this motion are more uncertain. While
moderated temperature and greater cloud cover are a near
certainty, there is wide disagreement for rain potential. While
the low will pull up moisture form the south, the general
northeast flow around the low will not be favorable for widespread
wetting rain. Showers that do form will most likely be around the
rim of the Sacramento Valley where the wind best aligns with
topography. The vast majority of models suggest a cooler and more
moist pattern through the end of the month, with long range
predictions of above normal precipitation. /JHW
&&
.AVIATION...(06Z TAFs)...Considerable variability and uncertainty
continues this TAF cycle for coastal terminals. Rapid fluctuations
between VFR with broken mid clouds and LIFR with 1/4SM in fog have
occurred and may continue into Sunday morning at both CEC and ACV. A
transient front will pass into Oregon and Washington on Sunday. A
northerly surge will follow after frontal passage Sunday afternoon.
The strengthening northerlies could scour out the shallow moist air
and stratus during the day. Another possible scenario, shallow moist
air may advance down the coast and push onto the North Coast leading
to more widespread and persistent low cloud cover. HREF indicates
both with scattering out in the afternoon followed by low clouds
expanding in the evening. Meanwhile, inland areas will remain VFR
with lingering mid level clouds generally above 10kft. Stronger
northerlies over the coastal terrain may result in shallow
turbulence late in the day on Sunday into the evening.
&&
.MARINE...High pressure will build offshore over the NE Pacific and
toward the PAC NW coast on Sunday after the passage of a transient
frontal system north of the waters. Northerly winds and steep wind
waves will build through the day on Sunday, eventually satisfying
criteria for small craft advisory. Initially the strongest
northerlies will occur south of Cape Mendo late Sunday afternoon
into early evening, and eventually expand northward by Monday into
the northern waters. A few gale gusts >35kt are probable in
expansion fans that shed off Cape Mendo and Cape Blanco. In fact,
HREF chances for gale gusts are about 70% in the lee of Cape Mendo
and 50% for the northern outer waters. Coverage appears insufficient
to warrant a gale warning. Seas will respond to these stronger
northerlies with wind waves building up to 7-9 ft by Monday
afternoon and evening as a short period NW swell around 6 ft at 12
seconds builds. These two wave groups will combine into significant
wave heights around 10-12 feet with spectrum maximum wave heights
from 18-22 feet possible by Monday evening. Northerlies are forecast
to slacken off Tue into Wed with steep northerly wind waves falling
off on Wed. This break down in the pressure gradient will be in
direct response to another trough the will approach Central
California. Northerly winds and steep wave may begin to increase
late next week after this trough heads eastward into the Great Basin
and Desert SW. Inexperienced mariners, especially those operating
smaller vessels, should avoid navigating in hazardous conditions.
&&
.FIRE WEATHER...High pressure building early this week will
quickly warm and dry conditions. Highs will likely peak Tuesday
with the hottest valley just shy of 100 and min RH in the upper
teens. Northeast afternoon winds will also be slight enhanced
Monday and Tuesday afternoon around the rim of the Sacramento
Valley with some gusts in Lake County likely up to 25 mph.
Conditions will slightly ease (particularly daytime RH) Wednesday
and beyond. There is a slight chance of thunderstorms for
Mendocino and Lake Counties on Wednesday. /JHW
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 3 AM to 11 PM PDT Monday for
     PZZ470.
Small Craft Advisory from 3 PM Sunday to 11 PM PDT Monday
     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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NWS EKA Office Area Forecast Discussion