National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KEKA 221221
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
521 AM PDT Mon Apr 22 2024

.SYNOPSIS...Dry weather with above normal temperatures are
expected to continue today. Isolated thunderstorms are possible
for mostly Trinity county on Tuesday as daytime temperatures begin
to trend down. Much cooler temperatures, a chance for rain and
high mountain snow will return Thursday through Friday.

&&

.DISCUSSION...Dry weather and above normal temperatures will
continue today as the upper level ridge moves over the region. Aside
from some high level cirrus clouds streaming across the area, skies
are mostly clear due to a large scale subsidence and light to
locally breezy offshore flow this morning. Today is forecast to
be the warmest day so far spring. Highs peaking into the mid to
upper 80`s across the interior valleys, with some of the hottest
valleys may reach the low 90`s in the eastern Mendocino and
Trinity County. Even the coastal areas are forecast to warm up,
with some coastal afternoon temperatures reaching into the mid to
upper 60`s before sea breezes develop. A bit inland away from the
cooling sea breezes, temperatures will likely (>70% chance) hit
the lower to mid 70s.

The upper level ridge will continue shift eastward into the Great
Basin today, while a H5 shortwave trough approaches the PAcific
NW. A surface cyclonic circulation will bring a southerly reversal
stratus surge tonight into Tuesday morning, with low clouds and
patchy fog charging up and lapping the coastal areas. This will
bring a push of marine air to the interior on Tuesday. Some
cooling is expected on Tuesday, but high temps will likely remain
above normal until the air mass cools down more drastically toward
the end of the week. A semi-closed low in the southern branch of
the split will also start to spread higher PWATS (200% of normal
or close to 1 inch) into the area from SW. This moist boundary-
layer coupled with daytime heating, will bring an increase
instability to around 150-300 J/kg. This instability will be
focused mostly over Trinity County where a chance of showers
(25-50%) and isolated thunderstorms is expected Tuesday afternoon
through early evening.

Potential for precipitation will increase Thursday-Friday as a
colder 500mb trough (temps <-25C) drops down from the NW. Timing
has tightened up to Thu- Fri with 24 hours probabilities for > 1
inch in 24 hours for the western slopes of Del Norte and northern
Humboldt Counties around 30%. Highest chances for precip are
forecast across the interior of Del Norte County (~1 inch over 2
days) with the lowest in southern Mendocino and southern Lake
where only a few hundredths may accumulate over 2 days. There is
still a great deal of variability with timing and precip amounts.
For now will highlight the major cool down and precip potential in
weather story graphic/social media posts.

A secondary trough in the NW flow on the backside of the main
trough may spark up more showers Friday night into Saturday (10-20%
chance). It is more certain that interior high temperatures will
cool down by late week. If snow levels fall to 5000-5500 feet on
Friday, high temps will struggle to reach the lower 40s in the
high mountains on Friday and may not recover much next weekend.
Precipitation amounts are forecast to be light, but this time of
year even light amounts will have impacts on outdoor plans or
activities. Stay tuned. ZVS/DB

&&

.AVIATION...Despite building high pressure, lingering north winds
and stubborn high cloud cover have largely inhibited the formation
of any marine fog and stratus overnight with fog only being reported
in the most protected near coastal valleys. With such a clear start,
VFR conditions will almost certainly prevail through the day.

That said, a rapidly building marine inversion will most likely
allow for marine stratus and fog to reform later this evening with a
vengeance. Just after midnight NBM has a 30 to 50% chance of at
least inconsistent IFR conditions at coastal terminals. VFR is
expected for the interior, though light southerly flow will bring a
very slight chance (10 to 20%) of a marine fog surge up to Ukiah
early Tuesday morning. /JHW


&&

.MARINE...Gusty northerly winds have continued overnight with gale
force gusts in the outer waters and short period seas remaining in
excess of 10 feet. High pressure building across the interior today
will help push the strongest northerly wind further offshore. Short
period seas will most likely fall in short order with seas below 6
feet in the inner waters by around noon today. By this afternoon,
any remaining gale force gusts will be isolated to the far outer
northern waters.

Northerly wind will turn mostly gentle to calm during the day
Tuesday with high resolution models even suggesting a minor
southerly wind reversal in the inner waters. A series of weak fronts
will increase winds again Wednesday through late week, though winds
look moderate at best with the strongest gusts up to 30 kts
restricted just around Cape Mendocino. Short period wind waves will
largely control the sea state through the week with a series of mid
period northwest swells up to 5 feet being the only other feature of
note. /JHW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 AM PDT this morning for PZZ450.

     Gale Warning until 9 AM PDT this morning for PZZ470.

     Small Craft Advisory until 3 PM PDT this afternoon for
     PZZ475.

&&

$$

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