343
FXUS66 KEKA 291216
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
516 AM PDT Sat Jun 29 2024

.SYNOPSIS...Dry and seasonable conditions will continue through
weekend along with gusty northwest wind in the afternoon. A strong
heatwave will build early through at least mid week.


&&

.DISCUSSION...An upper level trough is evident just offshore this
morning with a series of midlevel clouds streaming over the area.
Though the trough has weakened the marine inversion, it has also
helped push marine air along shore, helping to gradually reform a
layer of marine stratus along the coast. Otherwise, very seasonable
conditions have been observed overnight with lows in the 50s and 60s
alongside very stark valley inversions throughout the interior.

Seasonable weather will continue through the weekend with interior
highs around 90. The coastal marine layer, weakened by the passing
trough, will most likely quickly clear by late morning. The along
shore pressure gradient will peak this afternoon and Sunday
afternoon as the trough moves east and high pressure quickly builds
on its heals. This will bring gusty northwest wind this afternoon
gusting between 20 and 30 mph on exposed ridges and in channeled
terrain.

There is high confidence that very strong high pressure will build
early this week, generating significantly warmer than normal
temperatures by Tuesday. By Wednesday, NBM shows a 90 to 100% chance
of highs in excess of 100 throughout inland valleys of Lake,
Mendocino, and Trinity Counties. Focused on the Russian River
Valley, there is even a 60 to 80% chance of highs above 110 just in
time for the 4th of July. Such values will rival the daily high
record for Ukiah. Overnight lows will bring little relief, especially
along midslope areas of Mendocino and Lake counties where lows are
likely to stay above 70.

Such high temperatures are expected to bring Major to isolated
Extreme HeatRisk around Clear Lake and in the Russian River Valley.
where and excessive heat watch has been issued. Widespread Moderate
HeatRisk is expected throughout the rest of the interior. Despite
similar high temperatures, much cooler overnight lows in the 50s for
Trinity and northern Mendocino County will help lower the overall
HeatRisk. Though there are flagged areas of Major or even Extreme
HeatRisk beyond Lake and southern Mendocino, the vast majority of
the populated areas show only Moderate HeatRisk. These areas will
need to be watched closely in the coming days as the need for
further heat products may increase.

Above average temperatures are most likely to persist late into the
week. That said, the presence of a surface low pressure off the
coast late in the week may disrupt the heat depending on how
efficiently it can break up larger scale high pressure and pull in
marine influence. It is possible its impact will be negligible, with
about 50% of model ensemble members showing Major to Extreme HeatRisk
continuing even late into the week. /JHW


&&

.AVIATION...Pics from the sky shows coastal stratus redeveloping
along the Redwood Coast, and the Eel River valley overnight. IFR
ceilings and visibility in mist is impacting the coastal terminals.
Stratus are expected to scatter/clear out after 19Z and promote VFR
conditions with high clouds streaming across NW California as a weak
frontal system moves through. Short-term model guidance suggest
widespread marine stratus developing during the evening, with a
slightly deepen marine layer. After 4Z, expect IFR/LIFR conditions
returning at ACV and CEC. Inland areas, including UKI, VFR
conditions will persist through the foreseeable future. Surface
winds will remain very light and variable this morning, becoming
breezy NNW at 10-15 kts after 19Z with occasional stronger
gusts...primarily at KCEC and UKI where gusts to around 25 kt is
likely this afternoon and evening.


&&

.MARINE...Northerly winds will continue ease across the waters
today into Sunday, especially north of Cape Mendocino as a weak
frontal system moves through. Strong breezes will continue across
the southern waters today, with locally near-gale to gale force
gusts downwind of Cape Mendocino. NDBC buoys observations are
reporting steep short periods NW seas around 6-9 feet @ 6-7 seconds
overnight. These seas will continue slowly subside into Sunday, with
seas at 5 feet or less over the northern waters on Sunday. While,
steep seas around 6-8 feet will remain across the southern water
zones over the weekend.

Monday, winds are forecast to strengthen again as a high pressure
offshore begin to builds in quickly in the wake of the trough. A
thermal trough is then expected to develop near the coast Monday
night/early Tuesday and favor moderate to strong pressure gradient.
Widespread strong to near gale force winds and very steep, hazardous
seas (12-16 ft @ 10 s) are forecasted for early to mid next week.
Confidence is high for high for gale force gusts up to 40 kt over
the outer waters, with locally gales downwind of Cape Mendocino


&&

.FIRE WEATHER...Seasonable warm and dry conditions will persist
through the weekend. A tightening pressure gradient will continue to
enhance northwest winds today with gusts of 20 to 30 mph most likely
on exposed ridges and in channeled terrain. This is especially true
in southern Mendocino and Lake Counties. Onshore flow will slightly
increase humidity, but interior valleys will still be dry with
minimum RH down to 20%. In combination, wind and RH will create
locally critical fire weather conditions in the afternoon,
especially in fine fuels below 2000 feet in elevation. Thankfully,
such conditions will be short lived during the late afternoon and
evening. /JHW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Excessive Heat Watch from Tuesday morning through late
     Thursday night for CAZ113-115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 AM PDT Monday for PZZ455-475.

     Small Craft Advisory until 9 AM PDT Sunday for PZZ470.

&&

$$

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