802
FXUS66 KEKA 022135
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
235 PM PDT Sun Jun 2 2024

.SYNOPSIS...Light to moderate rain will continue to spread south
through early Monday morning with the heaviest rain restricted to
the Del Norte and Humboldt coast. Hot, dry weather will rapidly
build back in mid week with high heat risk for many interior
valleys, especially Lake County, Wednesday and Thursday.


&&

.DISCUSSION...Midlevel clouds and moisture have continued to
stream into the area today ahead of an upper level trough. This
pattern has brought muggy conditions along the coast with dewpoints
soaring into the upper 50s. Very light rain has already begun near
Crescent City with light showers on radar. Rain will continue to
strengthen and spread south through tomorrow morning.

Rain rates will be strongest in the terrain of Del Norte early
monday morning. Though winds are westerly aloft, generally southerly
winds will limit strong orographic enhancement to only the few south
facing slopes and highest peaks above 3000 feet. Most likely
rainfall over the 24 hour period ranges from 1.2 to 2.2 inches along
the highest terrain. Even Around Humboldt Bay, 0.3 to 0.6 inches is
most likely. More minor wetting rain of 0.1 to 0.2 inches is most
likely in Trinity and along the Mendocino coast through early Monday
afternoon with only trace amounts for the more southern interior.

Despite the time of year, the system has a very winter time profile
with very little surface instability, so any thunderstorms even over
high terrain are very unlikely (< 5% chance). ECMWF EFI highlights
how unusual such rain is for June, even for Del Norte County where
it is highlighted above the 90th percentile for climatology. That
said, impacts will generally be minor with debris on roadways and
slipperiness from oil buildup being the main concerns.

Rain and clouds will help cool interior temperatures into the 70s
for Monday, but such cool conditions will be very short lived. There
is very high confidence that high pressure will rapidly build across
northern California mid next week, brining the hottest temperatures
of the year so far. For the valleys of Mendocino and especially Lake
Counties, NBM is already showing a 60 to 80% chance of highs above
100 next Wednesday and Thursday. Though not quite record breaking,
such conditions will bring the first high heat risk of the year,
especially across Lake County where influence from the central
valley could help keep even overnight temperatures as high as 70.
Strong nighttime cooling and marine influence will generally limit
the heat risk elsewhere though afternoon highs will still be
oppressive in areas such as the Trinity River Valley and Round
Valley. /JHW


&&

.AVIATION...18Z TAF
ACV/CEC...Summary: Increasing rainfall this afternoon and
deteriorating CIGs and VIS tonight with LLWS at CEC. Some
improvement after 12Z Monday.

Light rain is spreading in from the north this afternoon. The
shallower stratus cleared out late this morning, but improvement is
proving to be short lived as rainfall rates steadily increase this
evening. IFR to LIFR CIGS and VIS are expected to develop with
moderate rainfall rates and TEMPO heavy rainfall rates. Gusty S
winds at the surface and SW winds aloft 1500 to 2000 ft AGL at 30
kts will create low level wind shear (LLWS) through 12Z, especially
at CEC. Rainfall rates will quickly lower after 12/13Z Monday behind
a frontal passage, and improvements in CIGs and VIS will follow.

UKI....Rainfall from a late season storm system will generally fall
mostly north of this southern terminal. Measurable precipitation in
the form of drizzle or light showers will make it into the valley
with the quickly moistening airmass. This will allow for low clouds
to settle in with likely accompanying mist and lowered VIS. Held the
category to MVFR levels for now in the TAF. /JJW


&&

.MARINE...Summary: A series of small mid period swells through
Tuesday will be followed by a seasonably large and long period WNW
swell on Wednesday. Northerly winds increase Tuesday in the southern
zones, and will strengthen and expand north Wednesday. The short
period N seas and long period WNW swell will create a chaotic seas
state Wednesday.

Southerly winds are increasing in the northern waters today ahead of
a late season frontal system. These winds will reach 15 to 20 kts
overnight and into Monday morning. A southerly swell is coming in at
2-3 ft at 17 seconds today, along with a small, mid period NW swell
at 3-4 ft.

On Monday, a slightly larger, mid period NW swell will move in,
building to 6-8 ft at 11 seconds early Tuesday morning. Light, split
wind flow will transition to strengthening northerlies in the
southern zones Monday night.

Tuesday, the NW swell will hold in size, then a slightly larger
reinforcing mid period swell then pulses in Tuesday afternoon with
seas 6 to 8 ft. Northerly winds in the southern waters will further
increase, reaching 22 kts south of the cape in the afternoon.

A strong gale on the southern periphery of a late season Aleutian
low pressure area, driving eastward, will deliver a long period
swell on Wednesday. A resulting seasonably large, long period WNW
swell (300 degrees) will build in early Wednesday morning, currently
forecast 10 to 12 ft at 15 seconds. Northerly winds will be on the
increase throughout the day, with gale conditions probable in
portions of the waters by late Wednesday. There looks to be some
shelter from the strongest winds in the northern inner zones. The
combination of steep, short period northerly seas and the long
period swell will generate a confused sea state up to 15 ft

On Thursday, the long period swell will begin slowly easing in size.
The northerlies will offer more potential Gale gusts in portions of
the waters in the wind favorable locations south of the capes, with
some shelter in the inner zones. /JJW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Heat Advisory from 8 AM Wednesday to 8 PM PDT Thursday for
     CAZ114-115.

NORTHWEST CALIFORNIA COASTAL WATERS...
None.
&&

$$

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https://www.weather.gov/images/eka/zonemap.png