Special Weather Statement, NWS Eureka, CA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
200 PM PDT Wed Jul 22 2020

.SYNOPSIS...Isolated thunderstorms will be possible over portions of
Trinity and northeastern Mendocino counties this afternoon.
Otherwise, warm to locally hot afternoon conditions accompanied by
near zero rain chances will occur across the interior during the
next seven days. Meanwhile, cool and cloudy conditions can be
expected along the coast during the foreseeable future.

&&

.DISCUSSION...A weak upper low was centered over the Bay Area this
afternoon. Lobes of modest ascent were evident in water vapor
imagery rotating around the low, and model guidance shows a plume of
steep midlevel lapse rates spreading west across NWRN CA. Those
features combined with PWAT values near 1.0 inch, and surface
dewpoints in the mid 50s are aiding in isolated thunderstorm
development, which will continue through early evening. The
strongest boundary layer destabilization is occurring over the
Trinity Alps and Yolla Bolly Mountains, which will be the most
favored locations for storm initiation. Vertical wind shear is
weak, however, a substantial amount of DCAPE exists per SFCOA
guidance, and CAPE in the -10 to -30 C layer ranges from 200 to
500 J/kg. Thus, thunderstorm wind gusts to 40 mph and hail near a
half inch in diameter will be possible with the strongest storms.

Storms are forecast to dissipate later this evening as the boundary
layer stabilizes. Dry weather will then be probable across the
region during the next seven days. Temperatures over the interior
will be warm to locally hot, and channeled valley winds could become
gusty during the afternoons and evenings. Otherwise, periods of
marine stratus will be probable along the coast during the night,
with partial clearing taking place during the afternoon.

JMG

&&

.AVIATION...The marine layer remains in place along the coast
this afternoon. Some locations have cleared out as of 1 pm, but
these locations are expected to quickly fill in again after 5 or
6 pm this evening. Visibilities are not expected to drop much
below a mile tonight as the marine layer remains around 2,000 feet
deep. Southerly winds will persist tonight in Mendocino county
and it is possible some stratus may briefly make it into KUKI
tonight, but confidence is low on this so have only included a
scattered group in the TAF. Late tonight into Thursday offshore
flow starts to pick up slightly as the upper level low moves out
of the area and a trough passes the area. Models are indicating a
slightly better chance of clearing in the afternoon on Thursday,
but stratus is still expected to return Thursday night. MKK

&&

.MARINE...Small Craft Advisories remain for the outer waters
through tonight, and the southern inner waters beginning this
evening. Have extended the southern outer waters through Friday
night. Winds to the lee of Cape Mendocino will have started to
increase this afternoon and will remain elevated through Thursday.
Moderate to locally strong northerly winds will continue to
expand across the coastal waters through Friday. This will occur
as a thermal trough over interior northern California shifts
inland, allowing the stronger pressure gradient offshore to creep
closer to the coast. While there may be a brief window of sub-
advisory conditions for the northern waters on Thursday, otherwise
advisories will likely need to be expanded across most of our
coastal waters through Friday. Have not extended the other
advisories as it looks like there will be a break in the stronger
winds Thursday afternoon and Friday. MKK/AAD

All signs continue to point toward weakening Pacific high
pressure late in the weekend and early next week, while the
thermal trough shifts closer to the coast. This pattern would
allow for very light winds and low seas across the inner waters,
and substantially better conditions across much of the outer
waters as well. /AAD

&&

.FIRE WEATHER...Isolated dry thunderstorms are expected this
afternoon and evening across portions of the interior mountains,
particularly in the vicinity of the Trinity Alps and Yolla Bolly
Mountains. Conditions will be very similar to yesterday, such
that dry thunder coverage will not be sufficient to warrant the
issuance of a Red Flag Warning. However, given the dry state of
local fuels, any cloud to ground lightning strikes that occur
will have the potential to ignite new fires.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until
     noon PDT Thursday for PZZ470.

     Small Craft Advisory from 8 PM this evening to 3 AM PDT Friday
     for PZZ455.

     Small Craft Advisory until 10 PM PDT Friday 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

Hazardous Weather Outlook
National Weather Service Eureka CA
427 AM PDT Wed Jul 22 2020

CAZ101-103-104-109-112-231130-
Coastal Del Norte-Northern Humboldt Coast-Southwestern Humboldt-
Mendocino Coast-Southwestern Mendocino Interior-
427 AM PDT Wed Jul 22 2020

This hazardous weather outlook is for northwest California.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected at this time.

CAZ107-108-111-231130-
Northern Trinity-Southern Trinity-Northeastern Mendocino Interior-
427 AM PDT Wed Jul 22 2020

This hazardous weather outlook is for northwest California.

.DAY ONE...Today and tonight.

Hot afternoon temperatures are expected in low elevations, reaching
the mid 90s to near 100 in many areas.

Isolated thunderstorms will be possible near the Yolla Bolly
mountains and Trinity Alps this afternoon.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected at this time.

CAZ102-105-106-110-113>115-231130-
Del Norte Interior-Northern Humboldt Interior-
Southern Humboldt Interior-Northwestern Mendocino Interior-
Southeastern Mendocino Interior-Northern Lake County-
Southern Lake County-
427 AM PDT Wed Jul 22 2020

This hazardous weather outlook is for northwest California.

.DAY ONE...Today and tonight.

Hot afternoon temperatures are expected in low elevations, reaching
the mid 90s to near 100 in many areas.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected at this time.

Special Weather Statement
National Weather Service Eureka CA
242 PM PDT Wed Jul 22 2020

CAZ108-222215-
Southern Trinity-
242 PM PDT Wed Jul 22 2020

...A STRONG THUNDERSTORM WILL AFFECT WEST CENTRAL TRINITY COUNTY...

At 241 PM PDT, a strong thunderstorm was located near Forest Glen, or
14 miles southwest of Hayfork, moving southwest at 20 mph.

Winds in excess of 30 mph and half inch hail are possible with this
storm.

This storm will remain over mainly rural areas of west central
Trinity County.

LAT...LON 4057 12332 4043 12323 4036 12347 4056 12348
TIME...MOT...LOC 2141Z 066DEG 17KT 4047 12339

Garner