Heat Advisory 5, NWS Eureka, CA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
541 AM PDT Sun Aug 13 2023

.SYNOPSIS...Above normal temperatures will continue into the middle
of the week. Isolated, mostly dry thunderstorms are possible
across portions of the interior early this week, with the best
chances tomorrow and Tuesday.

&&

.DISCUSSION...A cut-off upper low will linger off the Central and
Southern California Coast into this week, while an upper ridge
continues to build back over the Pacific Northwest. The building
ridge will bring a weak offshore wind component for Northwest
California. This will allow interior areas to heat up, with more
dry weather.

Lingering moisture from the former Tropical Storm Eugene along with
some sub-tropical monsoonal moisture will continue to spread north
into Northwest California through the middle of this week, but
mostly tomorrow and Tuesday. This, along with increasing surface
temperatures, will bring destabilization across the interior,
which will favor the development of interior mountain
thunderstorms each afternoon/evening today through Wednesday. Most
of these storms will be dry and high-based, although precipitable
water values will gradually increase by early next week. Storm
motion is expected to be slow through most of the period. The best
chance of thunderstorms now looks to be Monday afternoon and
evening, but storms could also form on Tuesday with some storms
even around on Wednesday. The best chance of wet thunderstorms is
expected on Monday and Tuesday.

A warming trend is forecast as the offshore ridge moves over the
area and continues to amplify into next week. Each afternoon today
through Wednesday, 850mb temperatures over Northern California
will approach 25C to 30C, this will make temperatures into the low
110s certainly possible for some interior regions of Northwest
California. But, generally, high temperatures are forecast to be
anywhere from 100 to 110. The hottest days are expected from
Monday to Wednesday. ECMWF Extreme Forecast Index (EFI)
highlights a high probability of above normal temperatures for
Northwest California for this time period, even including areas
along the North Coast with temperatures into the low to mid 70s
expected through the middle of the week.

Heat Advisories have been issued for Trinity, Lake, interior Del
Norte, interior Humboldt, and interior Mendocino counties starting
today. Excessive Heat Warnings have been issued for Trinity, Lake,
interior Humboldt, and interior Mendocino from Monday to Wednesday.
Heat Advisories will continue for Southwestern Humboldt and interior
Del Norte counties until Wednesday. Temperatures are expected to
remain above average into the middle of the week before decreasing
to more average values by the end of next week as a result of the
weakening upper level ridge. /JLW

&&

.AVIATION...Coastal stratus has gradually expanded and filled in around the
Humboldt Bay area overnight while clear skies have persisted farther
north. A few clouds are starting to appear on satellite near
Crescent City at this hour but generally east winds have prevailed
and clearer skies are expected along much of the Del Norte coast.
Through the day today southerly winds will develop along the
Humboldt/Del Norte coastlines and status should refill in this
afternoon or evening for all coastal areas. Inland areas will remain
VFR with a few cumulus forming over the interior mountains. /RPA

&&

.MARINE...North winds will continue to decrease today as the thermal trough
moves off the west coast and ridge builds. This will result in
gradually improving conditions and even light southerly winds in the
inner waters. Winds will remain light Monday into Tuesday across all
or most of the waters but some moderate fresh swell will propagate
into the waters potentially resulting in small craft conditions in
the outer waters through the period. North winds should increase
again beginning mid week. /RPA

&&

.FIRE WEATHER...Moisture will continue to move northward toward the
region into the new week. However, the latest models develop a
stronger ridge over N CA and S OR, and this will delay the bulk of
the moisture until tomorrow and Tuesday making the best chances
of thunderstorms on those days. The threat for fire starts due to
lightning will be further enhanced by another period of above
normal temperatures developing today and into next week. Will
continue to highlight this in the FWF headlines. The ECMWF model
is indicating an increased threat of lightning strikes Monday and
Tuesday, primarily focused over Lake, Trinity, and NE Mendocino
counties. We'll continue to monitor for the threat of more
lightning coverage. /SEC

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Heat Advisory from 11 AM this morning to 11 PM PDT
     Wednesday for CAZ102-104.

     Heat Advisory from 11 AM this morning to 11 AM PDT Monday
     for CAZ105>108-110-111-113>115.

     Excessive Heat Warning from 11 AM Monday to 11 PM PDT
     Wednesday for CAZ105>108-110-111-113>115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 PM PDT this afternoon for
     PZZ450.

     Hazardous Seas Warning until 3 PM PDT this afternoon for
     PZZ470.

     Small Craft Advisory until 3 PM PDT Monday 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