448
FXUS66 KEKA 031154
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
454 AM PDT Wed Jul 3 2024

.SYNOPSIS...Extreme, record breaking heat will begin to peak across
the southern half of the area today with heat continuing to spread
northward at the same time. Heat will bring continued Major Heat
Risk alongside enhanced fire weather concerns.


&&

.DISCUSSION...A strong dome of high pressure has properly built over
the area over the last 24 hours. Across the southern half of the
area, highs were will in excess of 100 degrees with even a few
locations such as Ukiah breaking 110. Heat will continue to
intensify and move north today especially with gentle offshore flow
this morning help to push heat closer to the coast, especially in
the King Range with highs above 85 at least briefly most likely
today around Shelter Cove. Today will most likely be the day of
greatest HeatRisk for the southern half of the area with most likely
highs of 108 to 116. Areas if extreme risk are expected especially
in midslope location which have seen virtually no overnight relief
with lows this morning struggling to drop below 80.

While most models still show a weak surface low forming off the
coast of Central California over the next couple days, few models
show it having much impact on the heat. Though it may slighlty
weaken heat for the southern half of the area, it will mostly just
shift the focus of heat further north into Trinity and Humboldt by
Thursday. Regardless, near record breaking heat will continue for
the entire interior through the week. Though conditions will be
dangerously hot along the Trinity River already today, NBM suggest
the peak heat further north around Friday. By this point, NBM shows
a 70 to 90% chance of highs above 110 all along the Trinity River
Valley. For Hoopa in particular, this could easily approach the all
time high temperature record of 111. Per usual, Big Bar is expected
to be the hottest station with highs around 120. HeatRisk is only
slightly diminished in the north thanks to lower nighttime
temperatures closer to 60 through the week.

Heat will even begin to move towards the coast as the week wears on
and onshore flow continues to weaken. High pressure settling through
the week will help create an increasingly shallow marine inversion
which may, at times, be totally pushed offshore by easterly
nighttime winds. While a triumphant sea breeze will certainly cool
off coastal areas each afternoon, increasingly clear and hot
mornings may allow high to approach 80 by late in the week. By
Thursday and Friday, NBM shows a 50 to 70% chance of brief highs
over 80 as close to shore as Arcata and downtown Crescent City.

The vast majority of cluster ensemble members show the ridge
persisting and only very slowly beginning to weaken by early next
week. Essentially no models show the ridge fully breaking down
within the next 10 days. With that in mind, dry and much above
average temperatures are here to stay for the foreseeable future.
/JHW


&&

.AVIATION...High pressure and broad offshore flow have crated an
extremely thin marine layer overnight, allowing for widespread VFR
conditions. Light mist has been able to form only in the most
stable valleys such as the Eel River Valley. Any mist will quickly
burn off this morning. Dry air will promote VFR conditions again
through the day today with gusty northerly wind and marginal
associated wind shear being the only notable concern for terminal
right on shore north of Cape Mendocino. A similar very weak and
shallow marine layer will support mostly VFR conditions through
Thursday morning. /JHW


&&

.MARINE...A tight pressure gradient over the coastal waters with the
thermal trough strengthening over the interior is resulting in
strong gales in the outer waters. Steep seas will propagate toward
the coast bringing hazardous seas to waters north of Cape Mendocino
through today. Winds will decrease sharply beginning tonight into
Thursday as the tightest pressure gradient moves west outside of the
waters. Light to moderate southerly flow is likely to return near
the coast with the potential for a coastal stratus surge Thursday
into Friday. Northerlies return over the weekend as high pressure
strengthens off the coast. /RPA


&&

.FIRE WEATHER...The building heatwave will continue to bring
enhanced fire danger through the week, but especially through
Thursday. As highs climb closer to 110, RH will crater with most
interior valleys very likely (80% chance) to see minimum RH between
5 and 10%. Overnight conditions will bring little relief with very
poor RH recoveries of 30 to 40%. Even with only gentle terrain
winds, such dry conditions will promote critical fire weather
conditions each afternoon.

There are several areas where enhanced winds will generate more
widespread and long lasting critical conditions. As the high cross
shore, a building pressure gradient has remained aligned with the
Sacramento Valley promoting gusty northeast winds along the
Sacramento foothills with sustained winds of 12 to 18 mph. Such
winds have been regularly observed over the past 24 hours alongside
RH recoveries barely above 20 percent. Though restricted to
ridgetops at night, such winds will mix down more broadly early each
afternoon. For the forecast area, afternoon mixing will promote
widespread critical conditions in southeast Lake County.

Elsewhere, periods of critical fire weather are expected
during the afternoon where terrain winds are enhanced, such as along
the Trinity River Valley. Strong thermal belts will help promote
critical conditions even at night, especially with moderate, dry
northeast winds building each night on high ridges, especially in
the Klamath Mountains. The power of thermal belts have already been
observed with some midslope areas not even dropping below 80 this
morning. Fire Weather conditions will only slightly begin to ease by
this weekend. /JHW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Heat Advisory from 11 AM Thursday to 8 PM PDT Saturday for
     CAZ102.

     Heat Advisory from 11 AM this morning to 8 PM PDT this
     evening for CAZ104-106.

     Excessive Heat Warning from 11 AM this morning to 8 PM PDT
     Saturday for CAZ105-107-108-110-111.

     Heat Advisory until 11 AM PDT this morning for CAZ107-108-
     110-111.

     Heat Advisory until 8 PM PDT this evening for CAZ112.

     Excessive Heat Warning until 8 PM PDT Saturday for
     CAZ113>115.

     Red Flag Warning until 8 PM PDT this evening for CAZ264.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Hazardous Seas Warning until 3 AM PDT Thursday for PZZ450.

     Small Craft Advisory until 9 AM PDT this morning for PZZ455.

     Gale Warning until 2 AM PDT Thursday for PZZ470.

     Gale Warning until 9 PM PDT this evening for PZZ475.

&&

$$

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