Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
699
FXUS66 KEKA 021216
AFDEKA
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
516 AM PDT Tue Jul 2 2024
.SYNOPSIS...A very strong heatwave will build in force today
bringing Major to Extreme HeatRisk and near record breaking
temperatures across the interior Wednesday through the weekend. Heat
and very dry humidity will also enhance fire weather concerns,
especially Tuesday and Wednesday.
&&
.DISCUSSION...Satellite imagery continues to show extremely dry air
settling across NW California under the influence of a building
upper level ridge. Even the marine layer, bolstered by a
strengthened inversion, is ragged at best and isolated to only the
most protected parts of the Humboldt Coast.
Temperatures will continue increasing today with interior
temperatures reaching above 100 throughout the interior, but
especially in Lake and Mendocino Counties. Rapid warming and drying
will continue through Wednesday. The southern half of the area will
see temperatures peak on Wednesday. Major to isolated Extreme
HeatRisk is expected throughout interior valleys, but especially
around Clear Lake and within the Russian River Valley. In both
areas, NBM shows a 60 to 80% chance of highs in excess of 110. Such
temperatures are either record breaking or very nearly so all across
the southern half of the area. HeatRisk is bolstered by the fact
that overnight conditions will bring very little relief. On valley
bottoms, most likely lows are around 70 with strong thermal belts
creating midslope lows closer to 80 by Wednesday morning.
Model ensembles have come to better agreement on the development of
the ridge through the week. While most models still show a weak
surface low forming off the coast of Central California, 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 through the week. Though conditions will
be dangerously hot along the Trinity River by Wednesday, 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. 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 break down late this
weekend. By Sunday, only 10% of members show the ridge pushing east.
Even by next Tuesday, 50% of ensemble members still have the ridge
sticking ridge sticking around, albeit slightly weakened. All that
is to say, all indicator point to strongly above average
temperatures being here to stay for the foreseeable future. /JHW
&&
.AVIATION...LIFR conditions have been impacting KACV with OVC layer
at FL003, while VFR conditions prevail at KCEC and KUKI. Pics from
the sky shows stratus advecting northward and attempting to
approaches KCEC. However, gusty N winds continues precluding any low
clouds reaching this terminal. Otherwise, low clouds and patchy fog
are expected to clear out with the diurnal heating late in the
morning. Thereafter, expect prevailing VFR conditions for all
aerodromes through at least Thursday. A period of visibility
reduction with haze will be possible at KCEC in the afternoon due to
the sea spray as the winds over the waters increase.
Surface gusty northerly winds continues at KCEC early this morning,
while calm winds at KACV and KUKI. After 19Z, winds becoming breezy
N winds at 15-25 kt along the coast, with strongest gusts from 25-35
kt in the afternoon. Dry E-NE flow is expected to increase tonight
as a high pressure continue building into the region. This will
inhibited stratus develop for the coastal terminals. LLWS will be
likely (60-75%)at CEC late tonight through Wednesday morning with a
stronger component wind aloft.
&&
.MARINE...Gale force northerly winds over the outer waters will
continue through Wednesday, with advisory criteria for the inner
waters. Locally gale force around Pt St George and downwind of Cape
Mendocino as well. Winds will continue to strengthen through this
evening, resulting in sustained winds around 35 kts with gusts to
around 45 kts. Very steep and hazardous seas of 15-17 feet @ 11
seconds are expected for the outer waters tonight. A Gale Warning
remains in effect for the outer waters through Wednesday evening.
This gales will propagate in a burst of very steep seas into the
northern inner waters this evening through late Wednesday afternoon.
A Hazardous Seas Warning will be in effect late this afternoon for
zone 450.
These winds will gradually ease from south to north throughout the
second half of the day on Wednesday. A southerly wind reversal will
move north along the Mendocino Coast and relax the pressure gradient
on Thursday. Seas will gradually subside Wednesday evening and
Thursday, but steep seas will persist across the waters into the
weekend. Followed by sub-Advisory conditions likely over the weekend
with light to moderate winds and seas generally around 5-6 feet @ 8
s.
&&
.FIRE WEATHER...The building heatwave will bring enhanced fire
danger through the week, but especially today and Wednesday. As
highs climb well above 100, 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. First, as the high
first builds across the area, a building pressure gradient aligned
with the Sacramento Valley will promote gusty northeast winds along
the Sacramento foothills with sustained winds of 12 to 18 mph. Such
winds have already been observed early this morning with very poor
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 today and
Wednesday, prompting a Red Flag Warning in the area.
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 on night, especially with moderate, dry
northeast winds building each night on high ridges, especially in
the Klamath Mountains. 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 to 8 PM PDT Wednesday for CAZ104-
106.
Excessive Heat Warning from 11 AM Wednesday to 8 PM PDT
Saturday for CAZ105-107-108-110-111.
Heat Advisory from 11 AM this morning to 11 AM PDT
Wednesday for CAZ107-108-110-111.
Heat Advisory from 11 AM this morning to 8 PM PDT Wednesday
for CAZ112.
Excessive Heat Warning from 11 AM this morning to 8 PM PDT
Saturday for CAZ113>115.
Red Flag Warning until 8 PM PDT Wednesday for CAZ264.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 5 PM PDT this afternoon for
PZZ450.
Hazardous Seas Warning from 5 PM this afternoon to 3 AM PDT
Thursday for PZZ450.
Small Craft Advisory until 9 AM PDT Wednesday for PZZ455.
Gale Warning until 2 AM PDT Thursday for PZZ470.
Gale Warning until 9 PM PDT Wednesday for PZZ475.
&&
$$
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