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FXUS66 KEKA 242251
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
351 PM PDT Sat Aug 24 2019

.SYNOPSIS...Sunshine and hot weather will persist across inland
northwest California, with triple digit readings likely for many
valley locations Monday and Tuesday. Overall dry weather will
continue, although there will be a slight chance of isolated
thunderstorms around the middle of the upcoming week.

&&

.DISCUSSION...It's another fairly typical late August day for
northwest California, with sunny and warm conditions inland, while
cooler cloudier conditions are generally found at the coast. The
Mendocino coast has stayed cloudy into this afternoon, thanks to
southerly winds and a strong marine inversion. The rest of the
coast managed to clear out after midday, but clouds are expected
to return this evening and tonight, probably tending to be thicker
and more persistent Sunday morning than they were this morning.
Inland temperatures have dropped back several degrees compared to
yesterday, though there will still be plenty of 90s across the
usual hotter valleys this afternoon. Expect similar readings on
Sunday, before a well-advertised bout of hotter temperatures
arrive Monday and Tuesday under building high pressure aloft. The
hotter interior readings will generally be in the 100 to 107
degree range, before temperatures start to fall off Wednesday and
Thursday. While the increasing afternoon temperatures Monday and
Tuesday may present a moderate heat risk for those groups that are
already sensitive to heat, low humidity and resulting cool
overnights should mitigate heat impacts at least somewhat in the
mountainous northwestern corner of the state, thanks in no small
part to cool air drainage in the valleys. Meanwhile, coastal
temperatures will also likely warm above seasonal averages
Monday and Tuesday as the California thermal trough gradually
shifts toward the coast. However, as winds turn southerly, a
surge of stratus and fog may begin to return on Tuesday or Tuesday
night, which could keep temperatures cooler than currently
forecast. More shallow stratus than currently forecast may be
present along the coast during the mid to late week period, but
elected to not to add that yet given the uncertainty.

This westward shift in the thermal trough will be driven by the
gradual approach of an upper level disturbance from the southwest,
which will help to weaken the Pacific high and allow the thermal
trough to expand westward. This impulse will result in a
transition to southerly flow aloft, and will bring a surge in
mid- level moisture Tuesday and Wednesday. It still appears that
there will be a slight chance of isolated thunderstorms, mainly
for interior areas of northwest California toward the middle of
the week. Otherwise, chances for measurable rainfall across the
bulk of our area appear to be minimal for the foreseeable future.
/AAD /BRC

&&

.AVIATION...Coastal clouds continue to hang around south of Cape
Mendocino this afternoon and will persist through at least tomorrow
morning. Meanwhile north of Cape Mendocino and across the interior
skies are clear this afternoon. This evening and into the overnight
hours expect stratus to develop along the entire coast leading to
IFR ceilings and reduced visibilities at all coastal sites.
Additionally, with southerly winds and a sufficiently deep marine
layer some low clouds may sneak up the Russian River valley around
sunrise tomorrow morning which may affect UKI. Other interior
locations will remain VFR through this TAF cycle. /WCI

&&

.MARINE...Moderate to fresh northerlies continue across the
outer waters this afternoon with light southerlies along the coast.
Wind waves are still dominating the sea state ranging from 4 to 8
feet across the waters this afternoon however a southerly (2ft at 15
sec) and westerly (2ft at 12 sec) swell are also moving through the
waters. Tomorrow morning, northerly winds will begin to increase
again across the outer waters, cape Mendocino, and Point Saint
George. By Sunday afternoon strong to near gale northerlies will be
in place across the northern outer waters leading to a ramp up in
wind driven seas to 10 to 13 ft by Sunday night. Higher seas will
also spread into the other waters Sunday night into Monday which may
necessitate headlines for the northern inner waters by early Monday
morning.

By mid week, an upper level trough will approach the area leading to
widespread gentle to moderate southerly winds and calmer seas. These
conditions are expected to prevail through the end of next week.
/WCI

&&

.FIRE WEATHER...Seasonably hot weather will continue this weekend,
with temperatures peaking on Monday and Tuesday. Inland afternoon
high temperatures are likely to climb from the mid to upper 90s
over the weekend, to between 100 and 107 degrees Monday and
Tuesday. In addition to the increasing heat, humidity will also
decrease, with low afternoon minimums expected and moderate to
poor overnight recoveries. Winds are not expected to be
particularly strong on a large scale, and will be driven by
typical daytime onshore and nighttime offshore fluctuations. Winds
may become locally gusty on a smaller scale, most likely in areas
where the terrain favors stronger upslope and upvalley wind
development.

Meanwhile, little to no wetting precipitation is expected for the
foreseeable future. However, the probability of isolated and
mostly dry thunderstorms appears to be increasing slightly across
parts of northwest California toward the middle of the week.
Confidence is low regarding the potential for thunderstorms and
any accompanying rainfall, and this threat will continue to be
monitored in the coming days. /BRC

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory
until 9 AM PDT Tuesday for PZZ470-475.

&&

$$

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