Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 182248
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
248 PM PST Mon Nov 18 2019

.SYNOPSIS...Some light rain is expected for Humboldt and Del
Norte counties tonight through Tuesday morning. Gusty north
winds will follow Tuesday afternoon through Wednesday. Dry
conditions are expected Wednesday through the end of the weekend,
with freezing overnight low temperatures in many of the interior
valleys and possible early morning frost at the coast.

&&

.DISCUSSION...A weak front offshore will bring a push of moist air
and low clouds to the region tonight. The front will generate
some light rain, primarily for Del Norte and northern Humboldt
counties. Del Norte county can expect 0.25-0.50 of an inch.
Amounts in Humboldt county will span a much wider range, 0.25in
for far northern Humbodlt to 0.01in or nothing in far southern
Humboldt. A few humdredth`s will also be possible for Mendocino
and Trinity counties, however confidence is low.

Moist conditions with some showers will linger on Tuesday as an
upper level trough drops down from the Pacific Northwest. We
will start to see drier north flow develop late in the day on
Tuesday, however there are still differences between the various
models on how quickly winds will increase and how fast skies will
clear out. The cooling aloft and stronger mixing will bring an
end to the fog which has been quite persistent and dense along the
north coast for the last several days.

Northerly winds will ramp up in earnest offshore behind the
trough by Tuesday evening, primarily over the coastal waters and
over the ridges. These winds will continue to increase through
the night, becoming quite gusty in coastal areas and at high
elevations. By Wednesday morning, these winds will turn toward the
northeast, and will remain gusty at high elevations for the
remainder of the day and into the overnight hours Wednesday. In
the windiest areas, particularly at high elevations and even a few
areas along the immediate coast, sustained winds of 20 to 25 mph
can be expected, with gusts to 45 mph. Winds will finally weaken
considerably Thursday morning, and remain light for the remainder
of the week. The biggest impact of these winds will be to
contribute to elevated to locally critical fire weather conditions.

Temperatures are expected to cool down considerably in response
to the drier/cooler air mass mid to late this week. Granted the
wind prone ridges probably will not cool down much at night. Many
of the interior valleys will likely dip below freezing, especially
in Trinity, Mendocino, and parts of Humboldt counties through the
end of the weekend. Guidance also indicates the potential for
frost along the coast.

The long standing dry weather pattern is expected to persist
through the weekend and probably into the early portion of next
week. The air aloft should warm up over the weekend. The warm air
aloft will probably lead to more fog and low clouds for coastal
areas. We are heading into the latter portion of November and so
far there are no sure signs of a pattern change to wet weather.
Another weak system from the NW may push through the area sometime
early next week and bring some light rain, but confidence is low.

&&

.AVIATION...High clouds continue to pass over the region today
as conditions at coastal terminals have bounced around between
flight categories. Conditions are expected to slowly improve this
afternoon as a weak front approaches from the north west, which
should should act to disturb the entrenched marine layer. Periods of
showers are anticipated starting late this evening at both coastal
terminals as well. Elsewhere, VFR conditions are expected to prevail.

&&

.MARINE...Elevated winds downwind of Cape Mendocino will return late
tonight and quickly Ramp Up through tomorrow, resulting in another
round of hazardous ocean conditions through mid week. Elevated winds
and seas extend northward tomorrow morning, and have upgraded to a
Gale Warning for both outer zones from Tuesday afternoon through
Wednesday afternoon in response. Current thinking is that the inner
zones may briefly flirt with Gales along the peripheries of the
zones, but coverage and duration is looking marginal. However,
large, short period seas for the northern waters look to be
spreading closer to shore, thus have replaced the small craft with a
Haz Seas Warning for tomorrow evening in this zone. Meanwhile the
Small Craft Advisory for the southern inner waters stands unchanged.
This situation will need to continually be monitored in case an
upgrade to a Gale Warning or another headline may be needed. Large,
steep, short-period seas will develop across all zones in response
to the increasing winds. Winds and seas will peak Wednesday morning
and slowly wane through Thursday morning. Otherwise, another solid
long-period northwest swell will move through the waters late in the
week.

&&

.FIRE WEATHER...The fire weather watch has been upgraded to
a Red Flag Warning for interior Mendocino and northern Lake
counties, fire weather zones 277 and 276. Confidence is higher
that this area will see elevated fire weather conditions due to
low humidity and gusty ridge level winds. The overlap of gusty
east-northeast winds and low RH`s will most likely occur Wednesday
afternoon and continue through late Wednesday night. East-northeast
winds from 15 to 25 mph with gusts between 35 and 45 mph are
expected at high elevations, above 1500-2500 ft. RH`s are expected
to drop to 15% to 20% Wednesday afternoon, with only 25% to 40%
recoveries Wednesday night at high elevations. If recent history
is any guide, fire weather zones 277 and 276 seem to be most
susceptible to rapid growth rates in offshore flow patterns. Plus,
these zones have received very little or no rain this Fall.

Locally elevated fire weather conditions are also possible for
southern Humboldt and Trinity counties, however there is still
uncertainty on the state of the fuels and how dry it will get.
For now will hold off on upgrading the fire weather watch to a
red flag warning for zones 283 and 212.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning from 4 AM Wednesday to 7 AM PST Thursday for
     CAZ276-277.

     Fire Weather Watch from late Tuesday night through Thursday
     morning for CAZ212-283.

NORTHWEST CALIFORNIA COASTAL WATERS...Gale Watch from Tuesday
     afternoon through Wednesday afternoon for PZZ470-475.

     Small Craft Advisory from 9 AM to 3 PM PST Tuesday for PZZ470.

     Small Craft Advisory from midnight tonight to 9 PM PST Wednesday
     for PZZ455.

     Small Craft Advisory from 11 AM Tuesday to 9 PM PST Wednesday
     for PZZ450.

&&

$$

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