Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 162211

National Weather Service Eureka CA
311 PM PDT Mon Oct 16 2017

.SYNOPSIS...Dry weather will continue through Wednesday as high
pressure holds over the area. A cold front will bring widespread
rain and significant cooling Thursday into Friday.


.DISCUSSION...Dry conditions will persist through mid week as an
upper level ridge remains over northern California. This means
above normal high temperatures across much of the region. Model
soundings indicate very dry air will persist near the surface into
Tuesday. Coastal stratus may return Tuesday night into Wednesday
after a front passes into the Pacific Northwest.

Mostly clear skies and low humidities will persist across the
interior through mid week. Winds will remain light for most areas.
We should see slight improvement in humidities each day through
Wednesday as winds favor an onshore direction and the ridge aloft

Significant improvement will hold off til late in the week when a
front is forecast to cross the area bringing widespread rain by
Thursday Night. The heaviest rainfall will fall across Del Norte
and northern Humboldt counties, but wetting rain (a tenth or more)
is also expected for eastern Trinity and southern Mendocino
counties. The models have sped up slightly and rain may start
Thursday afternoon for the northern portion of the forecast
area. There will be window for breezy southerly winds proceeding
the cold front Thursday afternoon/evening for the coastal ridges.
The GFS does indicate the potential for gusty southerlies over
the exposed coastal ranges of Humboldt and Del Norte counties
with 925mb winds of 35-40kt just offshore. The wind forecast for
the ridges may need to be beefed up as the event grows closer.

A shortwave trough in the cooler air behind the front will likely
bring an uptick in showers for mainly the northern portion of the
forecast area on Friday. There will also be a chance for a few
inches of high mountain snow, above 5000 feet, on Friday.
Shortwave ridging should bring a period of minimal showers Friday
night before another trough approaches on Saturday. The models
have been inconsistent with this feature for Saturday. Confidence
is not high we are going to see more widespread rain on Saturday.
For now will maintain a chance of showers due to the uncertainty.

Ridging near the surface and aloft should result in drier weather
conditions for remainder of the weekend. Primary issue Sunday into
Monday is the potential for another round of dry offshore flow.
It should be cooler and drier this weekend and frost will also
be possible in the river valleys of Humboldt and Del Norte


.AVIATION...Small areas along the North Coast briefly dropped
into IFR conditions this morning...especially at/vcnty CEC.
Expect a repeat of the these conditions on Tuesday morning. Also
conditions will allow for some patchy MIFG around Humboldt Bay to
ACV. Late morning today saw haze briefly reported near ACV, but
VIS remained VFR. Otherwise, mostly SKC and VFR conditions
prevailed over NW CAlifornia in the last 24 hours with various
degrees of Cirrus advection moving across the region...and will
continue. In Southern Interior Mendocino County, specifically at
UKI, wild fires have kept smoke (FU) and Haze (HZ) reductions
(mostly MVFR) continuing across the local areas. /TA


.MARINE...Fairly quiet marine weather will persist for the next
few days, with low seas and light to moderate north winds. A 6
foot northwesterly long period swell will continue to propagate
across our waters before rapidly building later this week due to a
low pressure system near the Gulf of Alaska. This system will
cause southerly winds to increase on Thursday ahead of a strong
cold front that will approach our area as well as build seas to
17-20 feet by Thursday night. /WCI




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