Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 211214

National Weather Service Eureka CA
514 AM PDT Mon Oct 21 2019

.SYNOPSIS...Aside from some areas of valley fog, expect sunny and
warm weather much of this week with high pressure in control.
Northerly winds offshore and along the immediate coast will
increase through midweek. Offshore winds and dry air will result
in fire weather concerns Wednesday into Thursday.


.DISCUSSION...Areas of valley fog have developed overnight across
most areas of inland Humboldt, Del Norte, and Trinity counties.
This will last through mid-morning before clearing, with an
otherwise sunnier day ahead for northwest California as high
pressure builds offshore. There have been some low clouds along
portions of the coast as well, but the bulk of these have stayed
offshore. A few coastal locations may start off cloudy early this
morning, mainly around the mouth of the Eel River, near the Oregon
border, and south of Fort Bragg, but otherwise almost all coastal
areas should turn out mostly sunny today. After very light winds
on Sunday, northerly breezes will develop this afternoon along the
coast, keeping those areas cool, while inland northwest California
heats up. Most inland areas will see highs 10 degrees warmer than
Sunday afternoon, with a few locations into the 80s; much above
late October seasonal averages. Warming will continue through
Thursday, with the warmest spots probably breaking 90 degrees.

Tuesday and Wednesday will feature northerly breezes along the
coast, continuing to keep temperatures cooler there. A few patches
of low clouds may be found along the immediate coast, but
otherwise expect sunshine to continue for the majority of
northwest California this week. As the tail-end of a dry front
passes by on Tuesday night, high pressure offshore will build
across the Pacific Northwest, while a thermal trough over
California shifts toward the coast. Along with high pressure aloft
building in, this progression will bring warm, dry offshore winds
Wednesday afternoon through Thursday. While much of our area has
seen a fair amount of rain over the last month, portions of
southern Trinity and interior Mendocino counties have stayed
drier, resulting in fire weather concerns during this next bout of
offshore winds. See the Fire Weather Discussion below for more

Temperatures along the coast may reach well into the 70s on
Thursday as the offshore flow peaks and the thermal trough drifts
offshore, but the winds may begin turning back onshore on Friday,
bringing a return to more seasonable temperatures. A much more
substantial upper- level trough will drop southward across the
Pacific Northwest this weekend, with a dry cold front sending a much
cooler airmass into northern California. Inland temperatures will
begin falling on Saturday, and will drop back below seasonal
averages next week. By the end of the weekend and into next week,
portions of our area will likely see frost. Additionally, this
trough may bring another shot of locally gusty offshore winds to
the ridgetops. /AAD


.AVIATION...Mainly clear skies have been found across northwest
California overnight, although a band of stratus lingering offshore
has brought occasional low ceilings to coastal terminals, with
periods of MVFR at CEC and IFR cigs at ACV. These sporadic lower
conditions will remain possible through mid morning at the coastal
sites, otherwise VFR conditions and generally light winds will
prevail across the area through the day. Guidance is hinting at
stratus returning to coastal terminals overnight, keeping the threat
of IFR ceilings at CEC and ACV through Tuesday morning. /CB


.MARINE...Northerly winds and seas will gradually increase today and
persist for the next few days as high pressure builds offshore. The
building short period seas coupled with a decaying NW swell on the
order of 7 feet at 12 seconds will produce combined seas in the 7 to
9 ft range. This will support Small Craft Advisories across the
southern waters from this afternoon through Wednesday, with some
localized gale force gusts possible downwind of Cape Mendocino at
times. Small Craft conditions will spread to the waters north of the
Cape during the middle of the week as a strengthening inland thermal
trough tightens the pressure gradient further, with some low end
gales possible during the latter half of the week. /CB


.FIRE WEATHER...We are still looking at a potentially critical
fire weather pattern for southern Trinity, interior Mendocino and
Lake counties Wednesday afternoon through Thursday afternoon.
While enough rain has fallen over the last month or so over the
rest of northwest California to keep fuels more moist and reduce
fire danger, that area has seen little rainfall. Model guidance
continues to bring a period of gusty offshore winds to the exposed
higher terrain of northwest California later Wednesday into
Thursday, with east- northeast 925-850 mb winds of 15 to 30 kt
carrying very dry air. The strength of the winds and the degree of
dry air does not look as great as with the event around October
9th, but conditions still may reach Red Flag Warning criteria.
Fire Weather Watches may be hoisted for portions of our area later
today. Winds will decrease later Thursday, and the airmass will
gradually moisten heading into the weekend, but no rainfall is in
sight. /AAD


   from 1 PM this afternoon to 3 AM PDT Thursday for PZZ455-475.



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