Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 111828

National Weather Service Eureka CA
1028 AM PST Tue Dec 11 2018

.SYNOPSIS...Tuesday will be a fairly wet day along the Redwood
coast as a weak storm system passes through, but some sunshine and
generally dry weather will be found over southern Mendocino county.
High pressure will bring dry weather for Wednesday and Thursday.
Stronger fronts are likely to push through on Friday and Sunday.


.UPDATE...Rain has been slower to move into the area than expected
so have adjusted the forecast slightly for this afternoon. The
rain is still expected to move into the area this aftenroon, but
it looks more like late afternoon. Otherwise the forecast remains
on track. MKK


.PREV DISCUSSION... /issued 516 AM PST Tue Dec 11 2018/

DISCUSSION...Clear skies across most of northwest California
overnight have allowed temperatures to fall into the 30s and 40s,
some 5 to 15 degrees colder than Monday morning. Fog and low
clouds have also developed through most of the inland river
valleys. Meanwhile, an approaching warm front is sending
increasing mid-level clouds over the Redwood Coast. Along with
light offshore winds, this is keeping temperatures from falling to
frosty levels along the coastal plain. These clouds will continue
to thicken and expand south and east, but Mendocino county and and
portions of eastern Trinity county will have a fair amount of
sunshine first. Light rain associated with the warm front has
already reached the Oregon coast this hour, and will reach
Crescent City shortly, then continue to spread across the rest of
Del Norte and Humboldt county this morning. Expect the rain to be
light and intermittent most of the day. A period of somewhat
heavier rain will reach the coast between Crescent City and Eureka
by late afternoon with a weak cold front. Rainfall amounts will
generally range from a couple tenths to a half inch across
Humboldt and Del Norte counties, with locally up to an inch over
the mountains of eastern Del Norte. Lighter amounts will be found
farther south and east, with just a trace at most in far southern
Mendocino county.

Showers will taper off tonight, followed by a couple of dry days
on Wednesday and Thursday as relatively strong high pressure
builds in. Outside of of morning valley fog, expect a fair amount
of sunshine for both days. Thursday morning could be frosty in the
coastal plain, however it is looking like some high and mid-level
clouds may keep temperatures from dropping below the upper 30s
there. Models are still taking strong low pressure into British
Columbia on Friday, with a fast-moving cold front pushing across
northern California. A period of heavy rain and gusty winds will
accompany the front, however the rainfall amounts and strength of
the southerly winds are still in question. A reasonable worst-case
would be brief small- stream or urban flooding on Friday, as well
as 40 to 50 mph wind gusts around Crescent City and the adjacent
mountainous terrain. Saturday is still looking like a generally
drier day at this point, before another front passes through on
Sunday. Next week looks like it will continue to have periods of
wet weather, but at this point it looks like the focus of the
Pacific moisture will be to our north. /AAD

AVIATION...VFR conditions prevail across most of the region this
morning, aside from some patchy ground fog in the vicinity of UKI
producing sporadic minor visibility reductions. An approaching front
will spread rain over the area from northwest to southeast beginning
late this morning at CEC and early this afternoon at ACV. The front
will be accompanied by MVFR conditions which should begin to improve
back to VFR during the evening as the front departs to the east. A
brief period of low level wind shear will be possible at CEC with
the arrival of the front, but wind shear is not expected at the
other terminals due to lighter surface winds. /CB

MARINE...Seas have subsided below advisory criteria as the westerly
swell has gradually diminished overnight, however another significant
mid period swell will move into the coastal waters tonight,
necessitating a new set of Small Craft Advisories beginning late
tonight which will last through the day on Thursday and possibly
beyond. This swell will increase to around 15 feet at 15 to 17
seconds by Wednesday morning. Moderate to fresh northerly breezes
will develop tonight into Wednesday behind another departing system,
then shift to the south on Thursday ahead of a stronger front
approaching the waters. This will yield increasing short period seas
by the end of the week in addition to the continuing mid period
northwesterly swell train. /CB


NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory from 6 AM Wednesday to 9 PM PST Thursday
     for PZZ450.

     Small Craft Advisory from midnight tonight to 9 PM PST Thursday
     for PZZ470-475.

     Small Craft Advisory from noon Wednesday to 9 PM PST Thursday
     for PZZ455.



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