Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 131213

National Weather Service Eureka CA
413 AM PST Wed Dec 13 2017

.SYNOPSIS...High pressure continues to remain firmly in place
over the west coast this morning. A weak shortwave will bring some
cooler air to the area Friday into the weekend, but dry weather
is expected to persist into early next week.


.DISCUSSION...High pressure remains in place over the region this
morning. A strong inversion is in place in the valleys.
Temperatures this morning on the ridges are in the 50s while
temperatures are near or below freezing in the valleys. Some of
the valleys in Humboldt and Trinity county are see fog and low
clouds once again. These areas will likely only warm into the low
40s today. Valleys that are free of clouds are expected to warm
to around 50. The smoke from the southern CA wildfires is thinner
this morning. This trend is expected to continue and by early
afternoon most of the smoke is expected to be out of the area as
the winds return to northerly. Tonight and Thursday are expected
to be very similar to today. Northerly winds are expected to
persist and keep the smoke out of the area.

Friday a weak system moves through the area. Current models are in
pretty good agreement that the precipitation will remain to north
of California. There will likely be an increase of mid level
clouds, especially in Humboldt and Del Norte counties. Behind this
system colder air filters into the area. This will allow the
ridges to cool quite a bit more than they have been at night.
Northerly winds will also increase Saturday and Sunday. This will
help keep temperatures from dropping as much overnight.

Early next week models generally show the high pressure remaining
in place. The ECMWF drops a fairly dry system close to the area on
Wednesday, but the area mainly looks to be dry. The GFS now keeps
the precip well to the north of the area. MKK


.AVIATION...Smoke aloft from S CA fires appears to have at least
thinned over the area. A modest increase in N winds at all levels of
the atmosphere should further thin the smoke by midday today. Some
patchy, mostly light fog early this morning along the Redwood Coast
and over some interior valleys should thin later this morning.
Otherwise, mostly VFR conditions are expected. Winds above the
surface of around 15 knots will provide a bit of low-level wind
shear, but this is expected to be below LLWS criteria. /SEC


.MARINE...N winds will gradually increase today as a thermal trough
develops along the CA coast. This will bring marginal Small Craft
Advisory conditions to the S outer waters, and the existing advisory
continues there. Winds will approach advisory criteria over the N
outer waters as well, but uncertainty is higher with less areal
coverage, so have kept that zone headline-free. Fresh NW swell will
arrive today with initial periods of 17 to 19 seconds. Strong high
pressure will build N of the area by late in the week, with further
increases in the N winds. Gale force gusts will be possible over the
outer waters over the weekend. /SEC


.SNEAKER WAVE POTENTIAL...The northwest swell building into the
area area will bring an elevated risk of sneaker wave from this
morning through Thursday evening. This swell is expected to build
to around 6 feet with a period of 17 to 19 seconds. These long
period waves develop set behavior which means there can be periods
of smaller waves lasting for 20 minutes or more. Then suddenly the
waves are much larger and can catch people off guard. Meanwhile,
we will have northerly short period wind waves starting to develop
today. These will mask the set behavior of the larger waves to
some extent, but they are not expected to be large enough to
completely mask it. The beach hazard statement looks to still be
on track. MKK


CA...Beach Hazards Statement from 10 AM PST this morning through
     Thursday evening for CAZ101-103-104-109.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PST
     Sunday for PZZ475.



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