Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 181135

National Weather Service Eureka CA
435 AM PDT Sun Mar 18 2018

.SYNOPSIS...Dry weather, accompanied by chilly mornings and mild
afternoons, is expected Sunday and Monday. Thereafter, a storm
system will enter the region Tuesday afternoon, resulting in
widespread rainfall through Thursday. In addition, a cooler
airmass arriving Friday will favor mountain snow.


.DISCUSSION...Sunday morning satellite imagery showed a pair of
upper troughs moving south across the NERN Pacific. One trough was
hugging the WA/OR coast, while the second was located well
offshore from the West Coast. Meanwhile, a subsident large-scale
regime was present closer to NWRN CA, and was aiding in mainly
clear skies. The lack of cloud cover was supporting morning
temperatures in the low to mid 30s over the interior, as well as
locally in the vicinity of Eureka. Thus, the inherited
frost/freeze headlines have been maintained through 9 AM Sunday.

A weak upper impulse is forecast to move across the region this
evening. Non-precipitating high level cloudiness will increase
along/ahead of the impulse, and then potentially clear late Sunday
night. This will result in mainly sunny skies Monday afternoon,
which will yield mild temperatures in the 50s to low 60s over much
of northwest California.

Meanwhile, the previously mentioned trough located over the WA/OR
coast is forecast to shear eastward during Tuesday. This will be
followed by broad upper ridging over the WRN CONUS, which will
allow stronger southwesterlies to emanate downstream from the
Pacific trough. In addition, an occluded surface front will
quickly progress east-northeast toward NWRN CA by Tuesday
afternoon, and will aid in rainfall development for much of the

Light rain will remain possible going into Wednesday morning, and
then increase in intensity Wednesday night and Thursday morning
as the offshore trough ejects eastward toward the West Coast. In
addition, several model solutions indicate south-southeast winds
could become gusty as surface low pressure approaches from the
west during Wednesday afternoon.

A showery post frontal regime will develop across the region
during Thursday, with showers persisting through at least
Saturday. The showers will be accompanied by fairly cold midlevel
temperatures that will aid in snow levels falling to around
2000-2500 feet. Accumulating mountain snow will be probable as a


.AVIATION...Mostly VFR conditions are expected during the next 24
hours. Some low clouds have developed over the interior valleys
early this morning, and an area of low clouds has also developed
well offshore the Redwood Coast. The NAM is hinting that low
clouds may advect toward the Redwood Coast during the late
afternoon as light winds become onshore. However, it then develops
enough offshore flow to push this cloud cover back westward.
Uncertainty is high with this scenario, so will likely only
indicate a scattered low cloud deck in the TAFs during the
aforementioned time frame. Other than some possible cumulus over
the nearby mountains, low clouds are not expected at KUKI.
Otherwise, high clouds will thicken and lower through the day
across the area. Winds will be light. /SEC


.MARINE...A weak pressure gradient will maintain light winds over
the next few days with generally S winds for Sunday and NE winds
for Monday. NW swells will impact the waters but the overall sea
state will be trending downwards through Monday. A developing
storm system over the E Pacific will bring increasing SE-S winds
and large, steep seas by the middle of the coming week. S Winds
near gale force will be possible late Wednesday, followed by a
period of westerlies. /SEC


CA...Frost Advisory until 9 AM PDT this morning for CAZ103-109-112-

     Freeze Warning until 9 AM PDT this morning for CAZ110-111.



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