Area Forecast Discussion
Issued by NWS Eureka, CA
FXUS66 KEKA 011035
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
335 AM PDT SAT OCT 1 2016
.SYNOPSIS...An upper level trough off the coast is bringing some
showers to areas of Humboldt and Del Norte counties this morning.
Tonight into Sunday morning additional rain is expected across the
area as a stronger system moves through the entire region.
Additional light rain is possible through Monday night.
.DISCUSSION...An upper level trough just off the coast is bringing
some showers and an occasional thunderstorms to the waters north
of Cape Mendocino. These have begun to move onshore into Del Norte
county. These showers and occasional thunderstorms are expected to
continue through this morning. Showers are expected to diminish
late in the morning and afternoon as the trough pulls out of the
Late tonight the next system starts to move into the area. Models
are in good agreement on the rain starting after midnight and are
showing a period of steady rain as a frontal boundary moves
through early in the morning. Behind this boundary showers are
expected and there will likely be some breaks in the rain through
the late morning and afternoon. With the upper low moving nearly
overhead it appears that there will be enough instability to give
a slight chance of thunderstorms. In the morning the best chance
looks to be along the Humboldt and Del Norte coast while in the
afternoon it shifts south of to Mendocino county where the best
energy looks to move in on the south side of the low. Confidence
is low on the timing and location of the thunder and this will
need to be watched. Total precipitation is expected to range from
a tenth to half inch with locally higher amounts over 1 inch in
northern Humboldt and Del Norte counties. The lowest amounts will
be in southern Mendocino County. The rain will not cause any
major issues with rivers and even small creeks will only have minor
flow increases. The rain will fall on road surfaces that have not
experienced rain for several months. Thus built up oil on the
roads from vehicles over the summer will make roads slick.
Monday another system is shown in the models approaching the area.
The models are still struggling with the timing on this one with
the GFS hold off on the rain until late in the afternoon and the
ECMWF bringing in the rain more quickly, especially to the
Mendocino coast. Southwest flow is fairly strong ahead of this
system to the coast may stay fairly dry due to down sloping.
Tuesday a few showers may linger around the area. Wednesday
through the weekend the models keep nearly zonal onshore flow with
occasional shortwaves moving through the flow and bringing rain to
the area. Friday the GFS brings a slightly more substantial
shortwave and associated rain onshore, but the ECMWF is dry.
Needless to say confidence is low in the extended. Temperatures
are expected to be fairly cool, especially overnight. Frost is
possible in the interior valleys. MKK
.AVIATION...VFR to MVFR conditions and light winds to calm
conditions will continue at KCEC and KACV through this morning.
The lower conditions will be due to reduced ceilings and/or
visibilities as a few showers move through the region at times.
VFR to MVFR conditions and light to moderate winds will prevail at
KCEC and KACV today with stratus reducing ceilings at times. VFR
conditions and light winds to calm conditions will continue at
.MARINE...A weak pressure gradient continues across the coastal
waters. Light winds will continue across the near shore waters
today. The winds will increase slightly across the outer waters as
a low pressure system strengthens off the Washington and Oregon
coast. A few showers will likely move across the waters at times
today. The winds and seas will increase the middle of this next
week as a low pressure system strengthens off the Canadian coast
and a trailing cold front approaches the waters.
NORTHWEST CALIFORNIA COASTAL WATERS...None.
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