Area Forecast Discussion
Issued by NWS Eureka, CA
FXUS66 KEKA 211150
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
350 AM PST Tue Feb 21 2017
.SYNOPSIS...Wet and unsettled weather will persist through much
of the week. A few thunderstorms will likely develop, with some
small hail possible, mainly on today through Wednesday morning.
Colder air filtering into the region aloft will allow some higher
elevation snowfall to develop with snow levels lowering toward
the end of the week.
.SHORT TERM...(Today through Wednesday) A surface low just north
of our northern coastal waters continues to progress northeastward
into Oregon this morning. A period of stronger winds has
developed as the low passes. The winds have not been as strong or
as wide spread as originally forecast so have dropped the high
wind warning and reduced the coverage of the advisory. a number of
location both at elevation and near the coast have been near or
above advisory level. Some lightning activity has occurred off
shore earlier last night and just to our east over Shasta County.
Satellite images do indicate another disturbance followed by a
colder air mass approaching the coast this morning. This will lead
to a more unstable atmosphere, mainly over the marine environs
and along the coast. Expect convection to develop in response with
the potential for small hail with some storms. The current
forecast has a good handle on this and no changes were necessary.
Cold air aloft will keep us under the threat for storms through
Wednesday morning. As an upper level trough approaches the coast
late tonight associated upper level forcing will enhance
thunderstorms. These enhanced thunderstorms have the potential to
produce large amounts of small hail.
The SPC mesoanalysis, model data, and area point soundings all
show increasing instability tonight with approaching cold air
aloft with the upper disturbances. The colder air aloft will
overspread the region today but mainly tonight. This continues to
be played out in the model data and soundings, as mid- level
(700-500mb) lapse rates continue to be modeled in the 7.8 to 8.2
deg. C/km range. This is due to a strong cold pool aloft behind
the approaching upper level trough which can now be seen m in
water vapor. A drying signature is also clear in the water vapor
with the approaching disturbance indicative of intensification.
Model 500mb temps are down to around -34 degrees C. This will lead
to the small hail treat Wednesday morning mentioned above. Please
use caution if you encounter hail while traveling on area roads.
LONG TERM... (Thursday through next Monday)
The unsettled weather pattern may continue. Mainly light showers are
anticipated through the first half of Thursday, before things dry
out briefly, before another system dropping south brings more
widespread precipitation back to the area. Colder air aloft will
continue to filter into the region through at least the start of the
weekend, with falling snow levels as early as Friday. These
levels will drop as low as 1500 to 2000 feet by Thursday, before
rising to around 2500 feet by the weekend. As such, pass level
snowfall will develop, with many locations seeing at least a
dusting of new snowfall. Passes will likely see some impacted,
some of which may approach advisory level. This is something else
we`ll be keeping an eye on with the later model runs. /PD/mkn
.AVIATION...MVFR conditions and moderate and gusty winds will continue at KCEC
and KACV through the early afternoon. VFR to MVFR conditions will occur this
afternoon with moderate winds at KCEC and KACV. The lower conditions will be
due to reduced ceilings and/or visibilities at times as showers move across the
region at times today. VFR to MVFR conditions will continue at KUKI today with
light to moderate winds occurring. The lower conditions will also be due to
reduced ceilings and/or visibilities at times as showers move across the region
at times today
.MARINE...The winds and seas will gradually diminish today as a low pressure
system moves northeastward into Oregon and farther from the coastal waters.
A high pressure ridge will build across the region Wednesday and Thursday.
A gale warning is in effect across the northern waters through the early morning.
Small craft advisories are in effect across the southern waters through late
this evening. Small craft advisories will be necessary across the northern waters
late this morning through this evening.
HYDROLOGY...A flood warning for the Navarro at Navarro is
currently in effect which has route 128 closed this morning. The
Eel River at Fernbridge is forecast to rise above monitor stage
this afternoon. The Russian river at Hopland has gone above 15
feet this morning which leads to minor flooding of HWY 175 south
of Hopland. See the CNRFC`s webpage at www.cnfrc.noaa.gov for the
latest on rapidly changing river conditions.
CA...Wind Advisory until 9 AM PST this morning for CAZ101>106.
NORTHWEST CALIFORNIA COASTAL WATERS...Gale Warning until 9 AM PST this morning for PZZ450-470.
Small Craft Advisory until 9 PM PST this evening for PZZ455-475.
Gale Warning until 3 AM PST early this morning for PZZ455-475.
Wind Advisory until 9 AM PST this morning for PZZ410.
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