Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 072235

National Weather Service Eureka CA
235 PM PST Sun Mar 7 2021

.SYNOPSIS...A cold upper-level storm system will gradually move
south along the west coast through mid week. As that takes place,
numerous showers will spread inland across northwest California.
Snow will occur across the interior mountains, while isolated
thunderstorms and small hail will be possible along the coast.
Mainly dry weather is expected during the second half of the week.


.DISCUSSION...Abundant lightning was observed within the basal
portion of a cold upper-level low positioned over the NERN PAC.
Downstream from the low, high level cloudiness was spreading east
across NWRN CA. Breaks in the cloud cover tonight will aid in
frost and freeze conditions over much of Lake and Mendocino
Counties, and possibly in the vicinity of Humboldt Bay as well.
Otherwise, an upper vort lobe/wave of ascent is forecast to spread
east across the EKA CWA by midday Monday. Showers will move inland
as a result, and persist through Tuesday morning. Another wave of
stronger ascent is then expected to move across the region Tuesday
afternoon and evening, which will invigorate shower activity. In
addition, steep low and midlevel lapse rates will exist across the
area and aid in favorable buoyancy profiles for thunderstorms
along the coast and adjacent foothills. Small hail will be
probable with the stronger shower/storm activity, and hail
accumulations across low-elevation roadways can`t be ruled out.

Meanwhile across the interior mountains, deep sub-freezing
temperature profiles, steep lapse rates, and persistent
westerlies will yield snow showers moving east across elevations
above 2000 feet Monday afternoon through Wednesday morning. Heavy
snow showers will be capable of producing snowfall rates from 0.5
to 1.0 inch per hour, which will accumulate over time resulting in
storm totals from 4 to 12 inches. A long duration winter weather
advisory has been issued as a result. Reference the latest
advisory statement for additional information.

The previously mentioned upper low is forecast to fill as it moves
inland across NRN/CNTRL CA Wednesday afternoon and evening.
Showers will continue nevertheless, particularly over Mendocino
and Lake Counties. NAM forecast soundings in the vicinity of Ukiah
also show fairly robust CAPE profiles during Wednesday afternoon
that that extend up through the -40 C level. Thunderstorms and
small hail will be possible across interior Mendocino County if
that thermodynamic environment materializes.

After Wednesday, upper heights are forecast to build over the west
coast. Lingering showers will subsequently dissipate, with upper
ridging favoring mainly dry weather through Saturday, if not



.AVIATION...Overnight rainfall and associated MVFR CIGs quickly
wrapped up this morning when VFR conditions returned. Winds turned
light offshore, but became westerly in the afternoon. Stronger
southerlies will develop very early tomorrow morning ahead of the
next weather system, and high clouds are already streaming in from
the SW ahead of it today. Rain will push in tomorrow morning with
lowering CIGs with the system, with hints of a possible
convective squall line on the front end. The precipitation will
transition to more isolated showers with some healthier showers
and perhaps embedded thunderstorms capable of small hail reaching
KCEC and KACV by late morning. This will produce widely varying
CIGs, with MVFR to maybe brief IFR conditions accompanying the


.MARINE...Light westerly breezes filled in today behind a front,
with some slightly stronger northwest breezes south of Cape
Mendocino. A fresh westerly swell is building into the waters
today, peaking at around 15-17 ft at 16 seconds late tonight,
dominating the sea state and supporting Small Craft Advisories
through much of the first half of the week. Periods of stronger
southerly breezes will also continue through the first half of the
week as weak fronts occasionally brush the northern half of the
area. It appears a northerly wind regime may develop during the
second half of the week as high pressure builds over the region.


CA...Frost Advisory from midnight tonight to 7 AM PST Monday for

     Winter Weather Advisory from 1 PM Monday to 4 AM PST Wednesday
     for CAZ102-105>108-110-111-114.

     Freeze Warning from midnight tonight to 7 AM PST Monday for

     11 AM PST Tuesday for PZZ450-470-475.

     Small Craft Advisory until 11 AM PST Tuesday for PZZ455.



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