Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 082236

National Weather Service Eureka CA
236 PM PST Mon Mar 8 2021

.SYNOPSIS...Showers and isolated thunderstorms will impact
northwest California through Wednesday. Drier weather along with
freezing temperatures across interior valleys will develop
Thursday morning. Dry weather will persist through Saturday,
followed by a possible round of light rain during Sunday.


.DISCUSSION...An upper-level low was positioned offshore from WA
this afternoon. Waves of ascent combined with very cold air aloft
and steep lapse rates have supported widespread shower
development and isolated thunderstorms. Recent radar imagery also
indicates stronger showers are likely producing small hail.
Showers and thunderstorms will continue to overspread NWRN CA
through Wednesday as the upper low gradually moves south along the
west coast. Elevations above 2000 feet across the interior
mountains will also experiences periods of snow through midweek.
Reference the latest winter weather advisory for more information.

The previously mentioned upper low is forecast to move inland
across the North Bay region during Wednesday afternoon. Heavy
showers and thunderstorms will occur near the low over Mendocino
and Lake Counties. Thereafter, large-scale subsidence is forecast
to increase across NRN CA. Showers and clouds will subsequently
dissipate, and widespread frost and freeze conditions will become
likely across the EKA CWA Thursday morning.

Upper ridging is forecast to prevail across the region through
Saturday resulting in several days of dry weather. However, model
spread becomes fairly substantial toward the end of the extended
range forecast period. Nevertheless, there are hints of possible
light rain occurring during Sunday as an upper trough moves east
across the PACNW.



.AVIATION...An upper-level storm system is moving in and bringing
numerous showers and gusty southerly winds with it. Flight
categories have dipped to MVFR during rain showers, along with
stronger wind gusts. The 925mb winds are being well tapped into
with the gusts at times, given the convective nature of the
precipitation. There will continue to be periods of improvement,
even blue sky between waves of showers and some isolated
thunderstorms that may produce small hail. This pattern will
persist overnight. There will more instability tomorrow, resulting
in more chances for thunderstorms which may produce accumulating
small hail. There will be some marginal directional and speed wind
shear tonight with the veering wind profile as SW winds aloft
pickup, mainly from 5Z to 12Z as a trough rotates by. Introduced
to LLWS to the TAFs to KACV where this was more pronounced.


.MARINE...Moderate to strong southerly breezes have developed
across the waters, with the strongest winds north of Cape
Mendocino as a storm system moves through. Winds will remain
elevated over the coastal waters through Tuesday night as the
upper-level trough slowly drifts south along the coast into the
middle of the week. This will also support fairly widespread
thunderstorm potential over the coastal waters for the next couple
of days. Meanwhile, a large WNW swell will slowly decay from
15-17 ft to around 10 ft by the middle of the week.

Late Wednesday afternoon, northerly winds will return and rapidly
accelerate behind the front as strengthening offshore high
pressure aids in tightening the pressure gradient. Winds will
continue generating small craft conditions with steeps seas from 7
to 8 ft in the outer waters on Thursday. Otherwise, advisory
conditions are expected to continue through the end of the week.


CA...Winter Weather Advisory until 4 AM PST Wednesday for CAZ102-

     9 AM PST Wednesday for PZZ450.

     Small Craft Advisory until noon PST Thursday for PZZ455-475.

     Small Craft Advisory until 11 AM PST Wednesday for PZZ470.



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