Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 271641

National Weather Service Eureka CA
841 AM PST Mon Feb 27 2017

.SYNOPSIS...An unsettled weather pattern will persist through
Tuesday, with rain showers and higher elevation snow showers
persisting through then. Drier conditions will return for the
middle of the week, as short- wave ridging aloft builds across the
region. This will come to an end by Friday though, as widespread
precipitation develops ahead of another approaching storm system.


Isolated small hail has been reported along the Del Norte county
coast early this morning. Granted the hail has been mixed with
rain and no significant accumulations are expected. Conditions
will remain favorable for small hail today and tonight with very
cold temperatures aloft and low freezing levels.


.PREV DISCUSSION... /issued 354 AM PST Mon Feb 27 2017/

(Today through Tuesday)

Early this morning, an upper-level trough axis was crossing the
region. shower development has been plentiful in the base of said
trough, as cold air aloft (-26 to -30 at 500mb) crosses the region,
helping to create some elevated instability. In fact, the latest SPC
mesoanalysis shows MUCAPEs along the coast and off shore running at
or slightly above 100 J/kg. Farther inland, instability is nil and
the Doppler radar loops illustrate this quite well, as it shows
showers struggling to make it over the coastal ridges. Still, given
the degree of forcing aloft and residual cold pockets, shower
development remains a good bet and some will make it to the interior
and beyond.

Additional vort maxes are also progged to continue moving across our
neck of the woods in the northwest flow aloft. Although mid-level
temperatures will warm some, sufficiently cold air will persist to
interact with bursts of ascent from the incoming waves of energy
(vort maxes) to generate showers/higher elevation snow showers. Some
enhancement to this is possible during the diurnal cycles today and
tomorrow, as instability may increase somewhat. Overall, the lift
and moisture are adequate for this to occur at any time.

(Wednesday through Sunday)

The middle of the week looks to be a great time to get out and enjoy
the sunshine. Short-wave ridging aloft will build across the region
from the southwest, with 500mb heights increasing from near ~540dkm
now, to near 570dkm. A similar response is seen in the lower-level
temperature fields, with 850mb temps going from negative single
digits to positive single digits.

What this means for us is temperatures will warm several degrees
during the afternoon for the middle of the week, compared to what
has been recently observed with these cooler, cloudier, and at times
wet days. The real tricky part of the forecast though will be the
low temperatures, as light winds and mainly clear skies offer ideal
radiational cooling conditions. Typically, lows are often lower
than what the majority of the short-range models indicate. This has
particular importance along the coast and across all of Mendocino
County, where the growing season starts Wednesday. Current
indications are for lows in the mid to upper 30s along the coast,
and lower to mid 30s across the Mendocino valleys, and this may be
be a little too high for reasons stated above. Thus, there`s a good
chance frost advisories may be need in the coming days.

All good things must come to an end, especially with this brief dry
spell, as another short-wave trough will move into our area from the
west just in time for your weekend. As the ridge flattens due to the
approaching trough, widespread precipitation will develop as
moisture and lift increases admist a cooling thermal profile aloft.
Get the galoshes back out folks, as we`re not quite done with the
rain just yet. /PD

Overnight, showers are still moving onshore, impacting
Crescent City and Arcata airports. Both airports see themselves
fluctuating between VFR and MVFR. Ukiah wasn`t impacted by the
showers. However, it is impacted by low clouds and fog moving in
and out of the airport. Conditions there fluctuated between LIFR
and VFR, as there was a broken deck below 1000 feet. Do expect the
low clouds and fog to dissipate this morning in Ukiah, and it
should be another VFR day for them. For Crescent City and Arcata
airports, the showers will persist through the day, before
diminishing this evening. Conditions should be VFR for both Arcata
and Crescent City airports. /RCL

NW winds continue to persist over NW California waters, as
a strong high pressure continues to park over the East Pacific
Ocean. Today, the NW winds will bring in a short period wave group
into the area, along with a weakening westerly swell group. The
combined wave height will be around 10 feet over the waters today.
Thus, have a small craft advisory in effect for today. Later this
afternoon, the short period wave group will weaken, dropping the
combined wave height to around 8 feet or so. The light to moderate
NW wind and relatively low wave height will persist from tonight
through the rest of the week. Starting in the middle of the week,
there will be a weak southerly swell group moving into the waters,
besides a persistent NW wave group. /RCL


until 3 PM PST this afternoon for PZZ450-470-475.



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