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Area forecast discussion
National Weather Service Eureka California
842 am PDT Mon Jun 26 2017

Update...expand the isolated thunderstorm area to cover eastern
del norte, and more of northern Trinity, and NE Humboldt counties
for this afternoon and evening. Models are showing increasingly
favorable cape, Li, precipitable water in the area mentioned above. The mid level
shortwave disturbance will be the culprit of these convection.
If this mid level disturbance slows down and track further north
and west, then it is likely to lead to a higher probability for
convection over the area mentioned above. Stay tuned to National Weather Service Eureka
for more update. /Rcl


Previous discussion... /issued 507 am PDT Mon Jun 26 2017/

Synopsis...isolated thunderstorms are possible near the Trinity
horn this afternoon and again Tuesday afternoon. Mostly dry
weather is expected to return by Wednesday and continue through
the weekend. After a brief period of near to slightly below
normal temperatures over inland areas today and Tuesday, very warm
temperatures will return by Wednesday and persist through the

Short term (today thru Wednesday night)...low clouds, along with
some patches of drizzle, continue to cover the coastal waters and
adjacent land areas. The marine layer is deep (around 2000 feet
deep) due to a shortwave moving across the area. As a result,
ceilings are higher than the last few days and there are minimal
visibility reductions. This will likely keep clouds from rapidly
clearing over land. Indications are that some partial clearing may
occur by evening just inland from the Redwood coast, but
uncertainty is high. Nighttime and morning coastal clouds will
continue over the next few days, but improvement should be noted
by each afternoon.

Thunderstorms developed about as expected on Sunday, with isolated
storms lingering just past midnight over del Norte County. The
chances for thunderstorms will be waning today as the shortwave
over the area moves NE and fills. However, may see some isolated
activity over the Trinity horn during the afternoon hours. Models
continue to indicate a vorticity maximum moving from northwest to southeast
across the area Tuesday afternoon and evening on the backside of
the departing and filling trough. There may be enough instability
over west Siskiyou County to support at least isolated thunderstorms,
and storm motion should carry them southeast into east Trinity County. Have
continued to include this in the forecast.

Inland temperatures will be near to slightly below normal today
and Tuesday before rising to about 10 degrees above normal by
Wednesday as an upper ridge builds back over the area. /Sec

Long term (thursday thru sunday)...the longwave pattern holds
ridging over the western United States Thursday through Saturday
before a broad trough dives across the west on Sunday. Thus expect
mostly dry weather for the late part of the work week with inland
temperatures above normal values for this time of year. Then
shortwaves embedded in the upper flow could bring some convective
precipitation, possibly a thunderstorm, across the interior late
in the weekend but it is still to early tell so there is no
mention in the forecast as of yet. Coastal temperatures will
remain more seasonal with stratus likely impacting parts of the
northwest coast in the mornings and overnight. /Kml

Aviation...a deep stratus deck continues to inundate much of the
northwest California coast and coastal valleys bringing lower
ceilings as of early this morning. Contrary to yesterday, the
visibility remained elevated through most of the night with the
exception of some coastal pockets that observed -dz and br. Ceilings
will lift to MVFR through the afternoon with possible clearing along
the Mendocino coast. The Humboldt and del Norte County coasts could
see patches of blue skies later today but stubborn clouds should
stick around through most of the day. IFR to LIFR conditions will
return to the coast tonight but troughing aloft will help keep the
marine layer deep and thus visibility should remain higher. VFR will
prevail across the interior, however, stratus may impact kuki late
tonight. /Kml

Marine...light winds and low seas will continue to persist for
just one more day. Starting on Tuesday, surface high pressure will
begin to build back towards the California coastline tightening
the pressure gradient across the ocean. This tighter pressure
gradient will increase the northerly winds across the waters which
will in turn begin to increase wave steepness.

A Small Craft Advisory will take effect Tuesday evening for the
outer waters. Some gale force gusts will be possible across the
outer waters starting Wednesday afternoon however with limited
spatial coverage and marginal strength will forego a Gale Warning.

The inner waters will most likely need a Small Craft Advisory for
steep waves by late Wednesday morning or early afternoon. Will hold
off on issuing that advisory until we get a bit closer to the event.

While the small craft for the outer waters only GOES through early
Friday morning this will most likely need to be extended or possibly
upgraded to a Gale Warning especially across the southern outer
waters. Due to the uncertainties this far out will allow future
extensions and or upgrades to be made later this week. /Wci


Eka watches/warnings/advisories...
Northwest California coastal waters...Small Craft Advisory from 9 PM Tuesday to 3 am PDT Friday for



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