Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 252211

National Weather Service Eureka CA
311 PM PDT Sun Jun 25 2017

.SYNOPSIS...Isolated thunderstorms will continue through the
remainder of the afternoon across portions of the mountainous
interior...particularly Trinity county. This will again be
possible near the Trinity horn tomorrow and Tuesday afternoon. Hot
temperatures will cool back to near normal values tomorrow through
the remainder of the week.


.DISCUSSION...After several days in a row of well above normal
temperatures throughout the area, a pattern shift is underway that
will provide relief for a large portion of Northwest California.
Just offshore an upper level low pressure system is slowly
approaching the coast, and as a result, the upper level ridge that
has persisted along the west coast is beginning to weaken.
Temperatures today will end up falling only a few degrees cooler
than previous days, but Monday and beyond will see high
temperatures fall into the 80s and 90s...a bit more tolerable and
closer to normal. Meanwhile along the coast, a steadily deepening
marine layer has allowed stratus to move farther into coastal
valleys, and has persisted much of the afternoon in many areas.
This is expected to continue for the next several days, with
cloudy drizzly nights and a slow dissipation of clouds during the
late morning and afternoon hours.

As for thunderstorms, the previously mentioned upper low has
brought southerly flow and increased mid-level moisture to the
region. As a result, thunderstorms have begun to fire early this
morning across Siskiyou county, and as of 3 PM are beginning to
develop across parts of Trinity county as well. These showers will
likely be capable of producing cloud to ground lightning strikes
and perhaps some gusty winds. However, dry sub-cloud layers will
likely result in significant rainfall evaporation, and many
valleys will not likely see much rain if any. Thunderstorms will
again be possible near the Trinity Horn Monday and Tuesday
afternoons, but most of this activity will be focused farther to
the north and east. Dry conditions will prevail through the
remainder of the week.


.AVIATION...Very widespread marine stratus this morning that
stretched from WA/OR border all the way down to the Bay Area and
point south. FOr us in the Redwood Coast, the stratus hangs around
in KCEC and KACV throughout the day. Both locations were reporting
LIFR this morning. Conditions gradually improved to MVFR/IFR.
However, do not expect the improved conditions to last long. With
continuing SW-ly onshore flow, that is going to bring in a deeper
marine layer into the area. Do expect conditions to worsen to
IFR/LIFR this evening, and then gradually improve tomorrow morning.
KUKI should stay VFR overnight, but there is a potential where some
stratus can sneak in overnight and potentially lower the conditions
down to MVFR. It will be back up to VFR during the day for KUKI.


.MARINE...Light winds and low seas into Monday. A trough of low
pressure remains off the coast of California through tomorrow. This
allows the pressure gradient to remain relaxed. Do expect light
winds and resultant low seas through Monday.

We will return to a strong northerly wind regime starting on Tuesday
as the East Pacific High re-establishes itself. With tight northerly
pressure gradient, the strong northerly wind regime will persist
through most of the week. Gale force wind gusts will be likely
starting middle of the work week.

Forecast is still on track. Little changes were made to the previous
forecast package. GFS is used to update the forecast package.


.FIRE WEATHER...Isolated to scattered thunderstorms have developed
across Siskiyou county this afternoon, and a few are beginning to
develop across central Trinity county as of 3 PM as well. This
activity is expected to continue to mature through the remainder
of the afternoon, with isolated lightning strikes and erratic
gusty winds expected. Dry sub-cloud layers will also limit the
amount of rain that reaches the lower elevations as well. However,
fuels remain marginal for large fire growth in the northwestern
mountains at this time...although fuels have dried considerably
over the past week. Isolated storms will be possible again
tomorrow afternoon and Tuesday afternoon near the Trinity Horn.




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