Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 212101

National Weather Service Eureka CA
201 PM PDT Mon Aug 21 2017

.SYNOPSIS...Thunderstorms will be possible over portions of
Trinity and northeastern Mendocino Counties through Wednesday
evening. Warmer and drier conditions will then develop across
interior areas during the second half of the week.


.DISCUSSION...A weak trough of low pressure positioned along the
coast the past few days is quickly dissipating Monday afternoon.
This will give way to predominantly onshore flow during much of
the week, which will aid in gradually clearing smoke away from the
Humboldt/Del Norte Coast. Meanwhile, an upper-low located
offshore from coastal SRN/CNTRL CA will aid in transporting
moisture and cooler air aloft north-northwest across NRN CA. This
will yield an environment favorable for isolated thunderstorms
over the Yolla Bolly Mountains this afternoon. Coverage is then
forecast to increase northward across much of Trinity County
during Tuesday afternoon/evening. Conditions then become more
marginal for storms during Wednesday. Thereafter, temperatures are
expected to warm to near 100 F over the interior from Friday into
the weekend as a ridge builds over the WRN CONUS.


.AVIATION...The coastal areas continued to be impacted by a
fairly deep and entrenched marine layer. Continuity indicators had
suggested that the stratus would lift early as in previous days.
However, the stratus was tough today with Cigs & Vis remaining
IFR-LIFR under a layer of smoke...which by-the-way had probably
caused at least "some" impact on flight operations in the northern
half of the forecast zones. Yesterday, to note, CEC & ACV were
both MVFR with Cigs 020-030 and > by late morning. Important to
mention that an onshore flow has been a factor in the "new
stratus" piling up along the coastal areas. Ahead, guidance
maintains low Cigs through the period, although limited low cloud
dispersal is still briefly possible by late afternoon/early
evening. Inland mountain and valleys areas will remain mostly VFR
with some smoke (FU) concerns in the North. A deeper marine in the
south plus southerly light winds may be enough to bring at least
a scattered deck to UKI from 008-015 in the morning. TA


.MARINE...Seas are slowly subsiding across the coastal waters,
but are still forecast to remain near small craft levels through
tonight over the outer marine zones. There should be a brief
period of relatively tranquil conditions Tuesday night, followed
by strengthening northerly winds (with occasional gusts to 30-35
kt over the outer waters) and building short period wind waves.
The elevated seas and winds will then persist through the start of
the weekend.

Changes to the previous forecast package were minor. The GFS,
NAM, and ARW were used for updates to winds through Tuesday night.


.FIRE WEATHER...A fire weather watch for abundant lightning is in
effect for most of Trinity County during Tuesday afternoon and
evening. These storms are forecast to move fairly slowly,
resulting in wetting rainfall. However, warmer and drier
conditions are expected to occur during the second half of the
week, which could result in holdover fires intensifying and
spreading. MKK/JMG


CA...Red Flag Warning from 2 PM Tuesday to midnight PDT Tuesday night
     for CAZ283.

     5 PM PDT this afternoon for PZZ450.

     Small Craft Advisory until 5 PM PDT Tuesday for PZZ470.

     Small Craft Advisory until 5 AM PDT Tuesday for PZZ475.



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