Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 260006 CCA

National Weather Service Eureka CA
342 PM PDT Tue Jul 25 2017

.SYNOPSIS...An upper-level low will continue to bring a chance
of thunderstorms to portions of northwestern California through
Wednesday. For the remainder of the week, high pressure will
regain control of our weather, bringing dry weather and warming
temperature for the interior. The coastal areas will continue to
see night and morning clouds.


.Short Term (Through Thursday)...An upper level low near Point
Arena is bringing some monsoonal moisture to the area. This
bringing some thunderstorms to northern Trinity county. Lapse
rates are good, over 8C/Km. The best instability looks to be over
Siskiyou and eastern Del Norte county. The storm motion is from
the east to the west. This may allow some showers or thunderstorms
to drift this way later in the afternoon. The showers have
diminished as of 3pm, but there is another weak wave that may
increase the coverage early this evening. The CU over the Yolla
Bolla`s is fairly widespread, but so far not very deep. It still
has the potential for a few showers. The model soundings show a
deep inverted V type sounding. This brings the potential for
downburst winds.

Tonight another vortmax is expected to move around the low. This
will increase instability in northern Humboldt and Del Norte
counties. MU Cape values of over 900 j/kg are shown on the GFS.
This should be enough to bring some nocturnal showers and
thunderstorms to this area once again.

Wednesday the upper level low starts to move out of the area. Once
any lingering morning thunderstorms diminish there may not be
anymore storms. High pressure starts to build back in late in the
day which will likely help keep most convection in Siskiyou
county. This will need to be watched however, because if the
upper level low is slow to move out of the area there is the
potential for a few more thunderstorms. The night and morning
coastal clouds are expected to persist. Temperatures inland will
continue to be near normal.

Thursday the low pressure pulls out of the area and heights build
over the area. This will warm temperature a few more degrees. Dry
weather is expected. The stratus is expected to pull back to the
coast or just off the coast in the afternoon. MKK

.LONG TERM.../Thursday evening through Monday night/

Hot weather in store for the interior through early next week, with
highs in the low triple digits in Weaverville area, and highs near
100 degrees in Ukiah. The long term forecast period will start with
rising 500 mb heights, as the upper level ridge tries to build into
NW California from the south. The height rise will be subtle,
however, as there is an upper level trough holding strong over Gulf
of Alaska. There will be no precipitation potential through the
weekend into early next week. Don`t really expect the weather
pattern to change much in this typical summer weather pattern. Hot
and dry inland, marine stratus along the coast. Changes to the
previous forecast package is minor.


.AVIATION...The situation along the North Coast remained quite
persistent and not so exciting as marine stratus continued...even
stretching into local coastal valleys. The marine layer was more
shallow this morning and a tad bit more stubborn. However, a brief
thunderstorm did bring some exuberance to the coast near Orick as
some convection move from the East.  Distant lightning was reported
at both ACV & CEC airports. Some convective activity is possible
mostly north of ACV today. Also, the trend of partial
afternoon/evening clearing of stratus expected before low clouds
once again return and straddle the coast overnight. Inland aviation
concerns: Inland mountain & valley areas will stay mostly VFR with
some isolated convective activity expected...especially north of HWY
36. For UKI, FEW-SCT morning stratus may creep to the periphery of
the airport as a southerly flow continues.


.MARINE...Summertime maritime pattern will continue over NW
California waters through the end of the work week into the weekend.
We have a semi-permanent ridge of high pressure set up over the East
Pacific, and a thermal low over Central Valley. The combined weather
systems will generate north winds over the waters through the
forecast period. The north winds, however, are not expected to be
exceptionally strong. There is a broad upper level trough over Gulf
of Alaska, and this has a surface low reflection over the Gulf of
Alaska. This low pressure system helps to keep the tightest pressure
gradient offshore, so do not expect gale conditions over NW CA

Seas are expected to remain fairly steep and elevated for the outer
waters through the work week. There will be a healthy northerly wind
waves, bringing wave heights of around 8 feet to the outer waters.
For the inner waters, wave heights will be around 4 to 6 feet.

Have extended the small craft advisory for outer waters to continue
through Thursday evening. Otherwise, changes to the previous
forecast package is minor.


FIRE WEATHER...The main concern lies with our thunderstorm potential
over the next couple of days. Dangerous cloud to ground lightning
and erratic wind patterns near thunderstorms will be the main fire
weather concern. The good news is moisture will continue to increase
through Wednesday. For the remainder of the week, dry conditions are
expected for all of our neck of the woods with increasing afternoon
highs and lower relative minimum humidities expected. /PD


Small Craft Advisory until 5 PM PDT Thursday for PZZ470.
Small Craft Advisory until 9 PM PDT Thursday for PZZ475.



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