Area Forecast Discussion
Issued by NWS Eureka, CA

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629
FXUS66 KEKA 250327
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
827 PM PDT Thu May 24 2018

.SYNOPSIS...Widely scattered showers with isolated thunderstorms
will be possible across much of northwest California tonight through
Friday. Building high pressure will then bring warmer and drier
weather conditions through Memorial Day weekend.

&&

.UPDATE...Made some minor adjustments to the POP and WX elements
tonight, mainly to account for coverage of shower and isolated
thunderstorm activity. Had a couple of isolated cells over Trinity
county earlier, but the focus has shifted to the northern
Mendocino and southern Humboldt coast for the rest of tonight. A
few strikes already detected between Fort Bragg and Shelter Cove.
Expect the bulk of the isolated thunderstorms to stay south of
Fortuna, but toward morning would not rule that out farther north
as scattered shower activity expands. /AAD

&&

.PREV DISCUSSION... /issued 250 PM PDT Thu May 24 2018/

.DISCUSSION...Showers and potential embedded thunderstorms will
still be possible across Northwest California this evening through
Friday as the upper low pressure system offshore begins to track
over central California. The primary areas that area expected to
see storm development are the typical regions across Trinity and
northeast Mendocino counties. However, east/southeast steering
flow will help potential storms propagate near coastal Del Norte,
Humboldt, and possibly coastal Mendocino tonight. Moving into the
holiday weekend building high pressure will usher in a dry,
subsident airmass that will bring a cease to thunderstorm chances
and cause daytime temperatures to gradually increase through
Memorial Day weekend. One change to the forecast was to increase
inland temperatures by a few degrees. Model guidance suggests that
interior locations, such as Ukiah, can reach the upper 80s on
Sunday and the low 90s on Memorial Day and Tuesday. Coastal areas
should remain more seasonable in the upper 50s and low 60s.
Another adjustment to the forecast was to decrease cloud coverage
along the coast over the weekend. A thermal trough, generated from
the hot interior temperatures, will shift west along the coast
which will enhance easterly winds Sunday and Monday. Although low
clouds are still expected to develop along the coast, this dry
east flow should inhibit widespread development and restrict the
intrusion of the marine layer across interior valleys. Plus robust
north winds over the coastal waters should help promote
scattering coastal clouds in the afternoon on Sunday and Monday.
However, the tradeoff will for any blue skies will be breezy winds
on the coast. /KML

.AVIATION...The marine layer was quite a hodgepodge of layers
through the afternoon...and was frequently masked by even higher
IFR-MVFR Cigs. It almost seemed as though the layers were in "hide
and seek" mode today. Portions of the entrenched stratus showed
brighter tops and some cu-like enhancement with a higher layer
quite visible, possibly a tell-tale sigh for partial clearing.
Then there were some , but overall the low cloud deck remained
fairly solid. Around noon, an even lower layer infiltrated the ACV
and CEC terminals. ACV reported BKN002 3/4SM BR. Expect mostly
MVFR late afternoon/early evening, but IFR conditions will remain
a concern for coastal sites. Inland: Low clouds spread deep
inland, but mostly dissipated before midday. UKI reported MVFR
Cigs through the morning. Convection over the mountain interior
were slow to jump start today compared to the previous 2 days.
Therefore, have reservation that any showers will reach coastal
areas in the late afternoon/early evening.

.MARINE...A weak system will cause north winds to increase
slightly on Friday which will causes 20-25 kt wind gusts across
the coastal waters. Although marginal, a very marginal small craft
advisory was hoisted for the outer waters for Friday. Other than
some choppy wind waves, a longer period south swell and a
northwesterly swell will dominate the sea state on Friday. Winds
will increase more significantly late Saturday afternoon as
building high pressure offshore causes the pressure gradient to
flex. This will result in robust northerly winds starting Sunday
through most of next week. Very steep seas will build in response
to the robust winds over Memorial Day weekend and continue through
much of next week. /KML

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory from 9 AM
to 9 PM PDT Friday for PZZ470-475.

&&

$$

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