706 
FXUS66 KEKA 152253
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
253 PM PST Mon Jan 15 2024

.SYNOPSIS...Residual coastal fog will continue to persist this 
afternoon and evening beneath broad high pressure. Southerly winds
and cloud cover will increase as another shortwave system sweeps 
in Tuesday afternoon. Gusty S winds and moderate rainfall is 
expected, enhanced by upsloping in higher terrain. Periods of 
light rain are expected through the rest of the week, before 
another potentially significant storm next weekend. 


&&

.DISCUSSION...A well defined deformation band of high level cirrus is 
dissipating on visible satellite imagery as a ridge pushes onshore 
from the Pacific. Light winds and drier conditions are expected 
through the remainder of today with intermittent high cirrus 
breaking into otherwise clear skies. A persistent shallow stratus 
layer has kept areas along the Mendocino coast and Humboldt Bay 
inundated with <1000ft vertical visibilities, and has slowly been 
working its way up toward Crescent City. This shallow fog layer 
will likely remain patchy but persistent until SE offshore flow 
strengthens early Tuesday, helping to mix out the low level
moisture. Isolated portions of interior Trinity will dip below 
freezing, but temperatures will be largely moderated by a 
southerly flow regime being set up ahead of the the next system. 

Clouds will thicken early Tuesday morning as an upper level 
shortwave and associated surface low swings into the PNW just north 
of California. Predominantly SSE flow will promote regional WAA, 
keeping all overrunning warm frontal precip falling as rain with 
freezing levels around above 9,000 ft, inhibiting chances for 
convection. With the BL already saturated, precip should begin in 
earnest mid Tuesday morning. Latest deterministic model runs are 
anticipating widespread rainfall of 0.5 to 1.25 inches with 
orographically driven higher accumulations of 2 inches likely. 
Terrain with a S facing orientation will likely see this enhanced 
rainfall including the King Range and mountains of Del Norte and 
Humboldt counties. With soils already saturated from this 
weekend's storm, minor flooding of creeks and streams and ponding 
in urban areas is not unlikely. Southern Mendocino and Lake 
counties can expect minimal rainfall totals of 0.25 to 0.50 
inches.

A low level coastal barrier jet will set up along the Northern 
California coast by midday Tuesday as this front moves onshore. Hi 
res model guidance is pushing 925mb winds close to 50kts, while 
ensembles are only hitting 30-40 kts by Tuesday afternoon. Highest 
surface wind gusts of 35 to 45 kts are expected to mix down along 
exposed terrain and coastal headlands, especially Cape Mendocino. 
Otherwise, most of the northern coastline will be protected from SSW 
flow and can expect widespread 15-20 kts with gusts up to 30 kts for 
a brief period in the afternoon. Winds will turn SSW and diminish 
behind the front as precip dissipates through late Tuesday evening 
into early Wednesday morning. This pattern will continue through mid 
week as another shortwave dips into the PNW on Wednesday morning, 
although QPF values will be closer to 0.50 to 0.75 inches and mostly 
confined Del Norte and northern Humboldt counties.

Gusty S winds are possible early Friday ahead of another frontal 
passage. Much uncertainty still exists for a storm beginning to 
take shape for next weekend. Cluster 500 mb anomalies are in 
general agreement on anomalous low heights off the Pacific coast 
for the weekend, although the depth and strength of this upper 
trough is still in question. Temperatures will be closely 
monitored to determine the snow levels for what is looking to be 
another round of impactful QPF.




&&

.AVIATION...The afternoon visible satellite imagery reveals a pseudo-
summer like stratus pattern, with a shallow band of stratus easing 
its way north along the coast. Building high pressure aloft, and a 
strengthening low-level inversion aided in fog to dense fog VIS 
under this southerly surge. ACV remains engulfed in the stratus with 
LIFR criteria, and CEC is next in line starting very soon.  

Overnight, the shallow stratus will continue to build up the coast 
through ACV and CEC and up the valley into UKI. Introduced TEMPO FG 
through the terminals as duration is in question. An approaching 
front will increase SE winds into the early morning hours, and this 
offshore component will help mix out the shallow stratus/fog. Rain 
chances and low level wind shear from SE to S winds up to 40 kts, as 
low as 1500 ft AGL, will increase by 16Z Tuesday. Ceilings will lift 
to MVFR to VFR, but IFR VIS will accompany moderate rainfall later 
in the afternoon.  

Ample lingering surface moisture continues to allow for inland 
valley stratus and fog development, including up the Russian River 
Valley and through UKI. This terminal should see improvement after 
12Z when the winds begin to increase, but IFR to LIFR conditions 
could linger in this sheltered valley. /JJW 



&&

.MARINE...Light breezes will persist this evening, followed by
steadily strengthening southerlies late tonight into early Tue. Gale 
force gusts are anticipated for mostly the northern outer waters 
(PZZ470) Tuesday with the approach on a frontal boundary. Localized 
gale force gusts will probably occur inside inside 10NM (PZZ450) 
around Cape Mendo and other headlands like Pt St George. Coverage 
will not be sufficient to warrant a warning at this time. Otherwise, 
small craft winds and steep waves are expected for the remainder of 
the area on Tue. A potentially stronger frontal system will 
approach toward the end of the week. Another round of steep wind 
waves and gale force southerly winds are expected on Fri. Timing 
is not 100% certain. Another low pressure system will rapidly 
follow during the weekend (Sat-Sun) and bring a renewed threat for
gale force and possible storm force winds with very steep and 
large southerly waves. A mid period W swell will continue today as
a long period NW swell arrives. This mid-long period NW swell 
will persist through the week and into the weekend. 


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 11 AM Tuesday to midnight PST 
     Tuesday night for PZZ450.

     Small Craft Advisory from 11 AM to 6 PM PST Tuesday for 
     PZZ455.

     Gale Warning from 9 AM to 7 PM PST Tuesday for PZZ470.

     Small Craft Advisory from 7 AM to 6 PM PST Tuesday for 
     PZZ475.

&&

$$

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