568
FXUS66 KEKA 301202
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
502 AM PDT Tue Apr 30 2024

.SYNOPSIS...Minimal amounts of cloud cover this morning, other than
high altitude cirrus, give way to cool morning temperatures in the
30`s. Mild pleasant weather is expected today with colder
temperatures expected overnight into Wednesday. Offshore flow and
high pressure will promote warming and drying for the interior, late
in the week.


&&

.DISCUSSION...The upstream ridging pattern continues although
scant amounts of integrated water vapor can be seen rounding the
isobars overlaid on the satellite imagery. Most of the moisture
remains north of our CWA as it interacts with shortwave features
over Washington and Oregon with a surface low cascading down the
coast. A similar set up is expected Thursday morning, this time with
a bit more of exposure to the wrap around moisture, circulating
around the offshore high. Accumulation will be isolated north of
Humboldt Bay and very light with probabilities >0.05 inches around
20%.

As the Pacific High builds into the PNW, the pressure gradient will
continue tightening along the coast and enhancing northerly winds.
HREF indicates that winds above 30 mph will stay confined to the
coastal headlands of Cape Mendocino south to Point Arena, and
exposed ridges in southern Humboldt, Mendocino and Lake counties
through early Wednesday.

A cold upper trough digging into the PNW is trending east, further
minimizing precipitation impacts for NorCal. Building high pressure
subsidence will continue to usher mid to upper-level dry air into
the CWA, encouraging temperatures to drop in interior valleys
beneath clearing skies into Wednesday morning which is looking to be
the final opportunity for cold morning temperatures as HREF clears
out coastal stratus in the pre dawn hours. Frost or freeze products
may be prudent for Trinity, Humboldt, Mendocino and possibly Del
Norte. HREF probabilities are 50-75% for temperatures <40 degrees -
something to consider for sensitive vegetation. Clearing skies and
increasingly breezy offshore(NE) flow Wednesday will promote
widespread warming and drying across the region, especially in the
interior as an inverted trough develops in the Sac valley. Winds are
forecast to mix down and extend inland, with 25-30 mph gusts likely
across Del Norte, Humboldt, Mendocino and Lake counties and exposed
ridges. RH values currently forecast to drop to 30% in interior
Mendocino, Trinity and Lake Counties. Models are still without
consensus on high valley temperatures Thursday and Friday - the NBM
has been trending cooler with <50% probabilities of temperatures >75
degrees even in Mendocino and Lake counties. Regardless, an overall
warming trend is expected with highs in the 70`s as the ridge builds
onshore.

Otherwise, long range cluster analysis continue to suggest a major
change in pattern sometime early this weekend, but with very little
model agreement at this point. As it stands, long range models
suggest a deepening trough may produce measurable precip sometime
between Saturday and Sunday.

&&

.AVIATION...VFR expected today (4/30) at all forecast terminals
(ACV, CEC and UKI). Satellite imagery did show some clouds over
higher terrain of the interior, mainly E-SE Humboldt, western
Trinity and far NW Mendocino. Based on scant reports of cloud bases,
MVFR cigs are probable. These clouds should dissipate with mixing
and solar insolation this morning. High and weak inversion forecast
to break late this morning with gusts to 25 to 30kt at coastal
terminals (KACV and KCEC) and gusts to around 20 kt at KUKI til
about 03z. DB

&&

.MARINE...Northerly winds will continue to strengthen through
Wednesday. Near gales with gusts to 35-40kt and large very steep
combined seas around 10 feet are forecast for the southern waters.
Coverage of gale gusts are marginal at best except for a 3-6 hour
window for the inner waters (pzz455) late this afternoon into early
evening. Combined seas will remain elevated and borderline for a
warning for seas so will continue with a marginal gale warning into
Wed morning. Northerly wind gusts will probably increase again to
near gale again Wed afternoon. Thus, gale headline has been extended
into the afternoon and evening on Wed. North of Cape Mendocino,
northerly winds will increase this afternoon through evening. Fresh
to strong breezes with gusts to 25-30kt are expected north of Cape
Mendocino this afternoon through Wed. Seas will build up to 10 feet
tonight into Wed as NW swell around 8 ft at 11 sec combines with
shorter period wind waves near 6 ft at 6 sec. DB


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Freeze Warning until 11 AM PDT this morning for CAZ102-
     105>108.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 1 PM this afternoon to 3 AM PDT
     Thursday for PZZ450-470.

     Small Craft Advisory until 1 PM PDT this afternoon for
     PZZ455-475.

     Gale Warning from 1 PM this afternoon to 8 PM PDT Wednesday
     for PZZ455-475.

&&

$$

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