138
FXUS66 KEKA 292247
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
347 PM PDT Mon Apr 29 2024

.SYNOPSIS...Coastal stratus and clearing skies inland will encourage
sub-freezing temperatures in interior valleys overnight. Strong
northerly winds, especially along the Humboldt/Mendocino coast, will
continue Tuesday night into Wednesday. Offshore flow will develop
mid-week to encourage warming through Friday before potential for a
wetter pattern change.



&&

.DISCUSSION...After another weak frontal passage this morning with
<0.10 inches reported around Crescent City, Trinidad, and Kneeland,
stratus along the northern Humboldt and Del Norte coasts has
scattered with midday diurnal heating. Moist NW flow continues to
moderate coastal and interior temperatures, with current
observations reading in the 50`s and 60`s following cold interior
morning temperatures in the 30`s. As the Pacific High builds into
the PNW, the pressure gradient will continue tightening along the
coast and enhancing northerly winds. HREF indicates that 25-30 mph
winds 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 tonight. A freeze watch has been extended
from interior Trinity county into interior Del Norte and Humboldt
counties early Tuesday morning with >75% NBM probabilities of <32
degrees. HREF anticipating broken coastal stratus north of the Cape,
potentially enhancing the probability for coastal temperatures to
dip into the upper 30`s early Tuesday morning. NBM has been more
ambitious with 30-50% probabilities for <38 degrees within 5 miles
of the coast, especially north of Trinidad, while HREF keeps sub 40
degree temps over the nearby coastal ranges. Otherwise, Tuesday will
present a similar pattern - possible light drizzle and in far
north Del Norte county and coastal stratus clearing in the early
afternoon. North wind gusts increasing to 25-35 mph expected from
Cape Mendocino to Point Arena.

Wednesday morning is looking to be the final opportunity for cold
morning temperatures as HREF clears out coastal stratus in the pre
dawn hours. Frost products are unlikely, but 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.

An upper trough complex complicates the forecast a bit for late this
week. The broad trough axis is currently forecast to remain over the
northern rockies as several shortwaves train downstream. Another
round of minor accumulations in northern Del Norte county is
possible, although confidence is low at this point. Long range
deterministic models indicate another weak front traversing the
north coast early Thursday with potential for up to 0.25 inches as
far south as Humboldt Bay while NBM has little to no QPF. Long range
cluster analyzes continue to suggest a major change in pattern
sometime early this weekend, but again, 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. Stay tuned.



&&

.AVIATION...Weak inversion allowed sky cover to give way this
afternoon over the coastal sites. Wind gusts should once again die
down at all sites and pick back up late morning Tuesday following a
diurnal pattern. Ensembles indicate a near 20 percent chance of MVFR
visibility for ACV. Leaving out any MVFR in the forecast for now,
but something to monitor for trends. Would not be out of the
question for a few sprinkles from mid-level cloud deck late morning
over CEC.



&&

.MARINE...A couple of persistent northwest swells for the next
several days gives us a combined wave height of 8 feet today, and
near 10-11 feet by Wednesday. North northwest wind speeds gradually
get stronger by mid-workweek as well. Small craft advisory extended
north by Tuesday evening as waves steepen, with winds also on the
increase toward small craft advisory potential.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Freeze Warning from 3 AM to 9 AM PDT Tuesday for CAZ102-
     105>108.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 9 PM Tuesday to 3 AM PDT Thursday
     for PZZ450-470.

     Small Craft Advisory until 3 AM PDT Thursday for PZZ455-475.

&&

$$

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