Frost Advisory 12, NWS Eureka, CA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
258 PM PDT Thu May 2 2024

.SYNOPSIS...Mainly dry weather is expected for tonight and
Friday. A colder storm with will generate moderate to heavy rain
Friday night through Saturday morning. Drastically colder
temperatures and light snow are expected for the mountains above
3500 feet on Saturday. Mainly dry conditions and below normal
temperatures are expected next week.

&&

.DISCUSSION...A weak cold frontal boundary brought some light rain
to Humboldt and Del Norte counties this morning. This evening and
tonight mainly dry weather is expected as some shortwave ridging
moves over the area and this will continue into Friday. Some
drizzle may linger this evening along the Humboldt coast north of
Cape Mendocino. It looks like there will continue to be clouds
around, especially in the north and along the coast.

Friday an upper level low dropping down from the gulf of Alaska.
This will bring a cold front to the area and a period of moderate
to heavy rain Friday night and early Saturday. Current NBM is now
showing widespread 1 to 2 inches of rain. The NBM is showing a 50
percent chance of over 3 inches in the mountains of Del Norte
county and in the King range. Southern Lake county and eastern
Trinity county valleys may only see a half to three quarters of an
inch of rain. Current models show the rain starting mid afternoon
Del Norte county and moving south quickly in the late afternoon
and evening with rain expected to reach southern Lake county by 10
pm to midnight. Snow levels are expected to drop to around 3500 to
4000 feet. Some of the rain will likely fall ahead of the colder
air, but several inches of snow is possible at 4000 feet. The
steady rain is expected to come to an end from north of south
Saturday morning. Showers are expected in the afternoon. There is
some instability and this will bring the potential for
thunderstorms in the afternoon. Models are showing CAPE of 100 to
200 j/kg. The NAM is showing some skinny cape in areas along the
coast. The question will be if surface temperatures will be warm
enough to generate this instability.

Saturday night into Sunday morning showers are expected to come
to an end, however it looks like clouds will linger over the
area. The cold airmass will bring cool temperatures, but with all
the moisture around there is not expected to be good radiational
cooling. Any valley areas that do clear even briefly will likely
see frost or freezing temperatures. However the coldest places
will likely be at the higher elevations. 850 MB temperatures are
-5C so elevations as low as 2,000 feet may see freezing
temperatures even with some cloud cover.

Sunday afternoon temperatures will remain chilly with highs in
many areas remaining in the 50s. Sunday night through Tuesday the
upper level trough is expected to keep some clouds and possible
light rain along the Humboldt and Del Norte coasts. This should
keep temperatures from getting as cold in these cloudy areas.
Farther south and east will likely see near freezing or freezing
temperatures. Wednesday drier air is expected to move in and this
may be the coldest night some of the valleys and the coast. MKK

&&

.AVIATION...IFR/LIFR conditions are improving slightly as a weak
frontal boundary drops south into the CWA, ushering in low to mid
level dry air. CEC and ACV will likely scatter out to broken mid-
level ceilings and VFR/MVFR conditions this afternoon and evening
with some reduced visibilities. Moist westerly flow will
gradually weaken and turn offshore (NE) overnight with broken
ceilings, warding off widespread fog at coastal terminals.
Otherwise, UKI remains quite clear with gusty northerly winds that
will diminish this evening beneath scattered high cirrus. LLWS
will return overnight as the the BL decouples beneath a shallow
inversion. Hi- res models hint at some scattered low level
ceilings in the valley, but temperatures will likely have a hard
time cooling to saturation. Winds expected to become southerly
with increasing cloud cover ahead of a frontal boundary
approaching Friday afternoon.

&&

.MARINE...NW winds continue to diminish and turn westerly as a weak
front drops into area waters, leaving winds and seas fairly light
through the end of this week.  Winds will gradually increase and
turn southerly ahead of a frontal boundary late Friday, enhancing
wave heights to 6-7 feet for the remainder of the weekend. Locally
generated NW wind waves will continue to be reinforced by additional
frontal passages early next week before a long period swell fills
into the waters.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
None.
&&

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For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png