Frost Advisory 1, NWS Eureka, CA

693 
WWUS76 KEKA 170904
NPWEKA

URGENT - WEATHER MESSAGE
National Weather Service Eureka CA
204 AM PDT Fri Mar 17 2023

CAZ110-111-114-171600-
/O.CON.KEKA.FZ.W.0001.000000T0000Z-230317T1600Z/
Northwestern Mendocino Interior-Northeastern Mendocino Interior-
Northern Lake-
204 AM PDT Fri Mar 17 2023

...FREEZE WARNING REMAINS IN EFFECT UNTIL 9 AM PDT THIS MORNING...

* WHAT...Sub-freezing temperatures as low as 30.

* WHERE...Northwestern Mendocino Interior, Northeastern 
  Mendocino Interior and Northern Lake Counties.

* WHEN...Until 9 AM PDT this morning.

* IMPACTS...Frost and freeze conditions will kill crops and 
  other sensitive vegetation.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold. Provide
adequate shelter for outdoor pets or consider bringing them
indoors.

Frost Advisories and Freeze Warnings are issued during the local
growing season as defined by climatology and local agriculture
experts. Once the growing season has ended these statements will
no longer be issued until the spring.

&&

$$

CAZ113-115-171600-
/O.CON.KEKA.FR.Y.0001.000000T0000Z-230317T1600Z/
Southeastern Mendocino Interior-Southern Lake-
204 AM PDT Fri Mar 17 2023

...FROST ADVISORY REMAINS IN EFFECT UNTIL 9 AM PDT THIS MORNING...

* WHAT...Temperatures as low as 33 will result in frost 
  formation.

* WHERE...Southeastern Mendocino Interior and Southern Lake 
  Counties.

* WHEN...Until 9 AM PDT this morning.

* IMPACTS...Frost could kill sensitive outdoor vegetation if 
  left uncovered.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold.

Frost Advisories and Freeze Warnings are issued during the local
growing season as defined by climatology and local agriculture
experts. Once the growing season has ended these statements will
no longer be issued until the spring.

&&

$$

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
258 PM PDT Thu Mar 16 2023

.SYNOPSIS...Dry weather and seasonable temperatures will continue
through Friday and should last into Saturday. Rain and mountain
snow will return for the latter portion of this weekend. Additional
storms will yield more rain and mountain snow next week.

&&

.DISCUSSION...Upper level ridging will maintain dry weather
with seasonable temperatures through Friday night and probably
for most of Saturday. A couple of transient mid level shortwave
troughs will generate multi-layer clouds tonight into Saturday.
Small small circulations offshore over the coastal waters in the
lee of Cape Mendocino have been producing southerly upslope flow
and some low clouds today along portions of coastal SW Humboldt
and coastal Mendocino Counties. Weak surface pressure gradients
should return tonight. This will favor a light offshore wind flow
and keep the bulk of the low clouds near the coast or over the
ocean, especially north of Cape Mendocino tonight. Frost will once
again be possible for the interior valleys and portions of the
coast late tonight. For coastal areas, higher humidity, southerly
winds and more low clouds will likely keep temperatures from
plunging into the lower to mid 30's again.

A deeper and stronger shortwave trough extending from a 500mb low
centered over the Gulf of Alaska will likely bring some light
precipitation late Saturday night into Sunday. Latest GFS and
ECMWF are in better agreement. Ensemble guidance and National
Blend of models lend support to this convergence as well. 24
hour rain amounts will generally range from 0.15-0.25in with
locally higher amounts up to 0.50-0.75in for the higher
elevations and mountains. Snow levels will be fairly high
initially, above 5000 feet, and then fall to 4000 feet by Sunday
evening. Another bout of light to moderate rain will follow
on Monday. Hydrological or flooding concerns are low or none
with these first couple of waves of rain.

Even into mid to late next week, potential for flooding remains
low due to lower snow levels and the progressive nature of
these storms. We will certainly keep on eye on the potential for
some urban and small stream flooding with each of these rain
events, but another atmospheric river storm and deluge that we
experienced earlier this week appears highly improbable. We could
see some snow and winter weather impacts for the higher elevations
and passes as we head into Tue and Wed. The models are in slightly
better agreement, but variations in the depth and location of the
500mb cold pool digging southward from the Gulf of the Alaska
will make or break the snowfall forecast for our area. It will get
colder and snow levels will lower to 3000 feet or perhaps a bit
lower by mid week. The multiple model ensemble guidance for
elevations around 2800-3200 feet indicate fairly low chances
(<30%) for an inch or more of snow even in 24 hours. Thus,
confidence in low elevation snow (<3000 feet) is quite low.
Chance for impactful snow amounts is higher for elevations above
3500-4000 feet. A lot of details still needs to be worked out.
We are getting into the latter portion of March and historically
the potential for low elevation snow diminishes. One thing that
will need to be watched as 500mb temperatures plunge to around
-29C by mid week is thunderstorms and small hail. Another cold
500mb height anomaly will likely impact the area with more
unsettled weather toward the latter portion of next week.

&&

.AVIATION...IFR conditions will possible at the coastal terminals
late tonight into Friday morning. Confidence remains low on the
timing and details. Also, low clouds and fog will form again over
the interior valleys tonight. Otherwise, VFR conditions are
expected to prevail into Friday.

&&

.MARINE...A few weak frontal boundaries will promote light to
moderate winds across the coastal waters over the next few days.
The wind direction will vary but generally south winds will
develop on Friday and increase slightly late in the weekend. The
sea state will remain low with a mix of northwest and southwest
swell systems impacting the waters. Both winds and seas are
predicted to remain below small craft advisory criteria through
the weekend with only a 20-30% chance of gusts greater than 20 kt
possible on Sunday morning. Marine conditions could deteriorate
early next week as a more robust trough impacts the region.
However, this weather system looks like it will be focused south
of our area so there is uncertainty in the wind strength across
northwest California 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

Hazardous Weather Outlook
National Weather Service Eureka CA
305 AM PDT Thu Mar 16 2023

CAZ101>115-171015-
Coastal Del Norte-Del Norte Interior-Northern Humboldt Coast-
Southwestern Humboldt-Northern Humboldt Interior-
Southern Humboldt Interior-Northern Trinity-Southern Trinity-
Mendocino Coast-Northwestern Mendocino Interior-
Northeastern Mendocino Interior-Southwestern Mendocino Interior-
Southeastern Mendocino Interior-Northern Lake-Southern Lake-
305 AM PDT Thu Mar 16 2023

This hazardous weather outlook is for northwest California.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected at this time.