Gale Watch 31, NWS Eureka, CA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
249 PM PDT Wed Aug 16 2023

.SYNOPSIS...Temperatures will gradually decrease over the next
several days. The threat of isolated thunderstorms will persist
across inland areas through the rest of the work week.

&&

.DISCUSSION...The persistent upper low off the CA coast continues to
meander. This feature is forecast to gradually deepen over the next
several days while remaining generally in the same area. This feature
will continue to tap into monsoonal moisture from the S, as well as
producing vorticity maxima that rotate counter-clockwise around the
broader circulation. This will continue the threat of at least
isolated afternoon and evening thunderstorms over the next several
days. The exact coverage and timing of these storms will be
complicated by ongoing smoke in the area. Temperatures have peaked
over the past 24 hours, with a gradual "cool down" expected through
the end of the week. The Heat Advisory and Excessive Heat Warning
products will expire late this evening.

As of 2 PM, cumulus clouds have blossomed across the interior, with
isolated thunderstorms firing over NE Lake County. Cumulus activity
is virtually non-existent in areas of N Humboldt and Del Norte
counties, where fairly thick smoke is present. Temperatures range
from the 60s along the immediate coast to the 100-107 degree range
across parts of the interior.

Over the next few days, expect mostly afternoon and evening showers
and thunderstorms to continue, with gradually increasing moisture
content. Storm coverage will continue to be affected by thick smoke
over N portions of the area. As long as the upper low continues to
circulate off the CA coast and thunderstorms billow into the stronger
circulation around its periphery, storm motion should continue to be
toward the NW-NNW. As a result, the bulk of the thunderstorm activity
is expected to develop toward the Yolla Bollys and spread into
Trinity, N Mendocino, and E Humboldt counties.

Both the GFS and NAM are indicating a rather robust vorticity maximum
moving from SE to NW across parts of the area after midnight
tonight. This will keep the threat of at least isolated showers and
thunderstorms through the night. As we move forward in time, these
disturbances will remain possible while gradually becoming harder to
pin down with regards to timing and strength.

As we get into early next week, we may begin to see moisture from the
remnants of Tropical Cyclone Hilary spread to the N. Looking at long
term guidance, there is uncertainty regarding the path this moisture
takes, but it appears that it may at least bring an increase in
shower and thunderstorm coverage to the interior, as well as
potentially producing wetter storms. Stay tuned! /SEC

&&

.AVIATION...Various cloud types at vastly different heights
presented possible aviation concerns/impacts along coastal areas
today. Cape Mendocino to the Oregon border: Thin wildfire smoke moved
over Del Norte, NW Trinity and N Humboldt; Convective showers brush
over Del Norte and CEC airport; and widespread IFR Vis/MVFR Cigs
reported at CEC. ACV also reported Low VFR-MVFR Cigs this morning.
However, stratus/fog were mainly confined to the Mendocino
Coast...aided by a well- defined eddy all day. Around noonday,
convective activity started to develop over Lake, S Trinity, NE
Mendocino Counties...then rotating into E Humboldt. The result:
Thunderstorms are forecast to develop over the interior again this
afternoon and evening, but storm cells expected to remain well
outside 10NM at all forecast terminals. Model and sounding data
indicated the potential for areas of fog and stratus to rebound at
the coast overnight. /TA

&&

.MARINE...Afternoon satellite data (i.e. ASCAT Scatterometer Winds)
observed 12-16 knot northerly winds across the outer waters with
generally light winds less than 10 kt nearshore. Additionally, an
eddy off the Mendocino Coast is bringing southerly winds to the
nearshore waters. The main change to the forecast was postponing the
start time of the small craft advisory for PZZ470 to 3 AM Thursday
morning. Marginal small craft wind gusts are expected begin tonight
and will further increase across the coastal waters Thursday and
Friday. Gale force gusts will be possible over the weekend across the
outer waters but the coverage is still in question. Steep waves will
ramp up in response to the winds over the next few days with 12 to
14 foot waves predicted in the outer waters Friday into Saturday.
Additional headlines will be needed in the coming days for other
marine zones. A headline for hazardous seas still remains in question
and will depend on the coverage of gale force wind gusts. Either
way, marine conditions are expected to be crummy into the weekend.
KMZ

&&

.FIRE WEATHER...Mostly dry thunderstorms are expected again this
afternoon. A Red Flag Warning remains in effect for the NE portion of
the area. The smoke that presently blankets that area is squelching
convection as of this writing, but storms may move into the area from
the S later this afternoon and this evening. Any thunderstorms will
bring a risk of gusty outflow winds up to 50 mph. Otherwise, very hot
and dry conditions will continue with interior valleys above 100
with minimum RH generally 15 to 20%. Cooler and more moist
conditions are expected late this week. Thunderstorm activity will
persist Thursday, albeit with a higher chance of associated wetting
rain (around 20%). /JHW&SEC

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning until 9 PM this evening
      for CAZ203-204-211-212-283.
     Heat Advisory until 11 PM this evening for CAZ102-104.
     Excessive Heat Warning until 11 PM this evening
      for CAZ105>108-110-111-113>115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 3 AM Thursday to 5 AM Friday for PZZ470.

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