Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 031103

National Weather Service Eureka CA
403 AM PDT Mon Aug 3 2020

.SYNOPSIS...Another day of clearing along the coast is expected by
at least the afternoon north of Cape Mendocino while areas farther
south could stay clear all day. Interior areas will remain clear
and dry. A stray mountain thunderstorm will be possible Tuesday
and Wednesday afternoons.


.DISCUSSION...Coastal Northwest California received some welcome
sunshine yesterday as the passing upper low was able to mix out the
coastal stratus at least for a few hours. The stratus has
redeveloped north of Cape Mendocino while offshore flow has kept the
entire Mendocino coast clear as of this writing. There may be a few
coastal clouds that develop along the Mendocino coast this morning
but generally sunny conditions are in store for all of Mendocino
County today. Stratus along the Humboldt and Del Norte coasts isn`t
too expansive and with increasing north winds just off the coast the
stratus should mix out for more sunshine this afternoon.

As the passing upper low moves northeast today, the low will leave a
small piece of energy behind which will park over Northern
California Monday through Wednesday. Though this will keep an
upper level troughing over the region, 850 mb temperatures warm
slightly, indicating the potential for a slightly stronger marine
inversion and more stratus along the coast. Have opted to keep a
persistence forecast at this point but the stratus forecast has
become a bit more uncertain than was thought a few days ago.

In addition to the coastal cloud uncertainty, the upper feature may
also bring just enough instability to allow for convective buildups
over the mountains and possibly a thunderstorm. The best instability
is currently indicated over the far northern reaches of the
mountains in Humboldt and Trinity counties Tuesday and Wednesday
afternoons, shifting farther east on Wednesday as compared to
Tuesday. At this point the upper end potential may be only a
single storm in the forecast area but still worth a slight chance

Late in the week this upper feature moves east out of the area
leaving split upper level flow over Northwest California. There
appears to be a decent potential for dry northeasterly flow in the
northern half of the forecast area with a substantial jump in warm
air aloft. A 5-10 degree jump in high temperatures across the
interior is likely from Thursday to Sunday and conditions might
become quite dry, especially at higher elevations, as offshore flow
develops. /RPA


.AVIATION...A northerly wind regime has coastal stratus
advecting south this morning. Coastal low lying areas from Brookings
down to the Eel River Valley have stratus, albeit thinner than
previous nights. KCEC ceilings have been overcast around 1200 feet
with MVFR conditions. KACV has similar conditions which settled
in much later. These MVFR categories should persist through to the
afternoon and improve on the North Coast. Later this evening,
this will be combated by increasing and deepening marine air with
more onshore flow heading into Tuesday and Wednesday, which will
likely make it cloudier at the coast and farther inland for
midweek. Thunderstorm potential near the Northern Trinity and
Northeastern Humboldt mountains Tuesday and Wednesday should be
considered in flight plans as well. Light north winds are expected
at KUKI this morning. Gusty north winds should increase by the
late afternoon and ease tonight at KUKI. /EYS


.MARINE...North winds are most prevalent in the southern outer
waters and South of Cape Mendocino, so SC.Y has been extended. The
winds will proceed to expand in coverage tonight throughout the
Northern Outer waters with marginal Small Craft Advisory conditions.
The Southern Inner waters have been included in the SC.Y, beginning
this afternoon.

Tuesday through the end of the week, fresh to strong northerly winds
will expand into the remainder of the waters, causing seas to
increase as well. As of now it appears that these winds will remain
below Gale strength until at least late in the week, although
seas could be slightly larger and steeper. Winds are expected to
increase slightly more Friday and beyond, although the magnitude
remains uncertain. /EYS


.FIRE WEATHER...An upper level feature will bring a small cooling
trend through mid week. With the slight cooling there will also be a
small increase in RH and higher minimum afternoon RH values through
Thursday. The upper level feature will also bring a slight potential
for a thunderstorm over the higher terrain of northeastern Humboldt
and northern Trinity counties Tuesday and Wednesday afternoons.
Potential remains very low and headlines in the fire weather
forecast still don`t seem warranted. Warmer temperatures and dryer
conditions are expected to return late in the week into this coming
weekend with light offshore flow possible, particularly in Del
Norte and northern Humboldt counties. /RPA


     Small Craft Advisory from 9 PM this evening to midnight PDT
     Wednesday night for PZZ470.

     Small Craft Advisory from 3 PM this afternoon to midnight PDT
     Wednesday night for PZZ455.

     Small Craft Advisory until midnight PDT Wednesday night for



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