693
FXUS66 KEKA 131149
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
449 AM PDT Sat Jul 13 2024

.SYNOPSIS...Very hot and dry weather will continue in the interior
through today. An offshore low will bring a chance of dry
thunderstorms to the interior this afternoon and especially
Sunday. Interior heat is forecast to moderate slightly Sunday and
early next week. Coastal areas will remain cool with occasional
fog and low clouds through the weekend.


&&

.DISCUSSION...After a final day of triple digit heat, oppressive
interior heat wave will at long last begin to significantly weaken
on Sunday. The Four Corners region high will further weaken next
week, but may restrengthen some after. Under a very strong low level
inversion, the coastal stratus will continue to have lingering
daytime presence.

Attention is focused on a mid to upper low advancing alongside the
CA coast. Guided between the Four Corners high and the low, a
healthy plume of mid level monsoonal moisture is currently moving in
from the south. This moisture will increase in the mid to upper
levels, with a very dry surface layer. There was abundant lighting
over the Sierras yesterday along the moisture boundary. Model
soundings hold the classic inverted V signature and present enough
elevated instability (MUCAPE) for strong "dry" showers and
potentially thunderstorms over the interior regions, mainly in
Lake, Eastern Mendocino, and Trinity counties.

The forcing and availably moisture will be ample, but the
instability was been questionable. Given the historical poor
modeling of elevated instability, and the surplus of remaining
ingredients, confidence is growing on dry thunderstorm development
on the heels of the lasting heatwave and dried vegetation. Isolated
thunderstorms are possible this afternoon over the far interior
mountains in the previously outlined regions. Chances will increase
tonight through Sunday (15-20%) as discrete areas of PVA rotate
in off the low and the moisture within interacts with the higher
terrain. Chances for dry thunderstorms will be highest around the
Yolla Bolly area and Northeast Trinity County on Sunday, but
coverage may expand west, and eastern Humboldt cannot be ruled
out for at least some gusty convective cells.

The Four Corners region high will continue to weaken into next
week when most of the warmer interior valleys drop below 100.
There are indications the high will then restrengthen some late
next week. /JJW


&&

.AVIATION...Coastal stratus has brought LIFR ceilings and
visibilities to CEC and ACV. Currently winds are forecast to remain
light and southerly at CEC for much of the day, with light WNW winds
at ACV, both supportive of stratus impacts. Daytime heating will
likely lead to some scattering by mid afternoon at both coastal
terminals. Stratus looks likely to make a return to the coastal
terminals this early evening. UKI is forecast to remain VFR through
the TAF period. Some mid-level cloudiness is expected as well as a
low brings some moisture. Some potential for thunderstorms is
possible in eastern Mendocino and Lake counties in the afternoon and
early tomorrow morning, but is not forecast to affect any terminals
at this time. JB


&&

.MARINE...Gale force northerlies have begun to trend downward
as the ridge weakens. Winds are forecast to continue trending down
through today, with winds dipping below gales by the early afternoon
in the southern outer waters and early Sunday morning in the
northern outer waters. Hazardous and steep seas will also slowly
trend down today, diminishing below 10 feet everywhere by Sunday
morning. Winds will continue to trend downward during the week, with
gusts of up to 25 kts in the outer waters Sunday diminishing to 15-
20 knots early week. Nearshore waters will see lighter winds. JB


&&

.FIRE WEATHER...Afternoon winds will remain breezy, primarily in
Lake and Mendocino counties along the rim of the Sacramento Valley.
Isolated patches of critical fire conditions are possible in
southern Trinity and Lake counties with these breezes as very hot
temperatures and low RHs continue.

Models are converging on a plume of monsoonal moisture arriving
Saturday afternoon. Moisture along with daytime heating will allow
for greater instability and a chance of dry thunderstorms Saturday
afternoon in Lake, eastern Mendocino, and eastern Trinity
counties. A Red Flag Warning has been issued for zones 283 and 277
for potential coverage of dry thunderstorms and gusty outflow
winds.

With ample forcing, moisture and currently looking like sufficient
elevated instability, ingredients for thunderstorms are looking
better late tonight through Sunday for portions of Lake, Mendocino
and Trinity Counties. Eastern Humboldt cannot be ruled out for at
least some gusty convective cells. Model soundings reveal the
classic inverted V signature, indicative of dry showers and likely
thunderstorms. There is still some uncertainty for available
instability for thunderstorms, but any thunderstorms or stronger
convective showers that form with be capable of strong and erratic
outflow winds. As moisture begins cutting off on Monday, an
additional isolated shower or thunderstorm will still be possible
Monday afternoon over Trinity County. JJW/JB


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Heat Advisory until 9 PM PDT this evening for CAZ104-106-
     112.

     Excessive Heat Warning until 9 PM PDT this evening for
     CAZ105-107-108-110-111-113>115.

     Red Flag Warning from 2 AM to 10 PM PDT Sunday for CAZ277-
     283.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 AM PDT Sunday for PZZ450.

     Gale Warning until 3 PM PDT this afternoon for PZZ470.

     Gale Warning until 9 AM PDT this morning for PZZ475.

&&

$$

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