877
FXUS66 KEKA 052213 CCA
AFDEKA

AREA FORECAST DISCUSSION...CORRECTED
National Weather Service Eureka CA
313 PM PDT Sun May 5 2024

.SYNOPSIS...Light rainfall will develop Monday with a weak front.
Building high pressure will increase northerly winds on Tuesday as a
significant warming begins that will span through late next week.


&&

.DISCUSSION...Shower activity has eased with exception for a few
30 - 40 decibel radar reflectivity returns, north of Cape Mendocino.
The cold upper level trough continues to transition towards the
southwest although it looks to be weakening with isobars appearing
diffuse and considerable warming in the four corners region. Local
effects from a more zonal flow pattern will be experienced with a
weak cold front coming through tomorrow and stronger winds to follow
Tuesday afternoon. Large scale ridging will follow as an area of
high pressure dominates the E. Pacific. This synoptic ridging and
zonal flow will bring high winds to bear on the West Coast. The
probability of sustained winds reaching over 30 mph is 85
- 90%, just off the coast of our CWA and south of Cape Mendocino.
Wednesday we will see an expansion of high winds reaching into the
Oregon waters while some higher elevations and headlands may get
exposure. Winds will also increase over the higher terrain of
Eastern Lake County Tuesday night through Wednesday. As the ridge
continues to amplify, an upper trough looks to retrograde west into
the Great Great Basin. This setup would be favorable to generate
offshore flow and further enhance the warming temperatures late next
week. Probabilities have been consistently high (80 to 90%) for the
inland valleys to exceed 80 degrees, and 50 to 75% chance to exceed
85 degrees in the warmest interior valleys late next week.

Otherwise, below average temperatures remain in the wake of the low,
though inland valley fog and lingering cloud cover will hold up the
temperatures for some local areas. Clearing in Trinity County and
southward will allow for freezing to frost conditions tonight, thus
Freeze Watches and Frost Advisories are out. A weak frontal system
will clip the region on Monday, bringing light rainfall over mainly
Del Norte County where 0.25 to 0.5 inch is forecast. Much lighter
values can be expected down to Trinity and Humboldt counties, while
Lake and Mendocino counties will begin to experience warmer daytime
temperatures.

&&

.Aviation...Aside from perhaps some locally gusty wind from
isolated showers this afternoon, the main problem will be lowering
ceilings along the coastal terminals by 12-14Z Monday. Ensembles
indicate that by 12Z, coastal terminals stand at least a 30-50%
chance of lowering to MVFR ceilings, with chances steeply rising,
with KCEC a bit ahead of the curve compared to KACV by a couple
of hours as the next weather system moves in. As for wind gusts at
KUKI, ensembles indicate that this should be at its peak near 23Z
today, generally decreasing overnight into Monday. Ensembles also
indicate timing of light precipitation to begin near 14-15Z for
coastal terminals, with higher gusts near any convective showers,
with rain not likely reaching KUKI.

&&

.Marine...Buoy observations have been over performing the
forecast wave heights by a foot or two for the past couple of
hours, producing waves steep enough for small craft advisories.
Latest trends of buoys indicate that this may only be temporary
and heights will be coming down to near 6 feet soon. This will
need to be monitored in case small craft advisories for tonight
need to start earlier. A northwest swell is prominent.

Winds have/will become generally westerly today then turn southerly
Monday in advance of an approaching cold front, as it moves east
through the waters. By Tuesday, ridging will build over the west
coast, allowing surface high pressure to strengthen off the coast.
Northerly winds will increase with gales likely beginning as early
as Tuesday/Tuesday night. Waves will become very steep as the winds
ramp up. A gale watch looks like a good bet, especially for outer
waters for Tuesday night into Wednesday night. Combined wave heights
top 10 feet by Tuesday night as well and increase into Wednesday and
Wednesday night.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Freeze Watch from 1 AM PDT Monday through Monday morning
     for CAZ107-108.

     Frost Advisory from 1 AM to 9 AM PDT Monday for CAZ110-111-
     113-115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 5 AM to noon PDT Monday for
     PZZ450.

     Gale Watch from Tuesday afternoon through late Wednesday
     night for PZZ450-455-470-475.

     Small Craft Advisory from 1 AM to noon PDT Monday for
     PZZ470.

&&

$$

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