799
FXUS66 KEKA 271206
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
506 AM PDT Sun Apr 27 2025

.SYNOPSIS...Rain and cloud cover are receding as the exiting low
proceeds southeast. Winds will build through the day along the coast
and exposed ridges this afternoon. A dry, warming trend is expected
through mid week. Chances of precipitation return late in the week.



&&

.DISCUSSION...With the procession of low pressure exiting the area,
remnants of moisture with stratiform effects continues this morning
as precipitation wanes. HREF has most of the rain out of our CWA
before noon, Global deterministic models are mostly in agreement
with legacy SREF also showing a southeasterly retreat towards the
four corners. Upstream ridging, with an asymmetric amplitude to the
passing trough, will help clear skies out as subsidence sets in.
HIRESW soundings at the Arcata/Eureka airport, do show low level
saturation and shallow inverted V tonight which hints at mixing near
the surface. Meridional flow will slightly enhance geostrophic winds
parallel to the pressure gradient as the ridge approaches the area,
further developing with mixing down to the ABL resulting in
northerly gusts near the coast today around 25 - 35mph. Temperature
wise, inland areas are expected to see highs from mid 50`s to mid
60s. Areas with valley fog are expected to develop Sunday night into
Monday.

Monday, expect mostly sunny with dry and warmer temperatures.
Inland high temperatures in the mid 60`s to mid 70`s. Coastal areas
may see high temperatures up to low 60`s, before sea breezes
develops by the afternoon.

.LONG-TERM...Tuesday-Saturday...24-hour cluster means continue to
indicate above normal 500mb heights with ridging over the Pac NW
Tuesday through Thursday. Greater variance and departures from the
grand ensemble mean start to arise as early Thu with subtle
differences in the eastward progression of the 500mb height anomaly.
About 30% of ensemble members indicate a slighlty wetter outcome on
Thu, with showers mostly over the mountains and perhaps a push of
marine moisture and low clouds. Otherwise, dry weather with above
normal high temperatures in the interior is the most likely outcome
Tuesday-Thursday. By day 6, Friday May 2, all cluster means depict
another 500 trough digging offshore or over the forecast area. There
are considerable differences with the depth and progression of the
splitting trough. Potential for more wet and unsettled weather
increases Friday-Saturday with NBM probabilities for over 0.25in of
rain in 24 hours increasing to 30 to 50% for Del Norte, Humbodlt and
Trinty counties. Chances are only 10-25% for Mendo and Lake. Thunder
chances are more elusive and uncertain, but NBM has a 13% chance in
Trinity Fri-Sat. Only about 18-26% of members were decisively wetter
than the grand ensemble mean by Saturday May 3. Also, our mid week
warm up will come to a halt late next week (Fri) into next weekend.
Trough evolution becomes much more uncertain by Sunday. The trough
may end up closing off into a cut- off low over the Desert SW and
SRN Great Basin by day 8 (Sunday May 4). A faster progression with
stronger ridging offshore suggests a gusty northerly wind scenario
for our forecast area by end of day 8 (Sunday May 4). A slower
progression with wrap around moisture suggests a wetter scenario
into day 8. Stay tuned for updates. /ZVS /DB /EYS


&&

.AVIATION...Conditions are transitioning from the exiting low
which brought multi-layered cloud cover, moist air and rain. Mostly
VFR/MVFR conditions have been occurring overnight with only brief
rain at KUKI. Cloud cover is forecasts to thin out as upstream
ridging sets in over the next few days. Northerlies will continue to
strengthen as the low tracks into the Great Basin and high pressure
offshore builds eastward. Probability for low level wind shear or
low level turbulence increases to 40-50% just outside the vicinity
of KACV and may persists through the early morning. Greater
probability for shear and shallow mountain wave turbulence increases
to 80% over the coastal mountains, particularly the King Range, as
low level northerlies ramp up. Trend is for shallow moist layers to
diminish through the day today, however gusty northerly winds are
forecast to quickly pick up again with diurnal heating. DB


&&

.MARINE...Steep large seas continue early this morning. Near gale
northerly winds will continue through today and Monday with
localized areas of gale force winds south of Cape Mendocino and
Point St. George in the afternoons. A high pressure center over the
eastern Pacific will migrate towards the California coast causing
upper level ridging through Monday. This ridging will sustain a
tight land-sea surface pressure gradient leading to the continued
northerly winds. A long period NW swell will mix with the locally
generated large, steep, short period wind waves creating a hazardous
sea state through the morning. HREF guidance shows a high
probability( 70-90%) for gale force gusts returning to the outer
waters on Monday, this time south of Cape Mendocino. A Gale Watch
has been issued for the southern outer waters (Z475) for Monday
afternoon.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Hazardous Seas Warning until 3 PM PDT this afternoon for
     PZZ450-470.

     Small Craft Advisory until 9 AM PDT Monday for PZZ455.

     Hazardous Seas Warning until 9 PM PDT this evening for
     PZZ475.

     Gale Watch from Monday afternoon through Monday evening for
     PZZ475.

&&

$$

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