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000
FXUS66 KEKA 141109
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
409 AM PDT Sun Apr 14 2024

.SYNOPSIS...Periods of moderate rainfall and high elevation snow will
continue through this morning before tapering off this afternoon.
Gusty NW winds will develop overnight into Monday as a high pressure
ridge builds into the coast. A return to summer-like conditions and
warm interior temperatures is expected this week, with coastal
stratus and elevated NW winds likely.


&&

.DISCUSSION...An additional surge of precipitation continues early
this morning along the northeast portion of a strong cutoff low.
Dry, cooler air wrapping around the low will enhance potential for
snowfall impacts in the higher elevations of interior Humboldt and
Trinity counties, including Highways 36 and 299, as a S/SE flow
regime develops. Forecasted snowfall for these areas remains at
1-3 inches through late this morning as snow levels hover around
3,000 ft, with 3-6 inches possible on the high peaks. Lower
elevations and coastal counties can expect periods of moderate
rainfall through the morning hours developing from the northeast.
HREF and WPC QPF forecasts have trended slightly higher - newest
model guidance anticipates widespread additional rainfall totals
of 0.30 to 0.70 inches through 5 PM this evening. Locally higher
amounts nearing 1 inch are likely in eastern Trinity County.
Depending on the timing of the shift to NW flow, minor additional
upslope precip is possible along wind facing terrain of the
coastal ranges. Otherwise, Southern Mendocino and Lake Counties
can expect lower amounts spanning 0.15- 0.30 inches.

This dynamic system will produce progressive shifts in wind
direction and shower development. The return to NW onshore flow this
afternoon will effectively cut off the supply of cold air and mid
level moisture to the system. As a result, precipitation will taper
off as the low continues to progress SE into southern CA. Gusty NW
winds are expected this evening into Monday morning as a strong
pressure gradient develops between the departing low and building
high pressure over the Pacific. Gusts approaching 30 mph are
possible along exposed ridges and coastal headlands of Cape
Mendocino, with breezy conditions likely along all coastal areas.

Remaining entrained cold air will dissipate early this week as the
ridge continues to build into the PNW. A rapid return to summer-
like conditions will ensue as interior temperatures warm into the
70`s by Tuesday, with potential for highs in the 80`s in the
valleys for the latter half of the week. Broad high pressure
subsidence will likely allow coastal stratus to return beneath a
marine inversion by mid week as NW winds subside.



&&

.AVIATION...The coastal terminals have been under intermittent MVFR
early this morning as a final front approaches the coast while
wraparound precip drifts in from the NE. Ceilings should slowly
lower to IFR or possibly LIFR around daybreak as the front moves
onshore, then lift again later this morning as gusty northerly winds
develop. Some scattered lower cloud is possible along the coast
through the day today, however ceilings are expected to lift
generally to high MVFR after this feature moves onshore. Clouds
continue to scatter though the TAF period for the Redwood coast,
with VFR expected by late tonight. MVFR ceilings with occasional IFR
vis may develop at KUKI late this morning and this afternoon as the
front progresses SE. Interior valley fog development is possible
late tonight as well.


&&

.MARINE...The second and final front of the current system will drop
down from the north and move onshore this morning, once again
resulting in a complex wind field across NW California waters.
Northerly gusts likely reach greater than 22kt behind this feature,
with sufficient coverage for an advisory today. Granted it will be
marginal initially, but the trend will be for northerly winds to
increase through the day and into the evening. Northerlies are
forecast to spread to all zones but the southern inners by late
this morning, finally reaching the southern inners by late
tonight.

Northerly winds will steadily increase tonight through Monday and
again on Tuesday. Increasing stability (warmer air aloft) will
result in more laminar flow versus the turbulent flow from mesoscale
circulations and localized convection this weekend. Supercritical
flow with expansion fans downwind of Cape Mendo and Cape Blanco will
probably (80% chance) yield localized regions or tight corridors of
gusts to 35-40kt. For now it looks most probable downwind of Cape
Mendocino on Tue, but would not rule out the northern waters with a
seemingly weaker fan breaking off from Cape Blanco. Steep northerly
short period waves will build in response to the steady state
northerlies with combined seas reaching 10 to 12 ft, mostly just
outside 10NM from shore.

Prevailing northerlies will continue for the remainder of the week
with decreasing probabilities (40-60% chance) for gusts >35kts
downwind of Cape Mendo after Tues. With warmer air aloft and trapped
flow nearshore/along the coastal terrain, nearshore diurnal varying
southerlies are highly probable. TJ/DB


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Winter Weather Advisory until 11 AM PDT this morning for
     CAZ107-108.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 3 PM this afternoon to 5 PM PDT
     Tuesday for PZZ450.

     Small Craft Advisory from 9 PM this evening to 5 PM PDT
     Tuesday for PZZ455.

     Small Craft Advisory from 7 AM this morning to 5 PM PDT
     Tuesday for PZZ470.

     Small Craft Advisory until 9 AM PDT Tuesday for PZZ475.

&&

$$

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