Area Forecast Discussion
Issued by NWS Eureka, CA

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109
FXUS66 KEKA 261230
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
530 AM PDT Tue Mar 26 2019

.SYNOPSIS...Northwest California will be between storm systems on
Tuesday, with another front tracking through on Wednesday,
followed by continued showery weather on Thursday. High pressure
may bring a break in the showers along with some milder
temperatures on Friday into Saturday.

&&

.DISCUSSION...Temperatures are running 8 to 15 degrees cooler
across northwest California on average compared to yesterday at
this time, in the wake of a cold front which pushed through during
the morning hours on Monday. Plentiful cloud cover overnight kept
temps from dropping even lower. Despite weak high pressure
building in for today, clouds will hang around, especially across
inland areas. Portions of the coast will be most likely to see
some breaks of sunshine, dimmed by areas of mid and high- level
cloudiness. Enough lingering moisture and instability will be
present this afternoon for some weak showers to pop up over the
inland mountainous terrain, but overall expect a dry day for most
locations. High temps will rebound into the 50s and 60s; near
seasonal normals.

Attention will turn toward the next system approaching this
evening, with vertically-stacked low pressure offshore sending an
occluded front across our area early Wednesday morning. Similar to
Monday`s system, a period of steady rain will push through with
the front, followed by showers for the rest of the day on
Wednesday. Southerly winds will be locally gusty at times late
tonight and on Wednesday morning as the front approaches and
pushes east, particularly over the mountainous terrain. Do not
expect a Wind Advisory will be needed though.

Colder air aloft in the wake of the front will result in a more
unstable atmosphere on Wednesday afternoon, enough so that we
continue a slight chance of thunderstorms for all of northwest CA.
That said, as mentioned by the previous shift, the timing of
shortwaves that would force stronger showers and isolated
thunderstorms does not match up with the `best` instability
Wednesday afternoon. For this reason was tempted to just remove
the slight chance of thunder, but it is hard to rule it out
completely just yet.

The main area of low pressure will gradually make it`s way toward
Washington and Oregon Wednesday night and Thursday, sending
spokes of energy in continued moist and unstable southwest flow.
This will result in a more prolonged period of showers, and a
rather wet day for much of our area on Thursday. That said, the
coast from Fortuna to Crescent City may see less rainfall due to
downsloping low-level south-southeast flow. Rainfall amounts for
Wednesday and Thursday combined will range from around an inch to
an inch and a half for most of the area; lowest around Humboldt
Bay and the deeper inland valleys, but with locally over 2 inches
around the King Range and South Fork Mountain. Snow levels will
range from 4000 to 4500 feet through Wednesday, dropping to 3500
feet at times by Thursday morning. This will keep any accumulating
snow above our major mountain passes, though over 6 inches will be
possible at Scott Mountain Summit on Highway 3.

High pressure will start to build in Thursday night and Friday,
but with weak low pressure still drifting off the Oregon coast,
there will still be a slight chance for a few showers from around
Cape Mendocino northward. Saturday appears to be mostly dry at
this point as mid and upper-level high pressure builds in.
Temperatures will warm toward 70 degrees across the inland valleys
with a fair amount of sunshine expected. Showers may begin to
increase again by Sunday, with increasing chances by Monday and
Tuesday as the next storm system passes by. Details are not clear
at this point, but it looks like rainfall amounts should once
again be in the half-inch to two-inch range at most for northwest
California. /AAD

&&

.AVIATION...VFR conditions prevail across much of the region this
morning beneath a scattered mid level cloud deck. The combination of
this cloud cover and light easterly winds at the surface has thus
far been enough to mitigate any fog development along the Redwood
Coast, however patchy fog will remain possible this morning and have
the potential to briefly introduce IFR conditions at CEC and ACV
through about 16z. Meanwhile, morning observations reveal low
stratus over some of the interior valleys including the Russian
River Valley. This will bring ceilings fluctuating between MVFR and
LIFR to UKI through the morning hours. Any stratus and fog across
the area should lift by the afternoon, yielding VFR conditions
through the end of the TAF period before the next system brings
another round of rain and possible wind shear to area terminals by
early Wednesday morning. /CB

&&

.MARINE...Light southerly breezes will prevail across the coastal
waters through the first half of today, leaving a mid period
westerly swell around 7 feet at 12 seconds as the only wave group of
note to begin the forecast. Short period seas will begin to ramp up
by late afternoon as the next front approaches the region
accompanied by another round of fresh to moderate southeast breezes.
This will support Small Craft Advisory conditions across the outer
waters this evening, then gradually spreading into the nearshore
waters tonight into Wednesday. Winds and short period seas will once
again trend downward behind the front on Thursday, however a pair of
mid to long period westerly swells propagating into the waters will
help to keep combined seas relatively elevated around 10 feet
through the end of the week. Winds then look to shift to the north
by the weekend. /CB

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory from
     9 AM to 11 PM PDT Wednesday for PZZ450.

     Small Craft Advisory from 5 PM this afternoon to 11 PM PDT
     Wednesday for PZZ470-475.

     Small Craft Advisory from 11 PM this evening to 11 PM PDT
     Wednesday for PZZ455.

&&

$$

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