904
FXUS66 KPQR 281257
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
545 AM PDT Sun Apr 28 2024

...UPDATED WARNING LIST AT BOTTOM...

.SYNOPSIS...Cool onshore flow will continue over the next several
days. Embedded disturbances in the westerly flow aloft will maintain
showers, along with snow at times above 2500 feet in the Cascades.
Back to milder weather later this week, with a dry day or two. Then,
return to unsettled weather for next weekend.
&&

.SHORT TERM...(Today through Tuesday)...Feels more like March
rather than late April across the region, with plenty of clouds and
showers. Zonal (westerly) flow off the Pac into the Pac NW persists
through Tuesday.

Next system will push across the region later today into this
evening. As such, will see showers increase in coverage and
intensity by afternoon. Still cool with temperatures staying in the
50s for the most part. Interestingly, main effect from this system
today will be to usher in bit cooler air aloft. This will allow for
instability to increase a tad, just enough to introduce a meager
possibility of thunder this afternoon into this evening. Does seem
that that potential will be over western Washington, and just
clipping far northwest Oregon. Models over past few days have been
back and forth on this potential, as to whether or not would be
there for today. But, based on current satellite and model trends,
can not ignore it. So, will maintain a slight chance (10-20%) for a
thundershower later today into this evening.

As cooler air aloft spreads inland tonight, will see snow levels
lower a bit more, settling around 2500 ft late tonight into Monday,
but down to 2000 ft over the Washington Cascades. While snow
accumulations are below standard criteria, it is late season and
with most cars no longe have snow tires or studded tires, will
maintain the current winter weather advisory. Accumulations
generally in the 2 to 8 inches range tonight, with the higher
accumulations being in areas above 4000 ft.

Not much change for Monday, as will see plenty of showers across the
region. Should see some breaks in the cloud cover for the afternoon.
Air mass still remains cool aloft, enough to maintain that small
chance of thundershowers, especially along the coast over the Coast
Range/Willapa Hills into the interior. Snow continues at times in
the Cascades. But, accumulations will vary thanks to showery nature
of the precipitation. Likely another 2 to 8 inches in the Cascades.

Yet another system arrives on Tue. This will be a bit stronger,
enough so could see couple of hours of steady light rain for a time
Tue morning as the low pushes into western Washington. Otherwise,
another showery day, with uptick of south to southwest winds. Ahhh,
April showers bring the May flowers.          /Rockey

.LONG TERM...(Wednesday through Friday)...Overall confidence is
low to moderate as the pattern stays rather progressive into
late next week. Deterministic and ensemble guidance continue to
struggle to resolve the longitudinal placement of ridge/trough
features going forward. Wednesday guidance has continued to
trend a little drier nudging a larger scale upper-level low
further north while a transient ridge glides over the region.
Out of all the ensemble solutions available, this scenario is
present in roughly 60% of them in addition to the latest
deterministic ECMWF and GFS. Thursday and beyond, model
uncertainty becomes truly significant with nearly a 50/50 split
between maintaining a ridge feature overhead or bringing a
potent trough into the region by Thursday and becoming most
defined Friday.

&&

.AVIATION...Expect a mixture of low-end VFR and high-end
MVFR conditions through the TAF period as a series of weak fronts
push across the airspace. This will result in scattered showers
which could also result in lowered visibilities and ceilings at
times. Generally a slight chance (20% probability) for thunderstorms
across the airspace starting around 20Z Sunday and persist through
at least 12Z Monday. Generally westerly winds through the TAF period
with coastal locations having gusts up to 20 kt, with southerly
winds for inland locations having gusts up to 15 kt.
Mountains being obscured through the TAF period will be likely.

Notes: The ASOS at KTTD is only available via the dial in option.
The AWOS at KMMV is still out of commission, but a tentative work
around has been implemented. There is no estimated time of
full repair and restoration for either of these locations.

PDX AND APPROACHES...Mixture of low-end VFR and high-end
MVFR conditions with scattered showers. Slight chance (20%
probability) for thunderstorms starting around 20Z Sunday and
persist through at least 12Z Monday. Southerly winds with gusts up
to 15 kt.     /42
&&

.MARINE...Active weather is expected to continue this weekend an into
the start of the week. A surface front moving through the waters
this evening will bring another round of elevated winds along
with steep and choppy seas. Therefore have issued a series of
small craft advisories through at least Monday afternoon.
Generally westerly winds through this time with gusts up to 25 kt
and seas of 6 to 9 ft at 10 to 13 seconds through Monday.

A series of weak fronts will move through the waters this week
bringing elevated winds and seas at times. Some models are
suggesting that small craft conditions could develop with each
frontal passage, will continue to monitor the situation as it
develops. /42
&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Winter Weather Advisory for tonight through Mon am for
       the Cascades ORZ126-127-128.

WA...Winter Weather Advisory for tonight through Mon am for
       the Cascades WAZ211.

PZ...Small Craft Advisory today through Mon afternoon on all
coastal waters P210- 251>253-271>273.
&&


$$

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