067
FXUS66 KPQR 280021 CCA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
520 PM PDT Sat Apr 27 2024

.SYNOPSIS...Front continues to bring rain this afternoon,
transitioning into showery conditions that will continue
through early next week. Wednesday and Thursday may have a
break from showers, but expect a return of precipitation into
next weekend.

.SHORT TERM...(Today through Tuesday)...Fast moving front
continues to move eastward, reaching the Cascades in the late
afternoon. Rain will transition to showers behind the front,
resulting in showers throughout the region by evening. Not much
rain expected from this front today, with 0.25 to 0.50 inch
(30-50% chance to exceed 0.5 inch) expected in the Coast Range
and Cascades, northward of Newport and Mt Jefferson (Oregon
Highway 20). Expect less rain across the coast and inland
valleys, around 0.10 to 0.25 inch. Otherwise, similar 24 hour
rainfall amounts for Monday and Tuesday, with Monday reaching
farther south in the Coast Range and Cascades unlike today and
Tuesday.

Cooler air aloft will push inland tonight as the front passes,
maintaining showers. This cooler air will steepen lapse rates
and bring some instability through Tuesday for southwest
Washington and northwest Oregon, as well as along the coast. As
a result, any cloud breaks during the afternoon could provide
enough warming to produce an isolated thunderstorm, most notably
Monday through Tuesday, with less chances Sunday. Will keep a
slight chance of isolated thunderstorms along the coast and for
inland areas north of a Lincoln City to Salem line through
Tuesday.

Sunday night, another fast moving system will move southeastward
into the region, bringing steady rain for a brief period before
transitioning to showers. As this system passes by and brings
cold air, snow levels of 4000-4500 feet will drop to 2000-2500
feet early Monday morning. As a result, 4-8 inches of 12 hour
snowfall across the Cascades is expected through Monday morning.
With chances around 50-60% of 12 hourly snowfall exceeding 6
inches Monday morning, as well as a late season drop of snow
levels, a Winter Weather Advisory has been issued from 11PM
Sunday to 11AM Monday for the Cascades.
-JH

.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. Current confidence in the forecast by Thursday
is low.
-JH/Schuldt

&&

.AVIATION...Scattered showers continue across NW Oregon and SW
Washington through Sunday, bringing lowered ceilings and
visibilities at times. Along the coast and higher terrain,
predominately MVFR conditions with local IFR in heavier showers
expected through the period. Elsewhere, including lowland valleys,
ceilings expected to hover right around the VFR/MVFR threshold,
generally bouncing around between 2500-3500 ft through around 07z
Sunday. Expect lower ceilings and visibilities in passing
showers.

Southerly winds across the airspace through around 02-04Z Sunday
with gusts up to 25 kt along the coast and up to 20 kt for inland
locations. Afterwards, winds along the coast will become more
westerly with gusts up to 15 kt as southerly winds persist inland
with gusts up to 10 kt through the remainder of the TAF period.

Notes: The ASOS at KTTD is only available via the dial in option.
The AWOS at KMMV is still out of commission. There is no
estimated time of repair.

PDX AND APPROACHES...Predominately VFR with rain showers. Ceilings
will hover around 3500-4500 ft through the TAF period along with
a 60-80% probability for MVFR conditions through 05z Sunday.
Southerly winds with gusts up to 20 kt through around 04Z Sunday.
Afterwards, winds will subside with gusts up to 10 kt through the
remainder of the TAF period. -HEC

&&

.MARINE...Active weather is expected to continue this weekend into
next week. A surface front is moving through the waters this
afternoon and is expected to push inland by early evening. Winds
remain elevated and southerly along and ahead of the front with
gusts up to 30 kt, creating steep and choppy seas. A Small Craft
Advisory remains in effect until this evening. Winds will shift
westerly and decrease quickly behind the frontal passage this
afternoon and evening with gusts below 20 kt. The next surface
front will move through the waters late Sunday night into Monday
morning. Winds will increase again with local gusts up to 20 to 25
kts. Seas will generally be 6 to 9 ft at 11 to 13 seconds through
Monday.

Another frontal system is forecast to move through the waters late
Monday into Tuesday, producing elevated winds and seas in the low
teens. -HEC

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Winter Weather Advisory from 11 PM Sunday to 11 AM PDT Monday
     for ORZ126>128.

WA...Winter Weather Advisory from 11 PM Sunday to 11 AM PDT Monday
     for WAZ211.

PZ...Small Craft Advisory until 8 PM PDT this evening for PZZ210-
     251>253.

&&

$$

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