FXUS66 KPQR 091054
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
254 AM PST Fri Feb 9 2024

.SYNOPSIS...A showery pattern persist across the area through
this afternoon in cool northwest flow aloft, with light snow
continues across the High Cascades. Expect a drier and more
pleasant day on Saturday, with unsettled weather returning
Sunday into next week. Overall not very impactful weather
expected into next week.

&&

.SHORT TERM...THROUGH SATURDAY NIGHT...Latest radar imagery
shows rain increasing in coverage across the northern half of
the area early this morning ahead of an upper level disturbance
diving southward over the Washington Cascades. Rain will
continue to spread across the area through this morning as this
feature digs southeastward towards the Great Basin. Rain amounts
today look generally on track from previous forecast packages,
with most valley locations expected to see a tenth or two of
rain from early this morning through this afternoon. Snow levels
will remain around 2000-2500 feet, with an additional 2-4 inches
of snow in the High Casacdes as precipitation amounts are aided
by favorable orographic ascent in northwest flow. Showers will
rapidly tape off from north to south by this evening as the
upper wave departs the region. Abundant cloud cover will likely
linger through the day, helping to hold high temperatures down
in the 40s across most valley locations.

A stout upper level ridge will build over the region tonight
into Saturday. This may yield some patchy fog development early
Saturday morning as subsidence increases atop a moist boundary
layer environment. High temperatures will rebound into the 50s
in most locations for Saturday afternoon as the ridge axis moves
directly overhead and yields pleasant, dry conditions
characterized by partly sunny skies. Dry weather will be short
lived, however, as the next system approaches Saturday night
into Sunday. /CB

.LONG TERM...SUNDAY THROUGH THURSDAY...Overall, the long term
period remains characterized by bouts of showery conditions and near
normal temperatures – significant weather related impacts are
not anticipated going forward. The transitory ridge of high
pressure responsible for the drier weather the first half of the
weekend likely flattens and shifts eastward into the Rockies by
Sunday allowing a weakening shortwave trough to bring
additional shower chances back to the region. Deterministic and
ensemble guidance do a decent job resolving this initial surge
of light QPF through Sunday, but model agreement deteriorates
Sunday night into Monday in regards to a potential secondary
upper-level shortwave feature and an accompanying cold-frontal
boundary. It’s the depth and temporal progression of this latter
secondary feature which will heavily modulate the degree of
showers through the day on Monday – a stronger and slower
feature like shown in the GFS and many of the GEFS ensemble
members would lead to better shower chances across the region
while a weaker and quicker moving feature depicted by the
Canadian and some extent the ECMWF/EPS would confine any
lingering shower to the higher elevations Monday leaving the
Willamette Valley mostly dry. The current forecast does include
the continuation of light precipitation chances through Monday,
however, should guidance trend towards the latter drier scenario
adjustments will have to be made to lower PoP chances across
the lower elevations. Tuesday into the middle of next week
modest model dissonance is the theme going forward as
deterministic/ensemble guidance see further disagreement in the
evolution of the large scale pattern. Most ensemble
guidance(~75%) suggests some form of a high pressure feature
attempts to build over western CONUS and/or the eastern Pacific
around Wednesday of next week but show significant variation in
the depth and longitudinal placement of the aforementioned
feature. Fortunately, even with all the model uncertainty in
mind conditions appear rather benign by February standards
through this time-period. /Schuldt

&&

.AVIATION...Predominately VFR conditions with scattered, light
showers across the air-space. Widespread MVFR conditions expected
to return around 12Z Fri (75%-85% probability) as a weak system
pushes through. Upper level high pressure will build as well
resulting in a low/mid level inversion developing that will likely
prevent conditions improving throughout the day. In addition,
starting around 15Z Friday IFR probabilities increase (20%-40%
probability) the majority of inland locations. These MVFR and IFR
conditions are expected to persist through at least the remainder
of the 12Z TAF period. Light precipitation is expected across the
air-space through around 06Z Saturday.

PDX AND APPROACHES...VFR thresholds expected to persist through at
least 12Z Fri, with MVFR cigs expected to develop afterwards. 20-30%
probability of IFR conditions starting around 15Z Friday. MVFR
and IFR conditions are expected to persist through at least the
remainder of the 12Z TAF period. Light precipitation expected
across the air space through around 06Z Saturday. /42

&&

.MARINE...A weak low pressure system approaching the area will
bring a southerly wind shift across all waters by early Friday
morning. As this low quickly moves out of the area, high pressure
will return and slowly develop through the weekend, with winds
remaining southerly. Another weak low will move across the waters
on Sunday, which will cause winds to become more westerly, the
northerly by Sunday night. Winds will also increase during this
time with gusts up to 25 kt expected.

Seas will hover around 7 to 9 ft at 14 seconds, but will start to
re-build Saturday afternoon as another long period, westerly
swell pushes into the waters. Seas will build back towards 10 to
13 ft by Saturday night and hold through Sunday. Seas then
gradually subside again below 10 ft on Monday. /42

&&

.BEACH HAZARDS...A long to mid period westerly swell is expected
Saturday afternoon through Sunday evening with waves building to
around 10 to 13 ft and a period of 15 to 17 seconds. Beachgoers
should maintain heightened awareness for waves running farther up
onto the beach than anticipated. Avoid rocks and jetties and never
turn your back on the ocean.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 2 PM this afternoon to 6 PM PST this
     evening for Columbia River Bar.

&&

$$

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