632
FXUS66 KPQR 250512
AFDPQR

Area Forecast Discussion...UPDATE
National Weather Service Portland OR
1012 PM PDT Fri May 24 2024

Updated aviation discussion

.SYNOPSIS...A weak cold front will move inland this evening
bringing showery conditions through Saturday. Accumulation
though will be minimal. High pressure begins to build Sunday
evening and intensify on Monday. These warmer and clear
conditions will be short lived as yet another trough moves in.

&&

.SHORT TERM...Now through Sunday Night...Radar shows the light
rain kicking in as a weak cold front drops down from the
northeast Pacific. This front, while it has some energy
associated with it, is beginning to decay as it nears our
shores. Because of this, the sensible weather impacts will be
minimal. Will see periods of rain showers through Saturday as it
slowly shifts eastward. Areas most in store for accumulating
precipitation is along the coast, the Coast Range and the
Cascades. Once again, there is a high probability that the
inland lowlands will be rainshadowed with only a maximum of 20%
chance for precipitation. The Cascades on the other hand are
around 60-80%. The main trough axis will move over the region
late this evening after 2200 which is when the most
precipitation will fall. Snow levels will lower as 850 mb
temperatures sit right around -1 degree Celsius. Will say that
winds are beginning to increase along the coast as they
transition to the south. Speeds are already reaching around 25
mph around Astoria, OR.

Temperatures will gradually rise on Sunday as winds aloft shift
a bit more northwesterly and a ridge slowly builds. Floating
along the upper crest of the ridge is another shortwave trough
though which could bring precipitation back to southwest
Washington. Most models are showing this precipitation well to
the north though with just the trailing ends bringing some very
light showers. Overall, though, no real concerns in the short
term forecast.
  -Muessle


.LONG TERM...Monday through Friday...The long awaited ridging
pattern is still in store...but don`t get too excited. While
conditions will be warmer and drier, conditions are not
necessarily going to be exceptionally different. But, if you`re
wanting to go honor those who served this Memorial Day, it will
be quite a pleasant day. As we transition into Tuesday, the
forecast has shifted a bit over the past 24 hours as guidance
depicts the ridge axis shifting farther east over the Rockies on
Tuesday. The net effect of this shift is to place the Pacific
Northwest closer to the influence of an upstream trough over the
NE Pacific, lowering temperatures and introducing a chance of
rain to the coastal areas as early as Monday night. The bulk of
the guidance continues to favor the return of a troughier
pattern towards the middle of next week. Despite some
differences in timing and location of specific features, there
is greater confidence in increasing rain chances as most
individual ensemble members depict at least some precipitation
across the area Wednesday into Thursday, with temperatures
settling closer to seasonal norms around 70 degrees. -Muessle/CB


&&

.AVIATION...VFR conditions prevailing inland with spotty MVFR.
Weak showers support brief MVFR conditions, so for now will leave
out of TAF forecast. Guidance shows VFR prevailing through 15Z Sat,
then HREF shows MVFR chances increasing to around 20% until 18Z
Sat.

Conditions at the coast slowly improving from IFR/LIFR to MVFR
with cigs in the 1500-2500 ft range as of 05Z Sat. Guidance shows
chance for MVFR decreasing tonight and Saturday with chances
dropping below 20% after 20Z.


PDX AND APPROACHES...VFR conditions becoming a mixture of brief
low-end VFR/high-end MVFR conditions through the night. For now
will keep MVFR out of forecast as majority of guidance shows VFR
prevailing. Winds west/northwest winds generally less than 10
knots. /42 /mh

&&

.MARINE...A slightly more active pattern through Saturday morning
as the next system drops south-southeastward into the Pacific
northwest. Along with precipitation, expect northwest winds with
gusts up to 30 kt and seas also building towards 8 to 10 ft with
a dominant period of 8 to 10 seconds with steep and choppy seas.
Therefore, have maintained the current timing of the issued Small
Craft Advisory. Another weak ridge of high pressure brings the
return of benign conditions by Saturday afternoon and these lower
conditions are expected to persist thought the start of the
upcoming week.Monday night another system originating from the
Gulf of Alaska will start to move southward and arrive around the
middle of next week again. Which will bring increasing
winds and seas across all waters. /42-Schuldt

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 AM PDT Saturday for
PZZ210-251>253-
     271>273.
&&

$$

www.weather.gov/portland

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