809
FXUS66 KPQR 231725 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1024 AM PDT Thu May 23 2024

.SYNOPSIS...Weak high pressure brings a brief period of warmer
and sunnier conditions today. Cooler and cloudier conditions
quickly return as another trough brings a chance of showers
back to the area Friday and Saturday. Medium range models hint
at a more sustained period of warmer and drier weather Sunday
into early next week.

&&

.SHORT TERM...Now through Saturday Night...Shower activity has
mostly ended across the area early this morning as an upper
level trough departs east of the Cascades, with a few lingering
radar echos noted over the High Cascades in the vicinity of Mt
Hood. Otherwise, partial clearing is depicted on satellite
imagery in the lee of the Coast Range as drier northwest flow
starts to work into the region. Conditions will continue to
improve through the day today as a transient shortwave ridge
moves overhead, with cloud cover gradually eroding and revealing
mostly sunny skies by later this afternoon. Modest height rises
and sunny skies will allow for much warmer temperatures than
recent days as highs climb into the upper 60s to near 70 across
much of the area.

The shift to warmer and drier weather will be short lived as the
next trough embedded in the large scale northwest flow regime
arrives early Friday. This will bring a return of showery
weather with cooler and cloudier conditions Friday into the
weekend as temperatures trend back down into the upper 50s to
low 60s through Saturday. QPF amounts remain fairly modest
through the weekend, with guidance generally depicting around a
quarter to a half inch of rain in the higher terrain of the
Casacdes and Coast Range and lighter amounts of a tenth or two
at best in the lowlands from Friday through Saturday. Snow
levels may briefly lower to around 4000 feet Friday night into
Saturday morning, allowing for a dusting of snow as low as the
Cascade passes. Conditions will begin to improve by later
Saturday as the trough departs to the east and makes way for the
next period of shortwave ridging. /CB

.LONG TERM...Sunday through Wednesday...Sunday looks to feature
drier conditions and rebounding temperatures as benign zonal
flow develops in the wake of the departing trough. WPC ensemble
clusters are in reasonably strong agreement on a warming trend
continuing into the early part of next week as a stronger ridge
builds somewhere between the Great Basin and the Rockies,
leaving the Pacific Northwest in warmer and drier southwest
flow aloft. Therefore expect temperatures to reach well into
the 70s for most area both Monday and Tuesday, with
probabilistic guidance depicting a 30-40 percent chance to
reach 80 degrees in the Portland area and closer to a 20-30
percent chance over other parts of the Willamette Valley.
Guidance remains in reasonable agreement into the middle of next
week as most models hint at some semblance of upper level
troughing returning to the region, albeit with some differences
in timing, strength, and position. In terms of sensible weather,
look for increasing shower chances again by Wednesday of next
week, with temperature falling back into the 60s. /CB

&&

.AVIATION...Generally VFR conditions with CIGs around 3500-6000 ft.
High pressure will continue to develop over the air space and
result in VFR with CIGs above 7000 ft. Isolated pockets of MVFR and
IFR conditions are being observed, but those are expected to improve
to VFR over the next few hours. Winds will remain westerly
and light. Next system will bring a return of clouds and light
precipitation to the airspace. Look for precipitation to start
along the coast around 09Z Friday with a 55%-75% probability of
MVFR conditions starting around the same time. Precipitation will
continue spreading inland and reach inland locations starting
around 17Z Friday with a 50%-70% probability of low end-VFR/high-
end MVFR conditions starting around the same time.

PDX AND APPROACHES...VFR conditions with CIGs around 4000-5000 ft
which will slowly break up over the next few hours. Winds remain
fairly light. Clouds and precipitation will return starting
around 17Z Friday with a 60-70% probability of low end-VFR/high-
end MVFR conditions starting around the same time. /42

&&

.MARINE...Today the region will see a brief break from the active
conditions as a transitory shortwave ridge of high pressure
shifts overhead leading to lighter winds, and decreasing seas to
4-5 feet at 8 seconds by the afternoon hours. However, another
low pressure system and attendant frontal boundary swings into
the region from the NNW Friday and Saturday bringing a return of
active weather. Seas build towards to 7 to 9 feet at 8 to 9
seconds on Saturday before subsiding towards 3 to 5 feet on Sunday
into early next week. Given the wave heights/periods on Saturday
seas will once again be fairly steep. Looking ahead, large scale
upper-level flow then turns more W-SW towards the middle of next
week with some guidance hinting at yet another weak weather
disturbance moving into the region around Wednesday - confidence
in timing and impacts remain low at this time. -Schuldt

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

www.weather.gov/portland

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