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000
FXUS66 KPQR 221815 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1115 AM PDT Sun May 22 2022

Updated aviation discussion

.SYNOPSIS...
Spring has sprung with more seasonable weather
expected over the next several days. Continued warming today
with a slight chance for rain on Monday. Warming further into
midweek with Wednesday likely to see the hottest temperatures of
the week. A stronger front expected on Friday.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
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High pressure remains
over the region which means one thing...spring is here! Saturday
brought near normal temperatures with that trend continuing
today. Broad upper level jet ridging is present today with a jet
streak over eastern Oregon. This ridge, both at the surface and
aloft, expecting little change in the weather between yesterday
and today. More consistent northerly winds though possible
today, with temperatures only slightly warmer than those
experienced on Saturday. One slight difference though will occur
late tonight or early on Monday. 500 mb heights and absolute
vorticity show a weak shortwave and associated enhanced
vorticity max moving southeast over the area early Monday. This
shortwave may bring periods of showers to the area, generally
north of Salem, OR. However, models have backed off of both PoPs
and QPF for this system over the last few runs. For example,
the NAM 12Z May 21st run showed rain starting in Portland around
Sunday morning, but now the latest output shows chances for
precipitation around Monday morning. The shortwave also appears
to be tracking further north with a bulk of the cooler air aloft
over northern Washington. Because of this trend, any
precipitation will likely skirt southwest Washington and stay
north of the forecast area. Could still see some cumulus forming
to the north and along the Cascades though. One thing that has
gained some confidence in regards to this pattern shift is the
chances for winds. At the surface, the pressure gradient between
the Dalles and Troutdale is around +3 mb on Monday afternoon.
This means that we could see some breezier winds through the
day, especially in the Columbia River Gorge and Hood River
Valley.

As this shortwave passes late Monday, a vertically stacked ridge
will once again build over the area. Winds will begin to shift
to the south in the afternoon which will usher in warmer air
from the southwest. This warm air development will form a
thermally induced trough over southern Oregon and northern
California. As the thermal trough forms, will likely see winds
follow the standard pattern of intensifying in the afternoon due
to the thermally induced enhanced pressure gradient. But what
about temperatures...a thermal trough means it will get warmer
right? That`s correct! Still looking at temperatures rising on
Tuesday and relative humidity dropping. While temperatures will
be warmer than those experienced on Monday (due to less cloud
cover), because there is still some slight northwesterly flow,
they are not going to be remarkable by any means.   -Muessle

.LONG TERM...(WEDNESDAY THROUGH SATURDAY NIGHT)... Dry mild
weather continues into Thursday. The thermal trough will
redevelop through the day which will bring temperatures to the
warmest levels for the week. Could see high temperatures in the
Willamette Valley in the mid to upper 70s, with the coast
closer to 60 degrees. A shift in the pattern though will start
on Thursday as clouds will increase along the leading edge of a
weakening front. The front will push across the region on
Thursday, with some spotty rain possible - mainly pre-frontal
showers. But, the big player in the long term arrives late
Thursday into Friday. A closed low aloft, stemming from the Gulf
of Alaska, will make its way southward extending a negatively
tilted trough over the region. This low is wrapped in cooler air
from the north and it will be advected over the region. As of
late, models have come into better agreement, especially in
regards to QPF. The ECMWF has backed off of the storm total QPF
while the GFS has increased. Because conditions are ever
shifting, not settling on any numbers as of right now, but can
say that the Cascades will likely see the most rainfall due to
the southwesterly flow and orographic lift. This front is slower
moving with a few shortwaves passing over the region
sequentially. This means that we could see the precipitation
linger through the weekend, but it is too soon to truly tell.

-Muessle


.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Dry mild
weather continues into Thursday. The thermal trough will
redevelop through the day which will bring temperatures to the
warmest levels for the week. Could see high temperatures in the
Willamette Valley in the mid to upper 70s, with the coast
closer to 60 degrees. A shift in the pattern though will start
on Thursday as clouds will increase along the leading edge of a
weakening front. The front will push across the region on
Thursday, with some spotty rain possible - mainly pre-frontal
showers. But, the big player in the long term arrives late
Thursday into Friday. A closed low aloft, stemming from the Gulf
of Alaska, will make its way southward extending a negatively
tilted trough over the region. This low is wrapped in cooler air
from the north and it will be advected over the region. As of
late, models have come into better agreement, especially in
regards to QPF. The ECMWF has backed off of the storm total QPF
while the GFS has increased. Because conditions are ever
shifting, not settling on any numbers as of right now, but can
say that the Cascades will likely see the most rainfall due to
the southwesterly flow and orographic lift. This front is slower
moving with a few shortwaves passing over the region
sequentially. This means that we could see the precipitation
linger through the weekend, but it is too soon to truly tell.

-Muessle
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&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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Marine stratus has all but eroded away from the coast, leaving
VFR conditions across the forecast area. Expect high clouds to
increase today as cirrus spreads out in front of a weather
system approaching the coast later today. Marine stratus will
once again push back in late this afternoon...HREF probs show a
roughly 60-70% chance for IFR cigs along the coast after 03Z,
improving to low end MVFR after 12z. Further inland, only high
clouds today, with ceilings lowering early Monday morning, but
remaining VFR.

For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse

KPDX AND APPROACHES...VFR through the period with only high
clouds and light winds. /Kriederman
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&&

.MARINE...
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Wind will generally diminish to 10 kt or less across the
coastal waters today as offshore high pressure shifts closer to
the coast and weakens the gradient. Could see some 15 kt gusts
in the central waters during the afternoon as the thermal trough
continues to reside to the south over northern CA, but do not
anticipate conditions approaching small craft headlines at this
time. Moderate northerly breezes will return Monday as high
pressure becomes re- established offshore. A weak front may clip
the waters late Tuesday as an area of low pressure passes well
north toward the BC Coast, which could bring about a brief shift
to southerly winds Tuesday night. Seas will remain relatively
tame through the next several days as a modest 3-5 ft W swell
moves through the waters, with little short period contribution
given the generally light winds. -CB
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&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

www.weather.gov/portland

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