339
FXUS66 KPQR 091019
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
319 AM PDT Sun Jun 9 2024

.SYNOPSIS...Expect warm and dry conditions inland today with
marine stratus along the coast. Cascades will see a 15-30%
chance of showers this morning. Warm and mostly dry weather
continues through Thursday, but coastal areas could see a
15-30% chance of precipitation on Tuesday. Toward the end of
the week, ensemble guidance suggests an overall cooler and
wetter pattern.

&&

.SHORT TERM...Today through Monday night...500mb analysis as of
230 AM PDT depicts an upper level shortwave trough beginning to
push into the Pacific Northwest, with SW-SSW flow aloft. This
shortwave could provide some lift to support isolated showers or
thunderstorms over the Cascades early this morning. However,
CAMs are suggesting that most shower and thunderstorm activity
will remain east of the Cascades. The westerly component to flow
aloft will provide an eastward push any showers or thunderstorms
that do develop over our Cascades. Thus, the forecast includes
low (15-30%) PoPs across the Cascades this morning, along with a
low (15-20%) chance for thunderstorms in the Lane County
Cascades. As the axis of the shortwave trough moves directly
overhead, winds aloft will shift northwesterly and mid-level
moisture will exit our area. This should end chances for
elevated showers and/or thunderstorms for the west side of the
Cascades by mid-morning.

Dry, quiet weather continues today. Satellite imagery as of 230
AM PDT shows a marine layer moving toward the coast, so expect
low stratus for coastal areas this morning. Model soundings
suggest that coastal stratus will linger throughout the day due
to a capping inversion and persistent onshore flow. This will
maintain mild temperatures along the coast with afternoon highs
peaking in the low 60s. Meanwhile, it will be another warm and
sunny day for interior valleys with high temps forecast in the
upper 70s to low 80s.

High pressure will begin to re-build by this afternoon and
strengthen into tomorrow (Mon). This will maintain warm temps
inland with sunny skies. NBM suggests a 40-60% chance that temps
exceed 80 degrees for interior valleys tomorrow. We may see
another marine layer along the coast tomorrow morning, but model
soundings are suggesting that increased mixing throughout the
day will support clear skies at the coast by the afternoon.
                                                   -Alviz

&&

.LONG TERM...Tuesday through Saturday...WPC cluster analyses are
in agreement of 500mb heights remaining above average through
Thursday, supporting near to above average temperatures and
mostly dry conditions. However, on Tuesday a trough from the
Gulf of Alaska will dip south and push into British Columbia.
This will flatten the ridge over the Pacific Northwest and lead
to a slight cooling trend. In addition, this will support a
15-30% chance for light precipitation over far northwest Oregon
and southwest Washington (mainly along the coast).

Wednesday, most of the clusters agree on zonal flow and/or
slight re-building of a ridge. By Thursday, ensemble members
agree on shortwave ridging over the region, supporting drier
and warmer conditions. Friday, this ridge begins to shift
eastward as another trough near the Gulf of Alaska dips
southward toward the Pacific Northwest. By Saturday, most
ensemble members (65%) agree on troughing entering the region
with below-average 500 mb heights. If this scenario pans out,
then we would see increasing chances for widespread precipitation
along with potentially below average temperatures. For now, the
NBM`s 15-45% chance of PoPs across northwest Oregon and southwest
Washington at the end of the week look reasonable.      -Alviz

&&

.AVIATION...A weak front will move inland today which will bring
MVFR/IFR stratus to the coast, and high level clouds inland.
Already starting to see MVFR CIGs north of KTMK, while a bit
further south conditions are clear. Over the next few hours, the
marine stratus will begin to fill. There is nearly a 90% chance
of IFR CIGs along the coast between 12-18Z Sunday. With the
strengthening westerly flow, cannot rule out the stratus moving
along the Columbia River to near KKLS. There is around a 30%
chance of MVFR CIGs there. Otherwise, all other locations will be
VFR through the period with stratocumulus. Along the Cascades,
winds will be a bit more gusty. Based on the track of the low
pressure, precipitation is not likely, however, there is around a
20% chance for thunderstorms right along the ridges of the
Willamette National Forest.

Late in the forecast, backbuilding is suggested in the models
which could bring increased chances for stratus around KTTD and
KPDX. However, confidence is low.


PDX AND APPROACHES...VFR through the period with high level
stratocumulus. After 05Z Monday, winds just off of the surface
will be around 15 kt up to 3000 ft AGL. There is a 20% chance of
MVFR CIGs between 14-18Z as the marine stratus moves along the
Columbia River. Higher likelihood of this stratus would be on the
west side of the terminal. -Muessle

&&

.MARINE...The weak front is settling in over the waters. Low
level clouds cover will develop which may reduce visibility
through the morning at times. Winds will remain elevated around 15
kt with gusts to 20 kt from the northwest through the day. Based
on high resolution models, looks like we will remain just below
small craft advisory criteria. Seas will remain around 6-9 ft at
15 seconds through Monday morning.

High pressure reforms on Monday which will settle both winds and
seas. The next period of concern will be on Tuesday into
Wednesday. Tuesday will bring yet another front, but this time
there is a chance for some precipitation. Wednesday has the
potential to bring breezier winds from the north-northwest. Gusts
up to 30 kt are possible from Cape Falcon southward. Seas too
will build to around 8-9 ft. During periods of strongest winds,
cannot rule out seas up to 10 ft.                   -Muessle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 AM PDT this morning for PZZ210.
&&

$$

www.weather.gov/portland

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