369
FXUS66 KPQR 091813 AAB
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1112 AM PDT Sun Jun 9 2024

Updated marine and aviation discussions.

.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.

&&

.UPDATE...Sent out a quick forecast update to account for the
measurable drizzle that has developed along the north coast this
morning. NBM`s 2% PoPs are clearly not cutting it for that area, so
we leaned on CONSShort, which includes many high-res models, for
coastal PoPs. It appears the deepening of the marine layer as an
upper trough moves onshore, along with the strengthening onshore
flow, are mostly responsible for the drizzle along the coast. Suspect
drizzle will become less widespread along the north coast throughout
the day, but clouds and cool temps should linger. Aside from the
coast, the forecast looks to be in good shape as elevated convection
has mostly shifted east of Cascades.  Weagle

&&

.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...At 18z Sunday, satellite and surface weather
observations depicted clear skies across the area, except at the
coast from KONP to KAST and along/near the Columbia River from
KAST to KPDX and KTTD where a marine stratus deck continues
impacting flight conditions. Cigs were ranging between 200-600 ft
at KONP and 600-1300 ft at KAST. Cigs were between 2000-2500 ft at
KPDX and KTTD; however cloud cover at KPDX and KTTD will scatter
out between 1830-1930z Sunday and give way to VFR conditions for
the rest of the day. Except the central OR coast (including KONP)
will see a brief improvement to VFR conditions after 20z Sunday
before a marine stratus deck redevelops after 01z Monday. Chances
for any substantial clearing at KAST are much lower (<25%) where
MVFR cigs are likely to continue through the day before lowering
to IFR Saturday night. Brief periods of light drizzle will also be
possible at KAST Sunday morning and Monday morning.

Models still show a chance for an MVFR stratus deck to develop
near the mouth of the Columbia River Gorge and backbuild into KTTD
and KPDX towards 12z Monday. Probabilities for this to occur have
increased to nearly 50% and forecast confidence has increased
from low to medium. As such, have now decided to include broken
cigs around 1800-1900 ft at KTTD and KPDX beginning at 12z.

PDX AND APPROACHES...MVFR cigs impacting the terminal Sunday
morning will scatter out around 19z Sunday, giving way to VFR
flight conditions for the rest of the day and evening. However,
probabilities for MVFR cigs around 2000 ft have increased
Saturday night, peaking near 50% towards 12z Sunday. This stratus
deck will likely develop over/near KTTD first before quickly
backbuilding westward towards KPDX. Expect northwest surface winds
between 5-10 kt Sunday afternoon/early evening with light and
variable winds Sunday night/Monday morning.  -TK

&&

.MARINE...Areas of marine fog over the inner waters will continue
lifting late Sunday morning into the early afternoon as cloud
cover begins breaking up a bit (especially over the southern
waters to the south of Cape Foulweather). 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 12 to 15 seconds through Monday morning.

High pressure reforms Monday afternoon which will settle both
winds and seas. The next period of concern will be 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 will
also build to around 8-9 ft. During periods of strongest winds
during the afternoon and evening hours, cannot rule out seas up
to 10 ft.  -TK/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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