969
FXUS66 KPQR 240355 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
855 PM PDT Sun Jun 23 2024

Aviation Discussion Updated...

.SYNOPSIS...Dry on Monday as a transient shortwave ridge will bring a
brief warmup across the region Monday and Tuesday. An upper level
trough brings relatively cooler temperatures for the middle of the
week along with periodic chances for rain showers. Warm and dry
conditions return for next weekend.

&&

.SHORT TERM...Tonight through Wednesday Night...Cooler and moister
conditions today will give way to dry conditions Monday as an upper
level ridge develops over the region through Tuesday. So, for the
start of this week, look for daytime highs in the upper 70s to upper
80s for inland locations, mid 70s to mid 80s for the Cascades and low
60s to low 70s for the coast, with the warmest day expected on
Tuesday. On Tuesday there remains around a 25% probability for
daytime highs to creep into the low 90s and around a 5% probability
to see daytime highs in the mid 90s for inland locations. As the
upper level ridge develops, a weak, thermally induced low will result
in increasing, northerly winds for the Willamette Valley, with gusts
up to 20 mph possible on Monday.

High resolution and deterministic models do show that the
aforementioned upper level will quickly push eastward as the next
system from the Gulf of Alaska brings another round of cooler, near
seasonal temperatures for Wednesday with high temps in the mid to
upper 70s for inland locations, low 60 to low 70s for the Cascades
and mid 50s to mid 60s for the coast. This trough will also bring
increasing chances for rain showers for the majority of the CWA.
Overall timing of this precipitation is still under review, but at
this time, conditions are looking to be moderate PoPs, but low QPF.
Still, have moderate confidence in most locations seeing some
measurable precipitation by early Thursday morning. It should be noted
that the system on Wednesday is resulting in favorable flow pattern
for thunderstorm development along the Cascades with around a 5-10%
probability at this time. /42

&&

.LONG TERM...THURSDAY THROUGH SUNDAY...A shortwave trough continues
pushing through the area on Thursday, bringing cooler temperatures
and some light rainfall. Daytime highs will fall to the low 70s for
inland areas. Rainfall looks light during daytime hours, with even
high end scenarios (10% chance) showing rainfall around 0.25", and
only in the northern areas (southeast WA). Rain should end around
evening-time as the trough moves out of the area, after which the
night looks dry and cool.

Friday sees zonal flow, with no chance for precipitation.
Temperatures begin to warm again, with a 30-40% chance of
temperatures above 80 in the Willamette Valley. WPC Cluster Analysis
shows continued trending towards some kind of ridging developing over
the weekend, but not much certainty yet regarding timing or exact
location. Expect warmer temperatures and generally drier conditions.
/JLiu

&&

.AVIATION...Moderate onshore flow continues, with VFR conditions
throughout the region (CIGS 4000 to 6000 ft). Clouds continue to
break apart through tonight, with areas south of KMMV already
clear.

Will see some brief morning clouds Monday morning along the coast
between 07-17Z Monday, with the chance of lowering to MVFR CIGs
around 50-70%. Should return to VFR conditions thereafter
(probability to stay MVFR around 10-20%). Inland terminals will
have prevailing VFR conditions, except for a small chance of MVFR
conditions between 11-17Z Monday (10-20% probability).

Low level flow will turn north to northeasterly around 12Z
Monday, then turn back to north to northwesterly by 16Z Monday.
Winds will increase and gust up to 25 kt along the coast and up to
20 kt inland from 17Z Monday to 04-06Z Tuesday.

PDX AND APPROACHES...VFR with broken clouds at 5000 to 7000 ft,
gradually giving way to mostly clear skies by 05-06Z Monday. Will
be predominantly VFR through the TAF period, except for a 10-20%
chance of broken MVFR CIGs between 10Z to 17Z Monday.
-JH

&&

.MARINE...High pressure will expand across the waters through
Monday, while thermal low pressure strengthens over far northwest
Calif into far sw Oregon. This will tighten the northerly pressure
gradient on Monday, enough to allow north winds to pop 20 to 25 kt
gusts Mon afternoon into Mon evening. But, this mainly over the
waters off the west central Oregon coast. As such, will put up
Small Craft Advisory for said conditions.

Otherwise, not much change in the pattern for early this week,
as high pressure remains anchored off the Pac NW. Low pressure
will arrive mid-week, with a weakening front arriving. This will
bring return of unsettled weather, with return of west to
southwest winds, but still mostly 15 kt or less.     /Rockey

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 4 AM to 10 AM PDT Monday for PZZ210.

     Small Craft Advisory from 2 PM Monday to midnight PDT Monday
     night for PZZ253-273.
&&

$$

www.weather.gov/portland

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