783
FXUS66 KPQR 132232
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
332 PM PDT Thu Jun 13 2024

.SYNOPSIS...High pressure today will give way to a low pressure
system this weekend. Friday will be the transition day with
strengthening onshore flow and a slight chance (20%) of thunder
along the north coast. This low pressure system will be the next
weather maker bringing showers, and southwesterly flow. Cannot
rule out another round of thunder north of Salem on Saturday
into Sunday. Persistent showers through early next week.


.SHORT TERM...Now through Friday Night...High pressure shifts
inland tonight and low pressure system drops down from the
northeast Pacific. The combination of these two features will
increase onshore flow in the evening. The pressure gradient
between Troutdale and the Dalles is around 5 mb which is
indicative of strong westerly flow. Based on today`s wind
speeds and how that pressure gradient compares to the forecast
tomorrow, have increased wind speeds through the Columbia River
Gorge around Cascade Locks and the Upper Hood River Valley.
Ultimately, weather on Friday will be uneventful with near
normal temperatures - though on the cooler side.

Friday night the low will begin it`s advection inland which
coincides with an upper level jet streak. The NBM is suggesting
around a 20% chance of thunder over the north Oregon/south
Washington coast and Coast Range in the afternoon. Very few
models are showing a true sign of this with minimal CAPE and
instability. However, the orographic lift with a slight
southwesterly flow will enhance convective potential. Shower
chances look to be generally confined to areas along and north
of a Lincoln City- Portland-Mt St Helens line through Friday
evening before more widespread shower activity spreads across
the area Friday night. Model QPF remains on the light side
Friday through Saturday morning. -Muessle

.LONG TERM...Saturday through Wednesday...Minimal change in the
long term forecast as models appear to be generally in
consensus. On Saturday, the onshore flow intensifies from the
southwest which may promote more convective potential. This
time, the convection could be more widespread. The NBM brought
in a 30-40% chance for thunderstorms in southwest Washington on
Saturday. However, areas aside from the Cascades wills struggle
to see enough "oomph". Decided to lower chances for
thunderstorms. Even if they do occur, not looking at any major
impacts. Ensembles show broad troughing from Sunday night
through Tuesday. Cool temperatures and isolated scattered
showers through mid-week.

Once we make it through this troughing and showery weather,
ridging is possible which will bring warmer and drier weather
our way. -Muessle


&&

.AVIATION...VFR conditions persist under mostly clear skies.
North/northwesterly flow with winds generally below 10 kt for
inland locations. Winds along the coast are slightly stronger with
gusts through the evening up to to 20 kt through around 03Z
Friday. A weak frontal passage around 10Z Friday will bring
southerly winds to the coast along with a the 25%-35% probability
for MVFR/IFR conditions to develop along the coast. Could also see
some very light rain showers as well.

Guidance is also suggesting that this weak front could push marine
stratus around the Coast Range as well as down the Columbia
River. If this happens could see some MVFR conditions (15-20%
probability) stating around 12Z-15Z Friday for KPDX and KEUG.
Will be leaving the MVFR conditions for inland locations out at
this time as the probability is minimal.

PDX AND APPROACHES...VFR under clear skies. Northwesterly winds
up to 10 kts. Weak frontal passage around 12Z-14Z Friday will
result in a 10-20% probability MVFR marine stratus, pushed along
the Columbia River impacting areas on or near the terminal.
However, will be leaving the MVFR conditions out of the current
TAF package as the probability is minimal. -42

&&

.MARINE...Small Craft Advisory linger through this evening for
zones PZZ252, PZZ253, PZZ272 and PZZ273 with northerly wind gusts
up to 25 kt. Seas around 4 to 6 ft at 9 to 11 seconds through
Saturday afternoon. A weak front, late tonight/early Friday will
be the signal for an upcoming pattern change late Friday and into
the weekend. Expect southerly winds tonight and into Friday
morning, before the stronger front late Friday will bring a return
to relatively stronger, westerly winds across all waters. Seas
will slowly build through Saturday towards 5 to 7 ft on Sunday,
before subsiding again towards 4 to 6 ft by the start of the
upcoming week. -42


&&


.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for
     PZZ251>253-271>273.
&&

$$

www.weather.gov/portland

Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland