950
FXUS66 KPQR 161023
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
323 AM PDT Sun Jun 16 2024

.SYNOPSIS...Low pressure maintains cool and showery conditions
today, with a chance of thunderstorms across much of the area
this afternoon and evening. A few showers linger into Monday then
much warmer and drier weather returns Tuesday through the end
of next week.

&&

.SHORT TERM...Now through Monday Night...An elongated upper
level trough has shifted southward from British Columbia to
Washington and remains the dominant feature over the Pacific
Northwest this morning. Latest satellite imagery shows broken
cloud cover lingering across northwest Oregon and southwest
Washington, with a lull in shower activity as radar echos are
mainly confined to northern coastal areas and parts of the
Cascades as of 2 AM Sunday. Expect a similar day to Saturday as
unseasonably cold air aloft yields another day of highs topping
out in the mid 60s. Shower activity will increase in coverage
with daytime heating as the trough axis shifts southeast across
the area, with steep mid level lapse rates and modest
instability again contributing to a chance of thunderstorms. The
best thunderstorm potential will reside from roughly Salem
north through early evening, but can`t rule out a few lightning
strikes with southward extent towards Eugene as well. Shower
activity will trend downward through Monday with temperatures
remaining in the 60s as northwest flow takes hold in the wake of
the departing trough. Showers will remain light and mostly be
confined to the higher terrain through Monday afternoon, then
wind down through Monday night and set the stage for the next
stretch of warmer and drier weather beginning Tuesday. /CB

.LONG TERM...Tuesday through Saturday...More summerlike weather
returns to the region on Tuesday as WPC ensemble clusters
continue to show broad agreement on the weakening of the trough
over the western CONUS and subsequent increasing 500 mb heights
across the Pacific Northwest. This will send temps back above
seasonal norms as highs climb into the mid to upper 70s across
the interior lowlands on Tuesday afternoon. Wednesday through
Friday looks to be the hottest stretch for the coming week as
most ensemble and deterministic solutions continue to depict a
weak Rex Block characterized by a low amplitude ridge over
western Canada and an open trough over northern California.
Ensemble temperature spreads have nudged slightly upward for the
latter half of the week, with probabilistic guidance now
peaking with around a 50 percent chance to reach 90 degrees in
the Portland area on Thursday and a 25-35 percent chance both
Wednesday and Friday. Notably, the probability to reach 95
degrees on any of these days is less than 10 percent from
Portland to Salem and closer to one percent in other locations,
serving to underscore the relatively high confidence in the
range of temperature outcomes for the coming week. The bulk of
the guidance then suggests that temperatures will begin to
trend back down next weekend with the approach of another
trough. /CB

&&

.AVIATION...A weak front is currently in the process of moving
ashore, and the next few hours (before 19z Sun) will see around a
15-30% chance of intermittent MVFR ceilings at all terminals, but
this will be very patchy and ceilings will bounce between low-end VFR
and MVFR during this time.

Some intermittent fog can`t be ruled out before the front fully
pushes ashore, and could produce around a 20% chance of IFR
visibilities at times before 15z Sunday. However, threat is low,
and exact area of fog formation will be difficult to predict.
Afterwards, with increasing precipitation and daylight heating
kicking in soon after, threat of fog ends by 15z.

Low chance for some weak thunderstorms at times after around 18z
Sun as instability develops due to post frontal conditions.
Daytime hours Sunday could see around a 25% chance of
thunderstorms at time, which could potentially produce hail and
brief gusty winds. Threat ends by 03z Mon.

PDX AND APPROACHES...10% chance of fog developing within the next
few hours, possibly reducing conditions to IFR briefly. However, a
frontal passage around 15z ends threat of fog. A few showers
associated with frontal passage begin at that time, allowing for
a 15-30% chance of intermittent MVFR ceilings before 20z Sun or
so. Afterwards, around a 25% chance of weak scattered
thunderstorms are possible once daylight heating begins, ending
around 03z Sun. /JLiu

&&

.MARINE...Seas around 5 to 7 ft at 9 to 11 seconds for the near
future. Winds are currently negligible, but will increase
following the frontal passage up to just under Small Craft
Advisory level Sunday evening. A stray gust or two above SCA
criteria may be possible Sunday night, but by and large the
majority of waters will remain under, with only a 10% chance of
SCA level winds. Next chance at more impactful conditions will
be Tuesday night, though uncertainty is still relatively high.
Marginal SCA winds look possible from Tuesday evening onwards,
with breezier marginal winds possible until at least the
weekend. /JLiu

&&

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

&&

$$

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