133
FXUS66 KPQR 310435
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
934 PM PDT Thu May 30 2024

Updated aviation discussion...

.SYNOPSIS..Warm and dry weather through Friday. A weakening front
pushes across the area on Saturday, which will result in a slight
cooling trend but generally remaining dry. Then, a much wetter
system associated with what remains of a tropical system is expected
Sunday through Monday. Warm and dry weather returns for the middle
of next week.

&&

.SHORT TERM...Tonight through Saturday night...Pleasant weather
continues as we flip the calendar from May to June. Weak upper level
ridging over the eastern Pacific will push east across the Pacific
NW on Friday. Temperatures warm Friday afternoon into the upper 70s
to near 80 degrees inland, while northerly winds turning back
onshore will maintain temperatures in the 60s at the coast. Breezy
northerly winds continue through the Willamette Valley, becoming
more westerly as onshore push begins.

Increasing clouds on Saturday as a weak shortwave trough pushes a
weakening front towards the area. Most areas are expected to remain
dry, with a few light showers possible at northern coastal areas and
in the Cascades. Temperatures return to near normal for June 1st
with highs expected into the lower to mid 70s inland. Winds remain
generally onshore through Saturday. /DH

.LONG TERM...Sunday through Thursday...Rain is expected to return
Sunday as a frontal system with an associated atmospheric river
pushes into the Pacific NW. The initial warm front will bring
generally steady, light rain through Saturday afternoon while
pushing snow levels above 9,000-10,000 feet. Zonal flow turns more
southwesterly as an upper shortwave trough approaches the region
late Sunday. Precipitable water values peak around 1.4-1.5 Sunday
evening through Sunday night while IVT values increase to around 500
to 750 kg/ms. Strong dynamics as nose of a strong upper level jet
pushes into Oregon. This will likely bring more moderate rainfall
through Sunday night into early Monday. Showers then follow behind
the front by Monday afternoon with a 15-20% chance of thunderstorms
Monday afternoon. Latest QPF from WPC and NBM suggest 36-hour
rainfall amounts at the coast of around 1.5 to 2.5 inches, 2 to 4
inches for the Coastal mountains as well as the Cascades and Cascade
foothills. Rainfall amounts are likely around 1.0 to 1.5 inches
across the inland valleys. Even with all this rain, not expecting
river flooding (less than 5% chance) or many hydro impacts. Will
need to continue to monitor for higher rainfall rates especially
near the Columbia River Gorge, although currently not expected to
exceed 0.25 inch per hour.

Another system then approaches on Tuesday, although there is
increased uncertainty as to how far south the front will drop.
Therefore will maintain a slight chance (10-20%) of rain from the
central OR coast/southern Willamette Valley to likely rain (60-70%)
across the northern coast into southwest WA. By Wednesday, high
pressure is expected to build offshore. Cluster analysis shows
varying degrees of strength of an upper level ridge over the western
US. A warming trend is likely by mid-week through the end of the
week, with highs most likely in the 80s by Thursday. /DH

&&

.AVIATION...VFR conditions under mostly clear skies prevail
through the entire TAF period as high pressure remains settled over
the region. Winds will be out of the north/northwest and under 10 kt
tonight. After 15-17z Fri, expect winds to begin strengthening along
the coast and southern Willamette Valley (including KEUG) as
pressure gradients begin to tighten. Winds along the coast and south
Valley could gust up to 25 kt Friday afternoon, weakening in the
evening.

PDX AND APPROACHES...VFR conditions through the entire TAF period
with mostly clear skies. Northwest winds will be under 10 kt.
                                                       -Alviz

&&

.MARINE...Weak high pressure continues to build across the the
waters today into tonight, slowly retreating west into the offshore
waters Friday. This will lead to increasing northerly winds off of
the central Oregon coast this afternoon and evening.
There is 60-80% chance that winds gust to 25 kt generally from
Tillamook and south with > 90% chance of winds exceeding 20 kt.
Winds will decrease for a few hours Friday morning before increasing
to gusts up to 21 kts (80-90+ % chance) Friday afternoon and
evening. A Small Craft Advisory remains in effect for zones PZZ273,
PZZ272, PZZ253, and PZZ252 through Friday evening.

A weak front is expected to move through the waters on Saturday,
shifting winds westerly to southwesterly. A more organized and
stronger storm system will move into the northeast Pacific Sunday
shifting winds southerly. Small Craft Wind gusts are likely with
90+% chance of gusts exceeding 21 kts and 50-60% chance of gusts
reaching 30 kts. There`s also a 50-70% chance of a brief period of
Gale Force winds of 35 kts Sunday afternoon or evening. -HEC

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT Friday for PZZ252-253-272-
     273.
&&

$$

www.weather.gov/portland

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