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000
FXUS66 KPQR 230409 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
908 PM PDT Mon Apr 22 2024

Updated Aviation Discussion

.SYNOPSIS...Transient ridging will keep conditions warm and
dry through Tuesday with mostly sunny skies. A week cold front
passes through the area on Wednesday but precipitation chances
are low and remain confined mainly to southwest Washington. A
cool and showery weather pattern will begin on Thursday as an
upper level trough settles over the area. This trough will then
maintain cool and showery conditions through the upcoming
weekend.

&&

.SHORT TERM...Now through Wednesday Night...Transient ridging
is located across the PNW into western Canada but will quickly
shift eastward tonight into early Tuesday. Upper and mid level
clouds will increase this evening into the overnight and will
keep temps from dropping as far as last night. Lows tonight will
be 5-10 degrees warmer than last night, ranging from the low to
mid 40s across much of the area and closer to the 50 mark
across the Portland/Vancouver metro. Surface heights will
increase Tuesday afternoon ahead of a disturbance dropping
southeast across the Gulf of Alaska. This will provide some
clearing during the day and temperatures rising into the low 60s
across the south and central portions of the Willamette Valley,
upper 50s to low 60s along the coast and Coast range, and mid
70s for the metro area. The NBM probability of PDX reaching 75
or greater is near 80% with the 80 degrees at the 75th
percentile (25% chance of occurring). Conditions will remain
dry for most of the area on Wednesday as a disturbance comes on
shore across central British Columbia. A weak cold front is set
to pass through the area on Wednesday but should only bring an
increase in cloud cover and slightly cooler temps. Some
precipitation is possible but should remain confined to the
Washington zones and the northern Oregon coast and even there,
PoPs top out between 10-30%. Wednesday highs across the
Willamette Valley top out in the low to mid 60s with mid to
upper 50s along the coast. A subtle short wave will rave across
the northern Pacific Wednesday and will bring a good chance for
rain areawide beginning late Wednesday night. -Batz

.LONG TERM...Thursday through Monday...The subtle shortwave
mentioned above will be just off the southern British Columbia
shore with a deepening surface low near Vancouver Island. A more
potent cold front will be associated with this system and will
approach northwest Oregon and southwest Washington through
Thursday, eventually coming onshore Thursday night. Ran chances
will increase through Thursday and should peak during the
afternoon with PoPs near 100%. PoPs remain above 80% into Friday
afternoon with PoPs dropping below 50% across the interior
valleys Friday night into Saturday. There remains some model
spread regarding rainfall totals with this system. The 24 hr
probability ending at 5am Friday of 0.25" or greater across the
low lands remains around 70-80% and above 90% across the Coast
Range and Cascades. The probability of 0.50" during the same
time period across the interior valleys is 20-40% and 60-80%
across the higher terrain. 48 hr probabilities for 0.50" ending
at 5am Saturday are 50- 70% for the Willamette Valley. In
general, this system looks like it will bring a good soaking
rain to the entire area Thursday through Friday.

Temperatures for the latter half of the week and into the
weekend will be on the cooler side due to cloud cover and
precipitation. Expect highs in the upper 50s to low 60s across
the interior valley and low to mid 50s along the coast. Cluster
analysis shows most members (~70%) keep zonal flow across the
PNW for the first half of the weekend. Agreement for the latter
half of the weekend and the beginning of next week degrades,
mainly into varying degrees of troughing across western Canada
and the PNW. -Batz

&&

.AVIATION...High pressure will maintain VFR thresholds with dry
conditions at almost all terminals through the entire TAF period.
A weak front will start to impact areas along the coast starting
around 14Z Tuesday. Guidance at this time is showing a 10-20%
probability of MVFR cigs near KONP starting around 15Z Tuesday
through 18Z Tuesday. Then as the front moves closer to the coast
there remains around a 10-20% probability for MVFR cigs developing
along the coast starting around 23Z Tuesday. Northerly winds will
continue to weaken through the overnight hours. Northerly winds
return along the coast around 18Z Tuesday through around 03Z
Wednesday with gusts up to 20 kt, with northerly/northwesterly
winds for inland locations up to 10 kt. The exception for inland
locations will likely be around KTTD and possibly near KPDX as
easterly winds will likely develop as the aforementioned high
pressure will result in a lower level, thermally induced surface
trough.

Notes: The ASOS at KTTD is only available via the dial in option.
The AWOS at KMMV is still out of commission. As it is not
maintained locally by the National Weather Service, there is no
estimated time of repair.

PDX AND APPROACHES...VFR thresholds through the entire TAF period
with intermittent high clouds, with northerly/northwesterly winds
up to 10 kt. Could see brief periods of easterly winds towards
the Columbia River Gorge from 18Z Tuesday through 03Z Wednesday.
/42

&&

.MARINE...Winds at buoy 46050 continue to be northerly, with winds
20 to 25 kts, gusting to 30 kt. Seas are currently around 7 ft at
11 seconds. Observations at buoy 46050 as of 230 AM PDT show
north- northeasterly winds gusting to 25-30 kt with seas around
8-9 ft at 11 seconds. The forecast looks on track, including the
current Small Craft Advisory. High pressure over the waters will
maintain these gusty northerly winds the rest of this afternoon
and evening with gusts to 25-30 kt. Locations south of Cape Falcon
have a 30-50% chance of occasional gusts up to 35 kt between 5-10
PM Monday when the pressure gradient is strongest. Due to low
confidence in Gales and its potentially sporadic nature, a Gale
Warning was not issued.

Monday night to early Tuesday morning, pressure gradients loosen
and winds will gradually weaken from north to south. Northerly
gusts around 20-25 kt continue south of Cape Falcon Monday night,
so the Small Craft Advisory remains for the central and southern
waters (PZZ272-73 and PZZ252-53) through mid-morning Tuesday.
Minimal changes to wave heights are expected as the predominate
wind wave is from the north and the background swell is from the
northwest. Quiet conditions prevail Wednesday before the next
system arrives over the waters Thursday. -Alviz/JLiu

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for
     PZZ210-251-271.

     Small Craft Advisory until 11 AM PDT Tuesday for
     PZZ252-253-272-273.

&&

$$

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