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000
FXUS66 KPQR 170442 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
942 PM PDT Tue Apr 16 2024

Updated aviation discussion...

.SYNOPSIS...Light showers will continue through this evening
before high pressure builds further into the region tonight,
with clearing skies. Tonight will be on the cool side, and with
light winds, will see rather chilly night with areas of frost.
After a cool start, a mild Wednesday is on tap. High pressure
remains over the region for later this week, with mild
temperatures and even a bit of offshore winds for Thu and Fri.

&&

.SHORT TERM...NOW THROUGH THURSDAY...Widely scattered light
showers will linger into the evening as westerly flow aloft
remains across WA/OR along the base of a short wave trough.
Showers will favor the higher terrain while the valley remains
rain shadowed with westerly downslope flow aloft. Short wave
ridging sits off the coast with surface high pressure centered
off of the British Columbia coast.

The surface high will continue to build into the area from the north
this evening and overnight. Clouds will dissipate and winds will
become light or almost calm in the valleys and less than 5 mph
elsewhere. This will set the stage for a chilly Spring night as
overnight lows drop into the upper 20s to low 30s for most
locations. This has warranted a Freeze Warning for the southern half
of the Willamette Valley (south of Corvallis), the Cascade
Foothills, the Coast Range zones, and Hood River Valley. Temperatures
elsewhere will fall into the mid 30s and will be conducive to areas
of Frost and therefore a Frost Advisory remains in effect 11PM to
9AM. Anyone with outdoor vegetation that is sensitive to cold
temperatures should bring their plants indoors if possible, or take
other appropriate actions to prevent freeze or frost damage.

Wednesday will turn out to be a nice Spring day after a chilly
morning. Ridging will continue to build into the area and will turn
winds offshore from the northeast. Temps will rise into the low 60s
across the Willamette Valley, mid 50s along the coast, and slightly
cooler temps along the Coast Range. The trend will continue into
Thursday as the high continues to build and thermal ridge begins to
stretch northward into Oregon from central California. E/NE winds
will pick up, especially within the Columbia River Gorge which could
see gusty east winds. There is a 50-80% chance of wind gusts of
30mph or greater on Thursday. Skies will be mostly clear with an
other jump in temps into the upper 60s to low 70s. -Batz

.LONG TERM...THURSDAY THROUGH SUNDAY...Probabilities increase
for strong wind gusts within the Gorge for Friday as the ridge
remains in place and the thermal trough builds even further
northward. Probabilities for 30 mph gusts are 80- 100% and for
40 mph probabilities are 50-80%.

Cluster analysis after Thursday shows the ridge continuing to
influence the West Coast. Around 80% of ensemble members
indicate the ridge will remain in place and a low chance around
20% the ridge will begin to weaken. Temps will increase through
the week with an 80-90% chance of highs >=70 on Friday across
the interior valley. Ensembles begin to show more uncertainty as
the weekend comes around. Around 40% of the ensembles indicate
the ridge will build across the area while around 20% indicate
the ridge shifting inland and falling heights moving into the
PNW. The chances of another day of >=70 on Saturday are lower,
30-50% with the higher probabilities closer to the Portland
metro. Beyond Saturday, ensembles indicate even more uncertainty
on days 6 and 7 with a split between continued ridging and a
trough digging into the West Coast. -Batz

&&

.AVIATION...VFR conditions prevail under mostly clear skies
through the TAF period as high pressure builds across the region.
Few/scattered clouds tonight will gradually clear early Wednesday
morning as the air mass dries. Clear skies, calm winds, and near-
to-below freezing temperatures will result in the possibility for
frost build-up on exposed and elevated surfaces at any given
terminal tonight through 15-16z Wed. Not expecting significant
frost build-up with these conditions. After late morning/early
afternoon Wednesday, winds along the coast and Willamette Valley
strengthen and turn northerly around 10-15 kt, with gusts up to
20-25 kt. Winds are then forecast to weaken Wednesday evening.

PDX AND APPROACHES...VFR conditions under mostly clear skies
through the entire TAF period. Clear skies, calm winds, and near-
freezing temperatures will result in frost potential tonight
through 15-16z Wed, especially for exposed and elevated surfaces.
Significant frost build-up is not expected. Winds turn more
northerly and strengthen to around 08-13 kt with gusts up to 20 kt
after 20-21z Wed.-Alviz

&&

.MARINE...Today an upper-level trough passes over the region to
the northeast and while impacts remain fairly minor overall,
northerly winds with gusts up to 25 kt through tonight. Thus, a
Small Craft Advisory will persist all waters through tonight. On
Wednesday and Thursday a ridge of high pressure amplifies over
the eastern Pacific winds increase further out of the north with
a 80-95% probability for wind gusts to once again meet Small
Craft Advisory criteria. As a result have issued Small Craft
Advisories for zones PZZ272, PZZ273, PZZ252 and PZZ253 starting
Wednesday afternoon. Then late week into the weekend the axis of
the upper- ridge moves overhead allowing winds to become more
offshore. General seas through the time period of 4 to 6 feet at
13 to 15 seconds. /42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Frost Advisory until 9 AM PDT Wednesday for ORZ101>105-108>115-
     119-120-122.

     Freeze Warning until 9 AM PDT Wednesday for ORZ106-107-116>118-
     121-123>125.

WA...Frost Advisory until 9 AM PDT Wednesday for WAZ201-202-204>207-
     209-210.

     Freeze Warning until 9 AM PDT Wednesday for WAZ203-208.

PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ251>253-
     271>273.

     Small Craft Advisory from 2 PM to 11 PM PDT Wednesday for PZZ252-
     253.

     Small Craft Advisory from 4 PM to 11 PM PDT Wednesday for PZZ272-
     273.
&&

$$

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