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000
FXUS66 KPQR 162249 AAA
AFDPQR

Area Forecast Discussion National Weather Service Portland OR 341 PM
PDT Tue Apr 16 2024

.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...(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
another jump in temps into the upper 60s to low 70s. -Batz

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)...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...Expect predominately VFR conditions to continue with
widespread mid and high level clouds continuing to decrease, with
clearer skies by tonight into Wednesday morning. North to
northwest winds at all locations with gusts up to 20 knots along
the coast through at least 00Z before decreasing afterwards.
Otherwise, winds generally remain 5-10 knots or less. Clear skies
along with near to below freezing temperatures will result in the
possibility for frost build up on exposed and elevated surfaces.
Not expecting significant build up with these conditions.

PDX AND APPROACHES...Expect predominately VFR conditions .
Northwest winds around 5-10 kt, strongest during afternoon and
early evening hours. Clear skies along with near to below
freezing temperatures will result in the possibility for frost
build up on exposed and elevated surfaces. Not expecting
significant build up with these conditions. /42

&&

.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 from 11 PM this evening to 9 AM PDT Wednesday for

     ORZ101>105-108>115-119-120-122.

     Freeze Warning from 11 PM this evening to 9 AM PDT Wednesday for

     ORZ106-107-116>118-121-123>125.

WA...Frost Advisory from 11 PM this evening to 9 AM PDT Wednesday for

     WAZ201-202-204>207-209-210.

     Freeze Warning from 11 PM this evening to 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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