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FXUS66 KPQR 070439 AAB
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
938 PM PDT Thu May 6 2021

Updated Aviation and Marine discussions

.UPDATE...Made a few adjustments to the forecast this evening, mainly
to take out the mention of thunder for most of our inland areas
tonight into Friday morning. Without any lightning to speak of being
detected within the cold pool, it is tough to justify much lightning
at all in our forecast, especially inland during the coolest hours of
the night and morning. Based on 18z NAM and GFS, the core of cold air
aloft and thus the greatest instability appears to be headed for the
Olympic Peninsula and Puget Sound. Will maintain the mention of
thunder for portions of SW Washington and the eastern PDX metro
Friday afternoon, as diurnal surface heating should provide the best
chances although the coldest air aloft will already be crossing the
Cascades at that point.  Weagle

&&

.SYNOPSIS...Today`s cold front will move east of the Cascades by
mid-evening. Low pressure and another cold front cross the region
Friday to bring additional showers and possible thunderstorms. High
pressure starts to build beginning Saturday, but another very weak
front will cross the region Sunday for a final round of potential
showers. The upper high then builds in earnest Monday through at
least Wednesday for dry weather and bringing temperatures near to,
and slightly above, normal.

&&

.SHORT TERM...Tonight through Sunday...No significant surprises as
the anticipated cold front is currently aligned with roughly I-5.
Showers and breezy winds accompanied the front and will see this
boundary continue to push eastward this afternoon and evening. There
is a very narrow secondary boundary trailing just along the coast
now, also moving east. It has shown brief moments of convective
enhancement and would not be surprised to see a one hit wonder bit
of lightning come out of it. This would easily be the exception
rather than the rule. Broad low pressure over the NE Pac will drift
across the PacNW tonight and Friday bringing cooling temperatures
aloft.

As the trough axis nears the coast late tonight and Friday,
may get enough dynamic enhancement to produce a better chance of
thunderstorms mainly north of a Tillamook to Salem line, including
the Portland Metro. Am not super enthused about these chances as
implied by the NBM as equilibrium levels stay somewhat limited in
depth, but also do not have strong reasons to go against the
calibrated guidance either. As such, will keep the suggested
thunderstorm mention in the forecast for our northern areas through
early Friday evening. Snow levels will also drop to around 3500 feet
later tonight with a couple inches of snow possible under a heavier
shower.

The upper trough departs late Friday as an upper ridge tries to
assert it`s influence through Sunday. However, weak shortwaves cross
from the northwest to southeast to hold it at bay and also bring
modest rain chances but generally minimal qpf amounts. Temperatures
through this weekend will be on the cooler side of normal. /JBonk

.LONG TERM...Sunday night through Thursday...Currently not much
debate between the operational models and their supporting ensemble
casts. They all agree on high pressure progressing east from off the
Pacific, though they differ in the details on the strength of the
ridging. Regardless, next week`s temperatures will start on the
cooler side of normal to then build to a few degrees on the warmer
side of normal. Also would expect repeating periods of afternoon and
evening onshore sea breezes to work through the Coast Range for
pseudo-summer diurnal wind patterns. /JBonk


&&

.AVIATION...
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Post-frontal showers now mainly over the Cascades and
offshore. VFR conditions prevailing, but Cascades will likely
remain mostly obscured as westerly flow continues through
Friday. Next batch of more organized showers will arrive to the
coast 06-09Z and likely bring occasional MVFR conditions with
heavier showers. These showers spread inland overnight as well
but expect primarily VFR conditions. There is a slight chance
for thunderstorms for the north Oregon coast and south WA coast
later tonight through Fri afternoon, and a slight chance for
thunderstorms inland Fri afternoon and north of about KUAO.
Showers decrease Fri evening as high pressure briefly builds into
the region. Wind westerly generally 10 kt or less but gustier
winds towards the east end of the Gorge this evening.

For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse

KPDX AND APPROACHES...VFR with cigs 4000-7000 ft expected. Will
see with showers increasing after 09Z, then a slight chance for
thunderstorms after 18Z. Showers tapering off Fri evening as high
pressure builds into the region. Westerly winds expected to
prevail tonight but generally below 10 kt, winds pickup a little Fri
later morning to around 10-13 kt and may gust to 15-20 kt briefly
Fri afternoon.
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&&

.MARINE...
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Winds easing over the waters this evening, but will
pick up some overnight as the next batch of showers move in. But
do not expect winds to reach advisory criteria. However steep
waves have not quite gone away. Buoy 46243 off the Columbia
River mouth around 7 feet at 7 seconds so will have an advisory
for that.

Seas remain 6 to 8 ft with a dominate period of near 10 seconds
through Friday then slowly falling into the 4 to 6 ft through
the weekend. /42
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&&

.PQR WATCHES/WARNINGS/ADVISORIES...
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OR...None.
WA...None.
PZ...Small Craft Advisory until 2 AM PDT Friday for coastal waters
     from Cape Shoalwater WA to Florence OR out 60 NM.
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&&

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