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fxus66 kpqr 212153 

Area forecast discussion
National Weather Service Portland or
254 PM PDT Mon may 21 2018

Synopsis...warm and dry through Tue days, as region stays under high
pressure. But, as a low over Nevada drifts northeastward to the
northern rockies late Tue and Wed, will see a chance of showers and
even a thunderstorm over the Oregon Cascades, mainly to south of
Santiam Pass. Another weather system will approach from the southwest
later in the week, with increasing southerly flow aloft. This will
bring cooler temperatures, along with increasing chance of showers
and perhaps a few thunderstorms. Though will see decreasing chance of
showers on Saturday and sun under mostly cloudy skies, does appear
may be able to salvage the last part of Holiday weekend with a dry
and mild Monday.


Short term...tonight through Thursday...surface high pressure over
Washington will maintain dry northerly flow across region tonight and
Tue. Will be a great late Spring afternoon/evening across region,
with clear skies. Though may see some patchy stratus reform along the
Washington coast this evening, possibly as far south as Astoria or

Not a lot of change in the pattern tonight and Tue, as high pres will
dominate our weather. Will see some patchy low clouds later tonight
into early Tue am, but any clouds inland will be very brief, and
likely confined to the lower Columbia River, from Kelso westward, and
in the south Willamette Valley. Think will have areas of low clouds
along the coast.

Now, the pesky upper low that has been parked over the Great Basin
will drift slowly northeastward towards Idaho Tue and Wed. As it
does, will see moisture wrapping around the low into eastern Oregon,
and possibly up against the Oregon Cascades. Have kept a minor chance
of showers/thunderstorms over the high Cascades for Tue evening and
again on Wed. Elsewhere, onshore flow will gradually increase Tue
night and Wed, with marine stratus spreading back along most of the
coast. Will add patchy drizzle or fog at that time for the coast and
river valleys into the western slopes of coast mtns. With the
increasing onshore flow, think will see areas of low clouds form
inland later Tue night into Wed am, primarily from Eugene northward
to around Salem or Woodburn.

Rather warm for Tue, with temperatures into the lower 80s for many
inland areas. Bit cooler on Wed, as deepening marine layer will keep
highs only to around 70 in south Willamette Valley such as Eugene and
Corvallis. But, may still get into the mid and upper 70s around
Portland/Vancouver Metro where will start the day with less clouds.

Thursday could be more interesting. Another upper low will be
approaching California, with upper flow over Oregon becoming more
southerly Wed night into Thu. Start getting better divergence aloft
with getting more south to southeasterly 700 mb flow as the day
progresses. This will bring increasing chance of showers for Thu over
the Oregon Cascades and perhaps over good part of Lane County. But,
still some question as to how much mid-level moisture is around for
the developing showers/thunderstorms during the day. Either way, will
continue to evaluate this over next several shifts. Rockey.

Long term...Thursday night through Sunday...models starting to have
a bit more agreement, but still enough differences in run to run
consistency to make no major chances. Will see the California low
lift into the Great Basin Fri and Sat. Seems highest chance of
showers and even a few thunderstorms will be on Fri, when have better
flow aloft over region. But, as the low passes farther eastward on
Sat, will generally see decreasing chance of showers. Will be tad
cooler, with coastal areas in the 50s and 60s to possibly lower 70s
inland. Mainly due to plenty of clouds on the onshore flow. Think
will be between systems on Sunday as ridging starts. This will make
for a mostly dry day sun with slow burn out of clouds. But, can not
rule out a few showers along the coast north of Lincoln City, and
over the foothills and Cascades. Seems more likely now that Mon will
be dry, with mild conditions over the region. Rockey.


Aviation...a northwesterly onshore flow pattern under building
high pressure aloft should result in high end IFR to low end MVFR
stratus returning to at least the north Oregon and South
Washington coasts overnight. It could sneak up the Columbia River
to Portland, but latest model guidance is rather pessimistic
towards this idea.

Kpdx and approaches...a northwesterly onshore flow pattern under
building high pressure aloft should result in predominantly VFR
conditions through 00z Wednesday. There is a small chance of high
end IFR to low end MVFR cigs developing around 14-15z Tuesday.


Marine...high pressure over the northeast Pacific and thermal
low pressure over northern California and/or the Great Basin will
more or less continue for much of the next week and result in a
Summer-like northerly wind pattern. Northerly winds look to be
strongest during the afternoon and evening on Tuesday and
possibly peaking again late Friday. An incoming front may begin
to shift winds around to a more southerly direction next
weekend, but confidence in details are low at this point. Expect
seas to hover between 3 and 7 feet through the weekend. /Neuman


Pqr watches/warnings/advisories...
Pz...Small Craft Advisory for winds until 3 am PDT Tuesday for
coastal waters from Cascade Head or to Florence or out 60



Pqr watches/warnings/advisories...
Pz...Small Craft Advisory for winds from 4 PM this afternoon to 3 am
PDT Tuesday for coastal waters from Cascade Head or to
Florence or out 60 nm.



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