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000
FXUS66 KPQR 032120
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
220 PM PDT Mon Aug 3 2020


.SYNOPSIS..A mixture of morning clouds and afternoon sunshine
with temperatures near to slightly above average for the next several
days. Widespread light rain is expected to start late Wednesday night
and persist through Thursday. Friday look for breezy conditions with
temperatures close to average.

&&

.SHORT TERM...Tonight through Wednesday...The morning marine clouds
along the coast will continue to recede into the evening hours as
shortwave ridging will build through tonight. This pattern will
maintain rather clear skies inland but, expect the coast to maintain
some clouds as moist onshore flow will persist. On Tuesday, expect
breezy conditions across the CWA as a thermally induced trough
briefly develops within the Willamette Valley, along with gusty
conditions within the central and eastern part of the Columbia River
Gorge and gaps along the Cascades. /42


.LONG TERM...Wednesday night through Monday...Models and ensembles
continue to remain in overall agreement that the next system will
start to slide southeast along the British-Columbia Coast starting
Wednesday night. This distended trough will extend down towards the
CWA and looks to provide a fair chance for rain starting Thursday.
There is remains a fair amount of uncertainty between the model
families as to the exact timing and amount of the precipitation but,
they all do agree that there is a chance for precipitation on
Thursday across the CWA.

Friday and into the weekend the forecast becomes a lot less cohesive
as model families start to diverge significantly in the overall
pattern. GEFS models have shortwave troughing developing Friday and
persisting through Monday. While EPS models have shortwave ridging
developing for the weekend and becoming more zonal by the start of
next week. CMCE models develop a zonal pattern for the weekend
followed by a shortwave trough for the start of next week. Taking
all of this into account have chosen to go with a blend of models
which has very little change if any from the NBM . Overall, what can
be expected is onshore flow to persist from Friday through Monday
along with closer to seasonal temperatures for the CWA. /42

&&


.AVIATION...Mainly VFR across the area early this afternoon. The
exception continues to be along the coast, where areas of MVFR
exist. These MVFR areas are likely to become more localized
through the afternoon. IFR to MVFR stratus returns to the coast
between 03Z and 06Z Tue, with the possibility of LIFR overnight.
Expect coastal conditions to gradually lift Tue morning and
become VFR by 19Z.

VFR will be rule inland through at least 07Z Tue. Guidance suggests
areas of MVFR stratus may push into the far western Oregon Coast
Range valleys overnight, as well as the southwest Washington
coastal lowlands. IFR to low-end MVFR stratus dissipates by 19Z.

KPDX and APPROACHES...VFR at the terminal and vicinity through at
least 12Z Tue. Latest high-resolution model cloud guidance indicates
MVFR stratus developing along the Columbia River from near KSPB
to KTTD around 13Z Tue and will dissipate by 19Z. Weishaar

&&

.MARINE...Surface high pressure over the waters will be the dominant
feature through Wed. Thermally-induced surface low pressure
builds over the far south Oregon coast Wed afternoon, which will
enhance the prevailing northerlies. The 12Z model guidance indicates
20-25 kt boundary layer wind speeds generally south of Cascade
Head late Tue afternoon through Tue evening. At this time, will
hold off on issuing an advisory. Gradients weaken Wed as a
frontal system approaches the waters. Guidance indicates a narrow
ribbon of 20-25 kt northwest wind gusts 12Z Thu behind the front,
but looks to be short-lived. Typical summertime northerlies
return Fri into the weekend for a much higher likelihood of small
craft advisory level wind.

Seas are currently around 3-5 ft and will remain in this range
through Wednesday. Seas look to then build to around 5-7 ft by
Thursday then to around 6-8 ft later this week. Longer range
guidance shows sub-10 ft seas Friday through the weekend.
Weishaar

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.

&&

$$

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