Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 232121

Area Forecast Discussion
National Weather Service Portland OR
220 PM PDT Sat Sep 23 2017

.SYNOPSIS...Mix of sun and clouds today and Sunday. A weak front
offshore may bring a little light rain or sprinkles to the coastal
areas today. Next front arrives Mon, with increasing chance of light
rain. High pressure builds later Tue, and remains over the region
through end of next week. This will allow for dry weather, with
above normal temperatures under some offshore flow.


.SHORT TERM...Tonight through Tuesday...Models edge the upper level
ridge a little close to the coast tonight, allowing the surface
ridge to extend ne towards the north WA coast. This brings an end to
the weak low level isentropic lift that brought light rain to the
coastal waters early today. As the ridge moves inland Sun, it
flattens out with a couple of weak shortwaves moving into WA Sun
night and Mon. With few clouds and weak ridging aloft, temps should
warm Sun a few degrees over todays highs.

Mid level moisture spreads in Sun night, but with little apparent
lift overall. However, the low level flow turns southerly along the
south WA coast to inject a some low level moisture as the surface
ridge sinks south, so will keep a slight chance for some light rain
there late Sun night. As upper level ridging rebuilds offshore Mon
and the surface ridge remains extending inland over far northwest
OR, the chances for rain will be slow to spread inland. Lingering
baroclinicity will keep a slight chance for rain over the northwest
part of the forecast area into Sun night.

Mon sees the building upper ridge pushing in closer to the coast. As
a thermal induced surface trough builds up the Oregon coast Tue,
flow turns offshore for most of the forecast area. This brings
warming temps, and decreasing clouds.

.LONG TERM...Upper ridge slowly pushes inland Wed and Thu, moving
east towards the northern Rockies Fri. Low level flow remains
offshore Wed through Fri as the inverted surface trough drifts
offshore and weakens. This will bring warmer than normal temps to
the region inluding the coast, with the warmest days likely to be
Wed and Thu. By Fri night models in general agreement with pushing a
weak shortwave through the Pacific NW, pushing down upper heights
and allowing a weak cold front to move in. While still likely too
dry to carry any sort of mentionable pop, the flattened flow should
still allow some clouds back in, while cooling temps down a few

.AVIATION...VFR all areas to start the evening. Coastal area cigs
look to fall under IFR around midnight, perhaps into LIFR cigs
shortly thereafter as winds ease. Inland areas will probably see
patchy stratus but cannot say with certainty if it will cover any
of the terminals. Conditions should again improve to VFR around

KPDX AND APPROACHES...VFR until perhaps around daybreak with
about a 30% chance of a 020 stratus cig. /JBonk


.MARINE...No significant changes. Previous discussion follows. Not
much marine weather to talk about for the next 5 days with winds
less than 15 knots and seas 6 feet or less. As the thermal
trough builds north along the coast early next week, small craft
advisory northerlies are possible by Tuesday night. /Bentley




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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is is the U.S. government's official web portal to all federal, state and local government web resources and services.