Area Forecast Discussion
Issued by NWS Portland, OR

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000
FXUS66 KPQR 261034
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
333 AM PDT Tue Sep 26 2017

.SYNOPSIS...High pressure will build into eastern Washington and
Oregon resulting in offshore flow and warmer temps through Thursday.
The next chance for rain comes around Friday, as a weakening cold
front moves into the Pac NW. Showers and cooler temperatures will
probably linger into the weekend.

&&

.SHORT TERM...Today through Thursday...KRTX radar is presently down
due to a mechanical failure it is unknown at this time when it will
return to service.  Fortunately fair weather will be with us for the
next several days as high pressure aloft builds over the PacNW.
Surface high pressure will increase east of the Cascades, inducing
offshore flow and a trough along the coast today and tonight. The
trough weakens Wed but the offshore flow continues.  The warmest days
will be Wed and Thu with inland and coastal temperatures above
seasonal normals. Coastal areas should approach 80 degrees
Wed and a few degrees cooler Thu while the interior lowland will
likely have max temperatures in the low 80s.

Models show thermal low pressure lingering near the Oregon coast Wed
night/Thu, while easterly flow aloft turns more southerly. This
should help induce a southerly wind reversal along the coast, likely
bringing areas of fog and low clouds back to coastal areas. With this
wind reversal and an approaching Pacific cold front, expect the
marine layer to deepen a bit late Thu/Thu night...perhaps enough to
bring some low clouds into the inland valleys by Friday morning.
/mh Weagle

.LONG TERM...Thursday night through Monday...Southwesterly flow
across the region Thursday night and Friday as an upper trough
advances through the forecast area. Forecast models in general
agreement with a weakening front pushing across the area. Boosted
PoPs even further as 00Z models are in better agreement for late in
the week and weekend with a cool trough transiting the region Sat.
After the weekend however, models then diverge a bit for the first
half of next week, so have maintained some low end PoP chances for
the start of next week in a nod to the ECMWF solution which provides
for a deeper upper trough with more moisture (compared to the drier
GFS solution). Expect that temperatures will trend back to slightly
below seasonal normals for the weekend through early next week.  /mh
Cullen

&&

.AVIATION...MVFR cigs are locked in at KAST this morning and
should remain there while KONP continues to bounce between VFR
and IFR. While the stratus will likely stay offshore, the valley
fog/stratus may continue to impact the terminal periodically.
3500 to 4000 foot cigs which built westward off the Cascades last
evening have started to break up as winds aloft switch from
north winds to east winds. Expect these inland cigs to remain
VFR. The only exception is KHIO where ceilings are occasionally
dipping below 3000 feet, but these clouds are transient and
conditions will likely return to VFR soon.

KPDX AND APPROACHES...VFR conditions expected through the period.
/Bentley

&&

.MARINE...Issued a short duration small craft advisory for winds
for all waters except for the northern inner waters with varying
start and end times. Small craft winds will start by pushing up
the coast this evening and by Wednesday morning will be relegated
to the outer waters as the thermal trough builds north and winds
turn offshore. Winds will remain light through the remainder of
the week and into the weekend. Towards the end of next weekend
and the beginning of next week there is still considerable model
uncertainty with the ECMWF indicating gusty southerlies ahead of
the next system to move through the area while the GFS continues
the northerlies.

Seas will remain small through the week until later in the
weekend when either a system moving in or persistent gusty north
winds will bring increasing seas across our waters. /Bentley

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds from 8 PM this evening to 2 AM
     PDT Wednesday for Waters from Cape Shoalwater WA to
     Cascade Head OR from 10 to 60 NM.

     Small Craft Advisory for winds from 5 PM this afternoon to 8 AM
     PDT Wednesday for Waters from Cascade Head to Florence OR
     from 10 to 60 NM.

     Small Craft Advisory for winds from 5 PM this afternoon to 11
     PM PDT this evening for Coastal waters from Cascade Head
     to Florence OR out 10 NM.

&&

$$

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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
commonly referred to as the forecast area.



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