FXUS66 KPQR 201012

Area Forecast Discussion
National Weather Service Portland OR
304 AM PDT Sat Oct 20 2018

.SYNOPSIS...High pressure over the region will continue to produce
mild days, cool nights and mostly clear skies before a more active
storm track brings cooler and wetter weather next week.


.SHORT TERM...Today through Tuesday...Upper level high pressure over
the region will slowly shift eastward over the next couple of days.
Thermal low pressure will reside over western Oregon through Sunday
before pushing east of the Cascades on Monday. This will result in a
continuation of the warm days and cool nights of late through Monday
for the Willamette Valley and points east.

Fog is once again developing in the coastal river valleys and along
the lower Columbia River between Kelso/Longview and the Portland
metro early this morning. Given dewpoints were in the mid to upper
40s to begin the night, fog formation has begun a little bit earlier
than last night. As a result, expecting fog coverage to be a bit
higher inland, particularly across the Tualatin River Valley and the
central Willamette Valley when compared to last night. Expect a near
repeat Sunday and Monday mornings except along the coast where marine
stratus should be on the increase and fog coverage should be reduced.

A front is still on track to push into the Pacific Northwest Tuesday.
However, models continue to weaken and slow down the front and as a
result, rain amounts and even rain chances continue to diminish. It
appears close to a 50:50 shot as to whether or not the coast will see
rain Tuesday. Farther inland, rain chances look pretty minimal
through Tuesday afternoon. /Neuman

.LONG TERM...Tuesday night through Saturday...The EC remains a little
more progressive with the front and produces light rain showers
across much of the area Tuesday night and Wednesday morning.
Meanwhile, the latest GFS has joined the GEM model in suggesting the
front will stall and weaken enough that rain will be primarily
confined to our coastal zones Tuesday night and Wednesday and inland
locations will remain dry. The latter scenario seems most plausible
given this will be the first storm system trying to breakdown our
long lasting ridge of high pressure. Nonetheless, can't discount the
EC scenario so have slight chance to chance PoPs to account for the
uncertainty at this point.

Regardless, a more consolidated and strong zonal jet is still
forecast to take aim at the Pacific Northwest during the second half
of next week. This should bring better chances of rain to the
region. Models continue to suggest Wednesday night into Thursday will
be quite wet across the area so have likely to low end categorical
PoPs to highlight this period. There is a decent chance an additional
round or two of rain will move across the area Thursday night and
Friday. Most models suggest shortwave ridging will build at least
temporarily back over the Pacific Northwest towards Friday night and
Saturday so PoPs were trended back down towards climo or slightly
below during this period. /Neuman


.AVIATION...12z TAF Package expectations: Areas of LIFR Cigs
across the region with the most significant impact along the
coast. Additionally, a stratus field has developed along the
Eastern Columbia River delta and is spreading up the lower
Columbia River. This finger rapidly accelerated as it crossed
Kelso and will soon reach KTTD. Just about any terminal across
far SW Washington and NW Oregon could see conditions drop to LIFR
over during he next few hours, but KEUG appears to have a
slightly better chance of staying out from under the soup.
Conditions expected to improve again to VFR between 17Z and 21Z
most areas, although IFR conditions are expected to remain or
even redevelop along the immediate coast after 21Z.

KPDX AND APPROACHES...Expect VFR conditions to continue through
10Z, although VCFG to the northeast will likely spread across the
field by 12z. LIFR Fog/low stratus is expected to prevail
between 11Z and 19Z. VFR conditions return after 19Z. /JBonk


.MARINE...Surface high pressure over the coastal waters will
give way to a surface thermal trough that will continue to spread
north today. North wind increases as the trough develops,
spreading from south to north. Winds have largely eased overnight
but am beginning to see buoy 050 gusts increase to 21 kt. Gusts
to 25 kt expected for PZZ275 late this afternoon, followed by
small craft advisory level wind gusts spreading into PZZ270
tonight. The south half of PZZ270 will be favored for 25 kt
gusts. Have added the inner waters (PZZ250 south of Garibaldi
and all of 255) to the advisory suite. Hi resolution models gave
additional confidence for issuing the SCA for winds to cover the
inner waters as well. Will run the advisory through about
midnight tonight, although the inner waters will likely see
winds ease a few hours earlier.

Wind speeds diminish tonight and Sun, remaining 15 kt or less
through Mon night. Models continue to trend slower and weaker
with the frontal system for early next week. It now appears the
front moves through the waters Tue. Small craft advisory level
wind gusts now look marginal, but have indicated 25 kt. Would not
be surprised if future model runs further weakened the system. A
more active pattern sets up for the latter half of next week,
but models differ on the strength and track of the mid-week

Seas holding around 4 to 5 ft through Sunday. Do not see much
change through early next week. The Tue system should increase
wave heights to near 10 ft.


PZ...Small Craft Advisory for winds until midnight PDT tonight for
Coastal Waters from Cape Shoalwater WA to Florence OR out
60 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
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