High Wind in Washington, November 25 to 26, 2017

Area Forecast Discussion
National Weather Service Portland OR
920 PM PST Sat Nov 25 2017

.SYNOPSIS...A warm front will lift north into Washington overnight.
A cold front will move east across the area Sunday for more rain.
The low pressure associated with the front will produce strong gusts
along the beaches, and breezy conditions inland late tonight and
Sunday morning. Snow levels will lower to near the Cascade passes
Sunday night and Monday with some showers. Another frontal system
will produce additional rain and mountain snow Monday night and
Tuesday. Drier conditions with east winds expected Wednesday and
Thursday.
&&

.SHORT TERM...Tonight through Tuesday...Rain associated with a warm
front has lifted mostly north into WA this evening. Air mass front
south of the warm front is unseasonably mild, with 850 mb temp at
SLE this evening +8C. The surface low was moving as models expected,
likely off the WA coast around 129W, and moving quickly north
towards Vancouver Island. Trailing cold front extended to the south,
with models indicating the front reaching the coast around 15Z Sun,
and spreading rain back in ahead of it. Gradients and model wind
fields, coupled with offshore winds ahead of the front tend to
suggest gusty winds along the coast, but not likely to be warning
level.

Remainder of short term discussion unchanged...Rain totals will be
highest for the higher terrain of SW Washington and NW Oregon where
0.75 to 1 inch is possible Sunday morning through Sunday evening.
Otherwise expect 0.5 to 0.75 inch of rain for the same time period.

Snow levels will drop rapidly with the cold front and there may be a
burst of snow as the cold front departs the Cascades Sunday evening.
Showers will continue Sunday night and Monday as the surface low
moves inland near the Washington Oregon border. Most of the
precipitation will be to the north and expect snow accumulations for
the south Washington and north Oregon Cascades. The Washington
Cascades has a better chance for snow accumulations greater than a
couple of inches, and they may flirt with advisory conditions. Do not
anticipate there will be a need for any winter weather headlines for
the north Oregon Cascades. Regardless, those travelling across the
Cascade passes Sunday night and Monday will likely come across snow
covered roads, and should prepare for winter weather driving
conditions.

Another low approaches Monday night and will bring another frontal
system to the Pacific NW. A warm front will continue rain and mountain
snow for SW Washington Monday night and Tuesday morning before the
cold (or occluded) front moves through late Tuesday morning into
Tuesday night. Snow levels will likely remain near or slightly below
the Cascade passes with this system.

.LONG TERM...Tuesday night through Saturday...No changes. Previous
discussion follows. Another system brings widespread rain Tuesday
night, but this front will be a fairly fast-moving system which
should limit the potential for excessive rainfall amounts. A
shortwave ridge builds over the Pacific Northwest Wednesday and
Thursday, bringing a break in the active weather. Expect morning fog
Wednesday and Thursday morning, breaking up midday with seasonable
high temperatures in the afternoons. Winds turn easterly Wednesday
evening, with gusty winds near the Columbia Gorge. The next system
starts its approach on Thursday, increasing high level clouds
Thursday afternoon and evening. Some differences in timing with the
system on Friday, but it looks like another fast-moving system, so
not anticipating excessive rainfall amounts. Showers continue into
Saturday, with snow levels dropping down to around 2000-3000 ft. -
McCoy &&

.AVIATION...A warm front lifted through the region during the
late afternoon and early evening. The associated rain band has
now moved north of the region, and conditions are mainly VFR.
Conditions are mostly VFR at this time. However, with a moist and
mild low level air mass in place, there is some patchy IFR fog
and low stratus forming in the southern half of the Willamette
Valley. Expect this will expand overnight. The coast and northern
valley should remain VFR due to the continuing offshore flow.
The cold front will approach from the west late tonight, reaching
the coastline around 15Z Sun and reaching the SW Washington
lowlands and Willamette Valley 17Z-21Z. MVFR conditions expected
along the coast late tonight and increasing MVFR inland with the
front. Conditions should improve to mainly VFR during the late
afternoon and evening behind the frontal passage.

KPDX AND APPROACHES...VFR conditions should continue overnight
with continued gusty E-SE winds. The strongest winds will be
toward the west end of the gorge, where gusts 35 to 40 kt are
expected. A cold front will move through the terminal around
18Z-20Z, which will turn the winds southerly. Conditions should
deteriorate to mainly MVFR for several hours with the front. Pyle

&&

.MARINE...A rapidly strengthening low pres system is located
around 47N/130W with a strength nearing 980 mb as of 9 PM. This
low will continue to strengthen and move north toward the
northern end of Vancouver Island overnight. An associated warm
front moved through the waters this evening and is now pushing
north of the region. S-SE winds will continue to strengthen
overnight in the warm sector of the storm. The winds are already
picking up considerably over the outer waters. The nearshore
waters will see winds increase later tonight as the trailing cold
front approaches. Expect widespread solid to high-end gales.
There may be occasional gusts to 50 kt late tonight and early Sun
morning. The front will move onshore around sunrise, but a
secondary surface trough will rapidly follow. This will prolong
the gale force winds into early Sun afternoon. Yet another low is
modeled to move from the west onto Vancouver Island Sun night,
which may be strong enough to bring an additional round of gales
to the northern waters. Another weaker frontal system is expected
Mon night into Tue. Then high pres builds into the waters late
Tue and remains for much of the rest of the week.

Combined seas expected to reach at or close to 20 ft late this
evening and tonight, but will be comprised of a large wind-wave
component. Models have backed off on the large swell train for
the Tue-Tue night time frame. Latest ENP now shows a 23-25 ft
bullseye off the Washington waters compared to 25-30 ft a couple
runs ago. Pyle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Gale Warning until 1 PM PST Sunday for Waters from Cape
     Shoalwater WA to Florence OR from 10 to 60 NM.

     Small Craft Advisory for winds until midnight PST tonight for
     Coastal Waters from Cape Shoalwater WA to Florence OR out
     10 NM.

     Gale Warning from midnight tonight to 1 PM PST Sunday for
     Coastal Waters from Cape Shoalwater WA to Florence OR out
     10 NM.

     Small Craft Advisory for Rough Columbia River Bar until 10 PM
     PST Sunday.

&&

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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 CWA, or forecast area.