High Wind in Washington, April 7, 2017

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
357 AM PDT Fri Apr  7 2017

UPDATED MARINE DISCUSSION

.SYNOPSIS...An unusually strong early April storm will track
northward just off the coast and produce strong winds today along the
coast and in the coastal mountains and very windy conditions in the
inland valleys and foothills, plus high seas along the coast. There
is a chance of a thunderstorm today. Cooler air and showers will
spread in tonight and Saturday with snow levels lowering below the
Cascade passes. The next front is expected mainly Sunday night into
Monday as snow levels remain mostly below the Cascade passes. The
next system is expected the middle of next week.

&&

.SHORT TERM...Today through Sunday...A strong low pressure system was
moving northward off the coast inside 130W early this morning, and is
forecast to move onshore near the northern tip of Vancouver Island
this evening. This low is forecast to deepen to near 970 mb while off
the coast, driven by an unusually strong early April jet stream of
nearly 160 kt.

This storm will produce strong winds today along the coast and in
parts of the coastal mountains, and very windy conditions in the
interior valleys and Cascade foothills. The associated cold front was
moving through the forecast area overnight and early this morning
with rain and mountain snow. The strongest winds and a good batch of
rain will be associated with the bent back occlusion around the low
center as it moves onto the coast in the 12z-15z time frame this
morning and then across the remainder of the forecast area through
the remainder of the morning. There will also be a chance of thunder
as this low pressure system moves through today.

Cooler air spreads into southwest Washington and northwest Oregon
tonight and Saturday and snow levels in the Cascades will drop below
the Cascade passes to around 2500 to 3000 feet by Saturday morning.
Amounts will probably stay below snow advisory criteria, but could
cause the passes to become snow covered. The models right now suggest
the south Washington Cascades will see the greatest accumulations,
but the Oregon Cascades could see several inches as well.

Showers will decrease Saturday night as the associated upper trough
moves east. Sunday could be rather dry as the next front is still
offshore, spreading rain onshore late Sunday and especially Sunday
night. Tolleson

.LONG TERM...No Changes. Previous discussion follows...
Sunday night through Thursday...A cool showery weather pattern on
Monday looks increasingly likely to take a break Tuesday as weak
shortwave ridging tries to build over the Pacific Northwest. Still
maintained some PoPs in this portion of the forecast, but seems
increasingly likely these can be cut further as confidence grows in a
24 hour dry period developing Tuesday. Models are in general
agreement that a closed low pressure system will then move eastward
towards California towards the middle of next week. While the bulk of
the unsettled weather looks likely to stay to our south, some cooling
aloft and south-southwesterly flow should lead to some showers
spreading back into the region during the middle part of next week.

&&

.AVIATION...A strong low will continue to move north off the
Oregon and Washington coast today. As rain spreads north across
the forecast area this morning expect coastal TAF sites to become
predominately MVFR. Inland TAF sites will likely remain VFR, with
occasional periods of MVFR under moderate rain. Conditions will
become showery this afternoon with a chance for thunderstorms.
Coastal TAF sites will likely improve to VFR by this evening,
with widespread VFR conditions expected tonight.

Strong southerly wins will develop across the forecast area
today. Expect winds along the coast to increase rapidly after
13Z, with gusts to 60 kt possible. Gusty south winds will spread
inland later this morning, with gusts to 45 kt possible after
15Z.

KPDX AND APPROACHES...Predominately VFR, with occasional periods
of MVFR under moderate rain. Conditions become showery this
afternoon with a chance of thunderstorms between 18Z and 03Z.
Strong southerly winds with gusts to 45 kt possible between 15Z
and 02Z. /64

&&

.MARINE...A 973 mb low will continue to move north today off the
Oregon and Washington coast, passing about 120 nm west of the
mouth of the Columbia River. Expect winds to increase rapidly
this morning, with widespread storm force gusts to 60 kt possible
after 7 AM. Storm force winds will continue through this evening,
with seas building into the mid 20s by this afternoon.

Winds will subside slowly tonight and Saturday as the low moves
towards British Columbia. Expect winds to drop below 20 kt by
Saturday afternoon. Seas will also fall as the winds decrease,
but likely remain near 10 ft on Saturday. A cold front will
approach the waters late Saturday and bring another round of
southerly gales on Sunday. Seas will likely build back into the
low to mid teens in response to the winds on Sunday and likely
remain above 10 ft through late Monday.

Weak high pres looks to move over the waters early next week and
could bring a day or two of winds less than 20 kt and seas below
10 ft. /64

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 7 AM this morning to 5 PM PDT this afternoon
     for Central Willamette Valley-Greater Portland Metro Area-
     Lower Columbia-South Willamette Valley.

     High Wind Warning from 8 AM this morning to 5 PM PDT this
     afternoon for Central Coast Range of Western Oregon-North
     Oregon Coast.

     High Surf Advisory from 7 AM this morning to 11 PM PDT this
     evening for Central Oregon Coast-North Oregon Coast.

     High Wind Warning from 8 AM this morning to 8 PM PDT this
     evening for Coast Range of Northwest Oregon.

     High Wind Warning until 2 PM PDT this afternoon for Central
     Oregon Coast.

WA...Wind Advisory from 7 AM this morning to 5 PM PDT this afternoon
     for Greater Vancouver Area-I-5 Corridor in Cowlitz County.

     High Wind Warning from 8 AM this morning to 5 PM PDT this
     afternoon for South Washington Coast.

     High Surf Advisory from 7 AM this morning to 11 PM PDT this
     evening for South Washington Coast.

     High Wind Warning from 8 AM this morning to 8 PM PDT this
     evening for Willapa Hills.

PZ...Storm Warning until 5 PM PDT this afternoon for Coastal Waters
     from Cape Shoalwater WA to Florence OR out 60 nm.

     Small Craft Advisory for Rough Columbia River Bar until 9 AM
     PDT Saturday.

&&

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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. The area is
commonly referred to as the forecast area.