[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Western Washington


239 
FXUS66 KSEW 232250
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
350 PM PDT TUE AUG 23 2016

.SYNOPSIS...Upper level high pressure over the eastern Pacific
will continue to expand its influence into western Washington
through Thursday night. In combination with some offshore wind
flow, a warming trend will take place through Friday. Cooling
onshore flow will pick up on Friday evening and persist well into
next week, with an upper level trough brushing by the area this
weekend.

&&

.SHORT TERM...An upper level high pressure ridge near 135W will
amplify and strengthen through Wednesday, resulting in northerly
flow aloft and rising upper heights over western Washington. From
Wednesday night through Friday, the upper ridge will retrograde
gradually to near 150W, strengthening all the while. The net
effect over western Washington will be upper heights and
temperatures aloft holding nearly steady on Thursday and Friday.
However, a day-to-day warming trend will continue through Friday
due to a weak thermal pressure trough along the coast and an
offshore component to the low-level winds. Friday will be the
warmest day for all but the immediate coast. Lowland high
temperatures on Friday should reach or exceed 90F along and south
of a line from Bremerton to Bellevue.

Otherwise, marine stratus will be confined to locations adjacent
to Grays Harbor on Wednesday morning, with no marine stratus on
Thursday and Friday mornings. No rain is expected through Friday
due to a dry air mass and large-scale subsidence.  Haner

.LONG TERM...With the upper ridge way out near 150W on Friday, it
will allow an upper trough to slide southeast through B.C. on
Saturday. For western Washington, westerly flow aloft will pick
up quickly on Friday PM, with a strong marine push ensuing from
Friday evening through Saturday. Strong day-over-day cooling is
expected, with highs on Saturday running 15-20 degrees cooler than
Friday.

A low amplitude longwave trough will then persist over western
Canada and the Pacific Northwest from Sunday through next Tuesday.
Cyclonic onshore flow and 500 mb heights in the 570-575 decameter
range will keep temperatures near or slight below normal for the
extended forecast. Marine clouds will be common, but 500 mb
heights in excess of 570 decameters should keep any shower
activity light, weak, and mainly confined to windward mountain
slopes. Just have slight chance of showers for parts of the
forecast area from Saturday through next Tuesday. Haner

&&

.AVIATION...Northerly flow aloft will prevail tonight and
Wednesday with an upper ridge offshore. At the surface, low level
flow will become north to northeast tonight as a thermal trough
develops along the coast. The air mass is dry and stable.

Low clouds just off the Central coast will push onshore later
tonight but remain confined to the immediate coast with northerly
low level flow. These clouds should burn off again Wednesday
morning. There will also probably be some patchy fog in the
valleys of the Southwest Interior Wednesday morning which will
burn off a couple hours after sunrise.

KSEA...Clear skies. Northerly wind 5-10 knots, strongest in the
afternoon and early evening. Schneider

&&

.MARINE...Weak northwest onshore flow will switch to offshore tonight
as a thermal trough develops along the coast. The Central and
Eastern Strait of Juan De Fuca might have a few hours of marginal
small craft advisory west winds this evening. The forecast is
10-20 knots for now.

The thermal trough will remain along the coast through Friday
morning then shift inland Friday afternoon and evening with
onshore flow returning. Small craft advisory west winds are
expected in the Central and Eastern Strait of Juan De Fuca Friday
night as onshore flow strengthens. Onshore flow will weaken Sunday
but models are in poor agreement by then and confidence in the
details is low. Schneider

&&

.FIRE WEATHER...About 15 days and counting since the last
measurable precip for most of the forecast area, and wildland
fuels are the driest that they have been all year. 

Thermal pressure trough will develop along the coast and Wednesday
and persist until Friday morning. This will produce dry northeast
breezes over the NW Olympic Peninsula, and a moderate north breeze
through the Puget Sound lowlands into the southwest interior. The
PDX-BLI gradient will strengthen in excess of -3.5 mb both
Wednesday and Thursday afternoons, supporting sustained winds in
excess of 12 mph. On Thursday afternoon, the Relative Humidity
will drop below 30 percent due to hot temperatures and dewpoints
in the upper 40s. So the forecast achieves Red Flag criteria for
Wind and Relative Humidity, prompting the issuance of a Fire
Weather Watch for the north-wind prone lowlands from Bremerton and
Seattle on south, as well as the northeast-wind prone NW Olympic
Peninsula near Forks, Quillayute, and Ellis Mtn. These kind of
conditions will push any new fire starts quickly, with rapid
rates of spread and downwind spotting. 

The Watch goes through Friday, but Thursday is the day that will
most easily reach Red Flag wind/RH criteria in the aforementioned
areas. Haner

&&

.SEW Watches/Warnings/Advisories...
WA...Fire Weather Watch from Thursday morning through Friday evening 
     for Black Hills and Southwest Interior Lowlands-Central and 
     South Puget Sound Lowlands-North Coastal Lowlands-Southeast 
     Puget Sound Lowlands Generally Below 1500 Feet.

PZ...None.
&&

$$

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.html

[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Southwestern Washington and Western Oregon


363 
FXUS66 KPQR 232205
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
305 PM PDT Tue Aug 23 2016

.SYNOPSIS...An upper level ridge will continue to build over the Pac
NW Wednesday and persist through Friday. Offshore winds and a thermal
low will bring hot weather Wednesday through Friday. Cooler weather
is expected this weekend into next week as a series of upper level
troughs increase onshore flow and morning clouds.

&&

.SHORT TERM...(Tonight through Friday)...Expect another beautiful
night tonight with mostly clear skies and near normal temps. However,
hot weather is on the way Wednesday through Friday. The good news is
that this round of heat does not look to be as bad as last week.

An upper level ridge will be the dominate weather feature through
Friday. High pressure at the surface will build east of the Cascades
Wednesday and Thursday as a thermal trough over California expands
north. This surface pattern will allow east to northeast winds to
develop and encourage further warming. Inland temps will likely warm
into the low 90s late Wednesday afternoon. The offshore winds may not
reach the coast until Wednesday night, so light onshore winds will
keep the coastal temps below 80 on Wednesday. East winds look to
become more widespread Thursday as the thermal trough strengthens
across western Oregon. This will result in inland temps in the mid to
upper 90s, with coastal temps in the mid to upper 80s. The upper
level ridge looks to weaken on Friday with weak onshore flow
returning to the coast bringing slightly cooler temps. The thermal
trough does not look to move east of the Cascades until late Friday
so the interior will see another day of temps in the mid to upper
90s. /64

.LONG TERM...(Friday night through Tuesday)...Models continue to show
an upper level trough impacting the region this weekend and early
next week with onshore flow strengthening during this time. This
should bring an extended period of cooler weather with temps a few
degrees below normal. A weak shortwave rounding the base of the
trough could bring some patchy drizzle to the north Oregon and south
Washington coast Saturday afternoon and Sunday but confidence is not
high. Another shortwave approaching the region late Monday or early
Tuesday provides our best shot at precip in the long term, but
accumulations look to be meager at best. /64

&&

.AVIATION...Low stratus and fog was hugging the coastline Tue
afternoon, leaving KONP near the edge of IFR conditions. stratus and
fog likely to increase again overnight coastal areas, with IFR
conditions becoming likely at KAST between 05z and 08z. Expect a
return to VFR conditions on the coast between 15z ad 18z Tue.
Inland areas generally expected to remain VFR tonight and Tue,
except for patchy valley fog in the Coast Range and up the Lower
Columbia between 09z and 16z.

KPDX AND APPROACHES...VFR conditions expected to continue tonight and
Tue.

&&

.MARINE...High pressure will linger across the northeast Pacific
through at least the end of the work week. A trough of low pres along
the s OR coast will develop north up the coast Wed and remain through
Fri. This will bring gusty north winds with short period choppy seas
generally in the 4 to 8 ft range. Will likely see wind gusts in the
20 to 25 kt range in the afternoons and evenings across the southern
waters through Fri. As the trough of low pres moves inland this
weekend winds likely to remain below 20 kt through the weekend.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 11 PM PDT this evening for
     Coastal Waters from Cascade Head OR to Florence OR out 60 nm.

&&

$$

Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland

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.

[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Southeastern Washington and Northeastern Oregon


219 
FXUS66 KPDT 240216
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
716 PM PDT TUE AUG 23 2016

.SHORT TERM...Satellite showing clear skies for the remainder of
the evening and overnight. The airmass remains very dry and lows
will drop into the 40s to lower 50s. Some locations in central
Oregon may fall into the upper 30s. Northerly flow Wednesday with
a weak disturbance moving through the area. Lapse rates indicate
scattered cumulus clouds developing otherwise a mostly sunny day
with high temps about 1-3 degrees above todays readings. Little
change for Thu and Fri as northerly flow aloft continues with
mainly clear skies. Temperatures will be a few degrees warmer each
day. 94.

&&

.PREV DISCUSSION... /issued 233 PM PDT TUE AUG 23 2016/ 

SHORT TERM...Tonight through Friday...An upper level low pressure
system over southern Saskatchewan will drift east to southern
Manitoba tonight into Wednesday. Meanwhile a weak wave will rotate
around the system's back side and across the Pacific Northwest
Wednesday. Still expect dry conditions across the region tonight
through Wednesday, despite the wave, as the air mass remains fairly
dry. May see just enough moisture increase over portions of
southeast Washington and northeast Oregon for a few clouds Wednesday
afternoon and evening. Surface winds will be light tonight and
expect another cool night due to good radiational cooling. Winds on
Wednesday will be generally 5 to 15 mph and from the north and
northeast. High temps Wednesday will warm 2-4 degrees over today. A
dry northerly flow aloft will persist over the region Thursday
through Friday. Surface winds will mainly be north to northeast in
the afternoons, and terrain driven at other times. Temps will warm a
few degrees each day as well. 90 

LONG TERM...Friday night through Tuesday...The 12Z GFS run has come
into better agreement with the 12Z ECMWF run in the extended period.
Both models are now showing a mid/upper level long wave trough
dropping south across British Columbia friday night, which places
the forecast area in a dry NW flow aloft for Friday night. Saturday
the aforementioned trough moves into southern British Columbia with
a mid/upper level short wave moving SE in the western flank of the
trough. The mid/upper level short wave will back flow aloft from
northwest to west, which yields a westerly flow aloft that produces
sinking east of the Cascades for a continuation of dry conditions on
Saturday. Sunday the short wave digs the mid/upper level long wave
trough farther south along 130W, which backs flow aloft to the
southwest on Sunday and Sunday night. The models are hinting at some
potential for showers east of the short wave axis overnight into
Monday morning along the east slopes of the central Washington
Cascades when the short waves reaches the coast. Have decided for
now to keep a dry forecast for Sunday night and Monday along the
east slopes of the central Washington Cascades. The low amplitude,
mid/upper level long wave trough remains over the Pacific Northwest
on Tuesday, which puts the region in a dry westerly flow aloft east
of the Cascades. Polan 

AVIATION...00Z TAFs...VFR conditions will occur for the next 24
hours. Skies will be mostly clear through this evening with terrain
driven winds mainly less than 10 kts. KRDM and KBDN may get gusts to
18 kts at times late this afternoon. Clouds will become SCT 8000-
9000 ft AGL overnight at KYKM, KPSC, KALW AND KPDT. KRDM and KBDN
will have clear skies through the 24 hour forecast period. Polan 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  49  83  52  85 /   0   0   0   0 
ALW  55  85  57  87 /   0   0   0   0 
PSC  52  88  53  89 /   0   0   0   0 
YKM  50  90  52  91 /   0   0   0   0 
HRI  48  88  51  89 /   0   0   0   0 
ELN  50  89  51  90 /   0   0   0   0 
RDM  39  82  41  84 /   0   0   0   0 
LGD  41  81  44  83 /   0   0   0   0 
GCD  45  84  47  86 /   0   0   0   0 
DLS  54  92  56  95 /   0   0   0   0 

&&

.PDT Watches/Warnings/Advisories...
OR...None.
WA...None.
&&

$$

94

[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Northeastern Washington and Northern Idaho


935 
FXUS66 KOTX 240104
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
604 PM PDT Tue Aug 23 2016

.SYNOPSIS...
Isolated showers and thunderstorms are possible in north Idaho
and extreme northeast Washington this evening. Winds will increase 
out of the north to northeast overnight into Wednesday. This will
help move areas of smoke away from their sources and southward.
Expect a gradual warming trend with mostly dry conditions through
the work week. Another dry cold front should arrive by Saturday
with more breezy winds.

&&

.DISCUSSION...
Tonight through Thursday night: Mostly dry and mild weather will 
continue with a few short term challenges. 

Winds/Smoke: Winds will be the main issue for the next several days 
especially dealing with where the smoke will go. Areas of smoke
still linger around the Spokane area and near area fires with the
north-northwest winds. The winds will shift to the northeast
tonight as a weak front moves down across north Idaho. Could see
gusts of 15 to 20 mph over north Idaho and the Okanogan Valley
early this evening and again by early Wednesday morning. An area
of high pressure will set up in western MT and keep easterly winds
across much of the region. This will push smoke from area fires to
the south and west of the source regions, so away from the Spokane
area and into the Columbia Basin, the Palouse and even Shoshone
county from a fire in the Bitteroots. This trend is seen in the
HRRR smoke models. The east to northeast winds look to persist
through Thursday night, keeping smoke trends fairly similar
through mid week barring any change in fire development and lack
of breezy winds.

Showers/Thunderstorms: There looks to be more low level instability 
than yesterday and convection is developing just north of the
border from Bonners Ferry. Expect this activity to continue to
grow and track to the south-southeast through the remainder of the
afternoon and early evening hours. There is a small chance of
thunderstorms over north Idaho early this evening. The HRRR has
been fairly robust on this convection and showing development back
to the west across northeast Washington, more so than the NAM4km.
With any convection that does form over the Okanogan Highlands/NE
Washington and the current NW steering flow, there is small chance
that this would push convection into the Spokane/Coeur d'Alene
area early this evening. Not much in the way of precipitation is
expected as most of the activity would be high based, but winds
would be a concern with northerly and even gusty outflow winds
from the north are possible. This will continue to be monitored
this evening. Otherwise for Wednesday, there is another small
chance of afternoon to evening showers and thunderstorms for the
northeast Washington and panhandle mountains. A lesser chance
exists for Thursday.

Temperatures: Despite the passage of the weak front, temperatures
will gradually moderate Wednesday and into Thursday. Expect
temperatures reaching near seasonal daytime levels, meanwhile cold
pockets are possible overnight in sheltered areas. /rfox. 

Friday through Tuesday...Offshore ridge retrogrades westward a
bit and away from the coast as a low pressure system drops down its
east edge. The low is still expected to be positioned over Southern
British Columbia Friday early on so sensible weather for Friday
remains the same with a generally sunny forecast. Saturday, however,
should see remarkably increased southwest wind along with increased
cloud cover and pops added in order to mention a chance of
precipitation near the British Columbia Border. Moisture remains
limited so pops will not be too high. The disturbance finishes
dragging a cold front through and allows for some weak shortwave
ridging to build into part of Washington Sunday but the longwave
pattern at about this point on favors a general persistent trof
lingering in place with nothing too substantial in the way of
disturbances with good dynamics and moisture passing through it.
Therefore the end result is a forecast that depicts Friday and/or
Saturday as the warmest days ahead of the cold front/trof passage
that allow for cooling and increased wind (especially on Saturday)
that diminishes going into Sunday and beyond. /Pelatti

&&

.AVIATION...
00Z TAFS: Scattered showers will drift southward through the north
Idaho Panhandle this evening. At this time, it looks as if the
convection will dissipate before reaching the Couer d'Alene or
Spokane airports. However, Bonners Ferry and Sandpoint will
experience showers capable of light to moderate rain...as well as
a handful of lightning strikes through 04z. As for the smoke...
fire activity today has decreased compared to the last couple of
days. There is not as much smoke in the "air shed" so the chance
for visibility restrictions tonight into Wednesday should be
less. A transition to a northeast transport wind may bring smoke
from Spokane and Lincoln counties toward the Moses Lake airport
Wed morning. /GKoch

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        55  79  56  82  54  83 /  20  10  10   0   0   0 
Coeur d'Alene  52  78  52  81  50  81 /  20  10  10   0  10   0 
Pullman        47  80  48  81  46  82 /   0  10  10   0   0   0 
Lewiston       55  86  56  88  56  88 /   0   0   0   0   0   0 
Colville       50  82  51  84  50  84 /  10  10  10  10  10  10 
Sandpoint      50  76  50  78  48  78 /  20  10  10  10  10  10 
Kellogg        49  74  49  77  48  77 /  20  10  10  10  10  10 
Moses Lake     54  88  56  90  53  89 /   0   0   0   0   0   0 
Wenatchee      60  86  60  88  59  89 /   0   0   0   0   0   0 
Omak           58  87  58  88  57  90 /   0   0   0   0   0   0 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&

$$

[ W WA | SW WA and W OR | SE WA and NE OR | NE WA and N ID ]

Back to U.W. Weather Page