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

Western Washington


171 
FXUS66 KSEW 232304
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
404 PM PDT Tue May 23 2017

.SYNOPSIS...A strong cold front will sweep through Western
Washington this evening, bringing windy conditions to areas near
the Strait and Admiralty Inlet. A much cooler air mass will be in
place on Wednesday. Warmer and drier upper ridging will rebound
off the coast on Thursday, then pass Western Washington on
Saturday. 

&&

.SHORT TERM...An upper trough with a strong height fall center
will move east-southeast across southern B.C. through tonight. 
This will sweep a strong cold front out of the northwest through 
Western Washington this evening. Strong onshore flow has now
developed in response, with the observed 3 pm UIL-BLI pressure 
gradient at an impressive +6.6 mb. A strong surge of westerly 
winds continues to gather steam through the Strait of Juan de 
Fuca, which will take aim at Whidbey Island and the Admiralty 
Inlet area early this evening. Later this evening around 8-10 pm, 
the west-northwest winds will penetrate all the way into western 
Snohomish County, where gusts to 40 mph are expected. For the
Everett area in particular, W-NW is a less common direction for 
stronger winds, which could increase the impacts of 40 mph gusts.
The current configuration of wind highlights looks good, so no 
update to the wind advisories and warnings in the near future. 
Westerly flow will gradually weaken during the overnight hours. 
Otherwise, a few light showers are forecast tonight where upslope 
flow into the mountains or low- level convergence downwind of the 
Olympic Mtns can maximize low- level lift. 

An enhancement of showers is expected on Wed morning as the main 
upper trough axis swings through. The main upper trough will then 
exit to the Northern Rockies later Wednesday. A piece of the 
upper trough along with some colder air aloft will linger over the
Inland Northwest until Thursday night, so afternoon showers and 
thunderstorms near the Cascade Crest are forecast on Thursday PM. 
The lowlands are forecast to be rain-free on Thursday.

A well-defined upper ridge axis will move to near 130W on Friday,
bringing the biggest day of day-over-day temperature rises in the
week ahead, aided partially by significant weakening of cooling 
low-level onshore flow. Haner

.LONG TERM...A warm and dry upper ridge axis will pass directly
over Western Washington on Saturday. The upper ridge axis will 
be over Eastern Washington on Sunday. Cooling seabreezes will
strengthen at the immediate coast, but the rest of Western
Washington should have little change on Sunday. Some towering
cumulus and an isolated shower could form near the Cascade Crest
in the afternoon as a turn to light southerly flow aloft takes
place. 

For Monday and next Tuesday, the long-range models are pretty
close with their 500 mb height values. The main difference is that
the GFS is a little more amplified with the pattern than the
ECMWF. So the GFS's forecast of a stronger southerly component to
the upper flow is more supportive of late afternoon and early
evening shower/thunderstorm development along the Cascade Crest.
The ECMWF in contrast does not show this outcome, given its more
westerly component to the upper flow. For the lowlands, both
solutions are rain-free.  Haner

&&

.AVIATION...A cold deep upper level low over central B.C. at 23Z
will move SE across southern B.C. arriving over southern Alberta 
around 15Z Wednesday. Strong NW flow aloft will prevail over W WA.
Low level onshore flow will be quite strong through this evening.
Areas around the north interior including the Strait of Juan De
Fuca have localized very windy conditions. 

Overall, the air mass will remain generally dry with VFR 
conditions. Stratus currently along the coast will move part way 
inland through the Strait of Juan De Fuca and between KHQM and 
KSHN, but strong mixing from the onshore flow should prevent 
widespread coverage of MVFR/IFR stratus. In addition, low level
convergence may develop between KPAE and KSEA 00Z-08Z for
localized CIGS BKN025-060.

KSEA...Good VFR conditions through 00Z. A convergence zone may be
in the vicinity from 02Z through 06Z with CIGS possibly down to 
BKN025 for short periods of time. With the convergence zone lying
across central Puget Sound winds at KBFI and especially will be
erratic. Confidence is low. Best guess is that SW winds 5-15 KT
will last until around 02Z then become variable 02Z-04Z as the CZ
is overhead. Around 05Z winds may shift E-NE 5-12 KT as the CZ 
shifts S and weakens. Kam


&&

.MARINE...An upper level low is moving SE across southern B.C. 
this afternoon and tonight. Onshore flow has increased 
dramatically with a 6.6 MB gradient through the Strait at 3 PM. 
Race Rocks was 44G49KT at 3 PM so in coordination with Canada the 
central and east strait will be upgraded to a storm warning for a 
few hours through 8 PM. The gale through the Strait will spread 
over the N inland waters around the San Juans and through 
Admiralty inlet albeit with slightly weaker winds. A gale is also 
in effect for the north part of Puget Sound, north of Seattle. 
This gale is a little shakier and NW winds could end up topping 
out around 30 KT. Winds will likely peak in the Strait early this 
evening then weaken gradually overnight. Winds in Admiralty inlet 
and N Puget Sound will peak a couple hours later and ease a little
later than winds in the strait. Winds should ease fairly rapidly 
after midnight, but SCA conditions in the Strait may persist into 
Wednesday morning.

The surface ridge offshore will maintain light to moderate 
onshore flow the rest of this week. 

A steep fresh swell 10 to 13 feet at 8 to 10 seconds is expected 
to reach the coastal waters later this evening and persist into 
Thursday morning. Kam

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...High Wind Warning until 1 AM PDT Wednesday for Admiralty Inlet 
     Area.

     Wind Advisory until 1 AM PDT Wednesday for Eastern Strait of 
     Juan de Fuca-San Juan County.

     Wind Advisory until 1 AM PDT Wednesday for Everett and Vicinity.

PZ...Small Craft Advisory until 5 AM PDT Thursday for Coastal Waters 
     From Cape Flattery To James Island 10 To 60 Nm-Coastal 
     Waters From Cape Flattery To James Island Out 10 Nm-Coastal 
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From James Island To Point Grenville Out 10 
     Nm-Coastal Waters From Point Grenville To Cape Shoalwater 
     10 To 60 Nm-Coastal Waters From Point Grenville To Cape 
     Shoalwater Out 10 Nm.

     Small Craft Advisory for rough bar until 9 AM PDT Thursday for 
     Grays Harbor Bar.

     Storm Warning until 8 PM PDT this evening for Central U.S. 
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters 
     Strait Of Juan De Fuca.

     Gale Warning from 8 PM this evening to 5 AM PDT Wednesday for 
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance 
     U.S. Waters Strait Of Juan De Fuca.

     Gale Warning until 2 AM PDT Wednesday for Admiralty Inlet-
     Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory until 5 PM PDT Wednesday for West Entrance 
     U.S. Waters Strait Of Juan De Fuca.

     Gale Warning until 1 AM PDT Wednesday for Puget Sound and Hood 
     Canal.

&&

$$

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.wrh.noaa.gov/sew/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


597 
FXUS66 KPQR 232139 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
238 PM PDT Tue May 23 2017

.SYNOPSIS...An upper level disturbance dropping south will move
inland through Washington and northeast Oregon tonight. The onshore
flow will strengthen this evening and tonight. The parent upper
trough will remain over the Pacific Northwest Wednesday for
additional cooling, more clouds, and spotty light precipitation. The
upper trough hangs back over the forecast area Thursday. High
pressure returns Friday for drier, sunnier and warmer weather. Warm
and dry conditions continue through the holiday weekend.  
&&

.SHORT TERM...Tonight through Friday...Early afternoon water vapor
imagery showed the strong upper ridge that was over the Pac NW Sun
and Mon well east into the Northern Rockies and Great Basin. A low
pres area was also noted along the Southern British Columbia Coast
with the leading edge of the dry cold front near the N Washington
coast. As of 20Z the thermally-induced surface trough was located
from near KLMT through the Columbia Basin. Models shift this feature
to the Idaho border by late evening. Early-afternoon visible imagery
indicated stratus solidly along the coast and pushing well into the S
Washington and far N Oregon coastal valleys. The KTTD-KDLS gradient
has gone from nearly neutral at 15Z to 3.5 mb as of 20Z. West wind
has pushed through the Columbia Gorge into K4S2. Some of the more
wind-prone sites in the Willapa Hills and North Oregon Coast Range
have also noted stronger West to Northwest wind.  

Models are in general agreement showing the low-level onshore flow
continuing to deepen along the coast and make more penetration into
the coastal valleys through the evening. The Hi-RES ARW suggests
stratocumulus and/or cumulus will develop and back-build from the
Cascade foothills late this afternoon and through the evening. Based
on latest trends have scaled back the drizzle potential for this
evening. Generally confined any drizzle threat west of the Oregon
Coast Range and SW Washington coastal valleys and Willapa Hills this
evening. 

The strengthening onshore flow, in conjunction with increasing west
flow aloft, will result in breezy to windy conditions through this
evening. The strongest wind will be through the coastal gaps, the
Columbia River Gorge and over the mountains. Breezy to windy
conditions are also likely in the interior valleys as well,
especially those aligned west-to-east. 

The primary short-wave moves south and east tonight, but, in its
wake, an upper trough carves out over the Pacific Northwest
Wednesday, which lingers into Thursday. The NAM would suggest a
marine layer to nearly 5000 feet MSL across the northern two-thirds
of the forecast area through early Wed afternoon. NAM forecast
soundings for KPDX and KSLE have the top of the marine layer close to
6000 feet MSL 19Z Wed. Models also show a short wave disturbance
rotating through the broad upper trough Wednesday, which should keep
clouds fairly solid over much of the area and possibly result in an
over-turning of the marine layer for more drizzle or even light
showers.  

The forecast area will be on the back side the upper trough Thursday.
NAM indicates a fairly solid marine layer across the forecast area
Thursday morning, other than the southeast quarter. GFS and ECMWF
show the Cascades will get backdoored with the possibility of some
showers or even a few thunderstorms in the afternoon and evening
associated with the circulation on the back side of the upper trough.
The GFS and NAM are not overly excited about convective prospects
Thursday afternoon. NAM sounding for a point in the N Oregon Cascades
valid 23Z Thu shows little to no CAPE. Will leave the mention in for
now as not to yo-yo. The increased sunshine should push afternoon
temps inland back into the 70s. Friday looks to be quite pleasant
with minimal morning stratus or fog. Model 850 mb temps rise to +13C
in the far NW to +17C in the Lane County Cascades, which should
translate to lower to mid 80s in the interior valleys. Weishaar

.LONG TERM...Friday night through Tuesday. 500 mb high pressure
remains the dominant feature through the weekend. Sat looks to be as
warm as Fri, based on forecast 850 mb temps. Sunday is expected to be
a few degree warmer, pushing into the upper 80s for interior valleys,
Columbia River Gorge and Upper Hood River Valley. The ECMWF has the
500 mb ridge axis squarely over the forecast area Sat through Sun
morning, then slowly shifts the ridge axis east Sun afternoon. The
GFS shifts the ridge axis east a little sooner and also tries to
develop some minimal QPF near the Cascades, hinting at possible
convection near the Crest. The ECMWF maintains more of a SW mid-level
flow Mon, although it does hint at a short-wave off the N California
coast resulting in a slightly more unstable S-SW mid-level into the
Central Cascades. High pres aloft remains sprawled over the Western
U.S. Tue for continued warm and dry conditions. The ECMWF and GFS
maintain some light QPF over the Cascades Tue, but will not mention
thunder at this time due to higher uncertainty based on the GFS
ensembles and GFS and GEFS comparisons. Weishaar
&&

.AVIATION...Coastal TAF cigs are hovering between IFR at 008 and
MVFR at 015. May still see some periods of drizzle
this evening but am now beginning to question if there will be
much of a Vsby impact. Stratus has not penetrated inland to 
speak of with Cig free skies largely continuing through the
evening and overnight hours. Will continue on bringing a stratus
layer inland after 09z for the norther inland terminals and 
closer to sunrise for KSLE and south. Recent hi-res models are
starting to lean against the idea of impactful stratus, however,
so would not be surprised if the 00z or 06z TAF package removes
the mention entirely. Main impact inland will continue to be a 
surge of winds through the Coast Range gaps. Expect several hours
of wind gusts 20-25 kt this evening as the marine layer surges 
inland.

KPDX AND APPROACHES...VFR conditions most likely through this 
evening under a rather strong marine wind surge. Expect northwest
gusts around 25 kt to prevail. Once winds began to ease that will
allow a stratus Cig to develop perhaps around 015 AGL. Am losing
confidence this overnight deck will develop as near-term hi-res
model runs are keeping rather dry conditions in place for a few
hours. If it does develop, then it appears to remain through at
least 24/18z. /JBonk

&&

.MARINE...High pressure over the NE Pacific and a thermal low
inland combine to continue SCA wind gusts through Wednesday and
likely a significant portion of Thursday. A weak cold front 
reaches our northern waters later this afternoon, resulting in 
increased NW winds, but still at small craft advisory speeds. 
Winds will start to diminish late Wednesday into Thursday, but it
may not be until Thursday night before gusts drop below 21 kt 
across all of the waters. Longer range guidance suggests lighter 
wind speeds thereafter through this weekend. 

Have expanded the SCA for Seas through Wednesday morning across
all waters. a 4 foot background swell may produce a dominant 12
second period at times, but feel the 7 to 9 ft very steep/short
period/longer fetch wind waves will be prevailing much more
often. Will start to see a 9 to 10 second fresh swell mix in
later tonight and into Wednesday but had little confidence
regarding exact timing. Seas will ease by Thursday as winds ease
with little threat from winds or notable seas affecting the 
waters through the weekend.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 5 PM PDT Wednesday for 
     Coastal Waters from Cape Shoalwater WA to Florence OR out 
     60 nm.

     Small Craft Advisory for hazardous seas until 11 AM PDT 
     Wednesday 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. 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


978 
FXUS66 KPDT 232133
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
234 PM PDT Tue May 23 2017

.SHORT TERM...Today through Thursday...A short wave and associated  
cold front are moving over Vancouver Island this afternoon. Models
show that the mid levels in the atmosphere will remain very dry 
with this system so the main effects will be winds and much colder
temperatures. Water vapor satellite shows a strong dry slot that 
indicates strong winds in the jet. These winds will mix down to 
the surface after the front moves through WA and OR tonight. Tight
surface pressure gradients and higher winds aloft mixing to the 
surface will increase the northwesterly winds tonight and 
Wednesday over the lower Columbia Basin and adjacent areas. A wind
advisory has been issued for the Kittitas Valley starting at 
midnight. 

The upper level trough will remain over the area Wednesday with
much colder temperatures. Afternoon high temperatures today 
reached the mid 80s to mid 90s. By tomorrow high temperatures will
be 15-20 degrees colder when colder air moves into eastern WA and
OR behind the front. The trickiest part of the forecast will be 
low temperatures tonight. Winds will be strong enough to inhibit 
nighttime cooling especially in the Columbia Basin. 

A pair of short waves moving through the upper trough Wednesday 
night and Thursday morning will increase the moisture and 
instability over eastern WA and OR. By Thursday morning skies will
be partly to mostly cloudy skies and some showers will develop. 
Weak instability and steep lapse rates may trigger a few 
thunderstorms Thursday afternoon/evening, mainly over the WA 
Cascades and northeast Oregon mountains. Winds will be lighter.

Friday an upper level ridge will build again offshore. Subsidence
from the ridge will start to dry out central and eastern WA and OR
but enough moisture and instability may linger over far eastern OR
to trigger a few showers and thunderstorms in the afternoon. 
Coonfield

.LONG TERM...Friday night through Tuesday...A ridge of high pressure 
will build in from the west late Friday and remain over the region 
through the extended period. This will place temperatures at above 
normal and winds generally light. Main weather concern will be the 
possibility of thunderstorms developing on Monday and Tuesday mainly 
over the mountains areas.   


&&

.AVIATION...00Z TAFs...VFR conditions will prevail over the next 
24 hour. Skies will just have a few cirrus clouds and perhaps some 
cumulus over the mountains. A dry cold front will move into the area 
this evening increasing becoming windy over the next 24 hours with 
15-30 kts winds and higher gusts. 



&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  54  68  42  67 /   0   0  10  20 
ALW  56  71  48  70 /   0  10  10  20 
PSC  57  74  48  75 /   0   0  10  10 
YKM  54  73  46  76 /   0   0  10  10 
HRI  56  73  47  74 /   0   0  10  10 
ELN  54  65  44  73 /   0   0  10  10 
RDM  43  69  33  71 /   0   0   0   0 
LGD  48  65  42  62 /   0  10  10  20 
GCD  46  67  38  66 /   0   0  10  20 
DLS  56  69  47  78 /   0  10   0   0 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory from midnight tonight to 10 PM PDT Wednesday for 
     WAZ026.

&&

$$

76/91/91

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

Northeastern Washington and Northern Idaho


582 
FXUS66 KOTX 240003
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
503 PM PDT Tue May 23 2017

.SYNOPSIS...
A strong cold front will plow through the region this evening 
bringing gusty winds especially to Central Washington. Blustery
conditions will persist into Wednesday with afternoon temperatures
a solid twenty degrees cooler than today. Scattered showers and
thunderstorms will be possible on Thursday. Sunny and warmer 
weather will return for the Memorial Day Weekend with high 
temperatures warming back into the 80s.

&&

.DISCUSSION...

...WINDY TONIGHT WITH GUSTS OF 45 MPH OR MORE AROUND WENATCHEE...
WATERVILLE...AND VANTAGE...

Tonight into Wednesday: Moses Lake hit 90 degrees for the first 
time this season, and for the first time in months we are looking
at the passage of a dry cold front. The calendar says it is late
May, and it appears that Mother Nature is starting to deal us some
weather representative of the season. Late spring is a time of 
big temperature swings and gusty winds. Temps near 90 today, Moses
Lake will be closer to 70 tomorrow. Region-wide, we expect
temperatures to be 20 degrees cooler tomorrow afternoon than they
were today.

Our abrupt cool down will be accompanied by gusty west winds. The
tightest surface pressure gradient and sharpest cold advection
will occur during the mid to late evening hours. The strongest
gusts will likely occur around Wenatchee, Chelan, Waterville, and
Vantage. These areas often experience the strongest gusts during
evening wind events as they are prone to Cascade gap winds. A Wind
Advisory will be issued for this evening and late tonight for the
aforementioned areas. Cooler and denser air spilling through the 
Wenatchee Valley, Kittitas Valley, and down Lake Chelan often 
increase the gust potential. Further east, places like Ritzville, 
Pullman, Lewiston, Spokane and Coeur d'Alene will experience windy
conditions this evening and through the night. However, the night
time arrival of the higher momentum air aloft may not mix to the 
surface efficiently. Look for gusts in the 30 to 35 mph range. 
Breezy winds will persist into the day tomorrow (Wed), but 
pressure gradients will be weakening through the day.

Wednesday night and Thursday: A cool upper trough will linger over
the Inland Northwest following tonight's cold front. The cool air
aloft will promote widely scattered showers Thursday. A few cells
Thursday afternoon may produce lightning, brief downpours, and
small hail. /GKoch

Friday through Tuesday...An upper ridge off the coast near 130W on
Friday will move east over the region over the Memorial Day
Weekend and remain in place through the middle of next week. With
the ridge axis to the west on Friday...some lingering convection
is possible over the Idaho Panhandle. Then significant warming and
drying Saturday through Tuesday as 850mb temperatures climb
towards 18-20C. Dry conditions are favored under the ridge
although with the warm temperatures GFS and ECMWF show increasing
surface based CAPE. There is expected to be a strong cap on
Saturday to limit convection. Sunday through Tuesday isolated
thunderstorms are possible in the mountains of northern Washington
and the Idaho Panhandle...but confidence in this is low with a 
lack of forcing over the region...and the ridge axis overhead 
possibly still providing a cap to get convection going. Main story
will be the warm temperatures with highs in the 80s...with the
warmest spots like Wenatchee, Moses Lake, Omak, and Lewiston near
90 for Memorial Day and Tuesday. JW

&&

.AVIATION...
00Z TAFs: The passage of a dry cold front this evening will 
produce a sharp increase in west winds for the Inland Northwest. 
The timing and strength of the winds will be the biggest challenge
for the TAFs. It is often difficult for strong and gusty winds to
persist all night long, but tonight's cold front is particularly 
strong. The strongest gusts will likely occur at the Wenatchee and
Chelan airports (up to 35kts from 01Z to 08Z) with the 
contribution of gap winds accelerating through the Wenatchee 
Valley and down Lake Chelan. Further east, places like Spokane, 
Coeur d'Alene, Pullman, and Lewiston will experience the tightest 
pressure gradient and strongest 850mb winds btwn 05Z and 12Z 
which is the toughest time for efficient low level mixing.
Breezy westerly winds will continue through the day Wednesday at
all TAF locations.


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        49  62  46  67  47  71 /   0  10  10  20  20  10 
Coeur d'Alene  49  62  44  66  44  70 /   0  10  10  30  30  20 
Pullman        49  62  44  64  43  69 /   0   0  10  20  20  10 
Lewiston       54  68  48  70  48  75 /   0   0  10  20  20  10 
Colville       49  64  45  68  46  74 /   0  10   0  40  20  10 
Sandpoint      48  62  40  64  41  69 /   0  20  10  30  30  20 
Kellogg        45  59  41  63  41  68 /  10  10  10  20  30  20 
Moses Lake     55  71  48  74  49  79 /   0   0  10  10  10   0 
Wenatchee      55  68  49  74  51  79 /   0   0  10  20  10   0 
Omak           51  70  49  74  49  79 /   0   0  10  20  10   0 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Wind Advisory from 9 PM this evening to 3 AM PDT Wednesday for 
     Moses Lake Area-Waterville Plateau-Wenatchee Area. 

&&

$$

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

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