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

Western Washington


526 
FXUS66 KSEW 200410
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
910 PM PDT Sat Aug 19 2017

.SYNOPSIS...Light onshore flow will give some areas of low clouds in 
the late night and morning hours through Monday. The areas of night 
and morning low clouds and fog should mainly on the coast and near 
the water. High pressure will shift over the region Monday and 
Tuesday for warmer temperatures. A trough will bring cooler weather 
and a chance of showers late Wednesday and Thursday. High pressure 
will build over the area again toward the end of the week.

&&

.SHORT TERM...A few areas of low clouds should form along the 
coast late tonight and there might be a few patches inland. Light 
northwesterly onshore flow will give another nice day on Sunday 
with highs into the 70s across much of the interior. Upper ridging 
amplifies just offshore Sunday night then progresses eastward across
the region Monday and into Western Montana Tuesday afternoon. This
ridge will give sunny weather except for shallow morning low clouds
and fog--but mainly for the coast and over the waters. Around Puget
Sound and up through the inland waters fog or low clouds should burn
off over land pretty quickly but could linger through mid morning
over the water.

.LONG TERM...Onshore flow later Tuesday will usher in a marine
push Tuesday afternoon and evening that will result in increased
clouds. The push will be followed by a frontal system that will 
move across the area Wednesday night and a rather deep upper level
trough Thursday through Thursday night. Long term models appear to
be converging on a solution (between the GFS and ECMWF) where 
there will be a threat of showers Wednesday afternoon through 
Thursday evening. Thursday high temperatures will likely not reach
the 70 degree mark across most of the area with the clouds, some 
showers, and the cooler air mass. Snow levels are expected to fall
to 6000 to 7000 feet in the North Cascades Thursday or Thursday 
night, and may impact campers and backpackers at higher 
elevations.

As high pressure builds into southeastern British Columbia Friday
through the weekend, offshore flow will give a good warming and
drying trend. Albrecht

&&

.AVIATION...Northwest flow aloft over Western Washington tonight 
and Sunday as an upper ridge remains over the offshore waters. At
the surface, onshore flow will continue with high pressure 
offshore and lower pressure east of the Cascades. 

Just some high clouds over most of the area through Sunday.
Shallow marine layer along the coast with mvfr ceilings 
developing for a few hours Sunday morning. 

KSEA...Just some high clouds at times through Sunday. North
northeast wind 5 to 10 kt backing to northwest again midday Sunday.
Felton

&&

.MARINE...A typical August pattern will prevail through the
middle of next week. Expect onshore flow of varying strength to 
persist due to high pressure offshore and lower pressure east of 
the Cascades. A weak system will approach the coastal waters on 
Wednesday and move inland Thursday. Small craft advisory west
winds are likely in the central and eastern Strait of Juan de 
Fuca in the evening and early morning hours each night. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 AM PDT Sunday for Central U.S. 
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters 
     Strait Of Juan De Fuca.

&&

$$

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


023 
FXUS66 KPQR 200401
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
859 PM PDT Sat Aug 19 2017

.SYNOPSIS...Weak onshore flow continues through Sunday, particularly
along the Columbia River and the north part of our forecast area. One
last very weak upper disturbance will pass through Sunday afternoon
and night, and maintain the onshore flow before an upper ridge builds
in on Monday and continues Tuesday for warmer temperatures. Low
clouds will mainly be along the south Washington and north Oregon
coast Monday morning and locally inland along the Columbia River. The
upper ridge will reduce the onshore flow for Tuesday. A significant
upper trough will approach Wednesday with increased onshore flow and
a bit of cooling, then some chance of showers Wednesday night and
Thursday. Another upper ridge starts to build by the weekend for
drying and warming.
&&

.SHORT TERM...Tonight through Tuesday...The evening models have come
in without any surprises. Still tracking a very weak short wave
passage Sunday afternoon/early evening, which will keep the modest
onshore flow going through Sunday night. By Monday morning, the
Pacific ridge axis noses northeast to NW Oregon/SW Washington
coastline. Surface winds remain generally onshore, but above 925 mb
winds turning north/northeast by early morning. Current forecast
grids call for shallow stratus SW Washington and along the lower 
Columbia River and appear right on track. Could see scattered areas 
of thin stratus Cascade foothills along the northern Willamette 
Valley, but nothing too substantial. High confidence continues that 
the path of total eclipse east of the the coast will be clear. Flow 
also turns offshore along central Coast Monday morning, so middle-
range confidence of partly-to-mostly clear skies there. The next two 
afternoons should bring plenty of sunshine again, with slightly 
above normal temperatures. The remainder of the forecast discussion 
is unchanged. DRB

The modest upper ridge will continue over the Pacific Northwest on
Tuesday. The models show some morning low clouds along the coast
Tuesday morning but that coverage inland will be sparse at best.
Temps will again approach 90 inland on Tuesday. 

A weak low develops over northern California early in the week and
there is a slight chance of a thunderstorm getting close to
Willamette Pass late Tuesday, though they mainly may end up being in
central Oregon. Tolleson

.LONG TERM...Tuesday night through Saturday...A decent late summer
system will approach Wednesday with increasing southwest flow aloft,
possibly increasing the onshore flow some with a bit of cooling.
There is again a slight chance of thunder near Willamette Pass late
Wednesday but the most likely scenario is that most will stay south
and east of our area. The approaching system moves through Wednesday
night and Thursday with plenty of clouds and some chance of showers.
Some lingering onshore flow will give way to more sunshine on Friday
as conditions begin to improve in the wake of the Thursday system.
Saturday is looking sunny and mild with perhaps a little fog or low
clouds at the coast. Tolleson
&&

.AVIATION...Delayed onset of stratus at KAST as waters remain
mostly clear at this time with no indication of coastal stratus
development yet. Otherwise, forecast seems on track with stratus
possibly extending as far inland as KPDX before quickly mixing
out in the morning. Gusty winds at several TAF sites this evening
will taper off in the next few hours. 

KPDX AND APPROACHES...VFR conditions tonight with breezing
conditions this evening tapering off by 05Z. Stratus expected to
reach the terminal for a few hours in the morning before clear
skies arrive for the remainder of the day. /Bentley

&&

.MARINE...A persistent weather pattern will result in little 
change in the marine weather the next several days. High pressure
holds over the NE Pacific while a thermal trough is along the 
south Oregon coast. This supports north winds across the south 
Washington and north Oregon waters. The thermal trough 
strengthens each afternoon such that the north winds will 
increase and become gusty each afternoon. The winds south of 
Cascade Head will have frequent gusts to around 25 kt which 
supports the current small craft advisory for winds.

The seas will be locally generated from these winds and generally 
remain 4 to 6 ft with periods at 9 to 10 seconds. The seas will 
be choppier in the southern waters for the afternoons with 
dominant periods possibly around 8 seconds. ~TJ/Bentley

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 11 PM PDT Monday for 
     Coastal Waters from Cascade Head OR 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 
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


502 
FXUS66 KPDT 200307
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
808 PM PDT Sat Aug 19 2017

.UPDATE...High pressure will be over the area the next several days.
A weak wave will move across the area Sunday with some mostly high 
clouds across the northern forecast area. These clouds will exit the 
area in time for the eclipse. At 10 am Monday temperatures in 
central Oregon should be in the lower 70s with light winds under 
clear skies. For tonight expect just a few thin cirrus and 
diminishing winds. Lows will be in the 50s with mostly 40s in the 
mountains. The current forecast is on track and no significant 
changes are needed for the text or gridded forecast this evening.
78 

&&

.AVIATION...06Z TAFS...VFR conditions with just a few high clouds 
will persist through the forecast period. Smoke from local fires in 
central Oregon has relaxed a bit so significant impacts are not 
expected at KBDN and KRDM. Winds will be light and terrain driven. 78

&&

.PREV DISCUSSION... /issued 400 PM PDT Sat Aug 19 2017/ 

SHORT TERM...Tonight through Monday night...A flat westerly flow 
will continue through Sunday and then a ridge will begin to amplify 
over the region on Monday. A shortwave passing to the north will 
spread some high clouds over the area on Sunday but then skies clear 
Sunday night and remain clear for the solar eclipse Monday. 
Temperatures will remain nearly persistent Sunday but then warm 
slightly Monday due to the building ridge. Overall winds will remain 
light with some locally breezy conditions along the east slopes of 
the Cascades in the late afternoon and evenings. 

LONG TERM...Tuesday through Thursday night...Mid/upper level ridge 
of high pressure remains over the region Tuesday for dry conditions.
High temps Tuesday for lowlands will be in the mid to upper 90s and 
in the mid 70s to upper 80s in mountains. Tuesday night the ridge 
axis moves into Idaho thus allowing winds aloft to back to the 
southwest while a low pressure system in California starts moving 
northward toward Oregon. On Wednesday a longwave trough in the Gulf 
of Alaska digs south and captures the low south of the CWA thereby 
transporting moisture and some instability into central Oregon 
overnight and then into the mountains of NE Oregon after daybreak on 
Wednesday. This sets the stage for a chance of showers and a slight 
chance of afternoon/evening thunderstorms Wednesday in central and 
NE Oregon with a chance of showers and a slight chance of nocturnal 
thunderstorms in the Blue Mountains continuing through overnight and 
daybreak to midday Thursday morning. The aforementioned longwave 
trough in the NE Pacific pushes a cold front toward the coast 
Wednesday night and then sweeps the cold front through the forecast 
area during the day on Thursday for cooler high temperatures in the 
upper 70s to mid 80s and upper 60s to lower 80s mountains. Tight 
pressure gradients associated with the cold front will produce 
breezy to windy conditions on Thursday with patchy blowing dust in 
the Lower Columbia Basin. The Cold front exits the region Thursday 
evening with decreasing winds overnight and dry conditions.  Polan

Friday through Sunday morning...Models are in reasonable agreement 
on a trend of gradually increasing heights as an area of low 
pressure continues to move eastward across the Canadian Prairies. 
High temperatures will rebound from the upper 70s to lower 80s on 
Friday to the upper 80s to lower 90s by Saturday. Winds will be 
light with no significant cloud cover expected. 74

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  58  84  53  87 /   0   0   0   0 
ALW  61  85  58  90 /   0   0   0   0 
PSC  56  88  56  91 /   0   0   0   0 
YKM  58  87  56  91 /   0   0   0   0 
HRI  59  87  55  90 /   0   0   0   0 
ELN  59  84  54  89 /   0   0   0   0 
RDM  46  84  46  88 /   0   0   0   0 
LGD  51  82  47  86 /   0   0   0   0 
GCD  52  84  51  87 /   0   0   0   0 
DLS  63  86  62  90 /   0   0   0   0 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

78/78

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

Northeastern Washington and Northern Idaho


102 
FXUS66 KOTX 200537
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1037 PM PDT Sat Aug 19 2017

.SYNOPSIS...
Our weather for rest of the weekend will feature dry weather and
seasonably warm temperatures. Skies are expected to be mostly
clear on Monday for the eclipse however there may be some smoke in
the northern valleys. Tuesday and Wednesday will be quite warm 
with afternoon temperatures in the 90s. A vigorous cold front on 
Wednesday night will have the potential to produce thunderstorms, 
with strong winds expected on Thursday.


&&

.DISCUSSION...
Evening update to adjust overnight low slightly, mainly for the
mountains. Also adjusted Sunday's high temperatures for NE WA and
N ID where smoke will be most prevalent. Smoke modeling combined
with the idea of a weak wave passing through the NW flow aloft
will bring some improvement but looks to be late afternoon which
should keep temperatures within 1-2 degrees of Saturday's 
readings while most other locations will be on the order of 3-5
degrees warmer.  /sb

&&

.AVIATION...
06Z TAFS: Main aviation concern will be smoke settling into the
valleys of NE WA and N ID with the overnight inversions. KCOE
brielfy went to 4SM but looks to be improving with winds switching
toward more SE. Overall, confidence remains low for restrictions
at the main terminals but is likely for Colville, Deer Park,
Bonners Ferry, and Sandpoint. Otherwise...expect generally light 
winds with afternoon gusts around 15 mph. /sb


&&

.FIRE WEATHER...
A strong cold front will move through the region Wednesday night.
Ahead of the front, thunderstorms will affect the Panhandle and
extreme eastern WA Wednesday night. Confidence isn't high of any
wetting rains from these storms, and the shower activity will
probably not be widespread.

Thursday will be a windy day. Wind gusts to 30 mph are possible
across the Basin. Despite the 10 degrees of cooling, relative
humidities will remain very low for continued fire danger.  RJ

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        55  81  57  86  60  91 /   0   0   0   0   0   0 
Coeur d'Alene  52  81  53  86  55  91 /   0   0   0   0   0   0 
Pullman        51  79  52  86  54  91 /   0   0   0   0   0   0 
Lewiston       58  87  60  92  62  97 /   0   0   0   0   0   0 
Colville       50  82  51  88  52  92 /   0   0   0   0   0   0 
Sandpoint      45  81  46  86  48  90 /   0   0   0   0   0   0 
Kellogg        49  77  50  84  53  90 /   0   0   0   0   0   0 
Moses Lake     53  86  55  90  57  95 /   0   0   0   0   0   0 
Wenatchee      60  86  62  90  64  94 /   0   0   0   0   0   0 
Omak           57  86  59  92  60  95 /   0   0   0   0   0   0 

&&

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

$$

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