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Western Washington

FXUS66 KSEW 260246

Area Forecast Discussion
National Weather Service Seattle WA
746 PM PDT SUN SEP 25 2016

.SYNOPSIS...A strong upper ridge will move across the area Monday
for a warm and mainly sunny day. A weak cold front will bring a
chance of light precipitation Monday night and Tuesday morning.
Expect partly to mostly sunny days Tuesday afternoon through
Thursday with dry southwest flow aloft. Then an an upper trough
will bring cool showery weather Friday through next weekend.


.SHORT TERM...A strong upper ridge build over the region last
night and today, with 500 mb heights over Western Washington
rising to around 5900 meters. Highs today were mainly in the 70s
with sunny skies and offshore low level flow. 

The upper ridge will move east of the Cascades tonight and into
the northern Rocky Mountains Monday. The air mass will warm
further tomorrow as the thermal trough moves across Western
Washington, and highs across the interior lowlands should be in
the mid 70s to lower 80s. If there's a fly in the ointment it's
that the latest model runs show the weak cold front upstream of
the upper ridge approaching more quickly than previous runs. There
is already some cirrus over the forecast area, and it could
increase Monday. It's even possible that some light precipitation
will reach the northwest corner of the forecast area Monday

The cold front and its upper trough will move through Western
Washington Monday night and Tuesday morning. The main threat of
precipitation will be in the north Monday night, and then in a
weak Puget Sound convergence zone and along the west slopes of the
mountains Tuesday. Any precipitation amounts should be light.
Tuesday should become partly sunny during the day as the threat of
showers decreases. Highs will be back into the 60s to lower 70s.

Relatively dry southwest flow aloft will prevail Tuesday night
and Wednesday as an upper trough begins to amplify well offshore
near 137W. Wednesday should be mostly sunny with highs again in
the 60s to lower 70s. McDonnal

.LONG TERM...Here is the long term section from the afternoon
forecast discussion -- Deep troughing around 135W late Wednesday will shift
slowly east through the period, finally moving across Western
Washington On Sunday. Long term models bring rain chances into the
area late Thursday night into Friday morning. Showers are likely
across much of the area next weekend. Snow levels will lower to
around 6000 feet on Friday and 5000 feet Saturday and Sunday.
Higher mountain passes like those on the North Cascades highway,
may see some snow next weekend. Albrecht


.AVIATION...An upper ridge and surface high pressure will shift
inland through Monday. Offshore flow will keep late night and
morning fog limited to the sheltered valleys around daybreak. A
cold front will reach the area Monday night. 

KSEA...Some cirrus at times, a northerly breeze, patchy valley fog
may form around daybreak Monday bit that will not effect Sea Tac.


.MARINE...Northerly flow will turn westerly Monday afternoon and 
strengthen Mon night as a cold front moves through Western WA. This
could result in gale force westerlies over the central and eastern
portion of the Strait of Juan de Fuca where a Gale Watch is in
effect. Onshore westerly flow will turn more northerly and decrease 


.SEW Watches/Warnings/Advisories...
PZ...Gale Watch from Monday evening through late Monday night for 
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance 
     U.S. Waters Strait Of Juan De Fuca.




You can see an illustrated version of this discussion at

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Southwestern Washington and Western Oregon

FXUS66 KPQR 260418

Area Forecast Discussion
National Weather Service Portland Oregon 
917 PM PDT Sun Sep 25 2016

.SYNOPSIS...A strong early autumn upper ridge over the northeast
Pacific and the Pacific Northwest today will slowly move eastward
tonight and Monday, continuing to produce mild and dry weather over
southwest Washington and northwest Oregon through Monday. A weak
front will brush the forecast area Monday night and Tuesday for more
clouds, onshore flow, and spotty light precipitation mainly near the
coast. The forecast area will be in between systems during the mid
week period. The next low is expected to affect the area later in the
week and on next weekend.

.SHORT TERM...(Tonight through Wednesday)...No changes. Previous
discussion follows...A strong upper level ridge over the Pacific
Northwest today will slowly move eastward tonight and Monday. The net
result will be plenty of sunshine during the days through Monday.
Tonight will be mostly clear, Monday will be warm again with temps 10
degrees or possibly more above normal especially inland, and just
some patchy late night and morning fog tonight and Monday morning. 

We have been seeing light offshore flow today under the upper ridge.
The models show a surface thermal trough building along the coast
tonight that will lead to some very modest east wind through the
Gorge late tonight and for a while on Monday. This should lead to
Monday being the warmest of the week.

After that, things change as a weak system approaches and moves onto
the coast Monday night and onshore early Tuesday. This will cause
clouds to increase along the coast Monday night and Tuesday with a
little drizzle or light rain, and for clouds to spread inland late
Monday night and especially Tuesday morning. Could see some patchy
drizzle inland around the Columbia River Tuesday morning. The onshore
flow should drop temperatures back to around normal on Tuesday. The
models indicate the clouds should break up some Tuesday afternoon,
with afternoon highs closer to seasonal normals, that is in the lower
to mid 70s.

Clouds continue to break up Tuesday night and Wednesday as we are in
between systems. Southwest flow aloft should keep some marine layer
going along the coast for at least some night and morning fog or low
clouds. Inland looks as though any morning clouds or fog will be
patchier with a decent amount of sunshine during the day. Temps
should be a little above normal. Tolleson

.LONG TERM...(Wednesday night through Sunday)...Onshore flow will
persist for the middle of the week, maintaining temperatures at to
slightly below seasonal normals. Clouds increase over the region
Friday with a upper level trough sliding south over the far
northeastern Pacific late Thursday and Friday. Several impulses
rotating around the upper low will bring a few rounds of
precipitation late Friday through Sunday. Slight timing differences
remain in the forecast model depictions of the impulses, so have
continued the period of generally higher PoPs late Friday through
the weekend, though it remains possible that there might be a short
period of a break in precipitation at some point over the weekend.
The upper low eventually pushes onshore into the Pacific Northwest
later Sunday before moving into the Great Basin. As a result,
temperatures look to be well below normal - only reaching the lower
60s inland - next weekend. With the colder air mass in place, snow
levels should lower to around 5,500 feet by Sunday, low enough to
bring some snow to the higher elevations of the Cascades.  Cullen

.AVIATION...VFR conditions with dry n-ne winds tonight through
Monday morning. Do not expect much fog to develop late tonight. Any
fog that does form will be shallow and clear quickly Mon morning.
Winds will become more onshore Monday afternoon and evening with
marine stratus returning Monday night.

KPDX AND APPROACHES...VFR conditions with light winds through
Monday morning. expected the next 24 hours. Northerly winds will
become light overnight. East winds near the Gorge should prevent
fog/low stratus development Mon morning. /64


.MARINE...The thermal trough is weakening over the waters
allowing north winds to ease a bit. North gusts have eased below
25 kt, and have cancelled the small craft advisory for winds. The
thermal trough will continue to weaken Monday and move inland
Monday afternoon and evening for northwest winds and high pressure
over the coastal waters. High pressure strengthens Tuesday and
north winds will likely increase to around 25 kt. Wind driven seas
will increase Tuesday and boost seas to around 8 ft. Otherwise the
seas will be 5 to 6 ft. TJ




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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.

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Southeastern Washington and Northeastern Oregon

FXUS66 KPDT 260338

Area Forecast Discussion
National Weather Service Pendleton OR
838 PM PDT SUN SEP 25 2016

.SHORT TERM...Tonight through Wednesday...Warming trend certainly
taking hold. 03z temperatures are 7-12 degrees warmer than last
night at this time. Current overnight forecast looks good.  Only
change was to make a slight increase in clouds over Washington as IR
satellite shows mid and high level clouds moving across the area. 

00z NAM continues trend of past few days and in good agreement with
12z and 18z EC/GFS/NAM with ridge decreasing amplitude on Monday and
a west to southwest flow aloft taking over for Tuesday and
Wednesday. Monday will be 15 degrees above normal and temperatures
will be slightly cooler though still 5 to 10 degrees above normal
for Tuesday and Wednesday. The cooler air will manifest in breezy
west winds in the Columbia Gorge and Kittitas Valley on Tuesday.
Otherwise, impacts should be minimal. 


.AVIATION...06z TAFS. High pressure ridge continuing. VFR to prevail
with SKC or SCT 15-20K and light diurnal wind pattern. 


.PREV DISCUSSION... /issued 433 PM PDT SUN SEP 25 2016/ 

SHORT TERM...Tonight through Wednesday. Other than some high level
clouds...high pressure will dominate the areas weather with dry
conditions and above normal temperatures into the beginning of the
week. Temperatures will climb into the 80s and some locations could
approach 90 degrees on Monday. Meanwhile a weak disturbance will
push across the region Tuesday which may lower afternoon temps
several degrees. Also the cascade crest could experience an isolated
shower while breezy northwest winds are possible in the kittitas
valley. The high pressure shifts east Wednesday but the dry
conditions and above normal temps are expected to continue into the
middle of the week. 

LONG TERM...Wednesday night through Sunday...An amplifying
mid/upper level longwave trough will be located between 130-140W
Wednesday night with forecast area on the eastern flank of the
trough, which brings a SW flow aloft that transports clouds into the
region, but not dynamic lift, so region will remain dry while the
trough slowly approaches the coast on Thursday. By Thursday
afternoon flow aloft east of the Cascades backs to the south
bringing increasing moisture and a slight chance of showers to
central and NE Oregon Thursday afternoon and evening and overnight
into Friday morning. During the day on Friday a strong shortwave
rounds the base of the offshore longwave trough and then moves
northeast across forecast area bringing strong dynamic lift and
elevated instability to central Oregon and the mountains of NE
Oregon and SE Washington for a chance of showers Friday afternoon
and evening. In addition, due to the elevated instability ahead of
the shortwave axis, I introduced a slight chance of thunderstorms
Friday afternoon and evening in Crook County, Grant County and the
eastern mountains of Oregon and SE Washington, including the
Foothills of the Blue Mountains in Oregon and Washington. Late
Friday night the shortwave exits the forecast area by moving into NE
Washington resulting in showers tapering off and ending by late
Friday evening in central and east central Oregon while a low chance
of orographic showers continues in the northern Blue Mountains
through Friday night and Saturday morning. Saturday afternoon and
Saturday night the forecast area will be dry due to sinking air
aloft immediately east of the Cascades. However, the east slopes of
the Cascades will still have a chance of slop over showers Saturday
night. Saturday night a strong mid/upper level low pressure system
dives southward just offshore, which transports increasing moisture
into forecast area for a chance of shower in central and NE Oregon.

Snow levels will lower to 5000-5500 ft Saturday night through Sunday
night along the east slopes of the Washington and Oregon Cascades as
well as in the eastern mountains of Oregon and the Blue Mountains in
SE Washington. Hikers and campers should be prepared for the
possibility of some snow above 5000 ft Saturday night through Sunday
night.  Polan

AVIATION...00Z TAFS...VFR conditions to prevail due to a building
mid/upper level ridge of high pressure over the Pacific Northwest.
FEW-SCT mid level clouds around 8000-15000 ft AGL for THE remainder
of this afternoon this evening will clear out by midnight with
clear skies continuing overnight through Monday afternoon.  Polan


PDT  53  85  56  80 /   0   0   0  10 
ALW  56  86  59  81 /   0   0   0  10 
PSC  49  88  53  85 /   0   0   0   0 
YKM  46  87  55  81 /   0   0   0   0 
HRI  48  87  51  83 /   0   0   0  10 
ELN  43  85  57  76 /   0   0   0   0 
RDM  43  89  44  81 /   0   0   0  10 
LGD  44  85  48  81 /   0   0   0   0 
GCD  45  87  49  83 /   0   0   0  10 
DLS  50  89  61  80 /   0   0   0   0 


.PDT Watches/Warnings/Advisories...



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Northeastern Washington and Northern Idaho

FXUS66 KOTX 260519

Area Forecast Discussion
National Weather Service Spokane WA
1019 PM PDT Sun Sep 25 2016

A mild and mostly dry weather pattern is expected through
Wednesday. Temperatures will be above average, with several days
of highs in the mid 70s to mid 80s. A pattern change is expected
to arrive late in the week with chances for showers beginning
Thursday and continuing into the weekend. By next Saturday and
Sunday, afternoon temperatures will likely be in the 60s.


Tonight through Monday night: High pressure will build into the
Inland Northwest with a return of late summer weather. Dry and
warmer weather can be expected under light easterly winds. May see
some sheltered spots radiate with some local chilly temperatures,
although no freezing temperatures are expected and may even see
some patchy valley fog. But overall, anticipate mostly clear skies
with some high clouds filtering through. Temperatures on Monday
will top out in the upper 70s to mid 80s, about 10 to 15 degrees
above normal. /rfox.

´╗┐Tuesday through Sunday: The Inland NW gradually becomes unsettled 
and eventually becomes cooler. This includes a shower risk and
maybe some thunderstorms, especially toward the week's end, and
occasionally breezy conditions. First Tuesday a weak cold front
pushes by. This will bring a shower threat to the Cascades and
perhaps near the Canadian border. The remainder of eastern
WA/north ID will see a band of clouds migrate by with the front
and maybe some sprinkles. Otherwise it looks dry. With and behind
the front expect increased winds. Some of the strongest winds are
expected near the Cascades and then down the Okanogan Valley
especially as the flow turns northerly and the air channels
through here. Speeds of 10-20 mph will be possible, with higher
gusts. There may be some elevated fire weather concerns near the
Cascades/Okanogan Valley too here but right now critical values
appears spotty. The northeast valleys and L-C Valley are apt to
remain more sheltered and see lighter winds. Between Tuesday night
and Thursday the front stalls and comes back north as the ridge
rebounds. This will largely result in variable clouds. Some shower
risk starts to develop around the mountains Wednesday night into
Thursday as a trough approaches. It will be accompanied by another
slight uptick in winds too.

Between Thursday night and Sunday the trough over the eastern
Pacific begins to move onshore, leading to the most unsettled part
of the forecast. Shortwaves rounding the trough will work with
deepening moisture and some instability to increase the shower
threat throughout the region. At this time the mountains have the
highest overall risk and the lee of the Cascades and deeper
Columbia Basin have the smallest risk. However some wet periods
are expected in the low lands; precise timing might need fine-
tuning but Friday appears to have the best risk for that. The
instability coming with this pattern change may lead to some
thunderstorms. Again forecast models point to Friday as having the
best overall risk, but some potential may linger near the Cascades
closer to the core of the trough into the weekend.

Snow levels between 9-12kft on Tuesday gradually drop to between
5-8kft by the weekend. The lowest of those will be toward the
Cascades near the trough core. So back-country/higher elevation
enthusiasts may have to watch for some snow there. Temperatures
are expected to slowly drop but remain above normal through
Thursday, holding in the mid 70s to lower 80s. Then Friday
temperatures drop back closer to normal, before dropping below
normal for the weekend. /J. Cote'


06Z TAFS: Clear skies and light terrain driven winds are expected
at the TAF sites through 06z Tuesday...except for high cirrus
around 30,000 feet AGL. JW


Spokane        50  82  55  79  51  77 /   0   0   0  10   0   0 
Coeur d'Alene  45  81  53  78  50  77 /   0   0   0  10   0   0 
Pullman        48  84  52  79  49  78 /   0   0   0  10   0   0 
Lewiston       52  88  56  84  56  82 /   0   0   0  10   0   0 
Colville       40  82  48  80  43  78 /   0   0   0  10   0   0 
Sandpoint      40  76  47  75  46  74 /   0   0   0  10   0   0 
Kellogg        44  79  49  76  49  77 /   0   0   0  10   0   0 
Moses Lake     45  84  52  82  48  79 /   0   0   0  10   0   0 
Wenatchee      53  82  59  79  50  78 /   0   0   0  10   0   0 
Omak           45  83  53  78  46  77 /   0   0   0  10   0   0 




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