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

Western Washington


512 
FXUS66 KSEW 221731
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
931 AM PST Wed Nov 22 2017

.SYNOPSIS...A relative break between wet weather systems will
occur today, although scattered showers will still be around. The
next wet frontal system will bring more rain to the area tonight
through Thanksgiving morning. Another relative break between 
weather systems, but with a little light rain still around, will 
occur Thursday afternoon through Friday. The next system to bring 
widespread light rain will arrive Saturday afternoon. This active 
weather pattern should continue into early next week. 

&&

.SHORT TERM...RADAR shows scattered areas of rain moving NE across
W WA this morning. The area will remain under moist SW flow aloft,
but between weather systems today. The air mass remains warm with
high temperatures expected to be around 60 today, despite cloudy
skies. This could set a couple of high temperature records for 
Nov 22. 

Yesterdays plume of sub-tropical moisture has weakened and shifted
S over Oregon. The next system expected tonight and Thursday
morning will develop out of the weak front offshore along roughly
132W at 9 AM. An upper level shortwave trough rounding the base of
the larger longwave trough along 140W, will move NE across the top
of the front tonight causing it to strengthen. Rain will reach the
coast this evening then spread inland overnight. The front should
be moving over the Cascades by late Thursday morning, then E of
the Cascades by later Thursday afternoon. Rain amounts should be 
less than what fell Tuesday - about 2-4 inches in the Olympics, 
1.5-3.5 inches in the Cascades and about a half to 1.5 inches in 
the lowlands. 

Scattered showers will be around Thursday afternoon and night as
the trailing upper level trough crosses the area. This system, 
coming in from the W, will bring a cooler air mass, allowing snow 
levels over the mountains to lower to around 4000 feet by Thursday
evening. 

A slow moving front will move SE down Vancouver island Thursday
evening then slow down to a crawl over southern Vancouver Island
Friday and Friday night. The front will be close enough to W WA to
bring a little light rain to the area, mainly the north part. Kam

.LONG TERM...Another large longwave trough will form along roughly
140W late Friday. The SW flow aloft downstream, aimed at W WA,
will strengthen, which will allow a shortwave embedded in the SW
flow to bring more widespread light rain to the area Saturday
afternoon through Sunday morning. Cascade snow levels will pop up
again to the 5000 to 7000 ft range late Saturday before dropping 
to around 4000 feet again behind the system Sunday. 

Recent runs of the GFS and ECMWF had been in fair agreement with
the trailing trough late Sunday, but have diverged a little this
morning. Regardless, it will remain an active pattern with some
rain or showers. The models are still hanging on to the warm front
that reaches the area Monday night. Kam

&&

.AVIATION...Moist southwest flow aloft will continue today and 
tonight. At the surface, southeasterly pressure gradients will 
continue. Strong south to southwest winds 35 to 50 kt will continue
at times between 3000 and 5000 feet. Rain at times will continue 
in the stable air mass.

Mostly VFR conditions today, though there are several cloud decks 
around and MVFR ceilings are likely in rain. There are some breaks 
in the clouds and under those there is patchy IFR fog. Conditions 
will change little today. More clouds and rain is forecast tonight, 
and this will probably bring widespread MVFR ceilings.

KSEA...VFR today, MVFR tonight. Light southerly winds today will 
increase to 8-12 kt tonight. CHB

&&

.MARINE...A frontal system will approach from the northwest this 
afternoon then move inland late tonight. Low end gale conditions are 
likely on the coast today into tonight, with small craft advisory 
strength winds over the inland waters. 

Southerly gradients will continue to be moderate to strong on 
Thursday, then they will ease on Friday. At least small craft 
advisory conditions are likely on Friday.

Another system will arrive around Saturday night. Strong southerly 
gradients are possible over the entire area Sunday. The preferred 
solutions would result in gales over most waters with small craft 
advisory conditions over Puget Sound and Hood Canal. CHB

&&

.HYDROLOGY...Many Western Washington rivers are above flood
stage this morning, and we may not be done yet - a few more are 
could still rise above flood stage today. Several rivers have gages 
registering moderate category flooding: the Skokomish, 
Stillaguamish, and Satsop Rivers. And the main stem Stillaguamish 
has reached major flood category.

Warnings and watches change as needed. For the current list, please 
check: www.wrh.noaa.gov/sew/get.php?pil=RVA&sid=SEW

Rainfall over Western Washington began decreasing late Tuesday 
evening, and the upper reaches of the rivers starting cresting 
overnight. The crests will be moving downstream today and tonight, 
but additional rain from the next front tonight and Thursday could 
push rivers higher with additional flood warnings necessary.

Precipitation from the Tuesday/Tuesday night system amounted to 
generally 2 to over 7 inches over the Olympic Mountains and 1.5 
to 5 inches over the Cascades, while the snow level was around 
9000 feet. There will be some rain at times today with the snow 
level around 7500 feet, but it will be - relatively speaking - a 
break between systems. The next front will move through tonight 
and Thanksgiving Day, with a forecast of generally 2 to 4 inches 
over the Olympics and 1.5 to 3.5 inches over the Cascades. The 
snow level will be around 7500 feet as this system arrives, 
falling to 4000 feet late Thursday as precipitation decreases.

With this second round of rainfall tonight and Thursday, there is a 
possibility that flooding will become more widespread and/or 
prolonged. Northwest River Forecast Center models show that flooding 
could develop on reaches of rivers such as the White, Nisqually, 
Dungeness and Nooksack. There is at least a minor threat that any 
flood-prone river in our area reaching flood stage.

In addition, there is a threat of landslides across the lowlands of 
Western Washington. The USGS landslide guidance shows soil wetness 
above the threshold of concern, and additional rain through Thursday 
will drive those numbers higher and act as the trigger for 
landslides. JBB/McDonnal

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch through Thursday afternoon for Admiralty Inlet Area-
     Bellevue and Vicinity-Cascades of Pierce and Lewis Counties-
     Cascades of Snohomish and King Counties-Cascades of Whatcom 
     and Skagit Counties-Central Coast-East Puget Sound Lowlands-
     Eastern Strait of Juan de Fuca-Everett and Vicinity-Hood 
     Canal Area-Lower Chehalis Valley Area-North Coast-Olympics-
     Seattle and Vicinity-Southwest Interior-Tacoma Area-Western 
     Skagit County-Western Strait of Juan De Fuca-Western 
     Whatcom County.

PZ...Small Craft Advisory for rough bar until 4 PM PST Thursday for 
     Grays Harbor Bar.

     Small Craft Advisory until 3 PM PST 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 until 2 AM PST Thursday for East Entrance 
     U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters 
     Including The San Juan Islands.

     Small Craft Advisory for hazardous seas until noon PST today for 
     West 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


144 
FXUS66 KPQR 221748
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
948 AM PST Wed Nov 22 2017

.SYNOPSIS...A series of fronts will continue periods of wet weather
into next week. Snow levels will remain above the Cascade passes
today and tonight. The snow levels will lower to near the Cascade
passes Thursday afternoon and night, but the precipitation will be
light. There is a better chance for snow to impact the passes on
Sunday. 

&&

.SHORT TERM...Today through Friday...A moist front is making its way
across NW Oregon this morning. A warm front associated with a low 
around 450 miles off of the Oregon coast will maintain rain across SW
Washington and the Oregon coast this afternoon and evening. This
front will slow down or stall the current front over the Oregon 
Cascades and foothills continuing rain there too. Otherwise, the
interior valleys including the Willamette Valley may see a brief
break in the rain late this afternoon through the early evening, but
do not expect much for cloud breaks.

It will be a seasonally mild day with high temperatures in the low
60s which is close to daily records for the lowlands.

The cold front will then come through tonight and Thursday for a wet
holiday in most areas. Precipitable water remains above an inch with
this front, and expect an additional 1 to 2 inches of rain for the
coast, coast range, and Cascades (north of Lane County) tonight
through Friday night with 0.5 to 0.75 inch for the interior valleys.
Snow levels will be above the Cascade passes through Thursday morning
then lower to near the Cascade passes behind the front Thursday
afternoon and night as the precipitation dwindles.   

A warm front passing by to the north may result in showers continuing
along the coast and SW Washington Friday morning, but precipitable
water values lower considerably (~0.5 inch) and the rain totals
should be fairly light. Areas away from the coast south of Salem will
be mostly dry late Friday morning into Saturday ~TJ  

.LONG TERM...No Changes. Previous discussion follows...Friday night
through Tuesday...The models say the next system spreads in with more
rain Saturday as snow levels rising well above the Cascade passes.  
Snow levels drop back near the passes in showers behind the front on
Sunday. A cool system moves through Sunday night and Monday with more
rain and mountain snow, followed by decreasing precipitation on
Tuesday. Basically the unsettled weather pattern will continue.
Tolleson

&&

.AVIATION...Mostly VFR inland today with a mix of VFR and MVFR
along the coast. Cold front offshore will slowly push towards our
area today, with rain gradually increasing later today into this
evening. Front will push predominantly MVFR cigs into the region
tonight, and will increase southerly winds at terminals along the
coast around midnight tonight and inland Thursday morning.

KPDX AND APPROACHES...Predominantly VFR through this evening,
with easterly winds 8 to 15 kt. Rain increasing this evening,
with cigs lowering to MVFR this evening around 03-06Z. -McCoy

&&

.MARINE...No changes. Previous discussion follows...
Rather extensive pressure gradient across the coastal waters, 
enough to maintain gusts 25 to 35 kt today, with stronger winds 
stay well offshore. Cold front will slowly push across the 
coastal waters tonight. This will bring the stronger gusts closer
to shore tonight. Will extend Gale Warning for all of the 
coastal waters today through tonight. Southerly winds will be 
just below gale force this am, winds will pick up again this 
afternoon as the front draws nearer. 

Seas generally 12 to 17 ft, but again, the higher seas will be
over the outer waters where the stronger winds reside. 

Brief break in the weather for Thu and Fri, with winds generally
15 to 20 kt, and seas relaxing back to near 10 ft. But, another
strong front will bring southerly gales and higher seas again on
Sat into Sun.					    Rockey. 

&&

.HYDROLOGY...The heavier rain over the S WA coastal mountains last
night resulted in the Grays River rising above flood stage. The rain
has eased this morning, and the river level has peaked. However,
additional moderate rain over the Willapa hills expected later today
and tonight will likely keep the river above flood level through
Thursday morning. ~TJ 

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Gale Warning until 6 AM PST Thursday for Coastal Waters from 
     Cape Shoalwater WA to Florence OR out 60 NM.

     Small Craft Advisory for Rough Columbia River Bar until 
     midnight PST tonight.

&&
$$

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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 CWA, or forecast area.

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

Southeastern Washington and Northeastern Oregon


425 
FXUS66 KPDT 221801 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
1000 AM PST Wed Nov 22 2017

Updated AVIATION Discussion

.UPDATE...A subtropical moisture plume along the back side of an 
upper level ridge will be over the area for the next several days. 
This will keep unsettled weather with a chance for rain/rain showers 
in the forecast. A weak wave is moving east of the region this 
morning so shower activity this afternoon should be mostly 
scattered. It will be warm today with highs in the 50s to lower 60s. 
A cold front will move across the region on Thanksgiving Day with 
the main threat from this system being gusty sw-w winds. As of now 
it looks like winds will be borderline for advisories but this will 
be evaluated for the afternoon forecast package. 78 

&&

.AVIATION...1Z TAFs...Mainly VFR conditions during next 24 hours, 
except when bands of -RA move over TAF sites, which may yield 
temporary periods of MVFR due to low cigs and visibility in fog, low 
stratus and -RA. VFR conditions will occur Thursday morning due to 
some drying taking place. Winds will be 5-10kt.  Polan 

&&

.PREVIOUS DISCUSSION... /issued 228 AM PST Wed Nov 22 2017/ 

SHORT TERM...Today through Friday Night...Widespread rain
continues to move east across the eastern OR mountains early
this morning in association with a weak shortwave in moist
SW flow aloft. Further to the west, precip is more scattered
in coverage, with little/no precip for the lowest elevations.
Patches of light fog cannot be ruled out in areas of lighter
precip coverage through the morning, but intensity of the fog
not sufficient for inclusion in the forecast. Rain will gradually
decrease in coverage for most areas by this afternoon as the
greatest forcing exits to the east. However, will keep low end
PoPs for the lowlands, and high end chance to likely PoPs for
the mountains as moist SW flow continues. Very warm conditions
exist aloft and with better deep layer mixing than yesterday,
expect today's highs very warm for late November, with upper 50s 
to lower 60s for the lower elevations and mainly 50s for the
maintains. Rain coverage will remain fairly low for most areas
tonight with a cold front still well off to the west. Will use
slight chance to chance PoPs for all but the east slopes of the
Cascades where likely and higher PoPs will prevail. Very mild
low temperatures can be expected tonight, with upper 40s to lower
50s for the lower elevations.

Thanksgiving Day/Thursday Night...The next cold front will
approach the Cascade crest in the morning, crossing the majority
of eastern OR/WA during the afternoon, then exiting Thursday
Night. With ample deep layer moisture, expect widespread rain
for the higher elevations in the afternoon/evening, with chance
to likely PoPs for the lower elevations/foothills. The other
forecast concern is the wind. Surface pressure gradients tighten
behind the front. In addition, winds at 5000-10000 feet reach
50-60 knots early Thursday evening. With a sufficiently thick
mixed layer, some of these high winds could work down toward
the surface. Will have to monitor the situation closely for a
possible wind advisory for the Columbia Basin down to the
Deschutes Plateau, but will keep winds just under criteria for
now. With a mainly afternoon frontal passage, another warm day 
is expected, with highs in the lower/mid 60s for the lowlands. 
Cooler air will work into the area Thursday Night, with lows in
the 30s for the lowlands and mid 20s to lower 30s mountains. Snow
levels of 8000-10000 feet Thanksgiving Day will fall to 4000-6000
feet Thursday Night, so expect precip to remain rain for all
passes.

Friday/Friday Night...Rather quiet conditions can be expected, as
the cold front is well to the southeast, and the next system is
progged to be offshore. Expect cooler temperatures than on
Thanksgiving Day, but remaining seasonably mild for late November.

LONG TERM...Saturday through Wednesday...The unsettled weather 
pattern will persist into the extended forecast period. There will 
be warm and cold frontal systems moving across the forecast area 
every couple of days. Models are in fairly good agreement with an 
upper ridge over the region, just east of the CWA, which puts the 
CWA on the warm southwest flow side of the ridge. An atmospheric 
river off the Pacific will continue to feed moisture up and over 
this ridge every couple of days resulting in periods of rain. Snow 
levels will be quite high through about Sunday with levels between 
6000-8000 feet MSL. There will be no winter weather concerns during 
this time period due to the high snow levels. Then on Monday a cold 
front will cause snow levels to drop to about 5000-6000 feet on 
Monday, and then further dropping to around 3500 feet by Tuesday 
with another cold front. Then snow levels rise back up to between 
5000-6000 feet again by Wednesday. These combined with mild 850 mb 
temperatures will keep conditions warmer than normal for late 
November. No real drying is expected through the entire extended 
forecast period...though it will become drier on Tuesday and 
Wednesday with precipitation by then mainly just in the mountains. 
Winds will be breezy to locally windy at times during frontal 
passages, especially on ridge tops, otherwise they will be fairly 
light.

HYDROLOGY...Abundant rainfall across the east slopes of the WA
Cascades will lead to rising levels on area streams and rivers. 
The main concern will be in the Yakima River basin, mainly along 
the Naches River. The Naches River at the Cliffdell and Naches 
gauges are forecast to rise above bankfull tonight, peaking
Thursday evening. Have issued river statements for these two
locations. At this point it does not appear that the Naches will 
reach flood stage, but the situation will continue to be monitored.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  62  51  63  38 /  40  20  70  40 
ALW  63  53  65  41 /  60  30  70  40 
PSC  58  48  65  40 /  40  30  30  10 
YKM  55  41  58  35 /  40  30  40  20 
HRI  59  47  63  38 /  40  20  50  20 
ELN  52  39  56  33 /  40  40  30  20 
RDM  63  47  61  31 /  20  20  40  30 
LGD  58  50  60  38 /  90  30  60  60 
GCD  59  50  61  37 /  60  20  30  60 
DLS  57  48  61  40 /  50  40  60  40 

&&

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

$$

78

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

Northeastern Washington and Northern Idaho


575 
FXUS66 KOTX 221238
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
438 AM PST Wed Nov 22 2017

.SYNOPSIS...
Wet and mild weather will linger through the week as a series of 
storm systems brings several rounds of precipitation to the Inland
NW. Snow levels will be quite high through Thursday allowing 
motorists to travel over mountain passes on wet pavement. Snow 
levels will begin to lower just as travelers are heading home 
over the weekend. Windy conditions are expected Thursday across 
the exposed areas of the basin and into the Spokane Area and 
Palouse.


&&

.DISCUSSION...
Today through Friday morning...The warm front responsible for
the precipitation today has shifted to the eastern zones 
overnight as the ridge axis amplifies and shifts east. Winds at 
the mid levels have turned southwest-west this evening and this 
combination is resulting in a break in the rain from the lower 
east slopes east to about the WA/ID line that will last into this 
afternoon. The upper level low currently in the eastern Pacific 
will begin to move towards the coast today. This will shift the 
ridge axis to the east and allow the the warm front to sag back to
the south for another period of stratiform precipitation, mainly 
north of the basin this afternoon, but continuing to sag south 
tonight and Thursday. Model guidance is in pretty good agreement 
that the cold front will cross the Cascades Thursday afternoon 
with drying from the west through Thursday evening. Southwest 
winds wind be on the increase ahead and will peak Thursday 
afternoon and Thursday evening in the well mixed atmosphere behind
the front. We are expecting sustained winds 20-30 mph with gusts 
35-45 mph during this period. With all of the warm air advection 
temperatures are expected to be 12-16 degrees above normal today 
and Thursday.

* Impacts: For today...cooler temperatures up in the Methow valley
  have finally warmed up, and while there may be some pockets of
  light freezing rain it will not be widespread and accumulations
  will be light. As such, the Winter Weather Advisory has been
  allowed to expire. For the remainder of the forecast
  period...Warm temperatures and light to moderate rain even at 
  the higher elevations will result in good runoff and rising 
  streams and small rivers. At this time no flooding is expected. 
  The exception is Paradise Creek near Moscow Idaho which is very 
  reactive to moderate precipitation and snow melt. So far 
  Paradise Creek has reached action stage and that could happen 
  again the next few days. Lastly, the strong, gusty winds 
  mentioned above will result in tricky driving conditions for 
  high profile vehicles and likely some damage to tree branches 
  and possibly some downed power lines. A Wind Advisory will be 
  possible for late in the day Thursday. Tobin

Friday and Friday Night: This will be the driest period of the
week with winds weakening into Friday. Weaker winds with the 
potential for less mid to high level cloud cover will increase the
potential for fog Saturday morning. Another moist frontal system 
will be approaching at this time though, so fog chances will 
depend how fast that higher level cloud cover increases over the 
region. Best chances will be in the mountain valleys as the 
greater basin will see moisture mixing out of the boundary layer 
with the winds on Thanksgiving. After a mild Thanksgiving, 
temperatures will be cooler but still above season average.

Saturday through Tuesday: The forecast turns wet again over the
weekend. There are some slight timing difference between the 00Z 
ECMWF and GFS solutions with when a warm front will push up across
the area on Saturday. The timing difference isn't that 
substantial and precip is expected to start up from the afternoon 
into the evening over much of the region. The the cold front will 
push across on Sunday and looks to stall across the southeast 
portion of the region. Snow levels through Sunday will remain high
with precip falling as valley rain and mountain snow. The 
potential for greater weather impacts will increase Sunday night 
into Monday. Both the 00Z GFS and ECMWF solutions show a dynamic 
upper level trough of lower pressure pushing in off the eastern 
Pacific during this time. Both also show that this trough may form
a closed circulation with a surface low tracking into eastern WA.
This is significant since it will allow moisture to wrap up 
around the northern mountain and into the east slopes of the 
northern Cascades as snow levels drop potentially down to valley 
floors. Mid level laps rates will also be steepening and we could 
see rain transitioning over to snow with periods of heavy snow 
possible. Confidence in these kinds of details is low, but it does
appear to be the best potential for snow impacts down below pass 
levels over the next seven days. /SVH


&&

.AVIATION...
12Z TAFS: Areas of light precipitation will track across the
region at times through the day. For this morning the main threat
for rain will be across southern zones, the Cascades, and the 
Panhandle mountains including KPUW/KLWS. VFR/MVFR conditions will 
likely deteriorate at times to IFR as fog/stratus develop in 
between precipitation. Otherwise the boundary layer is saturated 
and will promote fog/stratus development across the region. Winds
will transition from southeast to southwest through the morning 
and will promote VFR/MVFR and possibly lower conditons for the 
KGEG/KSFF/KCOE. KEAT/KMWH are in the deeper moisture and with 
less winds should see less mixing and should result in IFR/LIFR
through early afternoon, then expect conditions to improve.
Another round of widespread light to moderate rain is expected to
move into the region after 00z. Tobin


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        53  47  55  36  46  33 /  30  40  80  30   0  10 
Coeur d'Alene  53  46  55  35  45  32 /  60  50 100  40  10  10 
Pullman        57  47  57  37  48  36 /  70  50 100  60   0   0 
Lewiston       59  49  62  39  52  38 /  80  30  50  70   0   0 
Colville       46  40  53  33  45  32 /  40  60  70  20  10  10 
Sandpoint      47  41  51  34  42  31 /  70  70 100  40  20  10 
Kellogg        50  42  51  34  42  32 /  80  70 100  80  40   0 
Moses Lake     51  43  59  34  50  32 /  30  20  30  10   0   0 
Wenatchee      49  41  54  35  48  33 /  20  40  30  10  10  10 
Omak           48  41  54  34  45  33 /  20  40  50  10  10  10 

&&

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

&&

$$

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