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

Western Washington


871 
FXUS66 KSEW 101128
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
328 AM PST Mon Dec 10 2018

.SYNOPSIS...The weather pattern will be more active over the next
week as a series of fronts move through the area. The next one,
stronger than the front Sunday evening, will arrive on Tuesday. 
An upper trough and onshore flow will keep the weather cool and 
showery Tuesday night into Wednesday. Additional vigorous frontal
systems will affect the region through the rest of the week into 
next weekend.

&&

.SHORT TERM...An active weather pattern will bring periods of
heavy rain and mountain snow, gusty south winds and possible river
flooding this week (mainly the Skokomish). The first front pushed
through last night with 5-12 inches of new snow in the Cascades. 
We'll continue to see scattered showers across the region today as
the cool upper level trough crosses. 

A stronger and wetter Pacific frontal system will impact the area
tonight through Tuesday. This system will bring heavy snow to the
west slopes of the Cascades with 1-3 feet of new snow expected.
The orographics look better with this system due to strong 
westerly upslope flow combined with wet conditions. We'll also see
some gusty winds with this system, especially along the coast and
north interior with south winds 20-35 MPH with gusts to 45-50 MPH.
Heavy snow will continue to affect the Cascades through Tuesday
night as this system slowly exits. 

We'll see a brief break in the action on Wednesday, in between
systems. Then late Wednesday night and Thursday, another strong 
and wet Pacific system will arrive. Models are trending wetter 
with this system and advertising a period of heavy rain along the 
coast and in the Olympics. By then we may see river flooding on 
the Skokomish as it will be running high. The Cascades will see 
another round of possible heavy snow, especially during the 
morning as snow levels will remains low (around 3,000 feet). 33

.LONG TERM...Our active weather pattern will continue through the
end of the week with our third strong system arriving on Friday.
The main impact will be heavy mountain snow again as this system
will be cooler. We may see windy conditions along the coast and
north interior too. An upper level ridge will bring a lull on
Saturday. Then more rain and mountain snow on Sunday with an upper
level trough. Looking further ahead, the door remains open as
additional frontal systems roll through Western Washington. 33

&&

.AVIATION...Upper trough axis over the region this morning with 
westerly flow aloft. The air mass is moist and stable. Moderate 
northwest flow aloft developing later today as a weak shortwave 
ridge moves across the area. Widespread MVFR and pockets of IFR 
ceilings this morning will gradually lift toward midday becoming VFR 
this afternoon. High and mid level moisture associated with the next 
frontal system will begin to spread across the area late this 
afternoon and evening. MVFR ceilings in rain will develop along the 
coast around 08Z tonight and spread into the Puget Sound area around 
12Z Tuesday morning. Increasing low level east-southeast flow ahead 
of a warm front on Tuesday morning will lead to gusty surface winds 
especially coastal areas and the north interior of Western 
Washington.

KSEA...MVFR ceilings at times through 18Z...then lifting to VFR from 
early afternoon through this evening. Ceilings lowering again 
tonight ahead of a stronger frontal system...becoming MVFR by around 
12Z Tuesday in rain. Winds at 5000 feet will be SW near 50 knots by 
daybreak Tuesday. Surface winds southerly less than 10 knots through 
this evening...then shifting to SE and rising to 10 to 20 knots 
early Tuesday morning. 27

&&

.MARINE...A series of fronts will bring southerly gales as times 
to the Coastal Waters, entrances to the Strait, and Northern 
Inland waters. 

Today will be a relative lull in the active weather with the 
headline being for some 10 foot west swell over the Coastal 
Waters. 

Next front to reach the area will bring another round of gales 
tonight into early Tuesday afternoon. After a break on Wednesday
the next front will reach the area Wednesday night and Thursday 
with another round of gales likely in the usual spots. This system
is expected to hang up across the area into Friday with a surface
low eventually moving onshore. Models are in better agreement this
morning taking the low center to the north of the area Friday
which will result in another round of possible gales and at least
small craft advisory winds over most of the waters. Felton

&&

.HYDROLOGY...A series of fronts will cross the area over the next
week, bringing a period of rain roughly every other day. The 
cumulative effect could be enough to push the Skokomish river in 
Mason county to near flood stage by late this week. The best 
chance for flooding on the Skokomish is probably Thursday or 
Friday when a frontal system could hang up over the area. The
hanging up over the frontal system late in the week also brings 
up the possibility of flooding on other rivers flowing out of the 
Olympics.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 4 AM PST early this morning for 
     Cascades of Pierce and Lewis Counties-Cascades of Snohomish 
     and King Counties-Cascades of Whatcom and Skagit Counties.

     Winter Storm Watch from late tonight through late Tuesday night 
     for Cascades of Pierce and Lewis Counties-Cascades of 
     Snohomish and King Counties-Cascades of Whatcom and Skagit 
     Counties.

     Wind Advisory from midnight tonight to 1 PM PST Tuesday for 
     Admiralty Inlet Area-San Juan County-Western Skagit County-
     Western Whatcom County.

     Wind Advisory from midnight tonight to 10 AM PST Tuesday for 
     Central Coast-North Coast.

PZ...Small Craft Advisory for rough bar until 1 AM PST Tuesday for 
     Grays Harbor Bar.

     Small Craft Advisory until 1 AM PST Tuesday 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.

     Gale Warning from 1 AM to 1 PM PST Tuesday 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-East Entrance U.S. Waters Strait Of 
     Juan De Fuca-Northern Inland Waters Including The San Juan 
     Islands-West Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 1 AM to 1 PM PST Tuesday for Central 
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 1 AM to 6 PM PST Tuesday for Admiralty 
     Inlet-Puget Sound and Hood Canal.

&&

$$

www.weather.gov/seattle

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

Southwestern Washington and Western Oregon


458 
FXUS66 KPQR 101113
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
312 AM PST Mon Dec 10 2018

.SYNOPSIS...Showers will be mostly over the higher terrain today and
gradually decrease. Temperatures in the Gorge and Hood River Valley
will slowly moderate, and likely rise above freezing late this
morning. A warmer and wetter frontal system will bring additional
rain and mountain snow on Tuesday. The next front stalls over
Washington Wednesday and Thursday keeping most of NW Oregon dry. SW
Washington may see a prolonged wet period though with this 
stationary front. The front will finally move inland and across NW
Oregon on Friday. Wet weather is expected to continue for the weekend
and into next week.

&&

.SHORT TERM...Today through Thursday...Post-frontal showers will
decrease today. The east winds have been stubborn through the Gorge,
and the temperatures in the Hood River Valley and Central Columbia
Gorge are still below freezing. Radar shows the showers are more
orographic, and expect them to be less frequent in the valleys and
lower elevations than for the higher terrain. Any showers that make
it to the central Gorge and Upper Hood River Valley this morning will
likely be in the form of freezing rain, but accumulations will be
very light. Snow accumulations in the Cascades will be light too
(less than 2 inches).  Due to the decrease in snow and ice
accumulations and that the showers will be diminishing throughout the
day, have decided to end the Winter Weather Advisories. 

Showers will end late this afternoon, but rain and Cascade snow with
the next front is expected to arrive overnight tonight. This front is
stronger, wetter, and milder (temperature), and has the potential to
produce 2 to 3 inches of rain for the coast, coastal mountains, and
the Cascade Foothills Tuesday morning through Tuesday night.  Snow
levels in the Cascades will initially be around 2500 feet, and expect
3 to 6 inches of new snow Tuesday morning before the snow levels rise
above the Cascade passes Tuesday afternoon. The snow levels lower
below the passes behind the front Tuesday night as an upper trough
continues showers. The showers will be mainly confined to the higher
terrain Wednesday morning, and end around noon. 

A warm front will likely generate rain across extreme SW Washington
Wednesday evening through Thursday night as it stalls just north of
the Portland forecast area. NW Oregon may not see any rain with this
front and get a brief dry period. ~TJ	

.LONG TERM...No Changes. Previous discussion follows...Thursday
night through Sunday...A surface low riding up a stationary front
from the southwest will move the front eastward across NW Oregon on
Friday. There will be a decent amount of rain with this system, but
it probably won't be as wet as the system on Tuesday, due to it
moving through fairly quickly. 

Post frontal showers continue into Saturday, with snow levels 
dropping to 2500 feet. We could see a decent amount of snow in the 
Cascades with the showers behind the front Friday night into early 
Saturday. Some uncertainty in timing of the progression next 
weekend, but we should see a break between systems sometime Saturday 
afternoon/evening. Another system will bring widespread rain late 
Saturday night through Sunday. -McCoy/TJ

&&

.AVIATION...Onshore flow with orographically enhanced showers
will subside through the day. With the moist air mass in place
and little mixing, widespread IFR cigs and vis have developed.
Latest GFS, GFS-LAMP MOS guidance handles the current situation 
well and holds on to IFR conditions through midday or so then
trends to VFR after that. Mountains and higher terrain 
frequently obscured through Mon morning. Next system brings rain
to the coast late this evening with gusty southerly winds 
beginning Tue morning. 

PDX AND APPROACHES...IFR cigs at KPDX with reduced visibility in
fog in the surrounding area, especially in the Tualatin Valley. 
Expect improvement to VFR Mon afternoon. /mh

&&

.MARINE...Another gale event expected for most waters later
tonight into Tue. Some concern that models have winds that are
too strong. With the last system, models indicated gusts around
40 kt just ahead and with the front. But best observed was 35 kt
gust. 00Z models are in general agreement so will go with a gale
warning for PZZ250,270,275. Gales may reach PZZ255 briefly Tue
afternoon. Conditions settle down Tue night through Wed, but 
models show low-end gales developing again late Wed and Wed 
night. Much larger model disparity appears Fri through the 
weekend. Operational ECMWF and GFS show a rapidly-developing low
pressure area near 45N 135W 00Z Fri, but models differ on track 
and strength. Went with a blended solution due to such large 
model variance. 

Seas forecast to hover in the 11 to 13 ft range through this 
afternoon. Guidance shows seas in the mid to upper teens Tue 
night through Wed night. Model differences increase late in the 
week and into the nearly next week due to the differences in the
intensity and track of the strong lows mentioned above. There is
reasonable confidence seas will be close to 20 ft next weekend 
with the more extreme solutions showing seas closer to 25-30 ft.
Have gone closer to the WAM output for now, but would expect 
trends to change this far out in time. /mh

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Gale Warning from 11 PM this evening to 4 PM PST Tuesday for 
     Waters from Cape Shoalwater WA to Florence OR from 10 to 
     60 NM.

     Small Craft Advisory for hazardous seas until 4 PM PST this 
     afternoon for Coastal Waters from Cape Shoalwater WA to 
     Florence OR out 60 NM.

     Gale Warning from 4 AM to 4 PM PST Tuesday for Coastal waters 
     from Cape Shoalwater WA to Cascade Head OR out 10 NM.

     Small Craft Advisory for winds from 4 AM to 4 PM PST Tuesday 
     for Coastal waters from Cascade Head to Florence OR out 10 
     NM.

     Small Craft Advisory for hazardous seas from 4 AM Tuesday to 6 
     AM PST Wednesday for Coastal waters from Cascade Head to 
     Florence OR out 10 NM.

     Small Craft Advisory for Rough Columbia River Bar until 7 PM 
     PST this evening.
&&
$$

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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


769 
FXUS66 KPDT 101152 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
352 AM PST Mon Dec 10 2018

Updated aviation discussion

.SHORT TERM...Today through Tuesday night. A storm system that
effected our entire area was slowly moving east and will continue
to produce winter weather over the eastern third of the cwa that 
includes the blues and wallowa mountains with minor accumulating 
snow. As the bulk of the pcpn drifts away from this area by 
afternoon...lingering snow showers will persist and also along 
the cascades into tonight. Meanwhile another storm system will 
approach the two state area tonight. Light snow will again develop
along the wa/or cascades by Tuesday morning. The greatest chance 
for significant accumulating snow will be over the wa cascades and
a winter storm watch was hoisted for Tuesday and Tuesday night. 
The band of pcpn will track east and into the remainder of the 
area Tuesday. Low level winds shift more toward the warmer sw 
that should increase temps above the freezing mark over the 
columbia basin with rising snow levels. However the blue mountains
mainly above 3500 feet should continue to experience accumulating
snow that could approach advisory criteria into Tuesday night. In
addition pressure gradients tighten that could create breezy 
winds across portions of the region. 

.LONG TERM...Wednesday through Monday...Unsettled weather is 
expected to continue through the long term period. Wednesday will 
see a system departing the area with a chance of rain and snow 
mainly in the mountains tapering off in the afternoon. The mountains 
could see an inch or two of snow Wednesday. Wednesday night through 
Thursday night there will be weak ridging over the area with a 
stream of moisture riding over the ridge mainly to our north. There 
will be a chance of rain and snow in the Washington Cascades and a 
slight chance of snow in the eastern Oregon mountains with the rest 
of the area dry. Friday will see an upper low and front approach the 
coast and move through the area Friday afternoon and night. There 
will be a chance of rain and snow in the mountains and a chance of 
rain in the lower elevations. Saturday will be break between systems 
though there will be a chance of snow showers continuing in the 
mountains. Models begin to have timing differences at this point but 
another system will arrive Saturday night or Sunday and continue to 
affect the area through Sunday night. Have gone with a chance of 
mountain snow through this period with a chance of a rain/snow mix 
in the lower elevations changing to all rain Sunday afternoon. 
Another system may arrive Monday afternoon and have kept a chance of 
rain and snow in the mountains with a chance of rain in the lower 
elevations. Temperatures will be generally in the lower to mid 40s 
with mainly 30s in the mountains. Perry

&&

.AVIATION...12Z TAFs...A system that brought freezing rain, sleet 
and snow to the region is moving out of the area this morning with 
light showers continuing from the Blue Mountain Foothills eastward 
at this time. Have continued -FZRA at KALW and KPDT for a few more 
hours though any additional amounts should be minor. MVFR 
visibilities will continue until around 18Z this morning at KALW, 
KPDT, KYKM and KDLS with IFR and lower ceilings at KALW and KYKM and 
MVFR ceilings at KDLS. Skies will become scattered to broken above 
6000 feet AGL this afternoon then become broken to overcast again 
after 03Z as the next system approaches. Winds will remain below 10 
kts for the next 24 hours. Perry

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  41  27  45  32 /  20  10  70  80 
ALW  40  30  45  37 /  30  10  80  90 
PSC  39  29  44  38 /  10  10  70  70 
YKM  40  26  41  32 /  10  10  60  70 
HRI  42  28  46  35 /  10  10  70  70 
ELN  39  26  40  29 /  10  20  80  80 
RDM  45  22  46  29 /  10  10  50  80 
LGD  39  25  38  33 /  60  10  80  90 
GCD  38  22  39  31 /  30  10  60  80 
DLS  44  32  44  38 /  10  10  80  80 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 8 AM PST this morning for ORZ507.

WA...Winter Weather Advisory until 8 AM PST this morning for WAZ029.

     Winter Storm Watch from late tonight through late Tuesday night 
     for WAZ520.

&&

$$

97/83/83

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

Northeastern Washington and Northern Idaho


760 
FXUS66 KOTX 101200
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
400 AM PST Mon Dec 10 2018

.SYNOPSIS...
Bands of light snow will continue across eastern WA and northern
Idaho through mid-morning. A few showers will continue mainly over
the mountains this afternoon and tonight. A stronger storm system
arrives Tuesday, bringing the potential for heavy mountain snow,
light to moderate lowland snow, and locally gusty winds. Unsettled
weather will continue most of the week with periods of mountain
snow and a mix of rain and snow in the valleys. 


&&

.DISCUSSION...

Today and Tonight:
The first in a series of weather systems has been moving through
the forecast area early this morning. Snowfall rates have been
relatively light as this system passes through, with webcams
showing generally little to no accumulations on the roads across
the lower elevations. Precipitation should be tapering off across
eastern WA later this morning as the main precipitation band
pushes into Idaho. Snowfall totals with this system are expected
to remain fairly light: generally 1" or less across the lowlands,
up to a couple of inches across the northern WA highlands and
across northern Idaho, and perhaps 4-8 inches at pass level 
across the Cascades. Look for some locally slick conditions across
the region for the morning commute.

A few showers should persist mainly across the mountains this
afternoon and into tonight. With increasing boundary layer
moisture, look for low clouds and patchy fog to develop tonight
across much of the river basin and valley locations.
Dang

Tuesday and Wednesday: The next winter storm system is poised to pass 
through the region Tuesday into Wednesday. This will result in 
heavy mountain snow and mix of snow and rain in the lowlands. Some
mountain valleys of NE WA and ID will have the potential for 
moderate to heavy snowfall. A strong low-level jet developing over
southern WA will bring a punch of warmer air across the Columbia 
Basin northward and likely switch precipitation from snow to rain 
for communities along and south of Hwy 2. Timing this switch will 
be paramount to predicted snowfall amounts. 

First off...this evening's models remain consistent with timing.  
Light snow will spread into the region Tuesday morning...increase
Tuesday afternoon with a gradual switch to rain in the lower 
Basin...then precipitation will shift into the eastern third of WA
and N ID while intensities become moderate to heavy. During this 
time...warmer air will continue to surge northward reaching the 
Hwy 2 corridor, Palouse, and points north of Spokane-Cd'A. Bursts 
of heavy wet snow will be likely just prior to the switch to rain.
Steady precipitation will wane Tuesday night but snow showers 
will linger in the Idaho Panhandle and Cascade Crest into midday 
Wednesday. This storm will bring the potential for the first 
significant lowland snow and even if there is a transition to 
rain...possibility for treacherous travel conditions. 

Snow amounts will be quite variable along the northern periphery of the 
warm nose across NE WA and N ID. Given the latest data, forecast snow
amounts range from 1-3 inches in the Columbia Basin and Hwy 97
corridor...increasing into 3-6 inches for the mountain valleys of
NE WA and N ID. Some of these areas could see upwards of 6 to 8 
inches. The mountains could see around a foot or more with the
Cascade Crest closing in on 1-2 feet.

This system will bring gusty winds to the region, especially Tuesday 
evening and night with the passage of the cold front. The higher 
benches of the Palouse, Blue Mountains, and L-C Valley will carry 
the highest risk for wind gusts of 40 to 45 mph. Winds in excess 
of 45 mph will be possible on peaks above 40000-5000 feet. The 
remainder of the Columbia Basin could see wind gusts of 20 to 25 
mph.

Thursday and Friday: There will be two additional weather systems 
impacting the Pac NW Thursday and Friday. The main storm track on
Thursday will be across northern BC however the trailing cold 
front will suppress a decaying atmospheric river southward into 
northern WA/far N ID. This will result in steady snows across the 
northern mountains and wintry mix in the northern valleys and 
Upper Columbia Basin. South to southwest 850mb winds of 40 kts 
will bring another surge of warmer air so the threat for lowland 
snow will be low. The only exception will be for the mountain 
valleys north of Hwy 20 and in the Upper Methow Valley. A second 
slug of energy comes tracking across the Eastern Pacific and takes
a direct track through the Pac NW. This system will start off 
with a warmer environment and looks like mainly a mountain snow 
and valley rain event. It's a quick mover so precipitation amounts
look light but could be more of a wind maker. /sb

Saturday and Sunday: Models continue to show Saturday as a day in
between systems with a dry day favored except for lingering
showers in the Idaho Panhandle and Cascade crest. The next system
pushes in Saturday night into Sunday per most model guidance
although the past 2 ECMWF model runs have trended weaker with some
splitting of the incoming system while the GFS, GEFS, and 
Canadian are wetter with more consolidated flow. Models are all 
over the place with snow levels next weekend over northern 
Washington into the Idaho Panhandle so low confidence regarding 
precipitation type in these areas. South of I-90 it should be 
mild enough for valley rain and mountain snow.  JW

&&

.AVIATION...
12Z TAFs: Band of snow is now pushing through eastern WA into
northern ID, with widespread IFR and local LIFR conditions being 
observed. These showers will push eastward between 14-18z. With 
the increase in moisture, we're not expecting much improvement in 
flight conditions as low clouds persist through the day, and 
patchy fog returns Monday night. Most TAF sites will remain
MVFR/IFR today and tonight. KEAT may improve to VFR for a few
hours this afternoon before deteriorating again tonight.
Dang

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        34  28  37  31  37  31 /  50  10 100 100  10  20 
Coeur d'Alene  35  30  36  31  37  30 /  70  20  90 100  30  30 
Pullman        36  28  37  34  39  31 /  70  10  90 100  40  20 
Lewiston       41  31  42  36  46  32 /  70  10  60 100  30  20 
Colville       37  27  36  29  39  29 /  40  20 100 100  10  30 
Sandpoint      35  30  35  32  36  29 /  70  50 100 100  50  40 
Kellogg        34  29  34  31  34  28 /  80  50  90 100  80  40 
Moses Lake     35  25  38  33  43  33 /  20  10  80  50   0  10 
Wenatchee      37  29  36  32  39  31 /  10  10  90  50  10  40 
Omak           36  27  36  27  41  30 /  20  20  80  70   0  30 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Storm Watch from Tuesday morning through Wednesday 
     morning for Central Panhandle Mountains-Coeur d'Alene Area-
     Northern Panhandle. 

WA...Winter Storm Watch from Tuesday morning through Wednesday 
     morning for Northeast Mountains. 

     Winter Storm Watch from late tonight through late Tuesday night 
     for East Slopes Northern Cascades. 


&&

$$

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