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

Western Washington


466 
FXUS66 KSEW 162308
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
308 PM PST Sat Feb 16 2019

.SYNOPSIS...An upper level trough over the area this afternoon
will move south tonight and Sunday. Northerly flow aloft Sunday 
through Monday will give generally dry but cold conditions to the
area. The ridge will flatten Monday night with a system arriving 
from the northwest on Tuesday. Unsettled weather is expected later
Tuesday through the end of the week, with perhaps with a break 
between systems on Thursday. 

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...Satellite imagery shows
the upper low giving scattered showers to the area now over
Western Washington. This upper low is expected to slide southward
and out of the area late tonight into Sunday. Showers over the
coastal waters are moving into central and southern portions of
Washington while a weak deformation zone immediately north of the
center of the upper low is giving showers to the central Puget 
Sound area. All of these showers will drop slowly to the south 
tonight and out of the area, except maybe along the Cascade Crest 
and far south portion of the area where they will linger longer.
While cooler air will be filtering into the area overnight, lows
will be held in the upper 20s to mid 30s due to lingering cloud
cover.

Arctic high pressure centered over the Canadian Northwest 
Territories and Yukon is forecast to move southward into the 
central interior of British Columbia later tonight into Sunday. As
the upper low to the south moves away, expect north to northeast 
pressure gradients to increase allowing cold Fraser outflow to 
resume starting on Sunday. Both the NAM12 and the GFS give -15mb 
Bellingham to Williams Lake BC pressure gradients Sunday morning 
for breezy windy northeasterlies in Western Whatcom County and 
the San Juan Islands. There continue to be indications that the 
winds will stay below advisory strength in those areas, however. 

The north to northeasterly flow Sunday into Sunday night will
result in drying and clearing across the area. Highs will
generally be in the 30s to lower 40s and lows will fall mainly
into the 20s Sunday night and Monday night. 

Clouds will increase on Tuesday as a disturbance approaches the 
area from the northwest. There is a threat of some light 
precipitation on Tuesday that will increase Tuesday night. At 
this time it appears that conditions will be cold enough that many
locations in the interior will see some light snow. However, 
impacts are tough to predict at this time. Conditions are not 
expected to be as cold as what we experienced with the snow events
of the previous two weeks, and heavy precipitation -if it occurs-
may be more limited in area than with recent events. Small 
changes in temperatures and locations of stronger forcing will 
result in large differences in area impacts, so please watch 
latest forecasts for updates. Albrecht

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...At this time, the best
chance of accumulating snow in the interior lowlands of Western
Washington is Tuesday night through early Wednesday as a
disturbance moves through the area. Models generally show
accumulations between a trace to about 3 inches with the
operational GFS and experimental FV3/GFS models the heaviest. 
Behind the disturbance, the air mass cools and dries somewhat so 
that there may be a break between systems Thursday and Thursday 
night. Temperatures remain well below normal.

Friday and Saturday's system is now handled inconsistently between
the models. The recent GFS solutions are a bit warmer and wetter
with Friday's system resulting in snow being limited to the far
north interior and snow levels in the central and southern
portions of the area remaining at 800-1500 feet or so. The 
operational ECMWF has taken a twist in that the approaching 
disturbance for Friday now gets wrapped southwestward under the 
offshore block, reestablishing the REX block along about 140W. 
This would leave Western Washington dry and cool.

At this point the extended forecasts are a blend of model
solutions. Expect changes to the forecasts, their timing, and
potential impacts we move forward in time. Albrecht 

&&

.AVIATION...Southerly flow aloft with light rain over the central 
interior and showers  elsewhere this evening. Ceilings generally 
MVFR with IFR possible in the light rain. Surface winds will remain 
light and southerly winds this evening, with light northerlies after 
midnight from the north working southward into Sunday morning. MVFR 
ceilings this evening will lower again to IFR levels most areas 
early Sunday morning. 

KSEA...MVFR ceilings with a few scattered showers this evening. 
Ceilings will lower again to IFR levels around 09/10Z. Ceilings will 
improve late Sunday morning into the afternoon to MVFR and even VFR 
levels. Southwesterly winds 6-8 kts will veer to the northwest 
by early afternoon. 

&&

.MARINE...A surface low will drift southward through the 
Washington coastal waters through Sunday morning. High pressure 
developing over southern British Columbia late tonight and Sunday 
will help northeasterly outflow winds to develop over the northern
interior waters and offshore flow through the strait. This will 
support low-end gales over the northern inland waters and small 
craft conditions over most other waters. Westerly swell 10 to 11 
feet at 11 seconds tonight and Sunday will subside to 8 or 9 feet 
Sunday afternoon and evening. 

&&

.HYDROLOGY...Precipitation that falls through tonight will mainly
be in the form of rain, or a rain snow mix. The precipitation, 
combined with some snow on the ground that continues to melt and 
recent snowfall that has saturated the soil, has increased the
threat for landslides more than rainfall-based indices would
suggest. So, the Special Weather Statement for the landslide 
threat will be continued for one more day. 

As far as river flooding is concerned, none is expected for the 
next 7 days. Albrecht

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 4 AM PST Sunday for 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 4 AM PST Sunday for 
     Grays Harbor Bar.

     Small Craft Advisory until 4 PM PST Sunday 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.

     Small Craft Advisory from 6 AM Sunday to 4 AM PST Monday for 
     East Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Warning from 10 PM this evening to midnight PST Sunday 
     night for Northern Inland Waters Including The San Juan 
     Islands.

     Small Craft Advisory from midnight tonight to 4 AM PST Monday 
     for West Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from midnight tonight to 4 PM PST Sunday 
     for Central U.S. Waters Strait Of Juan De Fuca.

&&

$$

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


455 
FXUS66 KPQR 162336
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
335 PM PST Sat Feb 16 2019

.SYNOPSIS...Showers continue across southwest Washington and
northwest Oregon today, associated with the latest in a series of low
pressure systems affecting the Pacific Northwest. Snow levels remain
low enough to bring snow to the Cascade foothills, and occasionally
heavy snow is falling on the Cascade passes.  Precipitation will
decrease from north to south tonight as high pressure brings drier
northerly flow to the region. Below normal temperatures are expected
to persist through next week, with snow levels expected to remain low
as the next organized low pressure system spreads precipitation
across the forecast area midweek.

&&

.SHORT TERM...Tonight through Tuesday...The latest in a series of low
pressure systems is spreading numerous showers across the forecast
area. Some of these showers have decent updrafts and a lightning
strike was recently reported just outside of Silverton. With freezing
levels running low at around 2500 feet, any heavier showers may
produce small hail. We recently received a public report via social
media with a picture of small hail accumulating up to about an inch
in Dunes City. As a result of this confirmation, we issued a Special
Weather Statement earlier this afternoon to mention the potential for
brief, spotty accumulations of hail that may make roads locally slick
along the coast and in the Coast Range. Showers should gradually
decrease overnight as onshore flow weakens a bit and higher pressure
builds into the region from the north.

Otherwise the main weather challenge for today is the snow in the
Cascades and, earlier, in the Columbia Gorge and Hood River Valley.
Nearly a foot of snow has fallen in the Cascades above 2500-3000'
elevation, with lesser, slushier accumulations down to around 1500'.
Snow levels appear a little higher in the Coast Range, likely due to
moderating effects of onshore flow. As is the case with rain showers
at lower elevations, expect snow showers to decrease across the
Cascades tonight as high pressure builds from the north and the air
mass gradually stabilizes. Will maintain the Winter Weather Advisory
as-is for our Oregon Cascades and foothills, expiring at 11 PM as
precipitation dwindles across the forecast area.

As precipitation ends and skies start to clear, the potential for
temperatures to dip below freezing increases later tonight. This may
cause some black ice to develop on roads wet from today's rainfall,
especially untreated secondary roads outside of the urban centers.
Additionally, patchy fog may form overnight, which may also
contribute to slick road surfaces where temperatures fall below
freezing by Sunday morning.

Morning fog and low clouds should give way to at least a partly sunny
day Sunday as high pressure builds across Washington and Oregon.
Latest guidance (such as 12z ECMWF and 18z NAM) appear to be a little
more bullish with cold air spreading southward from BC through the
Okanagan and into the Columbia Basin...this may come into play later
as our next organized low pressure system arrives Tuesday. For
example, the 18z NAM pushes 850 mb temps down as low as -12 deg C at
The Dalles by Monday morning. At the very least, this will likely
lead to a chilly night with low temps in the 20s Sunday night for
much of the forecast area. Models had been toying with the idea of
bringing a weak low pressure system southward along the coast Monday,
but the cold, dry air high pressure system will likely keep
precipitation mainly offshore.

Clouds likely increase Monday night in advance of our next low
pressure system digging southward along the coast from British
Columbia. Most guidance suggests southerly flow will develop ahead of
this system, keeping snow levels just above the valley floors as
precipitation develops Tuesday. Additionally, robust W-NW flow aloft
ahead of this system will serve to weaken whatever is left of the
cold pool east of the Cascades. However, should this system come in a
little weaker than presently modeled, weakening both the low-level
southerly flow and W-NW flow aloft ahead of it, there may be some
concern for snow down to the valley floors Tuesday and/or Tuesday
night. For now, we will be non-committal with precip type associated
with this system in the Willamette Valley, mentioning both rain and
snow as possibilities. At this point it appears the odds of a
widespread high-impact valley snow event Tue/Tue night are 10 percent
or less, but it still bears close watching.  Weagle

.LONG TERM...Tuesday night through Saturday... The 12z GFS and 12z 
ECWMF have a cold front progressing across the area. This front 
looks to bring a slug of moisture, this pool of moisture look to 
hang around through the post-frontal environment. The surface low 
associated with the front will slide across the area through 
Wednesday. Thursday has a shortwave ridge starting to momentarily 
dry the area out. However, a new cold front meanders into the area 
Friday night into Saturday. Which looks to bring a new influx of 
moisture to the area. Overall, for the extended period temperatures 
look to remain slightly warmer than normal, with precipitation 
chances remaining elevated, through brief dry periods intertwined 
between cold fronts. 850 mb temperatures look to hold in between -6C 
to -5C and a steady onshore flow pattern continue to signal minimal 
snow chances for the valley floor. /42

&&

.AVIATION...Showers continue to spread across the region this
afternoon, though mostly VFR conditions through the evening. The
next low will drop south along the coast later tonight, providing
for another round of shower chances and areas of lowering cigs
with MVFR conditions possible at times. Late tonight as the low
passes, expect showers to taper off from north to south with
improvement to VFR. However, as the main cloud deck begins to
break up, it is possible that low stratus or fog may form, given
the light winds and abundant residual low-level moisture.

KPDX AND APPROACHES...Expect mainly VFR conditions, with possible
MVFR at times under heavier showers. Showers should taper off
later tonight with return to mostly VFR, though it's possible
than some fog develops late as a result of breaks in the main
cloud deck. Cullen

&&

.MARINE...Gusty NW surface continue across the waters this
afternoon. Gusts between 20 and 30 kt continue this afternoon,
but should gradually subside later this evening. Did extend the
advisory for winds across the northern zones through this
evening, as latest high res guidance shows more widespread 25 kt
gusts through the evening, especially across the outer waters.

Another low will drop south from Vancouver Island and move 
directly over the waters tonight into early Sunday. This should 
keep winds fairly light during this time. High pressure builds 
over the waters early next week. However, weak lows will move 
periodically through from the NW. The strongest system looks to 
be later Tuesday into Wednesday. This one brings the potential 
for small craft advisory winds, or potentially even gales. 

Seas remain in the mid teens this afternoon and will gradually 
subside tonight and Sunday, dropping below 10 ft by Sunday 
afternoon. The Tuesday night/Wednesday system may bring the 
potential for seas building into the upper teens, or potential 
even above 20 feet. Cullen

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 11 PM PST this evening for 
     Cascade Foothills in Lane County-Cascades in Lane County-
     Northern Oregon Cascade Foothills-Northern Oregon Cascades.

WA...None.

PZ...Small Craft Advisory for winds until 11 PM PST this evening for 
     Coastal Waters from Cape Shoalwater WA to Cascade Head OR 
     out 60 NM.

     Small Craft Advisory for hazardous seas until 2 PM PST Sunday 
     for Coastal Waters from Cape Shoalwater WA to Florence OR 
     out 60 NM.

     Small Craft Advisory for winds until 4 PM PST this afternoon 
     for Coastal Waters from Cascade Head OR to Florence OR out 
     60 NM.

     Small Craft Advisory for Rough Columbia River Bar until 5 PM 
     PST this afternoon.

     Small Craft Advisory for Rough Columbia River Bar from 1 AM to 
     4 AM PST Sunday.

&&

$$

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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


736 
FXUS66 KPDT 162242
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
242 PM PST Sat Feb 16 2019

.SHORT TERM...Tonight through Tuesday...A large and broad trough 
remains over the western states this afternoon. The latest in a 
series of weak lows is descending down the west side of the trough 
and will move ashore over the Willamette Valley tonight and into 
northern California tomorrow. This will keep a chance of light snow 
showers over most of the area tonight though the Washington Columbia 
Basin may not see much. Will keep the Winter Weather Advisory for 
the East Slopes of the Oregon Cascades though do not expect more 
than another inch or so tonight. Most of the rest of the area will 
see a half or less though the eastern Oregon mountains could get up 
to 2 inches. Have kept patchy freezing fog along rivers and streams 
in the Columbia Basin and adjacent valleys overnight and tomorrow 
morning as there has been some fog the last couple of mornings. 
Tomorrow the chance of light snow will be concentrated mainly in the 
eastern Oregon mountains with the Columbia Basin and central Oregon 
drying out. Sunday through Monday night another low will track to 
our east along the Continental Divide in Montana and Wyoming. A cold 
northerly flow will develop. It will be also fairly dry but there 
will be a slight chance of very light upslope snow showers in the 
Washington Cascades and eastern Oregon mountains tapering off to 
nothing by Monday night. A stronger system will approach the area 
out of the Pacific on Tuesday with most of the area seeing a slight 
chance of snow in the afternoon. Temperatures tomorrow will be in 
the upper 20s to mid 30s. With colder air arriving Monday, 
temperatures will be mainly in the 20s with few if any locations 
getting above freezing. Tuesday will be similar though The Dalles 
south to Bend may reach the mid 30s. Perry 

.LONG TERM...Tuesday night through Saturday. Cold temperatures will 
continue through the extended period.  A couple of systems will 
bring another round of snow to the area Tuesday night and Wednesday 
as a low pressure system drops south over Washington and Oregon. 
Behind this system, northerly flow will continue to allow cold air 
to move south over the area with some mainly mountain snow showers. 
Model diverge starting Thursday with the EC being much drier with a 
ridge and weak northwest flow through the weekend, while the GFS has 
more moisture and is showing another cold front by next Sunday. 
Either solution keeps temperatures below normal through the period. 
93


&&

.AVIATION...00z Tafs.  Area of low pressure will continue to move 
into Oregon tonight with snow showers across the region causing some 
MVFR/IFR with the heavier showers.  Some patchy fog is again 
possible at sites during the early morning hours except for RDM and 
BDN.  Northerly flow and a little drier air starts pushing in from 
north late in the day Sunday. 93 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  24  29  17  25 /  40  30  20  10 
ALW  26  31  18  25 /  40  30  20  10 
PSC  26  31  18  26 /  20  20  10  10 
YKM  23  32  19  27 /  20  10  10  10 
HRI  26  32  19  27 /  20  20  10  10 
ELN  18  32  14  26 /  20  10  20  10 
RDM  19  34  17  32 /  50  10  10  10 
LGD  25  32  18  26 /  50  30  20  10 
GCD  25  34  19  30 /  60  30  10  10 
DLS  26  36  25  33 /  40  10  20  10 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 AM PST Sunday for ORZ509.

WA...None.
&&

$$

83/93/93

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

Northeastern Washington and Northern Idaho


798 
FXUS66 KOTX 162345
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
345 PM PST Sat Feb 16 2019

.SYNOPSIS...
Scattered snow showers will continue over the Inland Northwest
this weekend, with light accumulations. Gusty north to northeast 
winds return on Sunday, and may bring localized blowing and 
drifting snow as cold temperatures return. Expect cold and dry 
weather Monday, then a return to snowy weather by Tuesday through
Wednesday and possibly again by the end of the week. Cold  
temperatures will continue for all of next week.  

&&

.DISCUSSION...
Tonight through Sunday night: The upper level trough will remain
over the Inland NW through the weekend. Will be watching the next
shortwave in the trough drop along the WA and OR coast. This will
enhance a low level westerly flow across southeast Washington and
the southern Panhandle with more instability snow showers 
overnight and more light snow accumulations. A moist boundary 
layer will give way to plenty of low clouds and patchy fog across 
the Columbia Basin and valleys in the wake of the showers.  
Overnight temperatures will be mostly in the 20s. As this 
shortwave drops south Sunday, a cold front in B.C. will sag into 
the region with the next round of modified arctic air. Northerly 
winds will increase in the Okanogan Valley and Purcell trench in 
north Idaho by Sunday morning. Snow showers will develop with the
front and spread across much of the region Sunday with light 
accumulations in both the mountains and valleys. High temperatures
will be achieved early in the day, before cold air advection  
overtakes the diurnal afternoon rises. Pressure gradients look to
be stronger across north Idaho, which will increase northeast 
wind gusts to 30 to 35 mph from north Idaho into the Columbia 
Basin and Palouse. Patchy blowing snow is possible in exposed 
areas leading to reduced visibilities and drifting snow Sunday 
afternoon and evening, although conditions do not look as intense 
as the last cold frontal passage earlier in the month. Northerly winds
gradually taper off Sunday night as the dry and colder air spills
into the region from the north. The colder air will send 
temperatures plummeting into the single digits and lower teens
regionwide. The blustery winds may bring wind chills to sub zero 
levels across the northern valleys by early Monday morning. At 
this time, no winter highlights look necessary. /rfox. 

Monday through Saturday...After the departure of Sundays arctic 
cold front, we should see a brief respite of dry weather as the 
dendritic layer dries out. We still might see a few light snow 
showers especially over the Idaho Panhandle Mountains due to a bit
of residual moisture combined with orographic ascent but 
significant accumulations aren’t expected. Staying consistent 
with the recent pattern of unsettled weather, it appears the next 
chance of widespread precipitation will arrive late Tuesday and 
Wednesday. The model guidance is surprisingly consistent with 
precipitation hitting the northern Cascades by Tuesday morning and
spreading across the remainder of the forecast area by afternoon.
Based on 850 mb and surface temperatures there is little doubt 
that whatever falls will fall as snow. However we aren’t 
convinced it will amount to much. Precipitation amounts over most 
of the region will be less than 0.20 inches but heavier amounts 
are expected over SE Washington and NC Idaho due to the track of 
the upper level low. Since we will be dealing with a cold air 
mass, 20:1 snow to liquid ratios are feasible and this could 
result in several inches of snow falling over much of the region 
by Wednesday. This could impact the Tuesday evening and Wednesday 
morning commutes. Most locations will see drying by Wednesday 
night and Thursday as the upper level low dives southward and 
drier air moves in from the north. After that, there are some 
model disagreements for the next chance of precipitation. The GfS 
suggests another system will move in from the northwest by Friday 
afternoon and the previous EC agreed. Now the EC shows a ridge 
developing over western WA as a deep low moves offshore. That
would keep us dry through Saturday. The latest Canadian is also 
hinting at that solution as well. So for now our confidence is 
low. If the GFS is right it could be a very snowy system, so we
shall see.  

What we are confident about is the cold temperatures will continue 
through the entire week. Most locations will struggle to get any 
warmer than the 20s during the afternoon (aside from Lewiston 
which could hit the lower 30s on Wednesday). Meanwhile lows will 
be in the single digits and teens. Just for reference, 
temperatures this time of year in Spokane should highs around 40 
and lows in the mid 20s so we will be a good 15 degrees below 
normal or so with no significant warming expected anytime soon. fx

&&

.AVIATION...
00Z TAFS: Low clouds will linger over the region tonight and early
Sunday with BL moisture under the long-wave trough and unstable -shsn
in the region. Some localized fog is possible away from the 
precipitation threat. A backdoor cold front will start to expand a
broader threat of light snow in from north Idaho later overnight 
into Sunday morning, increasing into the COE/SFF/GEG/PUW/LWS
toward 10-15z. Some heavier bursts of snow are possible. The
threat will expand toward MWH/EAT later in the day, while it
starts to decrease from the northeast later in the day and
evening. Expect MVFR/IFR conditions tonight and Sunday morning,
with the potential for some improvement Sunday afternoon as some
drier air tries to invade from the Canada. /Cote'

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        21  27   7  21   6  22 /  20  60   0   0   0  20 
Coeur d'Alene  22  28   8  22   8  23 /  30  60   0   0   0  20 
Pullman        24  29  11  20   8  22 /  50  60  20   0   0  20 
Lewiston       28  34  19  27  14  29 /  50  60  20   0   0  20 
Colville       20  32   8  29   8  27 /  40  60  10   0   0  20 
Sandpoint      23  25  10  23  13  23 /  50  60   0   0   0  30 
Kellogg        22  24   8  22  10  23 /  40  60  10   0   0  30 
Moses Lake     22  33  12  25  10  24 /   0  10   0   0   0  10 
Wenatchee      23  35  16  25  13  25 /  10  10  20   0   0  20 
Omak           23  33  13  24  11  22 /  20  20   0   0   0  10 

&&

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

&&

$$

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