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

Western Washington


523 
FXUS66 KSEW 041756
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
900 AM PST Sun Dec 4 2016

.SYNOPSIS...Much colder air aloft will filter into Western
Washington today as a cold front over Oregon moves south. Showers
will prevail today with mountain snow tapering off by midday. The
Puget Sound convergence zone will also be active today from around
Seattle northward. A surface trough brings a mix of rain and snow
down to sea level on Monday with light snow accumulation possible,
mainly above 500 feet. By Monday evening, fraser outflow develops
with snow showers down to sea levels moving south into the greater
Puget Sound area overnight. Mostly dry and colder temperatures
prevail Tuesday and Wednesday with lows in the 20s. Precipitation
may begin as snow across the area Wednesday night or Thursday
morning as the next system arrives before switching over to rain.
Unsettled weather persists Friday into the weekend with rain and wind
at times.

&&

.SHORT TERM...The freezing level is down to near 1500 feet this
morning as cold air aloft filters south into the region. Moist
westerly flow that brought 1 to 2 feet of snow to the mountains
overnight has shifted south over Oregon and precipitation has become
showery across the area. A few inches of snow could still fall in
the Cascades today, especially where the convergence zone lingers
over King and Snohomish counties. Scattered showers in the lowlands
will be around today, possibly mixed with some wet snow this morning
but no accumulations. Sunbreaks are also likely in some areas today
with a break between systems allowing highs to warm into the 40s.

A cold upper low along the B.C. coast will slide southeast toward
the Pacific Northwest tonight bringing a near -40C cold pocket at
500 mb into the area by Monday morning. Weak surface low pressure
will close off near the north Washington coast late tonight,
bringing a surface trough into the area Monday morning. Light
southerly/southeast flow will help keep temperatures near the surface
just above freezing but the air aloft will be cold enough to bring a
mix of rain and snow showers down to sea-level. The main snow level
will be near 500 feet and any accumulations will likely be on
hilltops and away from water. Model QPF amounts suggest local
amounts of a trace to 2 inches are possible, mainly on grassy
surface during the morning. Road temperatures will be warm initially
so not much more than some slush on some roadways outside the main
urban areas is expected. The exception to this could be near hood
canal where cold air can dam up, and also over Western Snohomish
county north to Whatcom county where slightly cooler temperatures
reside and where convergence zone activity is most likely. Locally 2
inches could fall from around Everett north. A winter weather
advisory was issued for interior lowlands for Monday morning but may
need to add Whatcom county to this. 

Models have trended toward a stronger surface high settling in over
southern B.C. Monday through mid week. BLI-YWL gradient reaches -12
mb by 21z on the new 12z GFS, similar to the 00z ECMWF. This should
initiate fraser outflow, with peak gradient close to -16 mb Monday
evening. This favors bringing colder low dew point air into the
north interior by late afternoon, and filtering south into greater
Puget Sound during the evening. The 4kmWRF and other meso models are
developing a convergence band along the modified arctic outflow
boundary which could reach the Seattle area during the evening and
possibly linger from north of Tacoma to Everett through early
Tuesday morning. Showers would fall as all snow down to sea-level
and some models produce locally significant accumulations around the
north Seattle to Everett corridor. If this occurs, temperatures will
probably be in the upper 20s with icing on roadways and potential
significant impacts on the Monday evening and/or Tuesday morning
commutes. Even if precipitation does not develop, black ice will
remain a hazard during the overnight and morning hours Tuesday
through Thursday. Will need to evaluate all the latest data and
consider if the chances are high enough to warrant a watch for parts
of the metro area Monday night. 4 inches of snow are needed to meet
warning criteria so a statement may have to suffice, will decide by
the afternoon forecast issuance. Outflow could also produce several
inches of lowland accumulation over the San Juans, and also the
Strait including Port Angeles and Sequim which can get upslope
accumulation in this pattern. 

Colder and drier air will filter in Tuesday. Highs will likely stay
in the 30s and lows dip into the 20s WEdnesday morning. Forecasts
should be monitored closely over the next several days. Mercer



.LONG TERM...Previous discussion...Extended models in good agreement
on wednesday with the upper level ridge over the area. Model
solutions for Thursday remain inconsistent with the GFS bringing a
front into the area on Thursday and the leading edge of the
precipitation ahead of the front moving into the area Wednesday
night. The cold air will still be in place bring up the possibility
of the precipitation being in the form of snow later Wednesday night
into Thursday morning. Strong southwesterly winds will scour out the
cold air later Thursday but not before a few inches of snow in the
lowlands. The ECMWF is much colder on Thursday with a slower arrival
of the front, not until Thursday night with the precipitation
beginning Thursday afternoon. Current forecast more in line with the
GFS solution and will stay with that scenario in the morning zone
package.

Both the GFS and the ECMWF have a warmer air mass over Western
Washington on Friday and Saturday. There are still timing
differences with the systems moving into the area but the
precipitation type will be rain for the lowlands. Felton

&&

.AVIATION...Moderate west to northwest flow aloft. Post frontal
onshore flow today will give decreasing showers to the mountains.
Convergence zones over the central portions of the Puget Sound area
and over Skagit and Snohomish counties will gradually dissipate this
afternoon. The air mass is somewhat moist and unstable. Moisture
will increase from the west late tonight into Monday morning and
snow levels will drop to around 500 feet with the onset of
precipitation. 

Conditions are mainly VFR across the region today with MVFR
conditions within showers with convergence zones. Expect conditions
to become VFR most places during the afternoon hours as showers
diminish. The air mass is unstable, so some showers will continue. 

Conditions will deteriorate from the west on the coast late tonight
and in the interior Monday morning as a system moves in from the
west. Rain or mixed precipitation can be expected at the lower
elevation terminals with snow or mixed rain and snow at higher
terminals like KPAE and possibly KSEA. KPAE could remain
predominately snow Monday morning with 1-3 inch accumulations.
Slushy accumulations of an inch or two is possible at KSEA.
Albrecht

KSEA...Variable wind 5 to 15 knots today will become southeast to
south 5-8 knots tonight. The convergence zone over the terminal this
morning will slowly dissipate during the afternoon hours with MVFR
conditions improving to VFR by 23Z. Snow showers will begin around
the terminal about 12Z-15Z Monday and 1-2 inch slushy accumulations
are possible Monday morning. Albrecht

&&

.MARINE...Post frontal onshore flow will gradually decrease today.
Winds will remain in the small craft advisory category on the coast,
but are expected to drop below that threshold later this afternoon
in the northern inland waters and through the central and eastern
portions of the Strait of Juan de Fuca. Seas will remain hazardous
on the coast through Monday. 

A weak low will move southward along the west coast of Vancouver
Island tonight. As the low continues south to the Washington coast
on Monday, a cold dome of high pressure will move south through
British Columbia. As a result, the flow across Western Washington
will turn northerly by late Monday. Cold Fraser River outflow winds
of 20 to 30 kt will likely develop across the northern inland waters
and Strait of Juan de Fuca Monday night and continue Tuesday, and
gales are possible.

A strong Pacific front will approach the area Wednesday night and
move through the waters on Thursday. Gales are likely for most
waters except for Puget Sound and Hood Canal. McDonnal/Albrecht

&&

.HYDROLOGY...No river flooding is expected over the next week.

&&

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...Winter Weather Advisory from 4 AM to noon PST Monday for 
     Bellevue and Vicinity-Bremerton and Vicinity-East Puget 
     Sound Lowlands-Everett and Vicinity-Hood Canal Area-Seattle 
     and Vicinity-Southwest Interior-Tacoma Area-Western Skagit 
     County.

     Winter Storm Warning until noon PST today for Cascades of Pierce 
     and Lewis Counties-Cascades of Snohomish and King Counties.

PZ...Small Craft Advisory for rough bar until 6 AM PST Monday for 
     Grays Harbor Bar.

     Small Craft Advisory until 6 PM PST Monday 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 3 PM PST this afternoon for Central 
     U.S. Waters Strait Of Juan De Fuca-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 3 AM PST Monday 
     for West Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 9 AM PST this morning for Admiralty 
     Inlet.


&&

$$

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.weather.gov/seattle/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


352 
FXUS66 KPQR 041104
AFDPQR

Area Forecast Discussion
National Weather Service Portland Oregon 
304 AM PST Sun Dec 4 2016

.SYNOPSIS...A strong cold front will push se through southwest
WA and northwest OR today today bringing a round of rain and
mountain snow. Cold air behind the front will lower snow levels and
support freezing temperatures Sunday night into Monday morning as
the next front arrives. Snow levels will drop close to the valley
floors Monday morning complicating the morning commute.
Precipitation will linger into early Tuesday. East winds Tuesday
night and Wednesday will set the stage for more winter weather
Wednesday night and Thursday.
&&

.SHORT TERM...Today through Tuesday...Rain has spread in across much
of the forecast area early this morning ahead of a cold front that
was moving through nw WA early Sun morning. Rainfall rates through
09z over western WA have been on the order of 0.3 to 0.5 inches per
6 hour, which agrees well with most model qpf estimates. These rates
expected to continue today as the main area of rain moves through nw
OR and cold front pushes south into Lane county by the end of the
day. Winter weather advisories for snow in the Cascades look on
track today, ending this morning in the south WA Cascades as the
cold front pushes through, but lasting through the afternoon in the
Oregon Cascades where another 6 to 12 inches are still possible. The
front will usher in colder air today and tonight, with snow levels
lowering into the Coast Range and Cascade Foothills by evening.

Moist onshore flow brings increasing pops tonight across the
forecast area for light showers, but more organzied precipitation
precedes a cold front arriving early Mon, originating today along
the se Alaska coast. 1000-500 mb thickness values on the order of
522 dm and h8 temps around -6 deg C continue to suggest snow levels
dipping by Mon morning to around 1000 feet. Cold front still appears
in models to be fairly dynamic, and moving south down the lower
Columbia Valley into the north Willamette Valley during the morning.
With the threat of dynamic cooling accompanying the front, there
remains a possibility for snow to temporarily lower to near the
valley floors during the morning Mon. As the front moves south
through the rest of nw Oregon during the afternoon hours Mon, the
likelihood of snow levels dipping below 1000 ft in the interior
valleys becomes less. For the Willapa Hills, North Oregon Coast
Range, and South WA Cascade Foothills, where snow begins late Sun
night and continues into Mon, will go ahead and issue winter weather
advisories for snow this morning. Further south the potential for
accumulating snow does not kick in in earnest until Mon morning, so
will hold off on any more advisories at this time. 

Behind the cold front later Mon and Mon night, precipitation will
decrease as the low level flow veers to the n. Air mass becomes more
continental looking in nature with the change to more of a light
offshore flow. With drier air moving in, chances for showers will
diminish, and largely come to an end on Tue except over the Oregon
Cascades. The colder air will likely keep high temps limited to the
30s over the interior Tue. 

.LONG TERM...No Changes. Previous discussion follows...Tuesday night
through Saturday...An upper level ridge will move across the Pac NW
late Tuesday/early Wednesday ushering in a brief period of dry
weather. With cloud cover decreasing slightly overnight we could see
the coldest temps of the season thus far, with temps at the coast
near 30. Temps in the interior valley will generally be in the upper
20s, with temps in the Cascades in the low teens. In addition to the
cold temps, residual surface moisture combined with clearing skies
could provide ideal conditions for radiational fog so decided to add
the mention of freezing fog for much of the interior valley. However,
brisk east winds near the Gorge should prevent any fog development. 

Unsettled winter weather looks to return by late Wednesday. The GFS
and ECMWF are starting to slowly converge on one another, but the
GFS remains the more aggressive solution. Both models continues to
suggest that moisture will initially overrun the cold air in place.
Model soundings show a brief period of valley snow will be possible
at the beginning. However, as the warm front lifts north Thursday
morning expect valley snow to transition to a mix of snow, freezing
rain, or rain before turning to all rain later in the day. However,
there is still a lot of uncertainty with this system, and the exact
threats and impacts will be influenced by how cold the surface gets
over the coming days.

Active weather looks to continue on Friday and Saturday as a series
of shortwaves move across the region. Both models show a warmer air
mass over the area, with snow levels generally around 3500 ft. As
such, the threat of valley snow will be minimal late next week. /64
&&

.AVIATION...A cold front is slowly moving through SW Washington
and NW Oregon from the northwest this morning. An associated band
of steady rain and a mix of VFR/MVFR cigs is draped across most of
the region as of 3 AM. Rain will taper to showers from north to
south through the morning hours. Expect conditions to transition
to mainly VFR behind the front, with occasional showers through
the rest of the day and this evening. The next cold front will
begin to spread in from the north late tonight...likely bringing
MVFR cigs into KAST between 09-12Z Mon.

KPDX AND APPROACHES...Expect a mix of VFR/MFR conditions in steady
rain through about 15Z-17Z. A cold front will move through around
14Z, with winds switching to the NW behind the front. Rain taper
to showers later this morning and this afternoon, with mainly VFR
expected. Pyle

&&

.MARINE...A cold front moving through the coastal waters this
morning is bringing low-end small craft advisory winds, with gusts
to around 25 kt. NW winds behind the front will continue to gust
20-25 kt at times through this afternoon. Another cold front will
move down tonight into Mon morning, likely bringing another round
of small craft winds. Winds subside below 20 kt late Mon through
early Wed. However, a strong storm system appears to be on tap for
the Wed through Fri timeframe. There is some considerable
differences in model timing at this point, but it appears likely
that gales will affect the waters sometime late Wed or early Thu,
with another round of gales possible toward the end of the week. 

A longer period westerly swell train will keep seas around 12 to
14 ft for the next several days. Expect seas to finally drop below
10 ft by Wed. However, the next approaching strong system is
expected to quickly push seas back into the teens later Wed or
early Thu. Seas may push above 20 ft again on Thu into Fri. Pyle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 PM PST this afternoon for 
     Northern Oregon Cascades.

     Winter Weather Advisory until 4 PM PST this afternoon for 
     Cascades in Lane County.

     Winter Weather Advisory from 1 AM to noon PST Monday for Coast 
     Range of Northwest Oregon-Lower Columbia.

WA...Winter Weather Advisory until 10 AM PST this morning for South 
     Washington Cascades.

     Winter Weather Advisory from 1 AM to noon PST Monday for I-5 
     Corridor in Cowlitz County-South Washington Cascade 
     Foothills-Willapa Hills.

PZ...Small Craft Advisory for winds until 10 PM PST this evening for 
     Coastal Waters from Cape Shoalwater WA to Florence OR out 
     60 nm.

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

     Small Craft Advisory for Rough Columbia River Bar until 10 AM 
     PST Monday.
&&

$$

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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.

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

Southeastern Washington and Northeastern Oregon


381 
FXUS66 KPDT 041642 AAA
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
829 AM PST Sun Dec 4 2016

.UPDATE...The latest radar was showing pcpn striking the or/wa
cascades and then lessening over the basin before the upslope flow
increases the pcpn along the blue mountains where ski bluewood
washington reported five inches of snow. Elsewhere and along the
east slopes of the Washington cascades three inches had fallen
around Roslyn and Cle Elum. Further south along the east slopes of
the Oregon cascades temperatures remained above freezing but a cold
front is forecast to move through the region today which will lower
snow levels later this morning/midday. The bulk of the moisture will
slip south into the Oregon cascades today while the upslope flow in
and near the blue mountains should persist with snow levels hovering
around 4000 feet. 

Pcpn will persist today and a cold front will sweep across the
region. Pressure gradients should tighten creating windy conditions
in portions of the area and a wind advisory was hoisted over
the kittitas valley and over the lower columbia basin of Washington. 

Elsewhere and across our far eastern zones a snow advisory remains
in effect for Wallowa county and so does a winter storm warning for
the blue mountains where additional accumulations can be expected
and the present short term forecast appears on track for now.

&&

.PREV DISCUSSION... /issued 340 AM PST Sun Dec 4 2016/ 

SHORT TERM...Today through Tuesday...A complex weather system will
move through the region today. Snow levels will rise some from
central Oregon to northeast Oregon this morning, then fall in the
afternoon as a cold front passes. Meanwhile snow levels of 2100 to
3000 feet over south-central Washington this morning will gradually
fall through the day behind the front. Precip amounts will be
decent, especially over the Blue mountains, Wallowa county and
immediately near the Cascade crest. Thus will continue all current
winter weather advisories. May have to add a winter weather advisory
for portions of the Oregon Cascade east slopes, but would like to
see how precip develops this morning. Locations below 2500 feet
should see mostly rain, with only a few snow flurries late this
afternoon or early this evening as precip ends in these areas. Winds
will be breezy to locally windy. Strongest winds still appear to be
over portions of the Kittitas Valley, and will continue the wind
advisory. Will see a wind down in showers overnight, then another
Pacific system will move into the region Monday morning. This system
will spread varying amounts of snow showers over the region through
Tuesday morning. These showers will wind down Tuesday afternoon.
Snow levels in the Basin may rise enough to mix with or change to
rain Monday afternoon. Overall snow accumulations with this system
will be light, though will have to take a look at central Oregon in
later forecast packages as there is the possibility of upslope
enhanced snow in this area. 90 

LONG TERM...Tuesday night through Saturday. High pressure will
build offshore Tuesday night and move east across the area
Wednesday. A few snow showers may linger in the northeast mountains
Tuesday night, but dry conditions are expected Wednesday. Another
storm system will approach the coast Wednesday afternoon and light
snow may develop along the Cascades Wednesday evening before rapidly
spreading east early Thursday morning. Cold air remains in place and
light snow is likely Thursday. Significant snow accumulations are
probable. Another problem is possible overrunning of warmer air
Thursday afternoon and night. The exact timing and location of any
warmer air remains uncertain. Snow showers will persist Friday and
Saturday, especially in the mountains, as a series of disturbances
move across the area.  Coonfield 

AVIATION...12Z TAFS...VFR or MVFR conditions today. Clouds will
lower and thicken as a cold front moves through the area today.
Rain has started in the favored upslope areas and Columbia Gorge.
Some locations such as KYKM and KPSC will likely be shadowed from
any steady rain...but will still likely see occasional light rain.
Cloud bases could lower to MVFR this morning...especially at KBDN
KALW KPDT and KRDM. Winds will increase late this morning and
afternoon as the front moves through. West or northwest winds of 15
to 25 KTS with gusts up to 30-35 Kts possible at times. Winds will
gradually decrease this evening...after 05/03z. 76 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  45  27  36  23 /  70  20  40  30 
ALW  48  31  37  28 /  80  30  40  30 
PSC  52  28  38  26 /  20  10  50  30 
YKM  49  21  37  22 /  20  10  30  30 
HRI  49  27  38  25 /  30  10  40  30 
ELN  43  23  34  21 /  40   0  40  30 
RDM  45  20  37  18 /  60  20  40  30 
LGD  40  23  33  23 /  90  30  30  40 
GCD  42  22  35  23 /  80  40  50  40 
DLS  50  33  40  29 /  70  10  40  30 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 10 PM PST this evening for ORZ502.

     Winter Weather Advisory until 10 PM PST this evening for ORZ050.

     Winter Weather Advisory until 3 PM PST this afternoon for ORZ509.

WA...Winter Storm Warning until 10 PM PST this evening for WAZ030.

     Winter Weather Advisory until noon PST today for WAZ520.

     Wind Advisory until noon PST today for WAZ028.

     Wind Advisory until 6 PM PST this evening for WAZ026.

&&

$$

97/

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

Northeastern Washington and Northern Idaho


034 
FXUS66 KOTX 041227
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
427 AM PST Sun Dec 4 2016

.SYNOPSIS...
Deep low pressure will bring rain, wind, and heavy mountain snow 
to the Inland Northwest today. The heaviest snow will occur over
the Cascade Crest, Northeast Blue Mountains, and the mountains of
the Idaho Panhandle. A second round of light snow is forecast for
the Columbia Basin, Palouse, and southern Idaho Panhandle on 
Monday. More snow will possible Thursday into Friday in most 
areas.


&&

.DISCUSSION...

...HEAVY MOUNTAIN SNOW TODAY FOLLOWED BY COLD TEMPERATURES FOR
MUCH OF THIS WEEK...

Today and Tonight: Early morning radar and satellite imagery shows
our mountains being buffeted by heavy snow. A cold low pressure 
trough over the Gulf of Alaska is descending southward this 
morning. The interaction between a deep plume of Pacific moisture 
with this advancing area of low pressure has produced widespread 
precipitation over western Washington. The strong westerly flow 
accompanying this system has contributed to an abrupt rain shadow 
in the lee of the Cascades which extends well into eastern 
Washington. Precipitation today will mainly be driven by 
orographic ascent with the Cascade Crest and mountains of the 
Idaho Panhandle receiving the brunt of the precipitation.

* Snow: This storm will likely produce up to 2 feet of snow over
  the Cascade Crest. Snow will continue in earnest through the
  morning hours, then decrease this afternoon as moisture sinks
  south into Oregon. Web cameras show a couple inches of
  accumulation as far east as Lake Wenatchee. The Leavenworth and
  Stehekin areas have remained too warm for accumulation. For the
  Central Idaho Panhandle, we expect 5 to 11 inches with most of
  the accumulation above 3000 feet. The heaviest precipitation
  will occur this morning through early afternoon. The snow level
  on the Camas Prairie is around 3500 feet with web cams at
  Winchester and Craigmont showing some wet accumulations. Snow
  levels will remain around 3500 feet until late in the afternoon.
  Look for 2 to 4 inches of wet accumulation on the Camas Prairie.
  Snow levels over the Blue Mountains will also be in the
  3500-4000ft range with 4 to 7 inches by early this evening.

* Winds: Breezy southwest winds this morning will transition to
  north or northwest this afternoon and evening. Strong cold
  advection from the north will steepen our low level lapse rates
  this afternoon. Sustained winds in the 15 to 20 mph range will
  be common over much of central and eastern Washington with gusts
  up to 35 mph in the Okanogan Valley, Upper Columbia Basin, and
  over the Palouse. Surface pressure gradients are expected to
  relax this evening leading to decreasing winds region-wide.
  Light winds and clearing skies will lead to rapidly falling
  temperatures. Afternoon low temps will fall into the teens and
  low 20s...our coldest night so far this season.

Monday: Light snow accumulations will be possible on Monday as low
pressure currently over the Gulf of Alaska moves across Washington
during the afternoon and evening. Our temperatures on Monday will
only reach the upper 20s and lower 30s. Chilly surface
temperatures combined with steep lapse rates under the cold upper
low will lead to relatively high snow to liquid ratios. At this
time, the GFS and ECMWF forecast the track of a 850-700mb low from
Ellensburg to Connell to Walla Walla. This track has the potential
to produce a band of 1 to 2 inches of accumulation over the
Columbia Basin, Palouse, and Camas Prairie. Dry north/northeast
winds will limit the northern extent of the snow with up to an
inch for Spokane and little to no accumulation for Colville,
Sandpoint, and Bonners Ferry. /GKoch

Tuesday and Wednesday: We switch to north-northwest flow Tuesday
as a weak upper ridge approaches from the west. Some snow showers
could linger in extreme southeast Washington on Tuesday, but 
otherwise the region will dry out with clearing skies on Tuesday 
and into Wednesday, before the next system arrives Thursday. The 
biggest story for this period will be the extreme cold 
temperatures ushered in by this northerly flow, certainly the 
coldest temperatures we've seen so far this season. Though models 
have been trending slower with the passage of the next system, 
temps still look to bottom out Wednesday morning with lows in the 
single digits to teens. This puts us 10-15 degrees below normal 
for this time of year. I dropped temps for Thursday morning a bit 
as clouds will likely be slower to move in overnight giving us 
more time to radiate. /bwilliams

Thursday through Sunday: Accumulating snow looks to return to the 
Inland NW late in the week as temperatures gradually warm. The 
jet stream will send a series of moist Pacific storms systems into
the region.

One minor change looks to be a slightly slower onset of the 
precipitation. ECMWF has slowed down the onset of the precipitation 
by almost 12 hours. Compared to the bullish GFS. Although the 00z
GFS has lowered its qpf so it's total qpf seems more in line with
the ECMWF solutions. Each of these models has been following its 
own independent solutions. The GFS has trended with a stronger 
upper low settling over Vancouver Isle Thursday afternoon, while 
the ECMWF has trended toward a more westward placement of the low 
and a stronger ridge over the region. In fact, the 00z GFS seems 
to be one of the more aggressive solutions within the ensemble 
members. At this point, will follow a compromise among the 
solutions. 

Given the cold snap early in the week and very low snow levels,
the precipitation type looks to be snow in most areas initially.
The main question is how much. Models again are not consistent on
amounts beyond day five. Yet the warm air advection and strong
isentropic lift brings a good possibility of widespread
significant snowfall for Thursday into Friday morning in most
locations. Showery and locally breezy conditions will develop by
Friday night into Saturday with the mountains receiving more of
the snow and a possible rain/snow mix in the Columbia Basin,
Wenatchee Valley and LC Valley. There is the potential for another
winter system to arrive by the end of the weekend with another
round of snow and low elevation rain. Overall temperatures will be
trending to slightly above normal levels by the weekend. /rfox.

&&

.AVIATION...
12Z TAFS: A strong westerly jet will produce orographic
precipitation this morning. The rain shadow in the lee of the
Cascades is extending as far east as the Idaho border.
Precipitation over the Panhandle will be primarily rain below 3000
feet this morning. The arrival of a cold front early this 
afternoon will shunt the plume of Pacific moisture southward, and 
precipitation will transition to rain/snow showers as drier cooler
and drier air advects southward. The mountains will be pommeled 
with heavy snow today, but our most of our airports will get 
little to no accumulation. Gusty west or northwest winds will 
impact most airports today through the 00z-02z time frame./GKoch

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        38  21  27  17  24   8 /  20  10  40  50  10  10 
Coeur d'Alene  38  21  27  15  21   6 /  80  10  30  30  10  10 
Pullman        40  20  29  19  26  11 /  90  10  50  50  20  10 
Lewiston       47  27  34  24  31  18 /  90  20  30  50  20  10 
Colville       40  17  28  15  25   9 /  20   0  10  30  10  10 
Sandpoint      37  20  26  13  19   3 / 100  10  20  20  10  10 
Kellogg        35  18  25  11  19   3 / 100  20  20  30  10  10 
Moses Lake     47  22  33  22  30  15 /  10   0  50  40  10   0 
Wenatchee      45  23  32  22  29  15 /  10   0  50  40  10   0 
Omak           38  17  28  17  26  11 /  10   0  30  30  10   0 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory until 10 PM PST this evening above 4000 
     feet for Lewis and Southern Nez Perce Counties.

     Winter Storm Warning until 7 PM PST this evening above 3000 feet 
     for Central Panhandle Mountains.

WA...Winter Weather Advisory until 10 PM PST this evening above 4000 
     feet for Northeast Blue Mountains.

&&

$$

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

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