Western Washington

285 
FXUS66 KSEW 150438
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
838 PM PST Mon Dec 14 2020

.UPDATE...As expected, rain has reached the outer coast at this hour 
and will continue to push eastward across the area over the next 
several hours. Made adjustments to the 06 and 12Z POP grids and 
weather to reflect these trends. With the heaviest snowfall 
accumulation expected in the Cascades Tuesday morning, those with 
travel plans across the passes should prepare for winter weather 
driving conditions. Be sure to check WSDOT for the latest road 
conditions before you go!

The rest of the forecast remains on track and the discussion is
below.

Pullin

&&

.PREV DISCUSSION... /issued 330 PM PST Mon Dec 14 2020/ 

SYNOPSIS...An exiting upper trough will result in some scattered 
showers over the area today. A system will move across Western 
Washington on Tuesday for lowland rain, mountain snow, and locally 
windy conditions. Active weather is expected through the weekend as 
a series of systems move through the area.

SHORT TERM /TONIGHT THROUGH THURSDAY/...Still some scattered 
showers over W WA this afternoon as a minor shortwave in the wake of 
the main exiting trough continues to take advantage of the plentiful 
low level moisture. In addition...looks like a small convergence 
zone has set up over portions of North Snohomish/Southern Skagit 
counties...but radar trends show this activity slowly trending 
downward.

Models suggest weak upper level ridging looks to bring a quiet 
period starting this evening/early tonight but not lasting too 
terribly long as the next frontal system will hit the coast is 
expected to reach the coast during the overnight period. Current 
satellite, particularly the IR imagery, suggests that this might be 
a touch on the optimistic side. As such, current forecast has 
chances for rain increasing after 10 PM PST this evening and that 
looks like it fits well with current satellite and radar trends. 
This incoming front looks to be more of a classic lowland rain/mtn 
snow type...although breezy to locally windy conditions are possible 
along the coast and the northern inland portions of the CWA 
/including the San Juans/. Wind speeds do look to fall short of any 
headline criteria. The same cannot be said of snowfall in the 
mountains as the forecast remains consistent with borderline Winter 
Weather Advisory snowfall amounts in both the Olympics and Cascades 
above 3000 ft. Most of the expected accumulation is expected during 
the morning hours Tuesday as best moisture looks to be along the 
leading edge of the front. Activity will taper off during the 
afternoon hours, but additional accumulations will still be 
possible. For the lowlands, rainfall amounts up to and around a 
quarter of an inch can be expected and, like in the mountains, most 
of this is expected to fall early in the day with PoPs slowly 
diminishing in the afternoon and evening. One last note on this 
system, incoming seas with the front look to be high enough to 
possibly result in some minor coastal flooding and, as such, a high 
surf advisory will go out with the afternoon forecast package as 
well.

Wednesday will see another weak upper level ridge introduce yet 
another meager break in the action with the next frontal system all 
teed up to enter W WA Wednesday afternoon. Precip amounts with this 
one look to be a little bit more than the Tuesday system, but snow 
levels will be on a gradual increase and as such, potential for 
winter weather headlines in the higher elevations seems minimal at 
this time. The associated upper level low will keep rain in the 
forecast for Thursday as the front and then the low itself exits.

High temps in the short term show little in the way of variance, as 
one might expect, with lowland locations seeing afternoon highs in 
the mid to upper 40s.

LONG TERM /FRIDAY THROUGH MONDAY/...Minimal rest for the weary and 
drenched as yet another system looks to make its way to the coast by 
late Friday morning. This pushes along quickly enough akin to 
systems from earlier in the week. The following system expected 
Saturday morning may prove wetter and windier than previous fronts 
this week. Fortunately, current model solutions continue to indicate 
that like the previous systems, snow levels will continue to rise 
and as such there will be minimal snow concerns for both lowlands 
and mountains this go round. In the bad news column though, this 
system looks to set up an atmospheric river, which, when combined 
will all the activity W WA will have seen at this point, may give 
rise to flooding concerns. It does need to be noted that ensemble 
members are all over the place with potential rainfall amounts, with 
latest operational deterministic models actually proving to be 
greater than the ensemble mean and, as such, inserting a degree of 
uncertainty in the forecast.

The upper level trough behind this front will swoop through the area 
Sunday and exiting quickly Sunday night. Brief ridging might prove 
strong enough to dry Monday out if one were to follow the thinking 
of the GFS while the ECMWF pushes another upper level low over the 
area. This has the benefit of pushing the atmospheric river to the 
south of W WA, but will still keep some lingering rain risk in the 
forecast for the remainder of the long term. Opted to lean more 
toward the wetter ECMWF and the general trend in the ensemble mean 
which shows overall less precip, but lingering precip nonetheless.
 18

AVIATION...The next system will approach the region overnight 
and into Tuesday, with radar this evening already showing rain 
moving into the coast as a warm front brushes the area. Current 
conditions for most TAF sites are a mixed bag this evening, 
however expect ceilings to lower to more widespread MVFR and IFR 
conditions by late tonight and through the overnight period. 
Conditions will likely remain MVFR to IFR through the morning 
hours as the bulk of the precipitation moves through the region. 
Cannot rule out localized LIFR conditions for a few hours in spots
as the more widespread rain moves through. Southerly winds will 
pick up near 09Z, mainly persisting at 10-18 knots with gusts to 
25 knots possible at times. Breeziest areas look to be in the 
vicinity of terminals along the coast and the northern interior 
(mainly KHQM, KBLI, and KPAE at times).

KSEA...VFR conditions expected to drop back down to MVFR
overnight. As a front moves through, expect periods of rain with 
reduced visibilities. Southerly winds 8-12 knots are expected 
during the frontal passage. 

Butwin/Borth

MARINE...Winds currently increasing as a frontal system moves into
the region tonight. Expect hazardous winds and seas to persist
through much of the day tomorrow, with gales expected offshore and
across the Northern Inland waters/Admiralty inlet/Eastern Strait.
While winds will decrease Tuesday afternoon and evening, westerly 
swells will be on the increase offshore. With another system
expected to affect area waters with strong winds on Wednesday,
swells will increase to around 25 feet offshore, with 20-22 foot
swells along the coast by Tuesday night. Swells will likely remain
elevated through at least the end of the week, if not into the
weekend as additional systems are expected to bring unsettled
weather to the area.

Butwin/Pullin

HYDROLOGY...A series of progressive weather systems are on track to 
impact the area this week. Rivers are expected to rise, but 
widespread flooding is not expected due to the fast moving nature of 
these weather systems. More sensitive river basins such as the 
Skokomish approach minor flooding later this week in response to 
higher QPF. Model trends continue to show a warmer and quite wet 
scenario starting Saturday and this could push the Skokomish River 
past minor flood and possibly into moderate flood level. This 
potential atmospheric river scenario may impact additional rivers
across Western Washington, with additional rivers approaching 
minor flood stage. Confidence in this scenario remains low at this
time due to model disagreements and given how far out in time the
scenario is expected to develop. Monitor future forecasts for 
more information. 18

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory from 3 AM to 4 PM PST Tuesday for 
     Cascades of Pierce and Lewis Counties-Cascades of Snohomish 
     and King Counties-Cascades of Whatcom and Skagit Counties-
     Olympics.

     High Surf Advisory from 4 PM Tuesday to 7 AM PST Wednesday for 
     Central Coast-North Coast.

PZ...Small Craft Advisory until 4 PM PST Tuesday for Grays Harbor Bar-
     West Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 9 PM PST this evening 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 until 10 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.

     Small Craft Advisory until midnight PST tonight for East 
     Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland 
     Waters Including The San Juan Islands.

     Gale Warning from midnight tonight to noon PST Tuesday for East 
     Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland 
     Waters Including The San Juan Islands.

     Small Craft Advisory until 10 AM PST Tuesday for Central U.S. 
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 4 AM PST Tuesday for Admiralty Inlet.

     Gale Warning from 4 AM to 10 AM PST Tuesday for Admiralty Inlet.

     Small Craft Advisory until 4 PM PST Tuesday for Puget Sound and 
     Hood Canal.

&&

$$

www.weather.gov/seattle

Southwestern Washington and Western Oregon

028 
FXUS66 KPQR 150504 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR 
901 PM PST Mon Dec 14 2020

Updated Short Term/Aviation/Marine Sections

.SYNOPSIS...The next frontal system will move through the area
Tuesday. Cascade snow levels will be well below the passes late
tonight and early Tuesday, but rise above the passes during the day.
Weak high pressure returns Tuesday night and Wednesday morning,
followed by another frontal system late Wednesday and Wednesday
night. Active weather will continue into the weekend as a series of
fronts move across the region. High surf and minor tidal overflow
conditions will continue through Wednesdsay morning.   

&&

.SHORT TERM...Tonight through Wednesday night (UPDATED)...Evening
GOES-17 water vapor imagery revealed a transient upper level ridge
shifting east of the Cascades as the next frontal system approaches
the coast. At 04Z the parent low was centered near 50N 142W with the
occluded front stretching over Vancouver Island and far NW
Washington. NWS dual-pol doppler radar showed some light returns
moving into southwest Washington and far northwest Oregon. At 04Z
KAST reported light rain. At 04Z the KAST profiler indicated snow
levels slowly rising, to around 3000 feet. Cascade observation sites
suggest snow levels are closer to 3500 feet. Low-level colder air
remains over the Upper Hood River Valley with Parkdale reporting 31
deg at 03Z. The Central Gorge is slightly milder with temps in the
mid to upper 30s.

The only change to the forecast was to add a chance of -FZRA to the
Upper Hood River Valley 12Z to 15Z Tue. The 01Z NBM 1D viewer for
Parkdale indicates a high probability (up to around 85%) of -FZRA
with the onset of precipitation. Fortunately, this appears to be very
short-lived, as the -FZRA probability drops to 0 percent by 18Z Tue.
The NBM suggests around a couple hundredths of ice accumulation and
possibly a half-inch or so of snow. The KTTD-KDLS gradient peaks
around -3 mb at 12Z-13Z then falls off fairly quickly. By 18Z the
gradient becomes slightly onshore. Thus, any -FZRA that does occur
should not result in much, if any, impact. Furthermore, the NBM
viewer forecasts a high temp of 42 for Parkdale. Onshore low-level
flow strengthens during the afternoon, with a peak KTTD-KDLS gradient
around 3.5 mb late in the day. Would not be surprised to see 20-25
mph southwest to west wind gusts in Hood River and the Upper Hood
River Valley Tue afternoon. Weishaar

REMAINDER OF SHORT TERM FOLLOWS: Stratiform rain will likely start
along the coast around midnight tonight and make its way inland
covering the CWA by early Tuesday morning. Snow in the SW Washington,
NW Oregon Cascades will be heaviest tomorrow morning when snow levels
drop to around 2500 ft and the bulk of the QPF arrives. However, snow
levels quickly rise to around 4000 ft Tuesday afternoon as the warm
sector moves over the region. A weak cold front will arrive Tuesday 
afternoon bringing a brief period of westerly winds and showers. 
Many of the GFS and ECMWF ensemble members continue to show 
measurable rain overnight Tuesday so have kept PoPs at a slight 
chance during this time. 

There might be a brief period of dry weather in the early afternoon
Wednesday but rain will quickly pick up again as the next system
moves across the Pacific. This system will track towards Vancouver
Island bringing another round of rain across the CWA Wednesday into
Thursday. 

The two aforementioned systems will keep a predominantly SW flow over
the region. 805mb temps will swing between -2 and 2 C as the fronts
pass and snow levels will stay around 4000 ft or higher throughout
the week. There are no major concerns for high winds, flooding, or
significant snowfall. 

Incoming swell and highest tides of the year are combining for a
couple of coastal land threats the next 36 hours. Have issued another
Coastal Flood Advisory for Tidal Overflow for tomorrow covering the
South Washington and North Oregon Coasts as increasing swell will
offset the slowly lowering high tides. Also, beginning late tomorrow
afternoon, a 20-22 foot westerly swell at 17-19 seconds will result
in a large amount of breaking wave energy on the beaches. Have issued
a High Surf Advisory for Tuesday afternoon through early Wednesday
morning. -BPhillips


.LONG TERM...Thursday through Saturday night...A busy week of weather
will continue through the weekend. On Thursday, a closed low pressure
system will move over Vancouver Island, moving eastward as it weakens
through the afternoon. With this transition, the associated front
that brought rain and snow on Wednesday will begin to ease and
precip will taper off through the day. While rain and snow likely 
will be less widespread, there is a chance that there could be 
periods of heavier precip at times, especially snow as conditions 
cool. Overnight through the Cascades, especially the Lane County 
Cascades, there is a chance for some slightly heavier accumulating 
snow at 4000 ft or higher Thursday night. These chances for snow may 
be hindered though as a flat ridge develops overnight on Thursday 
into Friday. Friday morning will likely be the coolest night of the 
week as there is more cold air trickling into the area, and likely 
more radiational cooling. 

The needed weather "break" will be short lived though as a long wave
trough extends south from a area of low pressure in the Gulf of
Alaska. A weak occluded front should push inland Friday afternoon but
there is still quite a bit of model disagreement; will discuss this 
later. Being the case, kept moderate PoPs in the forecast. 
Temperatures will likely start to rise as warmer air aloft is 
advected into the area behind this occluded front. Temperatures at 
850 mb (~5000 ft) rise to around 5C on Saturday, potentially becoming
the warmest day of the week. Could see Valley temperatures in the 
mid- 50s even. However, with that warm air comes the caveat of it's 
ability to hold on to more water. This comes into play on Sunday as a
strong system moves over the area. Now some guidance is suggesting 
that this is an atmospheric river like event but there is a lot of 
uncertainty. It does have some of the more traditional traits of an 
atmospheric river: zonal perpendicular flow to the coast, warm moist 
air from the Pacific, and upper air support with the jet stream. If 
the trend holds, can expect quite a bit of precipitation on Sunday 
with the highest accumulations along the coast. 

Will end the discussion by saying that there is not a lot of 
confidence in the long term forecast. Models continue to struggle 
coming into agreement with most of the previously mentioned systems 
both in strength and track. Ensemble model runs of the ECMWF and GFS
are showing different low centers, a wide spread of precipitation
accumulation and types, amongst many other forecasted factors. With 
the solution spread there will likely be a lot of fluctuations in the
forecast for the next few days. While the specifics in the long term
have been challenging to narrow in on, the overall pattern still 
holds through the remainder of the week.   -Muessle


&&

.AVIATION...06Z TAFs: Frontal system is approaching the WA/OR
coast, with spotty -RA already developing north of KTMK as of 
04z. Conditions are mostly VFR across the forecast area for the 
time being, with most of the lower clouds from earlier in the day
clearing out as the region begins to feel S-SE flow associated
with the incoming frontal system. VFR conditions will deteriorate
to MVFR later tonight as rain spreads across the forecast area.
There will likely be a brief period between 15/10z-15/14z where 
south winds gust 20-30 kt for coastal areas as the occluding cold
front moves onshore, along with heavier rain pushing vsbys into 
the 2-4 SM range. Winds with the front should be lighter for 
inland terminals, but MVFR cigs/vsbys will be likely by daybreak 
Tue. Cool, moist onshore flow develops behind the front, 
potentially giving the coast some periods of VFR Tuesday while 
inland areas remain under MVFR conditions and occasional -SHRA.

For detailed regional Pac NW weather information, go online to: 
http://weather.gov/zse

KPDX AND APPROACHES...VFR conditions prevail this evening with
light to moderate E-SE low-level flow. Light rain will develop
around 15/12z, with cigs/vsbys lowering into MVFR by 15/15z. 
Gorge outflow winds increase later this evening with SEly gusts 
20-25 kt probable beginning 15/12Z. Once cigs fall below 030, 
then expect little improvement for the rest of Tuesday under 
showery activity.  Weagle/JBonk

&&

.MARINE...Expect the swell train from last night to continue 
subsiding but perhaps not quite as much as previously expected. 
As a Pacific frontal system approaches and winds increase, wind 
waves will probably make up for the subsiding swell component, 
keeping combined seas in the 12-15 ft range as we head into early
Tuesday morning.

Gales continue to look likely with peak gusts around 40 kt so 
will keep the warning as is. Seas will steepen at the same time 
as wind waves build and perhaps reach the upper teens as the
front moves through around 0400-0600 PST. Another frontal system
is expected Wednesday, and will bring another chance for gales. 

Behind the front Tuesday afternoon, another long period swell 
train is expected to arrive, moving across the coastal waters 
Tuesday night with peak seas likely to reach the range of 20 to 
23 ft.	Weagle/JBonk

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Surf Advisory from noon Tuesday to 9 AM PST Wednesday for 
     Central Oregon Coast-North Oregon Coast.

     Coastal Flood Advisory from 9 AM to 4 PM PST Tuesday for North 
     Oregon Coast.

WA...High Surf Advisory from noon Tuesday to 9 AM PST Wednesday for 
     South Washington Coast.

     Coastal Flood Advisory from 9 AM to 4 PM PST Tuesday for South 
     Washington Coast.

PZ...Small Craft Advisory until 10 PM PST this evening for coastal 
     waters from Cape Shoalwater WA to Florence OR from 10 to 
     60 NM.

     Gale Warning from 10 PM tonight until 10 AM PST Tuesday for 
     coastal waters from Cape Shoalwater WA to Florence OR from 
     10 to 60 NM.

     Small Craft Advisory until 10 PM PST Tuesday for Columbia River 
     Bar.

     Small Craft Advisory until midnight PST tonight for coastal 
     waters from Cape Shoalwater WA to Florence OR out 10 NM.

     Gale Warning from midnight tonight to noon PST Tuesday for 
     coastal waters from Cape Shoalwater WA to Florence OR out 
     10 NM.

&&

$$

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Southeastern Washington and Northeastern Oregon

319 
FXUS66 KPDT 150108
AFDPDT

Area Forecast Discussion...updated aviation
National Weather Service Pendleton OR
508 PM PST Mon Dec 14 2020

.SHORT TERM...This afternoon through Wednesday...The active weather 
pattern continues with a parade of systems poised to drive through
the PacNW over the next several days. An upper level shortwave 
trough is still slowly departing our area to the east this 
afternoon. This has kept pockets of light snow along the western 
slopes of the Cascades and Blues this morning. Moisture will taper
off this evening as a transient ridge pushes into the region 
tonight, helping to dry out these higher elevations. This ridge is
rather weak and shifts quickly east, opening the door to a 
moderate frontal system and associated shortwave trough that will 
move into the PacNW Tuesday morning. Expect mountain snow and 
lower elevation rain through the day on Tuesday as the system 
passes. There is significant warm air advection ahead of the 
system, which will attribute to increasing snow levels through the
day. Snow levels will start out between 1500- 3000 feet in the 
morning, before increasing to 3000-4000 feet by the afternoon. 
Snow totals should stay below advisory criteria, as the WA 
Cascades are likely to pick up between 2-6 inches and the Blues 
between 2-4 inches. Breezy southwesterly winds will follow shortly
behind the frontal passage, as pressure gradients should be 
rather tight. As this trough exits our area, another transient 
ridge follows suit to briefly dry us out ahead of the next system.

This next system approaches the PacNW Wednesday morning, making into 
our area by the afternoon hours. This system is a bit more potent 
than the previous one, but the big difference will be snow levels. 
Levels will keep creeping up into the 4000-5000 feet range, so snow 
is expected above 4000 ft but below will all be rain. This system 
should be a little slower to exit our region, so there is a 
potential for snow amounts to reach advisory status for areas of the 
Cascades and Blues, but current confidence is still marginal. Stay 
tuned. 75

.LONG TERM...Wednesday night through Monday... Models in 
reasonable agreement with the extended period showing an active 
weather pattern. Mainly a westerly flow aloft with several systems
moving through and higher snow levels. An upper level trough will
be moving across the region Wed night into Thu with rain and 
mountain snow. Upper ridge with a brief break Thu night into Fri. 
Another weak upper trough Fri night and Sat with mostly rain. A 
much stronger system then moves across the Pacific northwest 
Sunday and Monday. This will bring rain and wind. A warm airmass 
will result in high snow levels over the weekend. Some models are 
indicating the potential for heavy rain on Sunday. Strong westerly
winds aloft will also mix down for a windy day. 94


&&

.AVIATION...00Z TAFS...Columbia Basin/Gorge taf sites will have low  
ceilings tonight with bkn-ovc 010-030. Visibility will likely 
decrease this over night as well into the 2-5sm br range. Front 
moving through tomorrow will bring a round of rain showers for the 
taf sites with mountain snow expected. Expect mountain obscuration 
during this time. Winds light overnight, becoming 10-15kts behind 
the front tomorrow.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  29  44  35  47 /   0  40  10  30 
ALW  31  45  37  47 /  10  60  20  20 
PSC  33  44  37  45 /   0  40   0  20 
YKM  28  40  29  41 /  10  40   0  40 
HRI  30  43  35  47 /   0  30   0  20 
ELN  25  38  27  39 /  20  50  10  40 
RDM  27  46  31  46 /   0  20   0  50 
LGD  27  36  31  40 /  10  80  30  20 
GCD  27  41  33  44 /   0  80  10  30 
DLS  34  43  36  45 /  10  40  20  60 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
&&

$$

SHORT TERM...75
LONG TERM....94
AVIATION.....84

Northeastern Washington and Northern Idaho

015 
FXUS66 KOTX 150556
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
956 PM PST Mon Dec 14 2020

.SYNOPSIS...
Anticipate flurries and fog overnight, then A Pacific front will 
bring snow to the Inland Northwest on Tuesday. Another system 
arrives Wednesday night into Thursday, but lowlands may only see a
mix of rain and snow. Another quick moving frontal system is 
possible Friday night. Then a stronger and wetter storm system is 
expected over the weekend. Snow levels will be rising to at or 
above pass levels. The weekend storm will also bring breezy to 
windy conditions to the Inland Northwest.


&&

.DISCUSSION...
Quick update: Added flurries for the evening based on web cams and
observations from Spokane, Deer Park to Pullman and Coeur d'Alene.
A westerly flow in the moist boundary layer that extending within
the dendritic zone aided in the light precipitation. Anticipate
these flurries to taper off. Meanwhile the next round of light
snow will push east of the Cascades overnight. Areas of freezing
fog will be found as a widespread stratus deck stretches over the
lowlands. /rfox. 

The Inland Northwest is currently sitting on the backside of an 
upper level trough that has dug all the way down to Arizona. This 
pattern is driving light westerly flow aloft and is producing very
light snow showers in orographically favored areas. Elsewhere, 
thick stratus exists and is clearly seen on visible satellite 
imagery this afternoon. It is this stratus that has held 
temperatures steady throughout the entire day and limited 
visibilities across our area. 

Tuesday: Our next weather disturbance will move in on Tuesday
bringing more rain and snow to our area. In general, snow levels
will start near 500 to 1000 feet Tuesday morning as precipitation
begins around 4am in Wenatchee and 8 am for the Spokane/Coeur 
d'Alene region. With strong warm air advection, snow levels will 
gradually rise between 2000 to 3000 feet by the evening hours
although most of the preciptiation will be over by then. 

In terms of impacts to our roads, our local road model shows wet
and slushy roads across the Columbia Basin and into Spokane. North
and east of Spokane road temperatures look to be cold enough to
support snow/ice on untreated surfaces. Because of this, we have
issued a winter weather advisory for our northern mountains, the 
ID panhandle, and down through Coeur d'Alene. 

However, there is still some uncertainty in the forecast for the
Spokane region as temperatures are quite marginal. While we 
expect an inch or less of snow in Downtown Spokane, a degree or 
two could make a difference. Additionally, there is some 
uncertainty as to how much precipitation we will actually see, 
which again, could change snow amounts by an inch or so in the 
Spokane area. Below is our latest forecast for snow totals 
through Tuesday. Wilson

	* Tuesday's Snowfall
	Spokane (Downtown): 1 inch or less
	Spokane (Airport) : 1-2 inches
	Coeur d'Alene	  : 1-3 inches
    Deer Park         : 2-4 inches
    Sandpoint         : 2-4 inches
	Wenatchee		  : less than 1 inch

Wednesday through Monday: The parade of storms will continue in a
progressive weather pattern with a series of shortwave troughs and
ridges pushing across. The next two attractions in this weather
parade will feature similar weather potential. We will see mixed
precipitation in the valleys: snow most likely up into the Methow
Valley over to the Okanogan Highlands, a mix of rain and snow
across the valleys of the Northeast Mountains to the Northern
Panhandle, and mostly rain into the basin. Timing will be
Wednesday night for one shortwave disturbance and then another 
one around Friday night. Snow amounts will be on the light side 
and not expected to be a big impact, but could see road surface a 
little slick for the morning commutes.

The strongest storm system still looks to arrive over the weekend.
There will be an energetic upper level jet pointed toward the
Northwest. The jet will carry with it ample amounts of moisture
falling within what would be classified as a moderate atmospheric
river. So a wet weekend looks likely, except in the rain shadow of
the Cascades where strong westerly flow will limit accumulations
around Wenatchee to Omak and out over the Waterville Plateau and
into the western basin. Heavy precipitation on the order of 2-4 
inches at the Cascade crest and 1-2 inches possible in the Idaho 
Panhandle. Much warmer air will move in as well, which should 
result in rising snow levels. As such, valleys will see mostly 
rain with snow pushing up higher and higher on the mountains with
mountain passes also seeing snow changing over to rain. Not to 
say that mountains couldn't see moderate to heavy snow 
accumulations depending on how fast snow levels rise.

The Methow Valley and associated valleys tucked up into the east 
slopes of the northern Cascades will also hold on to cold air the 
longest and may see some freezing rain Saturday night into Sunday 
morning. Temperatures will jump up into the 40s and 50s at lower 
elevations with rain on Sunday. The mild temperatures plus wind 
will contribute to melting snow at least at lower elevations. 
These winds could be quite gusty on Sunday as well and be in the 
neighborhood of gusts between 30-45 mph. All of these factors 
combined will also increase the risk for flooding impacts. The 
good news is that a decently healthy snowpack at higher elevations
should soak up a majority of the rainfall that falls there 
limiting impacts in the valleys. It is a situation that bears 
monitoring for mountain snowfall, winds and flooding potential. 
/SVH

&&

AVIATION...
06Z TAFS: The stratus deck will persist at the TAF sites through
the period with mostly IFR conditions along locally LIFR will be
found with patchy dense fog near KLWS or local flurries over north
Idaho. The next round of snow will push across the TAF sites late
tonight and through the daylight hours on Tuesday. The heavier
bands of snow will bring LIFR conditions especially in KGEG to
KPUW and KCOE. May see a rain snow mix from KCOE to KPUW before
the precipitation tapers off by early Tuesday evening. Winds will
remain light, although westerly winds will pick by Tuesday evening
and could lower cloud decks and decrease visibilities from KGEG to
KPUW. /rfox. 

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        28  36  31  38  32  39 /  10 100  10  10  60  40 
Coeur d'Alene  28  35  32  39  32  39 /  40 100  30  10  60  50 
Pullman        27  36  31  40  32  39 /  10  90  30  10  50  40 
Lewiston       30  40  35  46  37  46 /   0  80  10  10  40  40 
Colville       24  34  27  36  30  39 /  10 100  10  20  70  40 
Sandpoint      28  34  32  38  33  38 /  40 100  70  20  80  70 
Kellogg        30  35  35  40  36  39 /  50 100  70  20  80  80 
Moses Lake     29  38  29  41  31  42 /  10  70   0  20  60  10 
Wenatchee      29  37  31  36  32  40 /  20  70   0  40  80  30 
Omak           29  34  29  35  32  39 /  20  80   0  20  70  20 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory from 4 AM to 7 PM PST Tuesday for 
     Northern Panhandle. 

     Winter Weather Advisory from 4 AM to 4 PM PST Tuesday for Coeur 
     d'Alene Area. 

WA...Winter Weather Advisory from 4 AM to 4 PM PST Tuesday for 
     Northeast Mountains-Okanogan Highlands. 

     Winter Weather Advisory from 3 AM to 4 PM PST Tuesday for the 
     cascade crest including highway 2 between coles corner and 
     stevens pass for East Slopes Northern Cascades.


&&

$$