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

Western Washington


568 
FXUS66 KSEW 211728
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
928 AM PST Thu Feb 21 2019

.SYNOPSIS...Dry northerly flow will continue today for sunny skies
and quiet weather. A frontal system will arrive from the 
northwest on Friday. A cool upper trough will follow the front for
the weekend into the early part of next week. Low snow levels 
will continue through the period. 

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...Dry, northerly flow will 
prevail today for sunny skies. We're off to a chilly start (temps in
the 20s to 30s) but we'll warm back up into the lower to mid 40s 
this afternoon. The current forecast is on track. 33

Previous discussion...The leading edge of the next frontal system
looks to hold off until early Friday morning with best threat of 
widespread precip waiting until the late morning to afternoon 
hours. Interior snow levels will be pretty low during the morning 
hours...so any precip that kicks off early will likely be snow or 
a rain/snow mix. As already mentioned however...lowland amounts 
during this time period are expected to be light. By the time POPs
climb into likely category...snow levels will have jumped to or 
near 1000 ft...almost 2000 ft along the coast...and as such 
remainder of precip expected to fall as rain. The front moves on 
Friday night but a broad area of upper level low pressure will 
remain...keeping an active...showery period over the CWA for the 
bulk of the weekend. As the core upper level low finally 
approaches the area Sunday...the system looks to stall. This will 
keep the prospect for showers in the forecast for the bulk of the 
CWA...however model disagreement on the actual position of the low
may allow for the northernmost quarter of the CWA to meet with 
dry conditions. Given model disagreement...confidence in this is 
fairly low...but no harm in positive thinking at this point in the
winter.

Snow levels during the short term will oscillate between 1000-2000 ft 
during the day and 500 ft to near sea level during the overnight 
hours. As such...the threat for snow or mixed precip never really 
goes away. The plus side of this is that any lowland snow that does 
occur will be minimal with not much in the way of accumulations 
expected...and any localized accumulations that do occur will be 
gone by mid to late afternoon. Adding more proof to minimizing any 
snow threat will be both high and low temps throughout the 
period...with highs in the low 40s and overnight/morning lows either 
right around freezing or 2-3 degrees above. At the very least...one 
can surmise that the gradual march into...well...March may finally 
be taking a bit of the sting out of our lingering winter weather.
SMR

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Previous discussion...Models
fall seriously out of sync for Monday...as the ECMWF takes the 
upper low out into the Pacific and allows for a minor upper level 
ridge to take root Monday into Tuesday. The GFS shows this 
happening too...just almost 24 hours later than its Euro 
counterpart. And the current runs remain out of phase like this 
for the remainder of the forecast period...although...again...their
general patterns remain fairly similar...generally dry conditions
early next week followed by a return to active weather offset by 
a gradual climb in snow levels and daytime highs during the middle
of the week. Needless to say...even though specifics are hard to 
come by and confidence remains low...the general trend seems to 
show that any future lowland appearances of that other four letter
s word...snow...may have to wait until next winter. SMR

&&

.AVIATION...North to northeasterly flow will ease across the north 
interior, and remain generally below 10 to 15 kt across Western 
Washington. Patchy stratus is nearly dissipated and VFR skies 
are expected through this evening. Light flow aloft will become 
moderate southerly flow tonight under high pressure ahead of a 
frontal system. An upper trough and associated surface front will 
move into the region Friday morning. Light rain will develop by 18z 
Friday at most TAF locations, with areas of MVFR cigs. Precipitation 
will become showery but clouds will persist.

KSEA...North wind to 10 kt. VFR skies through most of tonight. High 
and mid-level clouds increase tonight and lower to MVFR toward 15-
18Z Friday as rain spreads into the area with the next frontal 
system. Surface winds N-NE 5 to 10 knots today shifting to southerly 
near or after 06Z tonight. dtm

&&

.MARINE...Northeasterly offshore flow will continue to ease this 
afternoon and turn southerly tonight as high pressure over British 
Columbia shifts to the southeast and a front approaches from the 
northwest. Westerly swell 10-12 feet will continue to subside this 
afternoon and evening. The gradients in the Strait and the northern 
interior waters have eased and will continue to remain below small 
craft criteria.

The aforementioned frontal system will move through the area on 
Friday. A trailing weak low over Haida Gwaii will move to Oregon 
Saturday and Saturday night. 

Northeasterly offshore flow will develop on Sunday and continue into 
Monday with high pressure over British Columbia and low pressure 
over Oregon. Schneider/DTM/SB

&&

.HYDROLOGY...River flooding is not expected for the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory for hazardous seas until 8 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.

     Small Craft Advisory for rough bar until 8 PM PST this evening 
     for Grays Harbor Bar.

&&

$$

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


913 
FXUS66 KPQR 211750
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
950 AM PST Thu Feb 21 2019

.SYNOPSIS...High pressure will bring dry weather today, albeit still
on the chilly side. While much of the region sees partly to mostly
sunny skies today, low clouds are expected to persist into early
afternoon for the inland valleys south of Salem. Meanwhile, a cold
front will be approaching from the Gulf of Alaska. This system will
spread valley rain and mountain snow across the forecast area Friday.
The front will likely stall over Oregon through the weekend, bringing
plenty of precipitation to portions of western Oregon. Snow levels
will lower to the north of the front, potentially approaching the
valley floors at times, though this remains uncertain. More certain
is the fact that another major dump of snow appears likely for the
Oregon Cascades this weekend through early next week.

&&

.SHORT TERM...Today through Saturday...No changes. Previous 
discussion follows. Weak high pressure will move southward across 
the forecast area today, bringing a break from the wet weather. Some 
patches of dense valley fog developed earlier Wednesday night, but 
these have generally lifted in favor of a low stratus deck. Low 
clouds will be most persistent south of Salem today, especially near 
Eugene. While our current high temperature forecast has Eugene 
reaching the lower to mid 40s today, Eugene could easily be stuck in 
the 30s today if low clouds fail to clear by late afternoon. A 
similar situation may happen in Hood River as well, due to the 
stratus and cool air that have pooled up in the Columbia Basin. 
Otherwise, northerly flow and high pressure should bring partly to 
mostly sunny skies for most of the forecast area today, with 
temperatures only slightly below seasonal normals.

Our next frontal system is taking shape as a potent shortwave trough
moves into the Gulf of Alaska. The resulting low pressure and cold
front will move quickly southeast, spreading precipitation across
much of western Washington by midday Friday and across northwest
Oregon Friday afternoon and evening. At this point it appears
precipitation will arrive too late to cause a snow or freezing rain
threat for low elevations Friday, especially as southerly flow
increases through the day. However, if the frontal timing speeds up
by 4-6 hours from latest guidance, there could be a brief period of
snow or freezing rain in the lowlands Friday morning. Again, this
appears unlikely based on latest guidance, with only about a 10
percent chance of significant snow- or ice-related problems for the
lowlands Friday. 

Latest guidance continues to suggest the front will stall somewhere
over west-central or southwestern Oregon Saturday as it begins to
interact with the subtropical branch of the jet stream. If and where
this front stalls will have major implications on the forecast
Saturday through early next week. Given that most models have some
variant of an atmospheric river aimed toward west-central or
southwest Oregon by late Sat night, suspect the front will stall
somewhere near Douglas County. This should allow a switch to
scattered showers for the north of roughly Salem, while areas to the
south remain in a steadier valley rain/mountain snow pattern. 

One potential wrinkle in the forecast Friday night and Saturday is
shown by the 00z and now 06z GFS, as another slug of jet stream
energy sets up right over our CWA. This may enhance shower activity
to the north of the front, primarily for our north coastal zones and
inland areas PDX metro northward. With a quasi-stationary front to
our south, southerly flow ahead of any showers would be limited and
there is a chance snow levels could be lower than would normally be
expected with the -6 deg C 850 mb temps and onshore flow shown by the
06z NAM. We kept snow levels above 1000 feet for the time being, but
this certainly bears watching.

Due to continued uncertainty in where the heaviest, steadiest QPF is
expected, and the fact steady snow is not expected in the Cascades
until Friday evening, will hold off on issuing any winter highlights
to allow the day shift a chance to take a gander at the 12z model 
cycle. However, confidence is high that some locations in the Oregon 
Cascades are going to see another foot or two of snow - or more - by 
the middle of next week.  Weagle

.LONG TERM...Saturday night through Wednesday...No changes. Previous 
discussion follows. As mentioned above in the short term discussion, 
the location where the frontal zone stalls Fri night/Sat, if it 
stalls at all, will have significant implications on the forecast 
through early next week. For now, our forecast is based on the 
admittedly weak assumption that the frontal zone will stall near 
Douglas County, with the steadiest, heaviest QPF aimed toward Lane 
County and points south. However, there have been model-to-model and 
run-to-run differences. For example, the 06z GFS shifted the quasi-
stationary front about 50-100 miles north of the 00z run, placing it 
closer to Salem. With waves of low pressure travelling along the 
front and remaining south of the Columbia Gorge while crossing the 
Cascades, this solution would bring the risk of lowland snow for SW 
Washington, Columbia Gorge, and perhaps even the Portland metro 
area. This also could bring a hydro threat to areas near and south 
of the front, which in the particular case of the 06z GFS, would be 
areas Salem southward. However, this is just one of many solutions, 
and the majority seem to want to stall the front further 
south...keeping areas north of Salem drier while Eugene flirts with 
low elevation snow and SW Oregon deals with most of the hydro 
concerns. 

This seems to be one of those situations a blend of models is made
for, especially when it comes positioning of the front, so we nudged
the forecast toward the National Blend. Confidence in any model
solution is lower than usual for the early to middle portion of next
week, as there is a complex pattern upstream complicated by a
potential blocking ridge over Alaska and interaction between the
polar and subtropical branches of the jet stream. Once the synoptic
pattern is settled on by the models, we will have a better idea of
the finer details.  Weagle

&&

.AVIATION...Areas of a low stratus with IFR cigs have persisted this 
morning in the Willamette Valley, and are likely to persist into the 
early afternoon, especially in the south Valley, before dissipating 
and leaving behind VFR conditions. Generally VFR conditions are then 
expected to persist for most of the area tonight, before low clouds 
begin to spread back into the northern part of the area Friday 
morning. The low clouds are likely to lead to MVFR cigs along the 
north coastal areas after about 15Z, while inland clouds are likely 
to remain VFR. There is a chance for seeing some low stratus or fog 
with IFR conditions redeveloping late tonight in the south 
Willamette Valley, most likely after 09z and continuing through 16Z. 

KPDX AND APPROACHES...KPDX is likely to remain on the southern 
fringes of an IFR cloud deck into the early afternoon, before clouds 
eventually break up leaving VFR conditions after 19-20Z. VFR 
conditions are then expected to continue through the night and into 
Friday morning, with a small chance of fog or low stratus 
redeveloping between 09Z and 16Z.

&&

.MARINE...No changes. Previous discussion follows. Winds and seas 
continue to ease today. Winds are below advisory criteria, but seas 
remain around 12 feet this morning and should then drop below 10 
feet this evening. Winds will then turn more northeasterly before 
winds back to the west Friday ahead of the next storm system. This 
front appears rather weak, but should be strong enough to produce 
Small Craft Advisory level wind gusts of 25 kt across at least the 
northern waters Friday. Winds should then be rather tame across the 
waters over the weekend as a weak surface low pressure develops off 
the Washington Coast and drops southward. A low pressure developing 
along a stalled front somewhere off the northern California or 
southern Oregon coast could impact the waters early next week, but 
where it will end up remains highly uncertain. Latest model 
projections generally keep it south, but if it tracks more directly 
into our waters or north of us then winds and seas will almost 
certainly be higher. /mh /Neuman

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for hazardous seas until 10 PM PST this 
     evening for Coastal Waters from Cape Shoalwater WA to 
     Florence OR out 60 NM.

     Small Craft Advisory for Rough Columbia River Bar from 4 PM 
     this afternoon to 8 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


342 
FXUS66 KPDT 211720 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
920 AM PST Thu Feb 21 2019

Updated Aviation Discussion

.SHORT TERM...Today and tonight...A deep upper level trough 
continues to push south of the region into the southwestern U.S. 
This is leaving the Pacific Northwest under a cold northerly flow. 
There is enough lingering moisture that the northerly flow banking 
up against the higher terrain of Oregon is generating some snow 
showers with minor accumulations. This will persist into the 
afternoon and then taper off and end going into tonight. 
Temperatures will remain below normal today and clearing skies 
tonight will allow temperatures to drop into the teens and single 
digits.   

&&

.AVIATION...18Z TAFs...Upslope flow northerly flow keeping light 
SNSH at RDM BDN PDT and ALW. Low level moisture at PSC and DLS 
producing BR/FZFG which will also dissipate as drier air moves in. 
By this afternoon, most sites will be VFR. Radiational fog may 
reduce visibilities tonight, particularly along the Blue Mtn 
Foothills. A northerly gradient may cause stratus clouds to develop 
at BDN and RDM. 76

&&

.PREV DISCUSSION... /issued 330 AM PST Thu Feb 21 2019/ 

SHORT TERM...Today through Friday Night...Although snow has tapered 
off across most of the forecast area, WSR-88D is picking up on 20-25 
dBZ returns over the Blue Mountains and foothills.  Scattered snow 
showers have been observed early this morning, and web cams are 
showing snow-covered roadways that were earlier plowed.  The center 
of the upper low is over SE Oregon and Nevada with continued wrap-
around moisture.  The HRRR forecasts QPF up to 0.1 of an inch for 
areas east-southeast of Pendleton and the Oregon Blues through 18Z. 
Forecast will reflect scattered morning snow showers with 
accumulations up to 1.5 inches. Typically, these wrap-around 
patterns can cause snow to accumulate fast in Wallowa County but the 
web cam at Joseph is showing very light accumulations since 
midnight. Snow has also tapered off or ended over central Oregon. No 
winter highlights are planned for this morning, but we will keep a 
close eye on precipitation over the Blue Mtn Foothills.  

Snow showers will taper off to isolated mountain snow showers over 
eastern Oregon this afternoon and end everywhere tonight.  Clearing 
skies will cause temperatures to plummet into the single digits and 
teens for most of the area.  Clouds will increase from the west 
Friday morning and will be mostly cloudy and cold Friday afternoon. 
The next front will bring snow to the Washington and northern Oregon 
Cascades Friday afternoon then over the remainder of the forecast 
area Friday night.  Frontogenesis begins to develop south of the 
Washington border after midnight with the front forming a line from 
Walla Walla to Heppner to Madras by 12Z Saturday.  More details on 
this upcoming system can be found in the long term discussion. There 
will be weak warm air advection ahead of the front increasing snow 
levels to around 1500 feet, therefore some of the lowest elevations 
will have a rain/snow mix Friday evening.  Wister

LONG TERM...Saturday through next Friday...The models are in good 
agreement to start with a mostly zonal flow with a northwest to 
southeast direction. This is where the jet stream will be, which 
will divide the cold air north of it in Washington and warmer air 
from north central Oregon southward. A weather system will move into 
the region again by Sunday. This next system will affect mostly the 
southern CWA with the cold/warm air boundary over north central 
Oregon. 1000-850 thicknesses are marginal for snow for elevations 
below 1500 feet MSL, but precipitation will be widespread this 
system will eventually bring a little light snow as the colder air 
moves into the CWA on Sunday. This wet pattern will persist for and 
through the beginning of the extended period, which will be around 
Monday. After conditions will dry out fast.  Then a short visit with 
an upper ridge will develop over the Pacific Northwest. Cold air 
will be trapped at the surface in the Lower Columbia Basin south 
through central Oregon. This time of year, the mixing out of warmer 
air under a ridge may transport warmer air and may cause rain or 
freezing rain through Wednesday and the rest of next week. 88

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  28  14  35  27 /  20  10   0  40 
ALW  29  16  36  28 /  20  10  10  50 
PSC  31  19  36  26 /  10   0  10  10 
YKM  34  18  35  22 /   0   0  30  10 
HRI  31  17  37  28 /  10   0   0  20 
ELN  34  15  33  19 /  10   0  60  20 
RDM  32  15  40  28 /  20  10   0  30 
LGD  30  12  34  25 /  30  10  10  60 
GCD  31  13  36  27 /  20  10   0  50 
DLS  37  23  39  31 /  10   0  30  40 

&&

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

$$

91/76/76

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

Northeastern Washington and Northern Idaho


341 
FXUS66 KOTX 211852
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1052 AM PST Thu Feb 21 2019

.SYNOPSIS...
A quiet but cold break period will envelope the region today.  
Another round of light to moderate snow accumulation snow is 
expected for Friday and the weekend. Cold temperatures will 
persist well into next week.


&&

.DISCUSSION...

The majority of the Inland Northwest will enjoy bright sunshine
this afternoon. High temperatures have been adjusted up a few
degrees over much of the region. As of 10 AM, much of north Idaho
and eastern Washington had temperatures in the low to mid 20s, and
should reach the low to mid 30s by mid afternoon. Omak, Chelan,
Leavenworth, and Wenatchee may get close to 40.

Our late February sun angle should break up most of the low clouds
and fog around Pullman, Lewiston, and LaCrosse this afternoon.
However, it may return this evening. If it does, chances are good
that a fog bank over the Palouse will spread into Spokane,
Davenport, Wilbur, and Ritzville by morning.

Our next round of light snow will develop over northeast
Washington and the far north Idaho Panhandle Friday morning and
spread toward Spokane/CDA and the central Panhandle by the 
afternoon. The morning model runs suggest up to 2 inches for
Spokane with CDA, Sandpoint, and Kellogg in the 2 to 4 inch range.
Compared to some recent snow events, this system seems relatively
tame. However, the late afternoon and early evening timing will
have the potential to impact Friday's evening commute and hinder
travel through the evening hours. /GKoch

&&

.AVIATION...
18Z TAFS: Clear skies will persist through the evening over most
of eastern Washington and north Idaho through this evening. The
exception will be an area of low clouds and fog around Pullman and
Lewiston which should dissipate at the terminals by early to mid
afternoon. There will be a good chance of redevelopment of this
fog bank this evening. If it does, fog will likely spread
northward into Spokane and possibly Moses Lake prior to sunrise.
/GKoch


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        31  10  27  17  30  19 /   0   0  30  70  20  30 
Coeur d'Alene  33  12  27  21  30  19 /   0   0  30  80  20  30 
Pullman        29   9  28  23  31  21 /  10   0  10  70  30  40 
Lewiston       32  15  34  29  37  27 /  10   0  10  60  40  40 
Colville       37  14  31  13  35  16 /   0   0  60  60  20  30 
Sandpoint      33  15  28  21  31  18 /   0   0  60  80  40  30 
Kellogg        31  13  28  23  31  19 /   0   0  30  80  60  40 
Moses Lake     36  15  30  16  31  23 /   0   0  30  10  10  40 
Wenatchee      37  17  28  18  29  21 /   0   0  60  20  40  50 
Omak           39  17  28  16  30  21 /  10  10  60  30  30  30 

&&

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

&&

$$

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