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

Western Washington


907 
FXUS66 KSEW 261629
GPHAFD

Area Forecast Discussion
National Weather Service Seattle WA
906 AM PDT Wed Apr 26 2017

.SYNOPSIS...Low pressure aloft will keep conditions unsettled 
through Thursday. A high pressure system will move over the region 
on Friday for a break from the wet weather. Another low pressure
system is anticipated by Sunday for more precipitation.

&&

.SHORT TERM...
There were scattered showers over the CWA at this time. Expect the
activity to increase this afternoon.
 
The next shortwave currently offshore will move onshore and enhance
showers later today, particularly over the southern sections of the
forecast area. At the surface, a ridge of higher pressure off the 
coast will increase onshore flow as well (PIC12). This pattern will 
help create a Puget Sound Convergence Zone later today that has the 
potential to sag south from northern Kitsap and Snohomish Counties 
south well into King County this evening thanks to the strong flow 
to develop in the Strait of Juan de Fuca. 

Another embedded shortwave is forecast to swing onshore Thursday to 
keep the showers going, but mainly in the mountains and higher 
terrain. High temperatures look to remain a bit below late April 
averages. 

Guidance strongly suggests that Friday may offer a break in the 
precipitation with some sunshine as a ridge of higher pressure 
builds off the coast. Have those sunglasses handy. Buehner/05

.LONG TERM FROM THE PREV DISCUSSION...The next question is will the
drier weather hang on into Saturday. The Canadian and ECMWF concur 
with the ridge holding for another dry day while the GFS is quicker 
in spreading precipitation onshore during the day. At this point, 
have indicated a growing threat of rain for the Olympic Peninsula 
and coast during the day Saturday and increasing clouds elsewhere. 
Then this weather system should provide more rain Saturday night 
with decreasing showers on Sunday. 

As the month of May begins, guidance again is not consistent. The 
ECMWF rebuilds the upper ridge while the Canadian and GFS swing yet 
another shortwave onshore for additional showers. But beyond Monday, 
restless natives eager for some sunshine may get some as it appears 
higher pressure aloft will build over the region. Buehner

&&

.AVIATION...Moderate westerly flow aloft today (PIC11) will become
northwest tonight (PIC10) as an upper trough moves east. At the 
surface, strong onshore flow will develop today (PIC12) and continue 
tonight. The air mass is moist (PIC13) and weakly unstable with 
showers (PIC14). Showers will decrease later tonight. The Puget 
Sound convergence zone is likely to form KPAE-KSEA this afternoon 
and evening. A wind shift to the northwest will occur over north 
Puget Sound this afternoon and could cause southwest winds at 
KBFI/KSEA to turn westerly or switch to northwest for a few hours 
late in the afternoon and early evening. Mostly MVFR ceilings, with 
isolated IFR, this morning becoming predominantly VFR this afternoon 
except lower in showers.

KSEA...Ceilings 1k to 1.5k ft this morning will become VFR this 
afternoon 3-4k ft with lower scattered decks. Southwest wind 10-15 
KT this morning will become northerly 5-10 KT around 00Z. CHB

.MARINE...Strong onshore flow will increase today (PIC12), with 
westerly gales forecast in the strait through tonight. Winds will 
ease late tonight but will generally remain moderately onshore 
Thursday and Friday (PIC15). Small craft advisories are in effect 
over all waters, with gale warnings in the central and east strait. 

High pressure over the area will give light winds Saturday (PIC16). 
A front will reach the area Saturday night, with strong onshore flow 
returning on Sunday (PIC17). CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Warning until 3 AM PDT Thursday for Central U.S. Waters 
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of 
     Juan De Fuca.

	 Small Craft Advisories are in effect for the remaining waters.

&&

$$

www.weather.gov

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

Southwestern Washington and Western Oregon


059 
FXUS66 KPQR 261634 RRA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
934 AM PDT Wed Apr 26 2017

.SYNOPSIS...A cold front is moving through the region this morning,
bringing rain and higher Cascade snow. Rain will transition to
showers later today. Showery weather will then continue through Thu.
Does appear will have a break for later Fri and Sat, with dry and
mild conditions. But, will see threat of rain return later Sat night
and Sun. With all these April showers, just imagine the size of those
coming Mayflowers. The weather appears to be trending toward warmer
and drier for next week.

&&

.SHORT TERM...(Today through Fri)...A strong Pacific jet stream of
160+ kt is aimed directly at the Pac NW today. IR satellite also
shows an extensive frontal boundary stretching from the Pac NW down
into the subtropics, with a fairly good late season moisture tap
feeding into the Pac NW. The frontal boundary has been pushing
through SW Washington and NW Oregon this morning, bringing a period
of steady precipitation to the region. Some areas in the Coast Range
and Cascade foothills have seen 24 hr rainfall totals in the 1 to 1.5
inch range. Totals along the coast and in the interior lowlands have
been closer to 0.5 inch. Precipitation has been falling as snow for
elevations roughly 4500 to 5000 ft and above. Area webcams show
accumulating snow at some of the higher passes this morning. Current
Winter Weather Advisory for snow above 4500 feet in the Cascades
continues, with 6 to 12 storm total snow likely. As usual, heaviest
snow will be on higher peaks/ridges, mainly above 5000 feet. 

The steadier rain will be transitioning to showers later this morning
and this afternoon as the front pushes east of the region. 
Showers will be decreasing in intensity from west to east across the
region this afternoon, but they will persist well into this evening
in the Cascades, thanks to favorable orographic flow. 

Showers will be gradually decreasing tonight. But not expecting much
change in overall air mass on Thu.  A few passing embedded
disturbances in the westerly flow on Thu will be enough to
destabilize air mass bit more, with showers increasing again later
Thu am into the afternoon. Snow levels remain between 3500 and 4500
feet, but with less precipitation amounts will result in only a few
inches of new snow.  Showers will gradually decrease Thu night.

Now, after all the rain, we will need a break. Indeed, it appears
that break arrives on Fri. Still a minor threat of showers, but think
even that threat will be over the Cascades. Otherwise, will trend to
partly sunny skies with mild temperatures. Pyle/Rockey


.LONG TERM...Friday night through Tuesday...Showers continue to
further diminish later Friday through Saturday as an upper level
ridge over the eastern Pacific will further amplify in between low
pressure systems both upstream and downstream. Not quite confident
enough yet to bring sky cover to mostly sunny wording, but did trend
things that direction. Meanwhile, temperatures will also respond
accordingly with high temperatures in the afternoon warming into the
mid 60s - all the way to around seasonal normals, at least for one
day! However, this will be yet another only short-lived intermission
in the season of steady rain. A weakening frontal system will bring
increasing round of clouds, another chance of rain, and slightly
cooler temperatures. Forecast models do diverge a bit the first half
of next week, but as we transition to May there is some potential
for a bit of shift in the pattern. At this point, trended the
forecast dry for Monday and Tuesday, but did so somewhat cautiously
for two reasons - first, ensemble members continue to suggest a
somewhat large spread in possible solutions; second, we've seen this
sort of pattern in the models several times in recent weeks, where a
seeming trend toward dry conditions and a building ridge fails to
appear. That said, this would be consistent with the latest CPC 6-10
outlook of warmer and drier than average May 1-5 period. An abundance
of words to say the forecast was trended this direction but with
lower than typical confidence.	 Cullen
&&

.HYDROLOGY...The lower Columbia River will be running above bankfull 
for the next several days. Primary areas of concern are the Columbia 
near Vancouver and downstream past the Columbia near Longview to the 
mouth. Contributions to the high flow are coming from high 
astronomical tides in addition to increased runoff from the Snake 
River and Willamette River basins. Lower reaches of tributaries 
flowing into the Columbia River may also experience periods of 
elevated water during the high tide cycles. Please continue to 
monitor the forecasts for the next several days. /JBonk
&&

.AVIATION...Main focus of rain and showers will continue to drift
south this morning with showers developing north shortly then
closer to 18-20z for salem and southward. In the meantime, will
see periods where heavier ran bands and showers will drag cigs
down to MVFR and perhaps Vsbys close to IFR. Expect conditions
will generally improve this afternoon likely as prevailing VFR
after sunset and through most of the night. May get some low 
MVFR stratus around or after 12z. 

KPDX AND APPROACHES...VFR should prevail although may see
frequent cigs 030-040 through 00z today as showers stream across
the terminal area. Expect Minimal, if any, impacts to visual
approaches beginning with the afternoon boxer arrivals and
continuing through morning boxer arrivals. There is a 20% chance
of a 015 cig beginning around 14z. /JBonk

&&

.MARINE...Winds and seas are gradually becoming more benign this
morning. 06z WW3 data shows a 9 ft swell crossing the northern
waters late this afternoon and evening, however, am feeling the
associated GFS winds are slightly too strong. As such, have kept
the seas capped at 9 ft. 

Broader high pressure builds over the NE Pac keeping a relative 
lull in winds through Friday. Seas may next reach 10-11 ft 
Thursday through early Friday as the southern end of a swell 
train clips the northern waters from a surface low crossing the 
Alaskan Panhandle. A deeper front may clip the waters Saturday
night for SCA level gusts. /JBonk

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 7 PM PDT this evening for 
     Cascades in Lane County-Northern Oregon Cascades.

WA...None.
PZ...Small Craft Advisory for Rough Columbia River Bar from 4 PM 
     this afternoon to 8 PM PDT this evening.

     Small Craft Advisory for Rough Columbia River Bar from 3 AM to 
     8 AM PDT Thursday.

&&

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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


633 
FXUS66 KPDT 261626
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
926 AM PDT Wed Apr 26 2017

.SHORT TERM...Today and tonight...a fast moving zonal flow over the 
region today with a weather system passing. This system will bring 
rain to the forecast area through the morning then we will see 
increasing westerly winds from midday through overnight. 
Precipitation will taper off when the winds kick in but continue to 
see some upslope showers into the Blue Mountains through the night. 
Snow levels will be 4000 to 5000 feet today lowering to 3000 to 3500 
overnight. This will mean 1 to 3 inches of snow for portions of the 
mountains overnight. The west winds will begin to increase midday 
and continue into the overnight period when they will reach their 
peak. Wind advisories have been issued for the Simcoe Highlands and 
the Kittitas Valley but may need to add some other zones. Will make 
this decision after the complete set of morning model runs come in.


&&

.PREV DISCUSSION... /issued 440 AM PDT Wed Apr 26 2017/ 

SHORT TERM...Today through Friday...An upper level storm system 
is moving out of the CWA this morning and another one is expected to 
move into Central OR this morning. This will bring another round of 
precipitation to eastern WA and OR. The precipitation will be 
heaviest in Oregon. The snow levels will be 4500-6000 ft so most of 
the precipitation will be rain. It will become windy/very windy 
after the cold front passage this afternoon. Wind Advisories have 
been issued for the Kittitas Valley and Simcoe Highlands for gusty W-
NW winds. Models have backed off on wind speeds across the lower 
Columbia Basin, but I kept the wind speeds similar to the previous 
forecast because models frequently underestimate how much winds mix 
to the surface after a cold front passage. Upper level flow will 
turn northwest this afternoon as a ridge builds offshore. Multiple 
waves in the northwest flow will keep showery precipitation over the 
area tonight and Thursday. Upslope regions of the eastern mountains 
will get the most rain/snow. Snow levels will drop to 2500-3000 ft 
by Thursday morning. However the showery precipitation will probably 
not produce enough widespread snow to justify a winter advisory 
though local accumulations may reach advisory criteria. This will 
need to be monitored. Friday a drier northerly flow will develop 
with decreasing chances for showers. Coonfield

LONG TERM...Friday night through Tuesday. A weak transitory ridge 
will push inland Friday night...and showers will end after midnight. 
A dry forecast is in store Saturday...but showers will return 
Saturday night when the ridge flattens and allows a Pacific front to 
gradually travel south across WA/OR.  A westerly flow will remain on 
Sunday for continued showers but also breezy winds. 
Models...particularly the ECMWF...are having some difficulty with a 
shortwave trough progged to move south on Monday.  The ECMWF has 
been flip flopping on the strength...and the latest run dampens the 
wave with little to no precipitation.  Leaning towards the more 
consistent GFS and Canadian with a stronger wave.  However, rain and 
mountain snow showers (snow levels around 4000-5000 feet) will 
mainly develop along the Cascades and far northeast Oregon and 
southeast Washington. The models are in agreement with an upper 
level ridge building Tuesday and a highly amplitude ridge on 
Wednesday. People wanting more sun and less rain will likely get 
their wish Tuesday and Wednesday. Wister

AVIATION...12Z TAFs. The forecast area is between fronts at this 
time with the next front spreading precipitation across eastern OR 
this morning then southeast WA this afternoon.  CIGS are currently 
VFR with bases around 4K-10K ft AGL.  Confidence is fairly high that 
light to moderate rain will occasionally bring CIGS/VSBY down to 
MVFR at KALW and KPDT...and this was included in the 12Z TAFs. KDLS, 
KYKM and KPSC may see little to no rainfall with this upcoming front 
and will remain VFR for the next 24 hours.  KRDM and KBDN should 
remain VFR but light rain may briefly lower CIGS to MVFR.  The main 
aviation concern will be the increasing wind.  SW-W winds increasing 
to 15-25 knots with gust 25-35 knots are expected at all TAF 
sites this afternoon and evening...possibly overnight.  Wister

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  56  41  55  37 /  80  20  30  30 
ALW  58  44  58  42 /  80  30  30  30 
PSC  63  44  63  41 /  40  10  10  20 
YKM  62  40  61  37 /  30   0  10  10 
HRI  61  43  60  41 /  60  10  20  20 
ELN  58  39  56  38 /  20  10  10  10 
RDM  52  29  51  24 /  90  10  30  30 
LGD  51  38  50  35 / 100  50  40  40 
GCD  49  34  48  28 / 100  30  50  60 
DLS  59  44  58  42 /  80  10  30  20 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory until 9 PM PDT Thursday for WAZ026-521.

&&

$$

91/83/83

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

Northeastern Washington and Northern Idaho


591 
FXUS66 KOTX 261607
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
907 AM PDT Wed Apr 26 2017

.SYNOPSIS...
Expect cool, breezy, and showery weather for the rest of this 
week. Showers will be most numerous today with isolated
thunderstorms possible. Mountain passes could see a few inches of
snow overnight Wednesday into Thursday morning. A ridge of high 
pressure moves in Saturday delivering a brief dry period before 
more unsettled weather moves in Sunday and into early next week.


&&

.DISCUSSION...
Morning update: One disturbance is lifting through North Idaho
with a second moving into the Pendleton area. Updated pops to
show a brief break between waves. This second disturbance will
pass through rather quickly allowing some sunbreaks across
southeastern WA by the late afternoon. This will help destabilize
the atmosphere and renew the threat for showers and isolated
t-storms. As such, thunder was added with the morning update. Main
threats with any storms will be heavy downpours and infrequent
lightning as well as small hail.  /sb

&&

.AVIATION...
12Z TAFS: A frontal band will spread light to moderate rain
through the early morning east of a line from KOMK to KALW. The
added rainfall will keep the boundary layer moist with MVFR/IFR
conditions persisting at KGEG, KSFF, KCOE and KPUW through much of
this morning. A stronger disturbance will push east of the
Cascade Mtns this afternoon. The bulk of the moisture with this
wave will remain across Oregon, but the northern fringe will
impact KPUW and KLWS after 19Z into the early evening. MVFR cigs
will be possible through the afternoon at KPUW. The atmosphere 
will destabilize across the northern mtns this afternoon with 
numerous showers and isolated thunderstorms possible with 
convection impacting the Spokane/Coeur d'Alene corridor by the 
late afternoon hours. In addition, winds will be breezy this 
afternoon, especially at KEAT with gusts up to around 35 kts by 
the late afternoon hours. /SVH


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        54  36  51  36  54  37 /  20  40  40  20  30  20 
Coeur d'Alene  52  35  49  35  52  34 /  50  40  70  40  30  20 
Pullman        52  37  50  36  52  36 /  90  50  40  20  30  10 
Lewiston       57  41  55  39  57  39 /  70  30  30  20  20  10 
Colville       52  37  52  37  57  36 /  90  70  40  10  30  10 
Sandpoint      50  36  47  36  50  34 /  90  90  80  50  40  50 
Kellogg        47  35  43  34  46  33 /  80  70  70  60  40  20 
Moses Lake     62  40  61  38  62  37 /  10   0  10   0  10   0 
Wenatchee      59  39  58  39  60  38 /   0   0   0   0  10   0 
Omak           61  38  59  38  62  37 /  30  10  10  10  20  10 

&&

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

$$

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