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

Western Washington


013 
FXUS66 KSEW 231028
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
328 AM PDT Mon Apr 23 2018

.SYNOPSIS...An upper ridge will build over the area today and 
remain through Thursday, bringing a stretch of sunny days to 
Western Washington. Low level offshore flow will result in the 
warmest weather since last September, with highs in the 70s over 
much of the area. An upper level low will approach from the south
late in the week bringing a return to more seasonal weather for 
the weekend.

&&

.SHORT TERM...Satellite imagery shows the beginning of the warm
spell for western Washington right on track this morning with an
upper level ridge building over the area. At the surface KOTH-KSEA
gradient already down to -6 mb with the cross Cascade gradient at
10z down to near plus 1 mb. The transition to offshore flow is in
progress. Under clear skies temperatures at 3 am/10z were in the 
mid 30s to mid 40s.

Nothing new in the 00z model run with the warm spell for western
Washington scenario remaining intact in the short term. Upper 
level ridge over the area today will remain in place through 
Wednesday. Cross Cascade surface gradient going negative today and
will remain negative into Wednesday. Cross Cascade peaking out 
around -6 mb Tuesday morning giving the Cascade foothills some 
breezy ( 15 to 25 mph ) easterly winds to start the day. 
Temperatures aloft warming each day with the 850 mb temperatures 
starting out in the plus 2 to 4C range this morning rising to 
around plus 8C this afternoon, plus 10 to 12C Tuesday afternoon 
and to plus 12 to 14C Wednesday afternoon. Highs warming into the 
60s and lower 70s today, 70s on Tuesday and 70s with possible 
lower 80s on Wednesday. The exception will be near the Strait of 
Juan de Fuca where the northeasterly winds coming off the cool 50 
degree water in the Strait will keep highs in the 60s. Lows will 
warm each morning with mid 30s to mid 40s Tuesday, 40s and lower 
50s Wednesday and Thursday morning.

.LONG TERM...Extended model solutions are once again inconsistent
beginning Thursday night into the weekend. On Thursday low level
offshore flow comes to an end with the transition to onshore flow
late in the day. This will cool off the Coast dramatically with
highs in the interior similar to Wednesday's readings. Both the
ECMWF and GFS remain at odds with what to do with a shortwave
spinning out of the upper level low over northern California. The
GFS has the shortwave rapidly intensifying Thursday night over 
the area with over a half inch of rain from about Seattle south. 
The ECMWF is much weaker, slower and further south with this 
feature keeping it mostly over Oregon and southwest Washington 
Friday night into Saturday. The ECMWF then develops an upper level
low to the north of Washington on Sunday while the GFS has a weak
open trough. Both models transition the low level flow to onshore
Thursday night and Friday cooling high temperatures over the 
interior back down into the 60s with highs back to near normal, 
mid 50s to lower 60s for the weekend. With the lack consensus 
precipitation wise in the models will stay with the broadbrush 
chance of showers forecast for Friday through Sunday. Felton

&&

.AVIATION...An upper level ridge axis is along the coast this 
morning with light northerly flow aloft. The air mass is dry and 
stable. The flow aloft will shift to light southerly tonight as the 
ridge axis shifts east of the Cascades. Near the surface, high 
pressure over interior British Columbia will combine with thermally 
induced low pressure along the coast for increasing low level 
offshore flow. VFR expected throughout the region.

KSEA...VFR with N-NE wind 5 to 10 knots rising to 10 to 15 knots 
during the afternoon hours.     27

&&

.MARINE...High pressure over British Columbia and Eastern
Washington along with thermally induced low pressure along the 
Oregon and Washington coasts will persist until about Thursday
morning. This will lead to northerly offshore flow. On Tuesday 
morning, small craft-strength easterlies are forecast at the West 
Entrance near Cape Flattery. 

The thermal pressure trough will move inland on Thursday, 
followed on Thu night and Fri by onshore flow.

&&

.CLIMATE...There is a chance Seattle could reach 80 degrees in the
middle of the week. Days in the 80's in April are rare in Seattle
with only 16 since records started at Sea-Tac in 1945. 25 percent
of the April days in the 80s on record at Sea-Tac were 2 years 
ago with the record setting 4 in a row from April 17th through the
20th that included the warmest April day on record, 89 degrees on
the 18th. Felton 

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&

$$

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


570 
FXUS66 KPQR 230949
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
249 AM PDT Mon Apr 23 2018

.SYNOPSIS...High pressure over the region will support mostly clear
skies through at least Wed and warm temperatures. Tuesday and
Wednesday will be the warmest days of the week with interior
temperatures likely peaking in the low 80s. Thursday will be slightly
cooler as an upper level low approaches. Then much cooler
temperatures expected Friday and through the weekend as an upper
level trough moves over the area.

&&

.SHORT TERM...Today through Thursday. The general weather pattern will
change very little the next few days with high pressure aloft and a
surface thermal trough. This will result in dry weather with minimal
clouds (high and thin), and warming temperatures. Water vapor imagery
shows the upper ridge axis just west of the coast early this morning.
At the surface, high pressure is across Washington and northern
Oregon with an inverted trough across south and central Oregon. 

The Troutdale to Dalles surface pressure gradient is currently weakly
negative (-1 mb), and the east winds will be fairly light this
morning. This gradient will increase this afternoon and evening to
around -5 mb as the thermal trough strengthens, with east gusts up to
20 mph possible near the Columbia River Gorge entrance. Clear skies
and a warming atmosphere will allow temperatures to warm quickly
today, with coastal temperatures possibly reaching 70, and the
inland valleys in the mid 70s. 

Temperatures will warm even more Tuesday and Wednesday as the 
thermal trough sets up over the Willamette Valley. These days will be
the warmest of the week, and of the year so far with interior valleys
expected to warm into the upper 70s or low 80s. Offshore winds will
weaken Tuesday afternoon, and a low off of the south Oregon coast
will result in south winds developing along the Central Oregon coast.
This will result in less warming for the Central Oregon coast and
south Willamette valley. The Central Oregon coast will likely peak in
the upper 60s or low 70s Tuesday and Wednesday afternoon with the
inland areas of Lane County peaking in the upper 70s. The overnight
temperatures will be warm too with minimum temperatures in the upper
40s or low 50s, and a subsidence inversion will allow mid slope
nighttime temperatures to be warmer than the valley temperatures. 

A large upper level low approaches Wednesday night and Thursday
weakening the upper ridge. The thermal trough will be more over the
Cascades, and the offshore winds may not make it to the coast.	South
winds will dominate the coast becoming slightly onshore in the
afternoon.  This will result in much cooler afternoon temperatures
for the coast, and slight decrease in temperatures inland. Diffluence
aloft may result in afternoon showers over the Cascades. ~TJ

.LONG TERM...No Changes. Previous discussion follows...Thursday night
through Sunday...The general idea of the cutoff low off the north CA
coast slowly approaching the coast late in the week suggests some
moisture spreading north in the  southerly flow aloft for increasing
chances of showers beginning late Thu or Thu night. The pattern with
a se flow aloft can also suggest the possibility for thunderstorms,
particularly over the Cascades, but for now will leave out the
mention as GFS soundings not indicating sufficient instability. Temps
will be cooling back down closer to normal as onshore flow resumes.
While models begin to show more significant differences by the
weekend, the net result is still plaint of clouds, chances for
showers, and seasonable temps.

&& 

.AVIATION...VFR conditions next 24 hours. Offshore flow will
increase today and continue tonight before easing.

KPDX AND APPROACHES...VFR. Easterly gusts peak at 20-30 kt from 
23/19 to 24/12. /mh 

&&

.MARINE...Surface thermal trough will extend to the south
Washington coast today, then drift offshore tonight. This will 
result in winds turning increasingly offshore. Main concern will 
be wind gusts of 20 to 25 kt possible downwind of the coastal 
river gaps including the mouth of the Columbia River. A long 
period westerly swell will arrive around this time and it will be
interesting to see how the winds and swell will interact. Would 
expect waves to stand up and become steep. As of now, wave 
guidance indicates seas will not reach 10 feet or become square 
with 7 second periods or greater, but worth paying close 
attention to. 

A southerly wind reversal may develop towards the 
middle to latter half of this week with seas likely remaining 
under 10 ft. Small craft advisory level winds, could return 
towards the weekend, as a front moves into the north Oregon and 
south Washington waters. /JBonk

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.

&&
$$

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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 CWA or forecast area.

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

Southeastern Washington and Northeastern Oregon


431 
FXUS66 KPDT 230917
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
217 AM PDT Mon Apr 23 2018

.SHORT TERM...Today through Wednesday...Skies are clear this morning 
which is allowing strong radiational cooling, but temperatures will 
rebound quickly in the morning after sunrise. High pressure aloft 
will dominate the forecast area for the next few days. The ridge 
will amplify and slowly shift eastward with time. As this occurs the 
flow will gradually become more southwesterly. This will result in a 
warming trend through the short term forecast with afternoon high 
temperatures becoming well above normal. Temperature readings by mid 
week will approach 80 degrees and possibly into the lower 80s. The 
southwest flow will also gradually increase the transport of more 
unstable air into the region. With the warm and dry conditions, I 
expect to see a significant increase in the number of Spot Fire 
Weather requests as lower elevation fine fuels cure. This upcoming 
warm spell will bring the warmest temperatures to the CWA so far 
this year. Normal highs for Pendleton for Wednesday is only 64, and 
with highs expected to be near 80, it will be about 14-16 degrees 
above normal. However the record high for Wednesday is 89 at 
Pendleton, so there is still a ways to go before reaching record 
highs. The warm and dry weather will persist into the early extended 
period. 88

.LONG TERM...Wednesday night through Sunday night...Models are very 
similar through Thursday morning with a large upper level ridge 
keeping warm and dry conditions over WA and OR. A closed upper level 
low will wobble eastward toward the northern CA coast Thursday. 
However the ECMWF is much farther southwest than the GFS. The GFS 
and ECMWF differ on how fast the ridge will break down Thursday and 
Friday. Thursday afternoon both models show some moisture moving 
northward along the Sierra mountains. However the ECMWF has very 
limited moisture and no precipitation while the GFS brings showers 
and enough instability for thunderstorms into eastern OR. I 
continued the existing forecast of a slight chance of showers and 
thunderstorms in central OR though confidence is low. The ECMWF does 
not bring wraparound moisture from the low into central OR until 
Friday. The GFS brings a broad trough over WA and OR Friday through 
Sunday with pinwheeling low centers. The ECMWF brings the low east 
into central CA with wraparound moisture in WA and OR through next 
weekend. Since both models spread showers across the CWA I expanded 
coverage Friday through Sunday. There is enough instability for a 
few thunderstorms Friday and Sunday during the afternoon. Coonfield 

&&

.AVIATION...12Z TAFs...VFR conditions with clear skies will prevail 
for the next 24 hours. Light winds.  76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  67  37  74  42 /   0   0   0   0 
ALW  70  40  76  45 /   0   0   0   0 
PSC  72  35  76  43 /   0   0   0   0 
YKM  71  36  74  44 /   0   0   0   0 
HRI  70  33  76  42 /   0   0   0   0 
ELN  67  37  70  41 /   0   0   0   0 
RDM  68  28  75  37 /   0   0   0   0 
LGD  64  35  69  39 /   0   0   0   0 
GCD  66  38  71  40 /   0   0   0   0 
DLS  73  37  77  46 /   0   0   0   0 

&&

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

$$

88/76/76

!--not sent--!

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

Northeastern Washington and Northern Idaho


261 
FXUS66 KOTX 231126
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
426 AM PDT Mon Apr 23 2018

.SYNOPSIS...
Dry weather is expected much of this week, with our warmest 
weather of the spring season thus far. By Thursday and Friday, 
some of our lowland areas will have a shot of reaching 80 degrees 
or more. Changes are expected by the weekend, with a threat of 
showers returning to the region as well as cooler temperatures.

&&

.DISCUSSION...

Today through Wednesday: High pressure steadily amplifies over 
Eastern Washington and Northern Idaho allowing for a a continuation 
of generally clear and sunny skies coupled with a warming trend. One 
possible interruption to this weather pattern may be in the form of 
a disturbance dropping down from the northwest and making a 
northwest to southeast oriented passage through the forecast area 
Wednesday. Current model runs suggest this disturbance passage will 
cause the prevailing winds to blow more from the north/northwest 
with perhaps some gusty wind and a bit more middle and upper level 
clouds Wednesday but the warming trend coupled with a dry 
forecast should continue uninterrupted. /Pelatti

Thursday-Sunday: General agreement on the fact that the region
will be affected by a slow moving low during this part of the
forecast. But the details aren't certain. The models have
struggled with this low in previous forecasts and this will
probably continue for another couple of days. Previous models
expected the low to go well south of our area, leaving us warm and
dry. But now they all agree that the low will track much closer to
us. The GFS and Canadian models would fire off
showers/thunderstorms Friday afternoon/evening, with much wetter
weather for the weekend. The ECMWF continues to insist on a slower
and drier solution. At this point I've kept Friday dry for the
most part, bringing in a better threat of showers on Saturday and
Sunday. 

The warm spell will reach it's peak on Thursday or possibly 
Friday with cooler temperatures for the weekend. This will have 
large implications for the snowmelt and potential river flooding.
At this point the river forecasts are all fairly well behaved as
this is only a minor "heat wave".  RJ 

&&

.AVIATION...
12Z TAFS: High pressure remaining over the aviation area 
will keep VFR conditions consisting of generally clear skies with
winds less than 10 kts. /Pelatti


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        65  41  70  46  73  46 /   0   0   0   0   0   0 
Coeur d'Alene  64  40  70  43  72  44 /   0   0   0   0   0   0 
Pullman        63  39  69  44  71  45 /   0   0   0   0   0   0 
Lewiston       68  41  76  47  78  49 /   0   0   0   0   0   0 
Colville       68  38  72  43  75  42 /   0   0   0   0   0   0 
Sandpoint      62  38  67  41  69  41 /   0   0   0   0   0   0 
Kellogg        62  36  69  42  69  42 /   0   0   0   0   0   0 
Moses Lake     70  41  74  45  78  47 /   0   0   0   0   0   0 
Wenatchee      67  43  72  47  76  49 /   0   0   0   0   0   0 
Omak           68  41  73  46  77  47 /   0   0   0   0   0   0 

&&

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

&&

$$

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