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

Western Washington


566 
FXUS66 KSEW 180943
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
243 AM PDT Sat Aug 18 2018

.SYNOPSIS...Today will be dry with high pressure aloft. A weak
upper trough will move over the area on Sunday. High pressure
aloft will rebuild over the area Monday and Tuesday with low 
level offshore flow developing for warmer weather. An upper trough
and onshore flow will bring cooler weather Wednesday and Thursday
with a few showers on Thursday. Smoke will likely return to the 
region Sunday and linger into the middle of next week. 

&&

.SHORT TERM...An upper ridge will give dry weather today. A weak 
upper trough will move over the area on Sunday with a hint of a 
cut off upper low just to the south by afternoon. Upper heights 
will remain high for mostly dry weather. The exception will be 
the Cascades where some instability and the upper low to the 
south could spark a few thunderstorms in the afternoon and 
evening. 

The cut off upper low will shift inland on Monday with an upper 
ridge nosing in from the west. It should be another mostly dry 
day. There is a small threat of afternoon and evening thunder over
the Central Cascades but even this might be overstated given
recent model trends.

Highs will be near or slightly above normal today and Sunday with
light northwesterly low level onshore flow. Low level flow will 
turn more offshore on Monday which should allow highs to warm 
several degrees. The wild card is smoke which could suppress highs
if it gets thick enough.

Regarding smoke - models show a gradual increase in smoke from the
north over the next few days. It will probably start moving into
the far north part of the area later today and be mostly aloft at
first. It should continue to increase across the area on Sunday. 
By Monday, we might see reduced visibilities and poor air
qualities again. Schneider

.LONG TERM...High pressure aloft will be over the area on Tuesday
with low level offshore flow. Earlier models showed a weak upper
trough and instability for a threat of thunder for parts of the 
area but this no longer looks like it will happen. It should be 
another smoky day as well. It looks like the warmest day of the 
upcoming week but the smoke will probably keep highs from getting
too warm. The current forecast undercuts MOS by a few degrees for
this reason but it will still be in the 80s to lower 90s for much
of the area. 

An upper trough will push into the area Wednesday and Thursday.
This should help push the smoke out of the area. It looks like a 
two day marine push scenario with the coast cooling significantly 
on Wednesday but only minor cooling inland. Low clouds and marine 
air should penetrate farther inland Wednesday night with highs 
back to near normal all areas on Thursday. There could also be a 
few showers on Thursday with the upper trough. Friday looks like a
typical summer day with morning clouds, afternoon sunshine and 
near normal temperatures. Schneider

&&

.AVIATION...Weak upper level ridging over the region today with 
westerly flow aloft and light low level onshore flow. Marine 
stratus along the coast will work into the south interior and 
south Puget Sound by daybreak resulting in areas of IFR CIGs/MVFR 
VSBYs.

KSEA...Marine stratus may develop west of the airport over the Puget 
Sound waters between 1200 (5 AM PDT) and 1600 UTC (9 AM PDT), but is 
not expected to impact the terminal. VFR conditions will prevail 
through today. Light and variable winds will become northerly 5-10 
knots during the afternoon hours. 

&&

.MARINE...Higher pressure over the WA coastal waters with lower 
pressure east of the Cascades will result in light onshore flow 
today. The flow will become northerly tonight due to higher pres 
setting up over British Columbia with lower pres over Oregon. 
Northerly flow will persist through Monday. The northerly flow 
will cause smoke from wildfires to begin drifting across the 
waters on Sunday.

Looking further ahead, strong onshore flow is anticipated to
develop on Wednesday for the possibility of gale force westerlies
(30-40 knots) over parts of the Strait of Juan de Fuca.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 2 AM PDT early this morning for 
     Central U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 6 AM PDT early this morning for 
     Coastal Waters From Cape Flattery To James Island 10 To 60 
     Nm-Coastal Waters From James Island To Point Grenville 10 
     To 60 Nm.

&&

$$

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


276 
FXUS66 KPQR 181011
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
310 AM PDT Sat Aug 18 2018

.SYNOPSIS...A classic summer day is on tap today for southwest
Washington and northwest Oregon. High pressure will result in a
shallower marine layer and thus temperatures will be several degrees
warmer than Friday inland, while the coast remains cool with
afternoon sea breezes. A weak upper low move into the forecast area
Sunday, then very slowly drift south of the area through midweek.
This system will bring a slight chance of thunderstorms, mainly to
the Cascades. Offshore flow is expected to develop Monday and
Tuesday, pushing inland temperatures into the 90s. Wildfire smoke
will likely wrap into this system, with air quality likely
deteriorating again Monday and Tuesday.
 
&&

.SHORT TERM...Today through Monday...High pressure both at the
surface and aloft will lead to a classic summer Saturday weather-
wise across the forecast area today. Onshore flow continues with
KTTD-KDLS gradients at +4.2 mb as of 09z. The marine layer remains
fairly deep near Astoria, sitting at around 2000-2500 ft per latest
readings from the ESRL profiler there. This is a little shallower
than yesterday, but there will probably be additional compression of
the marine layer as a shortwave ridge passes over the area today.
With 500 mb heights getting near 590 Dm, suspect onshore flow will be
less effective at keeping inland areas cool versus yesterday.

This appears to be a similar setup to the pattern where MOS
temperatures were routinely 3-5 degrees F too cool east of the Coast
Range earlier this summer. Following this pattern, decided to boost
our high temps today into the 85-90 deg F range for the inland
valleys, which is about 2-4 deg F warmer than MET/MAV/EC-based MOS.
Very dry air exists above the marine layer, with RH still in the 30s
and 40s across many of our higher elevation RAWS sites. The
combination of warming temps and low RH will result in elevated fire
concerns today, but winds will likely remain below Red Flag Warning
criteria for our forecast area. Overnight humidity recoveries may be
slightly better in the higher terrain tonight, but still not great.

A weak upper low in the vicinity of 42N/138W continues to lift
northeastward, but will take a sharp right turn as it runs into
increasing polar jet energy to its north. Models show good agreement
that this system will end up over Oregon by Sunday evening. Cooling
temperatures aloft and modest moisture flux will contribute to a
little more instability Sunday afternoon, possibly resulting in a
couple thunderstorms along the Cascades. This system will linger
nearby through Monday, keeping a risk of thunder in the Cascades.
Steering flow will be weak near the center of this upper low, so it
appears whatever develops in the Cascades will stay in the Cascades
for the time being. As such, we removed the mention of thunder for
the lowlands.

The incoming upper low will also enhance low to mid-level SW flow
Sunday, bringing a deeper marine influence into the south end of the
Willamette Valley and through the gaps in the Coast Range. This may
allow places like Eugene, Corvallis, and McMinnville to see some
cooling Sunday while other inland areas hold onto similar temps as
today. Temperatures Monday will be largely dependent on cloud cover
and, unfortunately for those struggling with air quality, increasing
haze and smoke from fires in BC/WA as flow aloft turns northeasterly.
With models showing warming 850 mb temps and increasingly offshore
flow, it appears Monday has a decent shot at being the day where
Portland Airport sees their 29th 90+ degree day of the season, tying
the record set in 2015.

For the coast, after a partly to mostly sunny day today, there will
probably be increasing stratus along the coast tonight and Sunday as
the upper low approaches. As the upper low moves inland, flow will
become increasingly offshore. After seasonably cool temperatures over
the weekend, areas north Tillamook northward may start to climb into
the 70s or perhaps even 80s Monday and Tuesday.  Weagle

.LONG TERM...Monday night through Friday...Once the weak upper low
arrives in Oregon Sunday, model agreement quickly devolves into a
mess of different tracks/positions of the upper low Monday through
Wednesday. Most guidance pushes the upper low center south or
southwest of the forecast area by Tuesday, which would encourage low
to mid-level offshore flow to develop. This would result in
considerably hotter temperatures Tuesday, with some guidance even
exceeding 100 degrees for portions of our forecast area. Depending on
the track and magnitude of offshore flow, the coast may even get hot,
especially north of Lincoln City. For now, we're leaning toward a
model blend for temperatures due to all the model uncertainty and
disagreement.

Held onto a slight chance of thunder for the Cascades Monday through
Tuesday due to the proximity of the upper low, but if the low tracks
too far to our south or southwest, the air mass will likely be too
dry for thunder. Model agreement then improves again Wednesday and
Thursday, suggesting a progressive upper trough will sweep the upper
low (or its remnants) east of the Cascades. This would likely improve
any air quality issues that develop from the wildfire smoke earlier
in the week. Weak shortwaves clipping the Pac NW in the increasingly
zonal flow may even bring an occasional chance for showers to our
north coastal and SW Washington zones as early as Thursday.
Temperatures likely return to near or perhaps even below normal in
this pattern by the end of the week.  Weagle

&& 

.AVIATION...MVFR marine stratus will continue to impact the north
coast through the morning hours. The central coast will likely
not see stratus this morning, but could see a few hours of local
IFR fog between 12-16Z. Coastal stratus is expected to retreat 
to the beaches by this afternoon resulting in widespread VFR 
conditions through this evening. MVFR stratus likely returns to 
the coast later this evening, with IFR stratus possible after 
midnight tonight.

Some marine stratus looks to filter up the lower Columbia River 
this morning and could bring a few hours of MVFR cigs between
12-18Z. Otherwise, the interior remains VFR the next 24 hours.

KPDX AND APPROACHES...Mostly VFR the next 24 hours. A few hours
of MVFR cigs are possible over the western approaches between 
13-17Z this morning, but based on the latest satellite trend
confidence is low. 

&&

.MARINE...High pressure over the northeast Pacific and thermally 
induced low pressure over northern California and the Great Basin 
will more or less continue for much of the upcoming week resulting
in little day to day change in the winds and seas. Winds over the
central Oregon waters have generally fallen below 20 kt so will 
drop the current SCA for wind for tonight a few hours early. Gusts
over the central Oregon outer waters look to once again flirt with
advisory criteria this evening, with gusts to 25 kt possible. Will
go ahead and issue a SCA for winds for this evening, but given how
marginal these gusts are would not be surprised to see it pulled
later today. Otherwise, winds through the forecast period look to
generally remain below 20 kt.

Seas will generally hover around 4 to 6 ft through the forecast
period, but could build to near 7 ft at times. Periods will
continue to be relatively short, around 7 to 8 seconds, so expect
choppy conditions on the waters. 

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds from 4 PM this afternoon to 1 AM 
     PDT Sunday for Waters from Cascade Head to Florence OR 
     from 10 to 60 NM.

&&

$$

Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland

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


622 
FXUS66 KPDT 180916
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
217 AM PDT Sat Aug 18 2018

.SHORT TERM...Today through Monday...A ridge of high pressure will 
be over the region through midday Sunday. Expect a nice day today 
with Sunny skies and warm temperatures. Highs will be 90-95 lower 
elevations and 80-85 mountains. It will be clear and cool tonight 
with lows 55-60 in the lower elevations and 45-50 mountains. It will 
be mostly sunny and hot on Sunday with temperatures a couple of 
degrees warmer than today. A trough of low pressure will be 
approaching the area toward evening. After 5-7 pm there will be a 
slight chance of thunderstorms from the central into the northeast 
mountains. Storms are not expected to be strong or severe. A few 
showers will linger overnight Sunday into Monday morning with a 
slight chance for thunderstorms east Monday afternoon. Highs on 
Monday will be in the lower to mid 90s in the lower elevations and 
in the lower to mid 80s mountains. There should be a bit less smoke 
and haze around the next couple of days but it could increase from 
the Canadian fires on Monday as the flow turns northeasterly. 78

.LONG TERM...Monday night through Saturday...Models continue to 
suggest a rather low amplitude and active pattern through the middle 
of next week over the Pacific Northwest with systems undercutting 
the broader ridging extending up into Alaska. Multiple models show 
decent mid-level moistening in northeasterly flow across a bulk of 
the area Monday evening as a weak disturbance back builds into the 
area from the east but think this may be a little overdone and have 
confined a slight chance of thunderstorms primarily in the eastern 
mountains for now. Operational models are much more modest in any 
mid-level moisture for Tuesday afternoon, but ensembles continue to 
hint at just enough to justify an additional round of afternoon 
slight chance thunderstorm PoPs across similar areas - even less 
confidence in this. With north/northeasterly flow with both of these 
weak systems will likely see haze/smoke from Canadian fires 
returning to the area early next week. The overarching ridge begins 
to break down toward the end of the week with dry and (hopefully) 
smoke free westerly flow bringing a slight cooling trend. Peck

&&

.AVIATION...12Z TAFs...Mostly clear skies with winds generally less 
than 10 KTs. Will see one more day of nearly unrestricted visibility 
in hazy skies before conditions begin to worsen again into early 
next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  90  62  94  62 /   0   0   0  10 
ALW  92  61  95  62 /   0   0   0   0 
PSC  93  59  95  61 /   0   0   0   0 
YKM  92  60  93  61 /   0   0   0   0 
HRI  93  59  95  61 /   0   0   0   0 
ELN  92  58  93  59 /   0   0   0   0 
RDM  91  50  91  53 /   0   0   0  20 
LGD  89  52  92  57 /   0   0   0  20 
GCD  90  57  93  58 /   0   0   0  20 
DLS  93  63  95  65 /   0   0   0  10 

&&

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

$$

78/74/74

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

Northeastern Washington and Northern Idaho


530 
FXUS66 KOTX 180924
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
224 AM PDT Sat Aug 18 2018

.SYNOPSIS...
This weekend will be hazy and seasonably hot with most of the
region reaching the upper 80s to mid 90s Saturday and Sunday. Dry
northerly winds will develop on Monday raising wildfire concerns.
Temperatures are expected to cool Thursday and Friday with the 
arrival of a cold front and breezy west winds.


&&

.DISCUSSION...

Today through Sunday night: A ridge of high pressure builds over 
the region today promoting light winds and subtle warming trend. 
This would typically lead to an abundance of sunshine however 
multiple layers of smoke will remain entrenched over the region 
leading to a hazy forecast with areas of smoke concentrated near 
and downstream from active wildfires. As we head into this evening
and overnight period, an area of low pressure approaches the Pac 
NW Coast then sags into NW Oregon Sunday. The low phases with a 
northern branch shortwave digging down the Continental Divide over
southern BC. The most noticeable change through Sunday afternoon 
will be a stronger diurnal push of northerly winds down the 
Okanogan Valley Sunday morning with speeds on the order of 15 to 
20 mph and a slight bump in northeast winds near 10 mph down the 
Purcell Trench of N Idaho between Sandpoint and Cd'A. The north to
northeasterly wind direction will continue across the region 
Sunday afternoon but speeds will become lighter in the afternoon 
hours. After midnight, northerly pressure gradients begin to stack
up and look for winds to increase by sunrise Monday morning. As 
for any chances of precipitation, we will see a some cumulus 
buildups in the N Cascades and N Idaho Panhandle Sunday afternoon 
with a very small chance for an isolated shower or weak t-storm 
yet. This carries low confidence and no support from SREF 
probabilities but deterministic models do show some areas of SB 
CAPE. Cam models indicate a few weak cells but nothing to get 
overly excited about at this time. The threat for a few 
showers/t-storms looks better over N Oregon and toward my Blue 
Mtns and Camas Prairie which will remain under a west to southwest
steering flow ahead of the low. This has more support from 
ensemble solutions but given the late arrival Sunday night, 
forecast trends were toward showers vs t-storms. /sb

Monday: The combination of cool high pressure building over
Montana and low pressure over Oregon will produce an unseasonably
strong northeasterly gradient across the region on Monday. Look
for sustained 15 to 20 mph northeasterly winds in the Columbia
Basin with gusts of 25 mph or more from mid morning through the
evening. The Highway 95 corridor from Sandpoint to Post Falls is
another spot that is prone to breezy northeast winds with
channeling down the "Purcell Trench". The combination of afternoon
temperatures in the upper 80s to mid 90s, humidity between 15 and
25 percent, and breezy winds will raise concern for wildfire
spread.

Tuesday: The pressure gradient should relax on Tue leading to a 
decrease in the wind by mid day. It is possible that Monday's 
northeast winds will bring "cleaner air" into the region. The 
biggest contributors to our haze and smoke are the fires in the 
north Cascades, west central British Columbia, and northern 
California. Haze has been maintained in the forecast for Tue and 
much of Wed, but it may be dispersed over the Panhandle and much 
of eastern WA by Tue after Monday's gusty northeast winds.

Wednesday: Forecast confidence is relatively low Wed into Thu as
the models have had difficulty tracking the upper low languishing
over Oregon. The GFS ensemble mean was used as rough guidance for
the addition of slight chances for showers and thunderstorms over
the Idaho Panhandle and the eastern third of Washington Wed
afternoon through Wed night.

Thursday and Friday: There is good model agreement late next week
that a broad trough over the Gulf of Alaska will produce
increasing onshore flow Thu and Fri. Look for breezy winds and
cooler temperatures for the end of the week. Westerly winds will
be a favorable direction to help disperse smoke and haze. The
Methow and Okanogan Valley/Highlands will probably continue to
experience smoke due to the proximity to the north Cascade fires,
but chances are good that much of the Inland Northwest will
experience improving air quality for a few days late next week.
/GKoch

&&

.AVIATION...
06Z TAFS: Smoke continues to be the forecast challenge. All TAF
sites have improved to P6SM visibility, but expect wild fire smoke
to move from the north Cascade fires into the Basin overnight.
From there it will move into most of the TAF locations during the
day on Saturday, with the exception of KLWS.  RJ


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        89  59  91  62  87  61 /   0   0   0   0   0   0 
Coeur d'Alene  89  56  90  58  86  58 /   0   0   0   0   0   0 
Pullman        87  53  90  58  88  56 /   0   0   0   0  10  10 
Lewiston       94  61  96  64  95  63 /   0   0   0  10  10  10 
Colville       93  52  92  55  90  53 /   0   0   0   0   0   0 
Sandpoint      87  53  87  53  82  51 /   0   0   0  10   0   0 
Kellogg        85  54  87  55  82  54 /   0   0  10  10   0   0 
Moses Lake     93  55  94  62  94  61 /   0   0   0   0   0   0 
Wenatchee      92  63  93  65  92  65 /   0   0   0   0   0   0 
Omak           94  61  94  61  93  61 /   0   0   0   0   0   0 

&&

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

&&

$$

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

Back to U.W. Weather Page