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

Western Washington


580 
FXUS66 KSEW 281608
GPHAFD

Area Forecast Discussion
National Weather Service Seattle WA
900 AM PDT Fri Jul 28 2017

.SYNOPSIS...Areas of morning low clouds will burn off to sunshine 
through Sunday. The upper ridge over the Western United States will
shift closer to the Pacific Northwest with rather warm temperatures
possible by around Tuesday of next week.

&&

.SHORT TERM...A weak upper trough is fading away and morning marine 
layer clouds will burn off through midday. Here is a loop of the 
satellite images for the past hour ending around 845am (PIC1). Upper
heights over the area will rise into the weekend as the upper ridge 
bulges a little toward the area. There are still likely to be some
morning low clouds and fog patches through the weekend, maybe less
of that on Saturday but more on Sunday, but it could go either way
and temps wont change much til next week.

.LONG TERM...The strong upper ridge over the Western U.S. will bulge
into the area. Thermal low pressure will probably stay east of the
Cascades--keeping low level flow weakly onshore, but highs should
get well into the 80s, and maybe the lower 90s for the warmer spots.
The sea breeze will likely keep highs at the coast in the 70s. 

&&

.AVIATION...A weak upper trough will skirt the region today (PIC10). 
Generally light west to northwesterly flow aloft. Air mass moist in 
the lower levels due to onshore flow and dry in the mid/upper 
levels (PIC11). Atmosphere stable. 

Satellite imagery (PIC12) shows marine clouds beginning to break up 
with some partial spots of clearing at 16z. Areas of residual MVFR 
cigs mainly around 2500 ft should lift and clear by 18-19z. Onshore 
flow through Saturday will probably allow for some MVFR status to 
form later tonight and early Saturday morning, but more limited in 
coverage with a faster burn off. 

KSEA...Satellite imagery shows the terminal on the edge of a 2500 ft 
ceiling and partial clearing to the east. There may be a couple of 
hours through 18z with periods of MVFR and also sunbreaks as the 
clouds gradually dissipate. VFR should prevail by 18z. The potential 
for stratus Saturday morning is less than today but MVFR is still 
possible. Will leave a scatter 2500 ft cig in the TAF until more 
model date can be evaluated. dtm

&&

.MARINE...Onshore flow will begin to weaken on Sunday with generally 
light northerly flow by Monday and Tuesday. Northwesterly winds may 
reach small craft strength over the coastal waters early next week. 
typical westerly winds in the central and eastern Strait could bring 
small craft winds or gales (PIC13), mainly during the afternoon and 
evening hours through at least Saturday night. More typical diurnal 
winds in the Strait Sunday through Tuesday could still produce small 
craft westerlies during the evening hours. dtm 

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale warning from 5 PM PDT today through midnight tonight 
     for the Central U.S. Waters Strait Of Juan De Fuca-East 
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 5 PM PDT today for the Central 
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters 
     Strait Of Juan De Fuca.

     Small Craft Advisory from 5 PM this afternoon to midnight 
     tonight for Admiralty Inlet-Northern Inland Waters 
     Including The San Juan Islands.

&&

$$

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.wrh.noaa.gov/sew/gafd/latest_webafd.html

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

Southwestern Washington and Western Oregon


803 
FXUS66 KPQR 281553
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
853 AM PDT Fri Jul 28 2017

.SYNOPSIS...An upper level trough over the NE Pacific will maintain
onshore flow with areas of low clouds night and morning low clouds,
near the coast and locally inland through much of the
weekend. The areal extent of the low clouds will lessen each day for
slow warming through the weekend. An upper level ridge amplifies
early next week pushing inland temperatures into the 90s, and
possibly close to 100 next Wednesday. 
&&

.SHORT TERM...Today through Sunday...Low clouds are primarily over SW
Washington early this morning with clear skies across NW Oregon. 
Looped satellite imagery shows that the areal extent of the low
clouds are still expanding, with some low clouds seeping into extreme
NW Oregon. Some low clouds may briefly impact NE Portland metro area
this morning. A sunny afternoon will lead to warming today with
afternoon temperatures peaking in the mid 80s for the Willamette
Valley, and the upper 80s for the Central Columbia River Gorge and
Upper Hood River Valley. An upper trough moves across the region
today influencing the surface pressure SE of the Cascades to lower
this afternoon and evening, for continued N-NW onshore winds  this
afternoon and evening. ~TJ

The remainder of the discussion is from the previous issuance sent at
318 AM...Not a lot of change Saturday. A weak short wave still
lingers near the coast, and we should see some night and morning low
clouds again along the coast, and a little bit inland especially
north. Again, anything that forms should not last long with plenty of
sunshine, especially inland. Temps inland on Saturday should reach
the mid to upper 80s.

Sunday starts to see the upper high in the southwest U.S. expand
northwestward into the Pacific Northwest. After some local morning
low clouds, 500 mb heights approach 590 dm. Temps inland should reach
85 to around 90 based on 850 mb temperature considerations. Tolleson
 
.LONG TERM...No Changes. Previous discussion follows...Sunday night
through Thursday...The upper level ridge that strengthens on Sunday
continues through much of the coming week. 500 mb heights approach
the lower 590s. Despite the southwest flow aloft, we should see less
low clouds even at the coast as the marine layer will be shallow. 850
mb temps are indicating temps inland will be in the 90s, perhaps the
upper 90s or even close to 100 during the mid week period. We might
start to see temps ease a little late next week but still remain
above normal. Tolleson
&&

.AVIATION...MVFR stratus has filled in much of SW Washington to
the Cascade foothills, the North Oregon coast and inland valleys
and up the Columbia River to near KPDX. Inland areas become VFR
by 17Z or so. Coastal areas hold on to IFR/MVFR through 19Z, but
improvement to VFR may not occur along the S Washington coast
until early afternoon. IFR to low-end MVFR returns to the
coastline after 03z Sat and moves up the Columbia, reaching KKLS
10Z to 12Z. 

KPDX AND APPROACHES...MVFR cigs reached the terminal around 1530Z
and will persist through 17-18Z. VFR clear thereafter, but there
is the potential for IFR to low-end MVFR stratus to return around
sunrise Sat. Weishaar


&&

.MARINE...Rather persistent pattern over the waters for the next
several days. High pres to dominate the waters in conjunction
with a surface thermal trough over the N California and S Oregon
waters. This thermal trough will vary in strength over the next
few days. Latest model runs suggest possible 25 kt wind gusts
over the the far south end of zones 255 and 275 during the
afternoon and evenings over the weekend. The best chance for
small craft advisory wind issues look to be Sun and Mon 
afternoons and evenings. 

Seas will be 5-6 ft or less for the next several days. Expect
choppy conditions due to relatively short periods. Weishaar

&&

.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 forecast area.

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

Southeastern Washington and Northeastern Oregon


285 
FXUS66 KPDT 281607
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
907 AM PDT Fri Jul 28 2017

.SHORT TERM...Morning Update...A weak disturbance moving into the 
Pacific Northwest this morning will move across the region today. 
This wave will weaken further through the day, but will remain 
strong enough to cause convective development over portions of 
northeast Oregon late this afternoon and this evening. The best 
coverages of storms are expected over Wallowa county, especially in 
the early evening. In general the current forecast package covers 
these trends, but did make some adjustments to timing and coverages 
of the showers/storms. Also made some tweaks to sky cover, temps and 
winds. 90 

.LONG TERM...Previous Discussion...Monday through Friday...The 
extended period will be dominated by high pressure aloft over the 
inland west with a southwest flow over the CWA. This will cause hot 
temperatures in the mid 90s to mid 100s in the lower elevations and 
mid 80s to mid 90s mountains. There will be a weak wave in the flow 
on Tuesday which will bring enough moisture and instability 
northward to cause a slight chance of afternoon and evening 
thunderstorms on Tuesday along the southern border of the CWA. 
Otherwise it will remain dry and hot through the period. The hottest 
day will be on Wednesday and Thursday of next week with 850 mb 
temperatures around 30 degrees C. This translates to about 100-110 
degrees F in the lower elevations...and 90s in the mountains. There 
are some differences in the models with the ECMWF drier than the 
GFS. Will lean toward the GFS for temperatures and the ECMWF for 
moisture and instability. Will probably need excessive heat 
highlights by the middle of next week. 

&&

.AVIATION...Previous Discussion...12Z TAFs...VFR conditions will 
prevail through the next 24 hours. A wave in the flow will bring 
some instability and moisture northward for some thunderstorms over 
the northeast mountains, but they will not affect any of the TAF 
sites. Winds will be light through most of the period...except that 
it will become breezy in central Oregon this evening with winds of 
15 to 25 kts. Winds will become light again overnight at all TAF 
sites overnight tonight. 

&&

.FIRE WEATHER...Isolated to scattered thunderstorms will develop in 
northeast Oregon this afternoon, and most of the lightning activity 
will occur in Wallowa County and southeast Union County. Lightning 
may cause new fire starts, and gusty winds from the storm could help 
spread the new fires rapidly in the dry vegetation. 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  92  61  95  62 /   0   0   0   0 
ALW  94  67  97  67 /   0   0   0   0 
PSC  95  59  97  62 /   0   0   0   0 
YKM  95  60  97  63 /   0   0   0   0 
HRI  95  61  98  63 /   0   0   0   0 
ELN  93  59  94  61 /   0   0   0   0 
RDM  92  50  93  51 /   0   0   0   0 
LGD  92  55  94  56 /  20  20  10  10 
GCD  93  59  95  58 /  10  10  10  10 
DLS  93  63  94  64 /   0   0   0   0 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 1 PM this afternoon to 10 PM PDT this 
     evening for ORZ645.

WA...None.
&&

$$

90/88/79/83

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

Northeastern Washington and Northern Idaho


936 
FXUS66 KOTX 281119
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
419 AM PDT Fri Jul 28 2017

.SYNOPSIS...
Expect very warm weather with light winds into the weekend.
There's a slight chance of thunderstorms from the Blue mountains 
to the Camas Prairie late today, but otherwise it will remain dry.
Hot weather will return for next week with some triple digits 
temperatures likely. 

&&

.DISCUSSION...
Satellite shows the Diamond Creek wildfire in the northern
Cascades has been very active overnight. Could see more areas of
smoke in the surrounding areas this morning. 

Today through Saturday night: More very warm and dry weather can
be expected across the Inland Northwest. A west-southwest flow
will be over the region with slight cooling from yesterday's dry
cold front. There is a stream of upper level moisture that is
moving across the region and will get hung up over southeast
Washington and the southern Panhandle. A weaker secondary impulse
in the upper flow will brush this area as instability increases
this afternoon. There is the potential for a thunderstorm over the
Blue mountains or Camas Prairie late this afternoon into the early
evening, although both models indicate a weak cap in this area
similar to yesterday. Also these areas are on the northern
periphery of the moisture/instability with a better chance of
activity forming to the southeast. The GFS has been trending
wetter under this scenario with actually measurable precipitation.
Think this is overdone with the scope of dry conditions across the
region the high cloud bases that develop from any possible
convection. Will lean toward mainly dry convection if it does
form. Otherwise expect temperatures similar if not a degree cooler
than yesterday with lighter west to southwest winds and less
gustiness. Patchy smoke may be an issue with the recent fires
especially in the late night and morning hours, especially across
north central Washington into northeast Washington. Downslope
northwest winds will increase across the Cascades tonight. By
Saturday into Saturday night, slight ridging aloft develops with
an influx of more dry air. Any mid to high level moisture slips
south of the region. Low level temperatures will start to climb
with a couple degrees of warming under light winds. /rfox. 

Sunday...Model consistency is good that a weak shortwave trough 
and cold front will ripple rapidly eastward through the region. 
This feature will be associated with little moisture but it will 
bring a subtle cooling as well as an increase in winds. Suspect 
the winds won't be quite as strong as what we saw yesterday as 850
mb speeds max out between 10-15 mph. Nonetheless with a packed 
surface pressure gradients in the lee of the Cascades we will 
likely see breezy winds in the Kittitas and Wenatchee Valleys and 
spilling out into the western Columbia Basin. These conditions 
will once again pair with relative humidity levels in the teens to
lower 20s and will likely lead to enhanced fire potential. 

Monday through Thursday...Model consistency is good with the 
overall synoptic pattern which features a deep low heading into 
the Gulf of Alaska and a very strong upper level ridge building 
northward from the southwest US. Each day we will see a gradual 
warming trend as the center of the high moves toward southern 
Idaho or northern Nevada. 500 mb heights over the Inland NW climb 
into an impressive 592-595dm range. This should result in 
continued dry weather for most of the forecast area. It will also 
push 850 mb temps above 27c by Wednesday and Thursday in eastern 
Washington. This 27c mark is important since it coincides with the
warmest temperatures we have seen this summer on July 7. If the 
EC and GFS are correct we could see 850 mb temps top out just shy 
of 30c on Thursday. This would certainly result in triple digit 
heat across most of the forecast area and we have trended the 
forecast accordingly. This heat will also combine with a very dry 
air mass with relative humidity values possibly dipping into the 
single digits. While our confidence in the temperature forecast is
rather good, things become much less confident in regards to 
monsoonal moisture. The GFS suggests it could pivot north-
northeast around the periphery of the high and could skirt the SE
corner of Washington and into NC Idaho. However the EC and 
Canadian models keep this moisture south of our forecast area. We 
will follow this idea for now, but pops may need to be nudged 
upward if model agreement grows. By Friday the upper level ridge 
axis shifts east of our forecast area and we should see the 
beginning of a cooling trend. Dry conditions will continue with
not much chance of measureable rain for the next 7 days. fx

&&

.AVIATION...
12Z TAFS: VFR conditions will prevail at the TAF sites through the
period. Anticipate more high level clouds from KLWS to KPUW and
there is a small chance of -tsra toward the Blue Mountains and 
Camas Prairie late today. Expect lighter and more terrain driven
winds. Wildfire smoke will persist in the northern valleys, 
especially west of KOMK. /rfox. 

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        89  62  93  63  92  62 /   0   0   0   0   0   0 
Coeur d'Alene  89  56  92  57  91  56 /   0   0   0   0   0   0 
Pullman        89  58  92  58  90  56 /  10   0   0   0   0   0 
Lewiston       97  66 100  67  98  65 /  10   0   0   0   0   0 
Colville       91  53  94  55  94  54 /   0   0   0   0   0   0 
Sandpoint      88  49  90  50  90  50 /   0   0   0   0   0   0 
Kellogg        88  56  90  56  89  55 /   0   0   0   0   0   0 
Moses Lake     93  57  96  59  96  58 /   0   0   0   0   0   0 
Wenatchee      92  63  94  66  94  65 /   0   0   0   0   0   0 
Omak           94  60  97  61  96  61 /   0   0   0   0   0   0 

&&

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

$$

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