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Western Washington


663 
FXUS66 KSEW 281047
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
347 AM PDT Wed Jul 28 2021

.SYNOPSIS...Building high pressure over the region will maintain 
steadily warmer conditions through the remainder of the week. The
forecast remains mostly dry, though a few showers are possible
near the Cascades Saturday night or Sunday. A cooling trend with
temperatures closer to normal is possible early next week with an
upper level trough approaching from the west. 

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...The upper ridge anchored over
the central and western U.S. this morning will remain in place and
continue to strengthen and shift west today. Heights will continue
to rise and weakening onshore low-level flow will limit the inland
extend of morning stratus. Together, these factors will lead to
temperatures warming another few degrees over yesterday's highs,
topping out in the upper 70s to mid 80s across the area. Temperatures
will rise a few more degrees Thursday and another degree or two 
by Friday, which will likely end up the warmest day for most of 
the interior portions of the area. Still some spread in ensemble
guidance with the Seattle metro area likely warming into at least
the upper 80s with some chance of reaching into the lower 90s. The
warmest locations - generally from Olympia southward and some of
the higher hills moving into the Cascades could reach well into
the 90s. Overnight lows likely remain in the 60s Friday night
across much of the area, and will be especially prominent in the
mountains where a strong subsidence inversion could lead to some
locations toward the mountains remaining quite warm overnight.

In addition to the warm conditions that will pose a moderate heat
risk to more vulnerable groups (including young, old, and those
without adequate access to cooling during the day), there is some
concern for some elevated smoke to move into the region from the
south as the flow aloft becomes increasingly southerly. For most 
of the area, this will likely remain elevated as haze with the
more impactful smoke remaining east of the Cascades. However, areas
immediately near the Cascades (especially the North Cascades) could
see some additional near-surface smoke as the week progresses. 
Cullen

.LONG TERM /SATURDAY THROUGH TUESDAY/...Expect temperatures to
cool slightly on Saturday but still remaining well-above normal
values as the ridge axis may slowly shift a little eastward. There
is some potential in some monsoonal moisture embedded in the flow
around the ridge making it as far west as our area, and as such
have maintained a mention of shower chances near the Cascades late
Saturday and into Sunday. It's even conceivable, albeit not
terribly likely given the latest ensemble guidance, that a stray 
shower or two could even sneak west into the lowlands. Will 
continue to monitor this potential over the next few days.

Otherwise, ensembles generally agree in the ridge shifting
eastward, though there remains some significant spread in just how
fast it pushes away from the region and how quickly the area could
be influenced by the next upper trough approaching from the Gulf
of Alaska. For now, have maintained the forecast in line with the
NBM, which reflects a slight cooling trend with temperatures 
returning closer to normals early next week but without any 
precipitation chances moving onshore from this next disturbance 
Tuesday or Wednesday. That said, confidence remains a bit lower in
the details for next week at this time.
Cullen

&&

.AVIATION...Upper level ridge over the area with southwesterly
flow aloft and low level onshore flow through Thursday.

Narrow ribbon of stratus in the Strait of Juan de Fuca along with
another area of stratus near Grays Harbor extending into the Lower
Chehalis Valley early this morning. The stratus will make a little
eastward progress this morning before dissipating by mid to late
morning. Ceilings in the stratus below 1000 feet with visibility
1-3sm in fog. For the remainder of the area most clear skies today
and tonight. 

KSEA...Mostly clear skies. Northeast wind 4 to 8 knots becoming
northwesterly around 19z then switching back to northeasterly
after 04z. Felton

&&

.MARINE...High pressure offshore with thermal low pressure
east of the Cascades will result in varying degrees of onshore 
flow into the weekend. Small craft advisory westerlies are 
expected most evenings in the Central and Eastern Strait of Juan 
de Fuca with gales possible Saturday evening. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 6 AM PDT early this morning for 
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance 
     U.S. Waters Strait Of Juan De Fuca.

&&

$$

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


653 
FXUS66 KPQR 281043
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
341 AM PDT Wed Jul 28 2021


.SYNOPSIS...Above normal temperatures continue through the forecast 
period as high pressure strengthens across the region. Increasing
monsoonal moisture will bring periods of showers and potential
thunderstorms primarily across the central Cascades and extending
into the northern Cascades through the weekend and will likely
continue into the start of next week.  

&&

.SHORT TERM...Today through Friday...A broad upper high pressure
currently centered over the central Plains dominating the weather
over the much of the western half of CONUS. Currently the forecast
area is on the periphery of high pressure with some mid-level
moisture moving south to north around the high. Radar showing some
showers moving north across southwest OR into the Lane Co. Cascades.
No ground rainfall measurement yet, and suspect much of it is virga.
Thunderstorm chances look best for the central Cascades next few day
as impulses rotating around the high pressure bring instability with
continued feed of moisture to fuel the diurnal convection. 

A warming trend will continue through Friday as the upper level ridge
amplifies over the PacNW. The hottest areas will be the interior
lowlands to include the Willamette Valley, southwest WA, Columbia
River Gorge and portions of the Cascade foothills. Current forecast
has low to mid 90s today, mid to upper 90s Thursday, and around 100
Friday. ECMWF ensemble and NBM have 90th percentile in the 100-105F
range for Friday the hottest day. Overnight lows expected to be in
the low to mid 60s, though some spots like the Gorge may be closer to
70 for overnight lows especially Thursday night and Friday night. So
will continue with the Excessive Heat Watch for The Willamette
Valley, Foothills of The Cascades, areas along The Columbia River
including the Columbia River Gorge and Hood River. This event is NOT
expected to produce anything near the extreme temperatures which
happened in late June of this year. However, even though the current
heat event is not likely to reach the caliber of the June event,
precautions should still be taken.

The coast will be the cool area with high temperatures in 60s and 70s
as light onshore flow remains in that area. Models do not indicate
any significant period of offshore flow. 


.LONG TERM...Friday night through Monday...Cooling is expected Friday
night into Saturday as the heat shifts east of the area, but will
still be in the low to mid 90s.  But uncertainty is high in how much
surface heating the area will see given the potential for convective
debris clouds to overspread the area Friday night/Saturday morning.
Southerly flow Friday night may bring nocturnal thunderstorms as
another slug of moisture develops over the area. May even see some
convection over parts of the valley into Saturday morning. Quite
uncertain at this time, but something to watch.  The highest chances
for convection look to be over the Lane and Linn County Cascades,
where the NBM has a slight chance for thunderstorms Saturday night
through early Sunday morning. However, confidence is moderate in that
Thunderstorms will happen along the crest of the Cascades, but
confidence is low on how widespread these storms could be. 

Sunday we cool down a bit more, and currently high temperatures are 
forecast to be closer to normal for this time of year. NBM has an 
interquartile maxT range of 82-88F for Portland, which is still 
warm, but substantially less so than Thursday, Friday, and perhaps 
Saturday. Convection is possible again Sunday, but uncertainty is 
even higher. The highest chances again appear to be along the
Cascades in Lane and Linn counties, where the NBM has thunderstorm
chances around 15%. If there isn't prolific convective debris to
limit radiational cooling, Sunday night could dip into the 50s in
many locations, especially in valleys and in rural areas where there
will be no urban heat island influence.

Cluster analysis shows uncertainty in the overall flow pattern by 
the end of the extended, with one solution suggesting a continuation 
of southerly flow, another suggesting zonal (i.e., westerly) flow, 
and others somewhere between the two. If the southerly flow regime 
favored by the GFS materializes, then chances for convection will 
continue through the end of the period. However, if the more zonal 
pattern favored by the ECMWF takes place, our area is both less 
likely to see convection and more likely to be cooler by the first 
part of next work week. Despite uncertainty in the upper-level 
pattern across our area, chances are high that early next week will 
be substantially less warm/hot than late this week. -Bumgardner

&&

.AVIATION...VFR prevails across the forecast area as of 0930z,
with high clouds streaming across the region. GOES-West fog
product indicates a narrow area of fog just off the central
Oregon Coast, with another area of stratus along the southern WA
coast. This may congeal some for areas of IFR along the coast
this morning, but poor upwelling within the coastal waters will
probably keep marine stratus somewhat limited today. 

Isolated showers and thunderstorms are possible this afternoon
over the Cascades east of KEUG, but bases associated with this
convection should remain well above 3000 ft.

For detailed regional Pac NW aviation weather information, go 
online to: https://weather.gov/zse

KPDX AND APPROACHES...VFR expected through the period. Northwest
wind will likely remain below 10 kt.  Weagle

&&

.MARINE...Northerly winds remained below SCA criteria for the
most part Tuesday afternoon, except for some gusts to 25 kt along
the coast near Florence. Southerly flow aloft continues to bring
cloud cover into southern Oregon, weakening the thermal trough
and thus keeping winds moderate across our coastal waters. Some
higher resolution models suggest gusts 25-30 kt will be possible
for our southern waters this afternoon, but this appears to be
similarly overdone as their forecast for Tue afternoon. Will hold
off on issuing any Small Craft Advisories for the time being, but
we may eventually need a marginal advisory for our southernmost 
waters this afternoon and evening. Similar diurnal northerly
wind pattern is expected Thursday and Friday. Seas will remain
primarily wind-driven with background swells generally remaining
3 ft or less through the weekend.  Weagle

&&

.FIRE WEATHER...Southerly flow into the area will bring hotter 
temperatures along with an increase in monsoon	moisture on 
Thursday. These may set up terrain focused thunderstorms in the 
afternoon and evening, near the Cascade Crest in Lane and Linn 
counties, which may result in numerous fire starts as fuels continue 
to be critically dry. /Kriederman

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Watch from Thursday morning through Saturday 
     evening for Cascade Foothills in Lane County-Central 
     Columbia River Gorge-Central Willamette Valley-Greater 
     Portland Metro Area-Lower Columbia-Northern Oregon Cascade 
     Foothills-South Willamette Valley-Upper Hood River Valley-
     Western Columbia River Gorge.

     Fire Weather Watch from Thursday afternoon through Thursday 
     evening for Willamette National Forest.

WA...Excessive Heat Watch from Thursday morning through Saturday 
     evening for Central Columbia River Gorge-Greater Vancouver 
     Area-I-5 Corridor in Cowlitz County-South Washington 
     Cascade Foothills-Western Columbia River Gorge.

PZ...None.

&&

$$

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Southeastern Washington and Northeastern Oregon


338 
FXUS66 KPDT 281036 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
336 AM PDT Wed Jul 28 2021

Updated aviation discussion

.SHORT TERM...Today through Friday. Main impacts for the next few
days will be thunderstorm potential and increasing temperatures.
Strong upper ridge remains centered over the Rocky mountains with
southerly flow into Oregon and Washington. Monsoon moisture and
weak impulses moving around the high will maintain partly cloudy
skies over the region with occasional showers or thunderstorms.
For today scattered showers lingering early this morning over the
eastern mountains with mostly cloudy skies as a short wave departs
the region. Clear to partly cloudy elsewhere. Another short wave
over northern California will move across the area later in the 
day and may bring scattered showers and thunderstorms to central
Oregon. Little change to the overall pattern for Thursday and
Friday. Southerly flow will maintain the instability each day.
Partly cloudy skies with a chance of showers and storms mostly
over Oregon. 850mb temperatures are warming and highs will
increase each day although this will be dependent on cloud cover.
At this point expecting today will be mostly in the 90s. For Thu 
and Fri 90s to 105. Not much as far as winds are concerned. Weak 
gradients with mainly 5-15 mph. Dew points still fairly high today
with 40s to mid 50s so a little more humid than normal. Low level
airmass dries some Thu and Fri with lower dew points. 94 

.LONG TERM...Saturday through Wednesday...Ensemble means are in
good agreement through the period.  However, there are minor 
differences in strength/position of 500 MB trough off the BC coast 
and the four corners ridge Tuesday and Wednesday.  These differences 
will have little overall impact on the CWA as southwest flow 
prevails.  Deep monsoonal moisture is expected to spread over the 
area Saturday into Sunday with PWATs approaching 200-250 percent 
above normal. This moisture spreads east Monday night. The 
aforementioned ridge is expected to peak Saturday with daytime highs 
likely peaking Friday over Oregon and Saturday over Washington. 
Increasing cloud cover and low level moisture will make daytime 
highs very tricky Saturday, especially on the Oregon side where 
cloud cover will decrease insolation. The ridge is expected to 
weaken and move to the desert southwest by Wednesday. In summary, 
the area will continue to be trapped between an upper level trough 
off the BC coast and ridge to our east/southeast resulting in south 
to southwest flow through the period. 

With plenty of low/mid level moisture, convection should develop 
over the mountains during the afternoon and move northward through 
the evening hours both Saturday and Sunday. At this time, the most 
widespread activity should be Saturday evening. Given the deep 
moisture over the area, some of these storms will produce very heavy 
rainfall. Showers will continue to move northward through Saturday 
night into the basin. Some lingering low level moisture will 
continue over the area through early next week for isolated 
showers/thunderstorms over the Oregon mountains. Earle

&&

.AVIATION...12Z TAFs...VFR conditions will prevail through the 
period. Isolated afternoon/evening thunderstorms are possible in 
Central Oregon, but should not affect KRDM and KBDN. Mid/high level 
clouds will continue to stream across the area today, but should 
begin to thin out overnight.  Winds will be 5-15 kts with higher 
gusts in the afternoon.  Earle

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  93  64  99  66 /  10   0  10   0 
ALW  94  68 101  71 /  10   0   0   0 
PSC  97  65 102  67 /  10   0   0   0 
YKM  96  63 100  68 /  10   0   0   0 
HRI  96  65 102  67 /  10   0  10   0 
ELN  93  61  97  63 /  10   0   0   0 
RDM  91  57  96  59 /  10  10  20  20 
LGD  90  60  95  60 /  10  10  10   0 
GCD  91  61  96  63 /  10  20  20  10 
DLS  96  66 101  69 /  10  10   0  10 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Watch from Thursday morning through Saturday 
     evening for ORZ041-044-507-510-511.

     Fire Weather Watch from Thursday afternoon through Thursday 
     evening for ORZ611.

WA...Excessive Heat Watch from Thursday morning through Saturday 
     evening for WAZ024-026>029-521.

&&

$$

SHORT TERM...94
LONG TERM....81
AVIATION...97

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

Northeastern Washington and Northern Idaho


575 
FXUS66 KOTX 281132
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
432 AM PDT Wed Jul 28 2021

.SYNOPSIS...

Above average temperatures are expected through the Saturday, 
with highs well into the 90s with some triple digit temperatures 
expected by the end of the week. Otherwise the forecast remains 
dry and occasionally breezy. Wildfire smoke will continue to 
impact portions of the Inland Northwest. Rainshowers and isolated
thunderstorms possible Sunday bringing a cooler start to next week.

&&

.DISCUSSION...
Today and Thursday: The plume of monsoonal moisture has shifted 
East as high pressure continues over the region. It will lead to 
another dry, warming trend for the Inland Northwest. Sky cover 
over Southeast Washington and the Lower ID Panhandle will clear 
out through the early morning. Smoke and haze will continue to 
impact the region from the wildfires. The 850MB temperatures 
during the afternoon reach into the low to mid 20C. It translates 
to surface temps of 90s to low 100s. Overnight lows are expected 
to be upper 50s and 60s.

Friday: While the weather is not expected to be much different 
from the previous days, the high temperatures for the day will be
widespread upper 90s and triple digits across the Inland 
Northwest. Smoke from area wildfires could help shave a few 
degrees from the highs but not expected to bring much relief from 
the heat through Saturday. The lows are expected to be in the 70s.
/JDC

Saturday through Wednesday: The upper level ridge will drive 
temperatures up with highs in the triple digits across the region on 
Saturday. Overnight there will be little relief from the heat, as 
lows will be in the 70s. As monsoonal moisture moves further north 
into the region, convection is possible in the southern Idaho 
Panhandle Saturday evening. On Sunday afternoon, thunderstorms will 
move into the region bringing rain and the potential for lightning. 
However, fire weather concerns are low as lightning is unlikely to 
start any new fires due to the rain and higher dewpoints expected. 
Sunday night into early Monday morning also has the potential for 
thunderstorms in the Idaho Panhandle. On Sunday, temperatures will 
cool down to the low 90s with light winds across the region. These 
temperatures and winds will remain the same for a few days. /KLE

&&

.AVIATION...
12Z TAFS: A few lingering showers mainly over Idaho as the
monsoonal moisture band continues to shift east and exit the area
in the next few hours. A clearing trend expected as drier air 
moves into the region. All TAF sites are expected to remain at VFR
conditions expected with limited impacts from haze or areas of 
smoke. /JDC



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        91  64  96  65 100  70 /   0   0   0   0   0   0 
Coeur d'Alene  89  62  95  62  99  67 /  10   0   0   0   0   0 
Pullman        87  59  93  59  98  65 /  10   0   0   0   0   0 
Lewiston       96  71 102  70 107  76 /  10   0   0   0   0   0 
Colville       93  55  97  55 101  60 /   0   0   0   0   0   0 
Sandpoint      89  57  93  58  98  62 /  10   0   0   0   0   0 
Kellogg        88  65  93  66  97  71 /  20  10   0   0   0   0 
Moses Lake     93  62  98  64 103  71 /   0   0   0   0   0   0 
Wenatchee      95  69  99  73 103  79 /   0   0   0   0   0   0 
Omak           95  66  98  68 103  72 /   0   0   0   0   0   0 

&&

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

&&

$$

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