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

Western Washington


999 
FXUS66 KSEW 210329
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
830 PM PDT Wed Jun 20 2018

.SYNOPSIS...Showers and thunderstorms over the mountains are 
ending this evening. Onshore flow will bring cooler marine air 
inland Thursday and Friday. High pressure aloft will cross the 
region this weekend, followed by an upper trough early next week.

&&

.SHORT TERM...Showers and thunderstorms over the mountains are 
ending this evening. Marine stratus will spread inland overnight as 
marine air pushes into the area. There might be some drizzle along 
the coast tonight and Thursday morning. Temps will remain cool on 
the coast and drop considerably for the rest of Western Washington, 
with highs in the upper 60s and 70s along the I-5 corridor Thu.

Another upper trough will move into Western Washington Thursday
night and Friday. This feature will be better defined, but will
only bring a chance of light showers to the area -- mainly the
coast, mountains, and eventually in the Puget Sound convergence
zone Friday evening. Friday will be a bit cooler yet, with highs
mainly in the mid 60s to lower 70s. 

An upper level ridge will follow...starting to impact the area 
during the overnight hours Friday night and dry conditions and 
warmer temperatures expected for Saturday. Temperatures will 
increase only a few degrees with mid to upper 60s expected along the 
coast and low to mid 70s in the interior lowlands.  

.LONG TERM...The aforementioned ridge does not last very long over 
the area as the ridge axis exiting Saturday night and the feature 
itself east of the area by late Sunday morning...setting up the next 
main weather factor over the area...an upper level trough with its 
associated low situated well north of the Canadian border. Models 
still not really syncing up with this feature when it comes to the 
details...and precip signatures with both GFS and ECMWF are pretty 
weak...so while POPs are present in the extended...they are confined 
to the northern third of the CWA and only get as high as low-end 
chance wording...while partly to mostly sunny skies are expected for 
the remainder of the area. This feature will keep temps over W WA 
right near seasonal normals...with lowland temps hovering right 
around 70 degrees.  SMR

&&

.AVIATION...Light southwest flow aloft tonight will become more 
westerly Thursday. The air mass is moist and unstable in mid and 
upper levels with thunderstorms over the Cascades and Olympics and 
adjacent lowlands. Most convection should die out by sunset at 04Z.
Thunderstorms may impact the terminals around Puget Sound before 
then and they are carried in several TAFs. 

Low level onshore flow will become strong this evening and will 
bring a marine layer inland across much of the interior of Western 
Washington for IFR or low MVFR ceilings Thursday morning.

KSEA...Discussion above applies. TAF has a TEMPO group for thunder 
23Z-03Z. Ceilings will be VFR until after 11Z when marine stratus 
will bring MVFR ceilings. Northwest wind 4-8 kt this afternoon 
becoming southerly 5-10 kt overnight. CHB

.MARINE...Strong onshore flow will develop late this afternoon and 
tonight. A gale warning is in effect for the strait, with small 
craft advisories for adjacent waters. 

Moderate to strong onshore pressure gradients will continue each day 
through the weekend. Winds of at least small craft advisory strength 
are likely each day in the strait, with gale force winds possible 
each day. For now have kept winds 20-30 kt each afternoon and 
evening. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Warning until 5 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 Advisory until 3 AM PDT Thursday for Admiralty Inlet-
     Northern Inland Waters Including The San Juan Islands-West 
     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


711 
FXUS66 KPQR 210555 AAA
AFDPQR

Area Forecast Discussion...Updated
National Weather Service Portland OR 
1055 PM PDT Wed Jun 20 2018

Updated Aviation Section

.SYNOPSIS...Increased marine clouds and cooler temperatures Thursday
and Friday will give way to warmer and sunnier weather over the
weekend before cooler and cloudier conditions return early next week.

&&

.SHORT TERM...Tonight through Saturday...Water vapor satellite
imagery reveals a shortwave trough moving northeastward across
southwest Oregon. Plenty of showers and thunderstorms developed in
advance of this feature across the Oregon and Washington Cascades
earlier this afternoon and evening. Speed shear was rather meager
across the area today, which led to updrafts struggling to sustain
themselves. A thunderstorm in the southern Lane County Cascades where
0-6km shear was slightly greater likely contained the largest hail of
the afternoon based on doppler radar signatures. However, we have not
received any ground truth reports verifying whether or not large hail
was observed under any of the thunderstorms in which warnings were
issued this afternoon and early this evening.

Several convective allowing models including members of the HREF and
HRRR suggested thunderstorms were a good possibility for the Portland
metro this evening. Several updrafts (in the form of towering 
cumulus) went up around the Portland metro during the time the sea 
breeze arrived, but no individual updraft could sustain itself for 
reasons not completely known at this point. A few models have 
continued to suggest elevated thunderstorms are a possibility 
between 8-11pm this evening as the marine layer deepens and is able 
to interact with the instability still present above 5000 feet. 
Given few signs this will materialize per latest radar and satellite 
imagery, it appears the chance of thunderstorms is certainly 
diminishing across most of the area. Will maintain a slight chance 
of a thunderstorm through the late evening hours to account for the 
uncertainty, though. 

Otherwise, the marine layer is quickly spreading into the Willamette
Valley with temperatures already in the low to mid 60s in
Kelso/Longview, McMinnville, Salem and Eugene. Expect marine clouds
to push well into the Cascades by daybreak on Thursday with sunshine
returning in the mid to late afternoon hours. Temperatures will be
slow to warm with high temperatures likely only topping out in the
mid 70s. Expect a near repeat Friday before upper level high pressure
shifts over the region on Saturday and results in fewer morning
clouds and afternoon temperatures approaching 80F in the Willamette
Valley. /Neuman 

.LONG TERM...Saturday night through Tuesday night...A surface thermal
trough strengthens along the N. CA and S. OR coast Saturday night as
high pressure dominates inland, and offshore flow should keep marine
clouds off the coast Saturday night. A sunny start Sunday will allow
slightly warmer temperatures Sunday afternoon with high temperatures
remaining above the seasonal normals. Models are in excellent
agreement that an upper level trough will send a series of shortwave
troughs over the region Sunday night through Tuesday for increased
morning clouds and cooler afternoon temperatures. ~TJ

&& 

.AVIATION...Thunderstorms are starting to diminish across the area 
this evening as cooler marine air fills into the interior. Will keep 
VCTS in the TAF for KPDX and KHIO for the next hour or so due to the 
storm near KHIO, but suspect it will not impact either terminal. 
Otherwise, the interior will see marine stratus continue to fill 
into the valley tonight, with MVFR cigs expected at all interior 
terminals by 11Z. Low stratus in the interior is expected to lift 
early Thursday afternoon, with conditions becoming VFR by 21Z.

Strengthening onshore flow will keep the coast socked in with marine 
stratus tonight and Thursday. Will see predominately MVFR cigs along 
the coast the next 24 hours, but several hours of IFR cigs are 
possible late tonight/early Thursday morning as high pressure builds 
into the coast. 

KPDX AND APPROACHES...VFR conditions continue through late tonight, 
with isolated thunderstorms possible for the next hour or so. MVFR 
stratus around 2500 ft is expected to move into the terminal by 10Z. 
MVFR cigs are expected to persist through early Thursday afternoon, 
but should lift and become VFR by 21Z. /64

&&

.MARINE...High pressure continues to sit over the NE Pac, with
weak gradients over the waters through Friday. As the thermal 
low starts to strengthen over norther CA this weekend, we could 
see northerly winds ramp up to 20 to 30 kt over the weekend. 

Seas remain around 3 to 5 ft through Friday as we remain under
relatively benign conditions. With winds ramping up this weekend,
seas may build up to 5 to 7 ft by late Sunday-early Monday, and
seas may become choppy. -McCoy

&&

.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


370 
FXUS66 KPDT 210544
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1040 PM PDT Wed Jun 20 2018

.SHORT TERM...showers and thunderstorms developed this afternoon
across the region associated with an upper level trough and  
strong short wave. The activity continues this evening with 
storms moving slowly northeast. Up to this point most reports 
have been heavy rain, small hail and gusty winds to 40 mph. With 
strong dynamics aloft expect showers and storms will continue into
the overnight period. High temps today were in the 80s to mid 90s
and with cloud cover increasing it will likely be a warm night. 
Lows in the upper 50s and 60s. The upper trough will be over the
forecast area through afternoon with showers and thunderstorms as
the airmass will remain unstable. The trough moves east into 
Idaho by evening and expect activity should decrease quickly.  
Temps will be about 5-10 degrees cooler. Fair weather Friday with 
a weak upper level ridge over the area.  94

.AVIATION...06Z TAFS. Showers and thunderstorms have decreased in 
coverage late this evening. Expect there will be some activity 
through the night into Thursday. Otherwise ceilings 060-120. Winds 
5-15kt overnight and 10-25kt Thu. 

&&

.PREV DISCUSSION... /issued 500 PM PDT Wed Jun 20 2018/ 

..MARGINAL RISK OF SEVERE THUNDERSTORMS THROUGH THIS EVENING...

SHORT TERM...Tonight through Saturday...A shortwave is moving
onshore northern CA early this afternoon. Ahead of this feature, 
initial showers/thunderstorms have developed across southern 
sections of central OR. Coverage and intensity of storms will 
increase through the afternoon as peak heating is reached. High 
resolution models continue to show the thunderstorms forming into a 
complex early this evening, moving northward late evening/overnight.
Will use the highest PoPs across central OR and the associated 
highlands, with less coverage further north through the evening with 
some increase in coverage overnight as the shortwave moves gradually 
to the east. With sufficient deep layer shear through at least 
early this evening, strong to locally severe storms will be 
possible with gusty winds and hail the main threats. Thunderstorm 
coverage will decrease some overnight, but at least a slight chance 
of storms will linger with residual instability. Lows tonight will 
be unseasonably warm, especially north of central OR, with lower 
elevation lows in the mid 60s to around 70.

The shortwave will continue to move east Thursday, exiting the 
area Thursday night. PoPs will remain quite high from the Blue 
Mountain foothills eastward with likely PoPs through Thursday 
afternoon. With some instability, chances of thunderstorms will 
continue. With the greatest shear to the east, do not expect 
strong/severe storms Thursday. Areas to the west will experience a
slight chance of residual showers early, ending by afternoon. 
Residual activity in the evening across the eastern mountains will
end by the overnight as shortwave ridging/drier NW flow enters 
the region. Dry conditions will prevail Friday and Saturday under 
NW flow. In the wake of the system, windy conditions will prevail 
on Friday/Friday evening with some local gusts approaching 
advisory criteria. Above normal temperatures Thursday will cool 
slightly Friday and Saturday.

LONG TERM...Saturday night through Wednesday...Saturday night an
upper trough will be departing the area while an upper ridge 
builds along the coast. Do not expect any precipitation Saturday 
Night except perhaps in eastern Wallowa county in the early 
evening but have gone with dry forecast. Sunday will see the ridge
move overhead for a dry and warm day with highs in the 80s and 
lower 90s. The ridge will move off to the east Sunday night as a 
trough moves to the coast. The trough will move east gradually and
come ashore Monday night and then through the area Tuesday. Most 
of the energy and moisture with the trough will remain up in 
British Columbia so our area should remain dry. The trough will 
bring breezy west to northwest winds of 10 to 20 mph Monday in the
late afternoon and evening. After the trough departs on Tuesday 
models have some timing differences but it appears that a westerly
flow will be over the area on Tuesday night followed by a weak 
trough that arrives Wednesday. All models continue fair and dry 
weather Tuesday night and Wednesday. After the warm day on Sunday,
temperatures will drop back to the mid 70s to mid 80s Monday and 
then to the mid 70s to lower 80s with mid 60s to mid 70s in the 
mountains on Tuesday and Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  65  82  58  84 /  50  60  10   0 
ALW  67  85  60  87 /  50  60  10   0 
PSC  69  90  61  89 /  40  40  10   0 
YKM  67  88  58  85 /  40  10   0   0 
HRI  70  89  61  88 /  40  40  10   0 
ELN  65  85  57  80 /  40  10   0   0 
RDM  54  83  49  83 /  70  10   0   0 
LGD  58  75  51  81 /  70  60  10   0 
GCD  56  80  51  82 /  70  30  10   0 
DLS  67  82  61  81 /  50  10   0   0 

&&

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

$$

94

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

Northeastern Washington and Northern Idaho


407 
FXUS66 KOTX 210448
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
948 PM PDT Wed Jun 20 2018

.SYNOPSIS...
A threat for rain and lightning is expected to spread into 
eastern Washington and north Idaho late tonight into Thursday. 
Slow moving cells will have the potential to produce locally heavy
rainfall. Breezy weather is expected Friday and Saturday with the
chance for mountain showers. The beginning of next week currently
looks dry but breezy.


&&

.DISCUSSION...
Recent thunderstorms have died out with some isolated showers
lingering northern mountains. The afternoon and evening showers
mainly dumped heavy rain.

...Heavy rain with Thunderstorms may cause local flooding issues 
Thursday...

The Main change this evening is to heighten awareness of 
potential for heavy rain with thunderstorms with an areal flood 
watch. Latest models are showing a very active period starting 
later tonight along the WA/OR border where showers will initially 
be elevated and light in rainfall. At this point areas around 
Lewiston/Clarkston and the Camas Prairie may not get the full 
effect of heavy showers with embedded thunderstorms however at 
least a half an inch or more is not out of the question just not 
all at once and over a longer period of time. Farther north 
toward late Thursday afternoon a moist and unstable air mass will 
spark a round of afternoon showers across northeast WA and the ID 
Panhandle. With the anticipation of embedded thunderstorms dumping
potentially over an inch in a short time it could cause local 
flooding issues. Just be aware if thunderstorms are approaching
that driving conditions may change rapidly and outdoor activities
should be delayed until the storms move through.

Thursday evening showers will die out for a quieter Summer night.
TC

&&

.AVIATION...
00Z TAFs: Thunderstorms this evening will avoid most TAF sites
with VFR conditions through the overnight hours. However 11 miles
south of KEAT on Mission ridge there will be thunderstorms on the
ridge which could bring wind gusts to 15 mph out of the southwest
until 02Z which is not typical for KEAT. General convection will 
diminish after sunset. Moisture moving out of the south will 
begin to impact KLWS after 12Z moving north toward KPUW,KGEG,KSFF 
and KCOE through the remaining TAF period. Showers with embedded 
thunderstorms in this area can be expected with MVFR conditions 
forecast at KPUW. Confidence is low bringing VIS and CIGS down for
KGEG, KCOE and KSFF but the weather will certainly be more 
unsettled. TC


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        62  75  58  80  55  76 /  10  70  50  10  20  20 
Coeur d'Alene  61  73  56  78  53  75 /  10  70  70  10  20  20 
Pullman        60  74  55  76  51  73 /  40  70  70  10  10  10 
Lewiston       65  81  59  85  57  80 /  60  70  40   0  10  10 
Colville       60  79  55  82  52  81 /  20  70  40  50  50  20 
Sandpoint      58  71  55  75  52  73 /  10  80  70  30  30  30 
Kellogg        58  69  53  74  50  70 /  20  70  70  10  20  30 
Moses Lake     65  89  56  87  55  84 /  40  30  10   0  10  10 
Wenatchee      68  85  61  83  58  83 /  40  10  10   0  10  10 
Omak           64  86  57  85  54  85 /  30  40  10  10  20  20 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Flood Watch from Thursday morning through Thursday evening for 
     Central Panhandle Mountains-Coeur d'Alene Area-Idaho 
     Palouse-Northern Panhandle. 

WA...Flood Watch from Thursday morning through Thursday evening for 
     Northeast Mountains-Spokane Area. 


&&

$$

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