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

Western Washington


983 
FXUS66 KSEW 271026
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
330 AM PDT Mon May 27 2019

.SYNOPSIS...Dry conditions over most of Western Washington this week
with slightly above normal temperatures. A few showers or 
thunderstorms are possible most afternoons and evenings over the 
Cascades.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...Another fairly quiet start to 
the day again this Memorial Day with the only item to discuss 
regarding current conditions is that some low level stratus/fog is 
making itself known over some locations. Largest reductions in 
visibilities can be found out by Arlington and Port 
Townsend...although patchy fog can also be expected in the usual fog 
prone locations such as Olympia and Hoquiam. These low clouds are 
expected to burn off by late morning for most locations...giving way 
to mostly sunny skies by this afternoon.

Upper level ridging over the Pacific will start to slowly move 
eastward closer to WA today as exiting upper level low pressure 
continues its journey into the Four Corners region. This will set up 
continued dry conditions for most of the area while allowing for 
wrap around moisture from the aforementioned low to give rise to 
afternoon showers and isolated thunderstorms over the Cascades. 
Those sunny skies and dry conditions will make for a warm day over 
the interior lowlands...with most locations hitting high temps in 
the mid 70s today. An onshore push expected tonight will ensure that 
highs today will be the highest of the week...as this cooler marine 
air will knock afternoon high temps back down to around 70 for the 
remainder of the near term.

Models remain pretty consistent for the near term period with the 
upper level ridge continuing to slowly move east...keeping 
conditions dry over the area except for the continued risk of 
afternoon and evening showers/isolated thunderstorms in the 
Cascades.  SMR

.LONG TERM /FRIDAY THROUGH MONDAY/...The ridge weakens some in the 
long term as an upper level trough remains camped out over the SW 
US. Models remain in disagreement as to what this would spell for W 
WA...as the GFS keeps conditions dry into next week while the ECMWF 
hints at a couple of instances of showers late Friday and again 
Sunday. Despite these details...the most recent solutions for both 
models are drier than those previous. As such...have opted to cut 
back on inherited POPs some. Temperatures during this time frame 
look to remain fairly stable...with highs in the interior lowlands 
not getting warmer than the lower 70s...and even dropping back into 
the 60s toward the end of the forecast period.  SMR

&&

.AVIATION...Northeasterly flow aloft with upper level ridge
centered over Central British Columbia and an upper level low 
well southeast of the area. Light flow in the lower levels 
becoming onshore this afternoon with the onshore flow 
strengthening late this afternoon and evening. 

Low clouds, ceilings below 1000 feet, confined to the coast this
morning. Mid level deck moving through the area during the day. 
Some patchy fog in the interior until 16z. 

KSEA...Just some mid level clouds at times today. Onshore push
tonight will bring stratus into the terminal early Tuesday morning
with ceilings near 1000 feet. Light and variable winds becoming
southerly 6 to 10 knots tonight. Felton

&&

.MARINE...Onshore flow will increase today with a moderate 
onshore push expected tonight. Onshore flow will continue through
the week as high pressure remains centered well offshore with 
lower pressure east of the Cascades. 

Gale force winds forecast for the Central and Eastern Strait of 
Juan de Fuca tonight with small craft advisory winds over the 
southern portion of the Northern Inland Waters. For the remainder
of the week small craft advisory west winds possible in the 
Central and Eastern Strait of Juan de Fuca each evening through 
Friday. Felton

&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Warning from 6 PM this evening to 5 AM PDT Tuesday for 
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance 
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 6 PM this evening to 5 AM PDT Tuesday 
     for Northern Inland Waters Including The San Juan Islands.

&&

$$

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


765 
FXUS66 KPQR 271025
AFDPQR

Area Forecast Discussion
Weather Service Portland OR
324 AM PDT Mon May 27 2019

.SYNOPSIS...Low-level onshore flow will prevail for the next several
days, keeping temperatures fairly close to normal for late May and
the first couple days of June. Night and morning low clouds will
likely clear to the coast by each afternoon. Similar to Sunday,
showers and isolated thunderstorms are expected to develop over the
higher terrain this afternoon, potentially drifting across the
Willamette Valley before decreasing this evening. Showers should
become less numerous Tuesday and the rest of the week. 

&&

.SHORT TERM...Today through Wednesday...GOES-17 water vapor imagery
shows a prominent, closed upper low encompassing much of the
southwestern United States. A weaker and smaller circulation was
drifting slowly S-SW into SW Washington and NW Oregon, wrapping
around the larger upper low to the south. This weaker circulation
will continue to move slowly southward across the Willamette Valley
and Cascades, reaching southwest and south-central Oregon by 00z Tue
per the 06z NAM.

Isolated showers persist over the forecast area early this morning.
While cooler nighttime temperatures have ended surface-based
instability, there still remains some very weak instability above
low-level inversions per the 08z HRRR. It is almost a stretch to call
this environment unstable, as MUCAPE values are generally in the
100-300 J/kg range, but forecast soundings show this very weak
buoyancy extending from roughly 850 mb all the way up to the
tropopause. This is likely why shower activity has been so persistent
overnight; any showers that develop have been maintained by this weak
instability, and some continue to produce brief downpours as a
result. That said, instability this meager isn't particularly
conducive for the shower development either; it appears synoptic lift
associated with the above-mentioned weak upper level circulation may
be the initial trigger for these showers. This will likely continue
to be the case through this morning, though the overall coverage may
dwindle slightly as mountain temps cool, removing any surface-based
help for the development of these showers.

Today seems likely to be very similar to Sunday overall, though a
deepening marine layer and strengthening onshore flow will likely
come into play. With pressure gradients aligned SW-NE it's likely the
marine layer will be deepest and most persistent along the coast and
across the southern half of the forecast area. At this point, it
appears any surface-based convection across the southern half of the
CWA will be strongly capped at 4000 ft MSL or so, leaving only the
Cascades above that elevation to provide surface-based support for
shower/thunderstorm development. It does not appear this type of cap
will be as prominent over much of the S WA Cascades, and 06z NAM
soundings suggest freer surface-based convection developing across
inland SW Washington and potentially some parts of the PDX metro this
afternoon. There will also be a small bit of contribution to lift by
the weak upper disturbance drifting across our CWA today. Thermal
profiles seem fairly similar today as Sunday, with weak, "skinny"
CAPE extending all the way to the tropopause. This seems to be an
indication that, similar to the last 24 hours, any showers or
thunderstorms that develop may be long-lived as they are supported by
the weak instability aloft. Veering winds with height may also help
sustain cells that develop, and could make hail a little more likely
than it was Sunday. Steering flow gradually backs from ENE early
today to more NNE later this afternoon, which will gradually make it
more difficult for Cascades showers/thunderstorms to drift over the
Willamette Valley.

Shower development should gradually decrease this evening as surface
temperatures cool, again eliminating the surface-based component to
convection. Onshore flow will likely be deeper and stronger than the
past 24 hours tonight through Wednesday, likely bringing widespread
low clouds inland tonight and again Tue night. Low clouds should
generally clear back to the coast by mid-afternoon Tuesday and
Wednesday, with plenty of sunshine inland and near to slightly above
normal temps inland each afternoon. Warmer temps aloft should make
afternoon convection less prominent on Tuesday and Wednesday, though
still cannot rule out a stray shower or thunderstorm over the high
Cascades.  Weagle

.LONG TERM...No Changes. Previous discussion follows...Wednesday
night through Sunday...Ridge of high pressure to our north midweek
keeps dry, mild weather in place. We may see a stray shower or
thunderstorm near the crest of the Lane County Cascades Wednesday
night, or a few showers in the Oregon Cascades on Thursday as we get
clipped by shortwaves passing mostly to our south. Weak onshore flow
will keep temperatures fairly close to normal for this time of year.
Next weekend should start out dry and mild as high pressure sits over
the area. Sunday, a shortwave trough moves through which will
increase cloud cover and may trigger a few showers, mostly along the
Coast, Coast Range, and in the Cascades. -McCoy


&&


.AVIATION...Widespread low end MVFR ceilings this morning are 
likely to persist through much of the day today, with a few areas 
breaking up and going to VFR conditions between 18Z and 02Z. Clouds 
then expected to fill back in along the coast after 02Z, with 
widespread MVFR ceilings and a few areas down into IFR flight 
category. Inland areas are largely expected to remain VFR today, but 
there will be areas of high end MVFR ceilings developing this 
morning and persisting as late as 19Z today. Expect mainly VFR 
conditions tonight. There is a slight chance of thunderstorms over 
the Cascades and north Willamette Valley between 21Z and 06Z. 

KPDX AND APPROACHES...Some high end MVFR ceilings were developing on 
the eastern approaches early this morning, and will likely linger as 
late as 19Z near the Gorge. Otherwise VFR is expected to prevail 
today, with just a 30 percent chance of seeing MVFR ceilings 
spreading to the field between 14Z and 19Z today.

&&

.MARINE...Northwest winds expected to remain under 20 kt through 
Friday as a ridge of high pressure remains offshore. In the same 
time frame, expect seas to be in the range of 4 to 6 feet, dominated 
by a moderately steep fresh swell. 

&&

.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


485 
FXUS66 KPDT 270959
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
259 AM PDT Mon May 27 2019

.SHORT TERM...Today through Wednesday...A large upper low 
will continue to dominate our weather for the next few days. 
Currently the low is centered over southern Nevada and is sending 
moisture into the area on an east to southeast flow. After a mostly 
dry morning with just a few showers possible south of Bend and in 
the higher terrain of northeast Oregon, am expecting another 
afternoon of scattered showers and isolated thunderstorms over most 
of the area. Convection will not be quite as active as yesterday as 
the low is further away today. Have limited scattered thunderstorms 
to the northern Blues and Wallowa county and have kept the Columbia 
Basin dry. Thunderstorms will end rapidly with sundown and showers 
will taper off as well, with a slight chance of showers overnight 
limited to the Oregon Cascades and the eastern Oregon mountains. 
Under the heavier cells, a quarter inch of rain will be possible, 
but most locations will just see a few hundredths of an inch. On 
Tuesday the upper low will be moving through the Rockies but there 
will still be moisture circulating around the low into our area on a 
northeast flow. The atmosphere will continue to be unstable and the 
moisture will allow a chance of showers and a slight chance of 
thunderstorms in the afternoon from central Oregon through the 
eastern Oregon mountains and also in the Washington Cascades and 
Simcoe Highlands with the rest of the area dry. Rain amounts will 
just be a few hundredths of an inch. By Wednesday the upper low will 
be weakening and located over Kansas. It's circulation will cease to 
affect us, but another weak low will form along the Oregon coast. 
This will lead to chance of showers and a slight chance of 
thunderstorms once again in central Oregon south of Bend and in the 
eastern Oregon mountains while the rest of the area is dry. Rain 
amounts in the higher mountains will be up to a tenth of an inch but 
generally just a few hundredths of an inch. Temperatures today will 
be 3 to 5 degrees higher than yesterday with highs in the mid 70s to 
lower 80s and mainly in the 60s in the mountains. Tuesday and 
Wednesday will be a few more degrees warmer with highs in the upper 
70s to mid 80s in the lower elevations and in the mid 60s to mid 70s 
in the mountains. Perry


.LONG TERM...Wednesday night through Sunday... Another shortwave 
will cause reamplification of the western trough starting Wednesday 
night and continuing through Saturday, with some weak ridging 
developing to the north by Saturday and another weak trough possible 
by Sunday. With the flow becoming almost split with a more zonal 
flow to the north over western Canada and a more amplified pattern 
to the south over southern California and the Great Basin around the 
trough/low, no major systems will be affecting our area. However, 
there will be enough instability and moisture for afternoon showers 
and thunderstorms basically each day, mainly over southern and 
eastern areas through Friday.  The large trough will begin to weaken 
and fill by Saturday and some ridging will build to the north. There 
are model disagreements what happen with the low after that, with 
the GFS continue to weaken it while the ECMWF cuts the low off, but 
both models bring a less amplified pattern over the north. However 
the GFS wants to bring another weak wave into Washington state and 
the ECMWF is weaker with this system.  Temperatures should see a 
nice warm up through Saturday, well into the 80s...at the lower 
elevations, before decreasing a bit on Sunday as the weak trough 
bring cooler temps for Sunday.  


&&

.AVIATION...12Z TAFS...VFR conditions are expected at all TAF sites 
today unless heavy SHRA or TSRA are seen, in which case local MVFR 
or even brief IFR are possible.  Due to the nature of these SHRA and 
TSRA they are not being forecast at any individual sites, but would 
not be expected until afternoon.  

The only exceptions are RDM and BDN which have MVFR CIGS this 
morning.  They will return to VFR  later this morning and remain 
there unless they have showers or thunderstorms as well.

A northwest wind, which could gust as high as 20 to 25 kts is 
expected during the afternoon at DLS, PDT, BDN and RDM.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  74  52  78  52 /  20  20  10  10 
ALW  76  53  81  54 /  20  30  10  10 
PSC  82  57  86  55 /  10  10  10  10 
YKM  78  57  84  52 /  20  20  10  10 
HRI  79  55  85  55 /  10  10  10  10 
ELN  75  53  80  50 /  20  20  10  10 
RDM  69  45  75  43 /  40  30  10  10 
LGD  67  51  74  48 /  30  30  20  20 
GCD  65  46  72  45 /  20  30  30  20 
DLS  77  58  79  51 /  20  20  10  10 

&&

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

$$

83/77/77

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

Northeastern Washington and Northern Idaho


168 
FXUS66 KOTX 271148
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
448 AM PDT Mon May 27 2019

.SYNOPSIS...
The main threat for showers and thunderstorms the next few days  
will be over the Cascades, southeast Washington, and the lower 
Idaho Panhandle. Look for this threat to expand into most mountain 
ranges throughout the week. Temperatures meanwhile will be 
warming with most communities expected to be well into the 80s by
Tuesday and throughout the week.

&&

.DISCUSSION...

Today and Tuesday: The area of low pressure that has been responsible
for sending several rounds of precipitation through the region 
this holiday weekend will begin to eject east across the 
Southwestern US and higher pressure centered over Western Canada 
will begin to sag southward. Our air mass will begin to warm but 
not stabilize completely keeping a threat for showers and storms 
for some areas. One last circulation pinwheeling around the 
departing low will clip the lower Idaho Panhandle and SE WA this 
afternoon bringing a good shot for showers and thunderstorms. 
Afternoon instability is expected to be slightly greater than that
experienced on Sunday which could equate to a few stronger cells.
Effective shear profiles will be less than 20kts, PWATS near 
0.80", and SB CAPE 700-1000 J/kg; thus the main threats with 
storms will be brief hail followed by potential for torrential 
downpours. Wind gusts of 25-35 mph will also be possible near the 
cores but the overall environment does not favor a strong wind 
threat. Storm motion will generally be from northeast to southwest
at 10 to 15 mph.

A secondary threat threat for thunderstorms will exist over the 
Cascades. Despite a 2C warming at 500mb, the lower levels will be
warming 5-7C promoting modest afternoon instability. We will lack
a forcing mechanism over Central WA but diurnal winds along the 
ridgetops should prove sufficient for cells developing near the 
Crest and adjacent ridgelines. PWATs will be drier, topping out 
near 0.6" and effective shear profiles indicate values of 
10-14kts....so looks like pulse variety storms capable of brief 
heavy downpours and small hail. Storm motion will be from north to
south around 15 mph.

Convection across the region will wane with sunset and Monday night 
will feature quiet weather conditions. Temperatures will continue
to warm on Tuesday with many locations punching into the upper 
70s to low 80s. With little change in temperatures aloft, surface 
heating will once again help destabilize the atmosphere and 
thunderstorms look to fire over the mountains. At this time, the 
greatest risk will be in the Cascades but thinking a few cells 
will expand into the Kettle Mountains around Sherman Pass. A few 
storms are also possible around the Blue and Clearwater Mountains 
which could potentially impact the Idaho Palouse, LC Valley, and 
Camas Prairie. The threat looks lower than Monday but something to
monitor for isolated activity. /sb

Wednesday through Friday...A split flow over the region on Wednesday
will be followed by a weak upper level low that will slowly move 
through the area Thursday and Friday. Some lingering moisture on 
Wednesday combined with afternoon instability will keep isolated 
showers in the mountains and more likely just some building 
cumulus clouds. The weak upper low will drag slightly deeper 
moisture into the region and enhance afternoon convection. This 
will support a better chance for afternoon showers and possibly a 
few thunderstorms, but mainly for the mountains. Some of these 
showers may move off the terrain and into more populated areas but
chances are low. Temperatures will remain on the warm side of 
normal with highs in the mid 70s to mid 80s.

Saturday through Monday...Flat westerly flow on Saturday will give way
to a little more potent shortwave Sunday and Monday. At this time
the main energy will track through southern British Columbia. 
Limited moisture will be with this wave, but enough for showers 
across the higher terrain along the Canadian border and the Idaho 
Panhandle mountains. For the remainder of the forecast area we are
expecting dry conditions with scattered clouds. Warm temperatures
on Saturday will give way to cooler temperatures Sunday and 
Monday. Afternoon highs will cool from the 80s down into the 70s 
by Monday. These temperatures will still be on the warm side of 
normal. Tobin

&&

.AVIATION...
12Z TAFS: Skies will be SCT to BKN across a wide area of the CWA 
and the TAF sites with showers and thunderstorms expected to 
return Monday over southeast WA and the central ID Panhandle. The 
best area for the possible development of significant convection 
Monday will be around PUW-LWS aft 21Z. Retained -SHRA for both 
PUW/LWS and it still remains the best area for development, but 
have higher confidence for the development of TSTMs vicinity of 
LWS. Confidence remains low, however, for TSTM development in the 
direction of PUW. /aky

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        75  51  79  53  80  54 /  10  10   0   0   0  10 
Coeur d'Alene  74  49  79  51  79  54 /  20   0   0   0   0  10 
Pullman        70  48  74  51  76  52 /  40  30  10   0  10  10 
Lewiston       73  55  80  57  82  59 /  40  40  10  10  20  10 
Colville       80  43  85  46  89  47 /   0   0   0   0  10  10 
Sandpoint      74  49  79  52  80  54 /   0   0   0   0  10  10 
Kellogg        71  50  76  53  76  55 /  30  10  10   0  20  10 
Moses Lake     81  54  86  55  87  57 /   0  10   0   0   0   0 
Wenatchee      79  57  84  57  84  58 /  10  10  10   0  10  10 
Omak           80  53  85  55  85  57 /   0   0  10   0  10   0 

&&

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

&&

$$

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