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

Western Washington


474 
FXUS66 KSEW 181523
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
825 AM PDT Thu Oct 18 2018

.SYNOPSIS...Dry weather will continue through the weekend. An upper 
ridge over the region will shifts east on Monday. Areas of fog and 
low clouds on the coast this morning will spread inland Friday 
morning. A front will arrive Tuesday followed by a stronger front 
later Wednesday or Thursday.

&&

.SHORT TERM...An upper ridge will remain over the Pacific NW through 
Saturday for dry weather. There are low clouds and fog on the coast 
this morning, but just patchy fog elsewhere. Some cirrus has arrived 
as well. For Friday and Saturday there will be more widespread areas 
of night and morning fog and low clouds with mostly sunny afternoons 
under light onshore flow. 

.LONG TERM...Dry weather will continue Sunday and Monday as an
upper ridge over the area gradually shifts inland. A weakening
frontal system will bring a little rain on Tuesday. Another front
will approach from the west on Wednesday but most of the rain will
probably hold off until at least Wednesday night. 

&&

.AVIATION...As an upper level ridge builds offshore today, westerly 
flow aloft will gradually shift to the northwest. Low level flow
will remain light. Clear skies expected again today.
Shallow/patchy fog possible Friday morning with visibilities
reduced to a mile or less where it does develop. Should quickly
burn off during the morning hours after sunrise. 

KSEA...A few high clouds today with light winds. Patchy fog
development after 12z Friday morning which could drop
cigs/visibility to IFR/LIFR. CEO

&&

.MARINE...Light onshore flow pattern will continue through the 
weekend. An approaching front on Monday will turn the low level 
flow southeasterly with small craft advisory winds possible over 
the outer coastal waters late Monday into Tuesday. CEO

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&

$$

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


680 
FXUS66 KPQR 181530 AAA
AFDPQR

Area Forecast Discussion...Updated
National Weather Service Portland OR 
0830 AM PDT Thu Oct 18 2018

Updated Aviation


.SYNOPSIS...High pressure over the region will continue to produce
mild days, cool nights and mostly clear skies before a more active
storm track produces periods of rain next week.

&&

.SHORT TERM...Today through Sunday...Water vapor satellite imagery
continues to reveal an area of upper level high pressure centered
over the eastern Pacific. Models are in a good agreement it will
expand northward over the next day before traversing eastward across
the Pacific Northwest over the weekend. This will result in a
continuation of the warm days, cool nights and mostly clear skies
through the weekend across the interior.

Along the coast it will be a different story, though. The latest
GOES-16 nighttime microphysics satellite imagery reveals fog and low
clouds filling in rather quickly across our waters and along the
coast. These clouds may temporarily retreat to just offshore this
afternoon and once again Friday afternoon, but should more or less
continue through Friday. This will greatly reduce high temperatures
along the coast when compared to the past few days. With that said,
thermal low pressure will temporarily shift towards the coast Friday
night, which should result in fog and low clouds pulling off the
coast Friday night into Saturday before returning Sunday. 

For those tired of the east winds near the mouth of the Columbia
River Gorge...the good news is that they should disappear later today
as pressure gradients turn either neutral or even weakly positive 
between KTTD-KDLS. However, the respite in the east winds will be 
short lived as they should return as early as Friday and linger 
through the weekend, albeit wind speeds will be lower than recent 
days. /Neuman  


.LONG TERM...Sunday night through Thursday...Models are in good
agreement that Sunday night and Monday will be a continuation of the
pleasant fall weather of late. However, that should begin to change
Monday night and Tuesday as the first in a series of fronts pushes
eastward into the area. The GFS is farther north with the shortwave
trough responsible for pushing the first front into the area. This
results in a weaker front and less QPF across the region than the EC.
Given this will be the first storm system to push into the area
following the high pressure, worry rain still isn't a given with this
system despite models suggesting between 0.1-0.5" will fall across
the entire area Tuesday. 

Nonetheless, models are in a good agreement a strong zonally oriented
jet will follow and push into the region Wednesday and Thursday. This
should result in better rain chances for the second half of next
week. It should be noted the GFS is slightly farther north with its 
placement of the jet axis, which would likely result in more 
distinct dry and wet periods across our CWA. Meanwhile, the EC would 
likely keep post frontal showers going between systems and even 
suggests a risk for thunderstorms exists along the coast. 

It should also be noted that models do spin up a 965-980mb low
pressure during the middle of next week well west of our region and
move it northeastward towards Haida Gwaii. While this track is
generally far enough away to keep impacts fairly minimal across our
CWA, our first coastal wind event of the season is not out of the 
question next week depending on whether or not the low pressure 
tracks a bit closer to the region. /Neuman


&&


.AVIATION... VFR SKC inland through 12Z Fri. IFR fog and stratus 
has reached the coastline. Forecast challenge is what happens
along the coast today? Models continue to suggest stratus may 
hug the coastline through the day. KAST and KONP might see a 
brief period of VFR conditions during the afternoon time frame. 
Look for a return to IFR conditions this evening into Friday 
morning along the coast. Patchy fog possible for the interior 
valleys after 09Z Fri.

KPDX AND APPROACHES...VFR SKC through 12Z Fri. 


&&


.MARINE...High pressure to remain over the coastal waters through
the weekend. Weak south flow reversal in progress along much of
the Oregon coast as of 09Z, but wind shifts back to North by 18Z.
The north wind gradually increases late Fri and Fri night. UW- 
WRF, NAM and GFS all suggest possible small craft advisory wind 
gusts beginning around 00Z Sat and continuing through Sat, 
especially for PZZ255 and PZZ275. Surface thermal trough develops
along the coastline Fri night, but shifts inland Sat. 

Models continue to be in general agreement showing a weakening 
frontal system moving through the waters late Monday night and
Tue morning for possible small craft advisory speeds. Multiple 
models show a rather deep surface low in the Gulf of Alaska 
around Wednesday, which may bring gale force wind to the waters.

Seas will hold around 6 to 7 feet through Fri and then ease to 4
to 5 feet Fri night through Sat. Guidance suggests seas building
to just over 10 ft Tue and possibly to near 15 feet next Wed
night or Thu. 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 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


034 
FXUS66 KPDT 181736 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
1036 AM PDT Thu Oct 18 2018

Updated aviation discussion

.UPDATE...Minor grid edits this morning. Fog has developed around
the Tri-Cities and along parts of the Columbia River and expect a
slight increase in coverage over the coming nights/mornings as the
upper-level ridge axis re-establishes itself over the Pacific NW
with low-level moisture and pollutants increasing under the
strengthening subsidence inversions. The low mixing heights and
transport winds under the inversion along with smoke and other
pollutants will lead to air stagnation issues and create poor 
quality. An Air Stagnation Advisory has been issued for today
through early Tuesday. Approaching system next week will bring
stronger winds and better air mixing and improve air movement and
quality.

&&

.AVIATION...18Z TAFs...VFR conditions will persist at all TAF sites 
for the next 24 hours. Expect few to scattered cirrus above 18K feet 
though 12Z tonight then clearing. Some local morning fog is possible 
along the Columbia River but is unlikely to impact any TAF site. 
Winds will remain below 10 kts for the next 24 hours. Perry

&&

.PREV DISCUSSION... /issued 110 AM PDT Thu Oct 18 2018/ 

SHORT TERM...Today through Saturday night...The high pressure ridge 
that has been along the Pacific Northwest coast and bringing dry and 
stable weather to the region is continuing to slowly push eastward 
into the Pacific Northwest. As it is doing so, the axis is leaning 
positively tilted. This pattern is not expected to break anytime 
soon and will persist throughout the short term period. This will 
result in sinking air aloft under the high pressure, which will 
cause a warming trend to take place. The higher elevations will have 
a greater warming trend than the lower valleys due to inversions in 
the lower valleys that area strengthening. There may be some late 
night and early morning patchy fog along the large bodies of water, 
such as the Columbia River, Yakima River and Snake River. However, 
any fog that does develop will be patchy and not widespread due to a 
lack of significant moisture at the surface. Temperatures today will 
range from the mid 60s to near 70 in the lower elevations with 
mostly 50s to lower 60s mountains. This will warm to the upper 60s 
to lower 70s lower elevations and mainly upper 50s to mid 60s 
mountains by Saturday. Winds will remain light and generally under 
15 mph throughout the short term period. 88

LONG TERM...Sunday through Thursday...The ridge of high pressure 
over the region will finally break down and allow weather systems to 
impact the Pacific northwest starting Tuesday. This first system 
will weaken as it breaks down the ridge so it will fall apart but 
still produce some showers leaving us under a westerly flow. The 
next system arrives Late Wednesday and Thursday in this westerly 
flow and will maintain its organization and strength resulting in a 
more widespread precipitation event. Snow levels will be around 6000 
to 7000 feet Tuesday into Wednesday and then lower to 5000 to 6000 
feet late Thursday. 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  64  43  65  43 /   0   0   0   0 
ALW  62  43  63  45 /   0   0   0   0 
PSC  64  39  65  42 /   0   0   0   0 
YKM  68  40  69  41 /   0   0   0   0 
HRI  66  41  67  43 /   0   0   0   0 
ELN  69  39  70  40 /   0   0   0   0 
RDM  70  34  71  37 /   0   0   0   0 
LGD  66  39  67  41 /   0   0   0   0 
GCD  72  42  73  42 /   0   0   0   0 
DLS  69  43  70  45 /   0   0   0   0 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Air Stagnation Advisory until 10 AM PDT Tuesday for ORZ041-044-
     049-050-502-503-505>511.

WA...Air Stagnation Advisory until 10 AM PDT Tuesday for WAZ024-
     026>030-520-521.

&&

$$

84/83/83

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

Northeastern Washington and Northern Idaho


956 
FXUS66 KOTX 181707
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1007 AM PDT Thu Oct 18 2018

.SYNOPSIS...
A ridge of high pressure will persist over the Inland Northwest 
through the weekend and into early next week. This will deliver 
mainly clear skies, light winds with chilly morning temperatures 
and mild afternoon highs. The next chance of precipitation looks 
like it could arrive by next Tuesday in the Cascades and over the
remainder of the Inland Northwest on Wednesday. Temperatures will
also cool considerably by that time. 

&&

.DISCUSSION...
The main update for this morning was to issue an Air Stagnation
Advisory through Tuesday morning. High pressure over the region
will result in stagnant atmospheric conditions with strong
inversions and weak winds. Strongest inversions will set up across
the mountain valleys where overnight temperatures will be coldest
with lows dropping to around freezing and mountains only cooling
into the mid 40s. Did not include the Idaho Panhandle, Spokane
Area and Palouse in the Air Stagnation Advisory as models show 
higher mixing heights through the weekend to between 2000 and 
2500 feet in the afternoon. Its possible that models are overdoing
the mixing potential in the Northern Panhandle and Spokane Area 
and they may need to be added to the advisory at a later date, 
especially if air quality sensors are indicating poorer air 
quality than just the moderate range. /SVH

&&

.AVIATION...
18Z TAFS: High pressure will bring VFR conditions and mostly 
clear skies and light winds to all TAF sites through Friday. 
Otherwise, some mountain valley fog near water bodies is probable 
late tonight into Friday morning. However, any fog that does 
develop is not expected to impact the TAF sites. /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        63  38  64  41  66  41 /   0   0   0   0   0   0 
Coeur d'Alene  64  37  66  39  66  37 /   0   0   0   0   0   0 
Pullman        65  38  67  41  69  43 /   0   0   0   0   0   0 
Lewiston       67  41  68  43  69  42 /   0   0   0   0   0   0 
Colville       66  32  66  34  67  34 /   0   0   0   0   0   0 
Sandpoint      60  33  63  34  65  33 /   0   0   0   0   0   0 
Kellogg        62  35  64  37  66  37 /   0   0   0   0   0   0 
Moses Lake     66  32  68  34  67  35 /   0   0   0   0   0   0 
Wenatchee      65  41  66  43  66  44 /   0   0   0   0   0   0 
Omak           65  36  67  37  67  39 /   0   0   0   0   0   0 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until 10 AM PDT Tuesday for East Slopes 
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Spokane Area-Upper 
     Columbia Basin-Waterville Plateau-Wenatchee Area. 


&&

$$

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