Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 200937
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
237 AM PDT Mon Aug 20 2018

.SYNOPSIS...
Gusty north winds will blow some of the smoke out of north Idaho
and eastern Washington today. However, the warm winds will raise
concerns for the spread of wildfires. Winds will relax during the
day Tuesday. A pattern change during the second half of the week
will bring cooler temperatures and cleaner west winds to the
Pacific Northwest which should improve air quality.

&&

.DISCUSSION...

...STRONG NORTH TO NORTHEAST WINDS TODAY...

Today: Today will be an active weather day across the Inland Northwest
will the main focus centered on strong north to northeast winds but
also a chance for thunderstorms for some. There are two main
features coming into play today which are clearly evident on 2AM
water vapor imagery. To the north, we see an area of darkening
dropping south through BC and very close to moving across the
International Border. This is the northern branch shortwave that
will usher in the northerly winds today. To the south over Oregon,
a broader cyclonic circulation is tapping into midlevel
instability and moisture and churning up some thunderstorms
across far southeastern WA and lower Idaho Panhandle. These two
features will phase over the next 24 hours and slowly drift to the
south/southeast.

Winds: The strongest winds today will focus in three areas. 1) North
winds will channel through the Okanogan Valley southward across
the Waterville Plateau and spill into Grant County impacting Banks
Lake, Ephrata, and Moses Lake. These winds will start early
Monday morning and continue into the afternoon. Speeds will be on
the order of 15-30 mph with gusts 35-45 mph but isolated stronger
gusts are not out of the question. 2) Northeast winds will channel
down the Purcell Trench of N Idaho from Sandpoint to Post Falls
and spill into the West Plains. Speeds will also be on the order
of 15-30 mph with gusts 35-45 mph and I anticipate the strongest
gusts to be observed on the Selkirks, Sandpoint AP, and around
Rathdrum. Timing also favors Monday morning and early afternoon.
3) The northeast winds will fan out into the Columbia Basin and
given the lack of vegetation and sheltering, pick up speeds of
15-25 mph. Gusts will be not be as strong due to less channeling
through narrow valleys but still on the order of 30-35 mph given
25-28kts through the mixed layer. For the remainder of the region,
an increase in winds will be noticeable but different degrees of
sheltering will result in speeds on the order of 5-15 mph with
infrequent gusts 15-20 mph but generally from the north/northeast.

Showers/Thunderstorms: We have one band of convection passing through
the Camas Prairie at this time. Look for this moisture in the
form of showers and embedded thunderstorms to linger from the
Camas Prairie to SE Shoshone County through much of the day and
re-organize into isolated to scattered thunderstorms this
afternoon while bending back into the Palouse, L-C Valley, and
Blue Mountains before clearing out this evening. There is also a
ribbon of instability draped northward along the MT/ID border
which will sag to the west as the northeast winds charge inland
this morning. GFS continues to show some spotty QPF along this
instability and NAM would support the idea of brief convection but
never really indicates any organization. Given the lack of
support from other hi-res models, opted to keep the best chances
along the MT border and to the southeast but will need to monitor
how this evolves through the morning hours.

Smoke/haze: Conditions are down right hazardous this morning for a
majority of the Inland NW. Our smoke models do give us hope today
and Tuesday with the strong north/northeasterly winds. The wind
change suggest areas of N WA and N ID will see improvement as
plumes of smoke from active fires will become more constricted and
aligned with the wind field. Initially this will get transported
toward Oregon but as winds trend more northeast/east and expand
over much of the region, thinking the Cascades will continue to
receive a heavy dose of smoke while conditons improve over N ID
and Ern WA. Of course, there are fires in Montana as well and a
lot will be decided based on what kind of smoke output these fires
produce so nothing is a guarantee at this time.

Impacts: The combination of strong winds and low humidity will result
in critical fire weather conditions today and red flag warnings
have been issued. Winds will result in choppy lakes and potential
for minor tree damage and isolated power outages. We will also
have to keep an eye out for localized blowing dust in the Basin.

Tonight and Tuesday: The region will be under north/northeasterly flow
aloft with a cool surface high sliding down the Continental
Divide. This will continue to bring breezy east to northeasterly
winds overnight and Tuesday. Speeds will lower from Monday but
gusts on the order of 20-25 mph will remain possible over exposed
ridge tops and across the open Columbia Basin. The axis of
moisture will be shoved well south of my area leading to dry
conditions. Heavy concentrations of smoke will continue to be
localized downstream of ongoing fires and could be shoved into the
East Slopes but thinking a good portion of Idaho and Eastern WA
will get continue to see drastic improvements in comparison to the
current hazardous conditions. /sb

Wednesday: The warmest day of the week is expected to be Wednesday
with lowland highs in the upper 80s to low 90s. The slow departure
of a shearing upper trough through southern Idaho will provide the
Camas Prairie and the Blue mountains with a small chance for
showers and thunderstorms, but the remainder of the Inland
Northwest will continue to be dry. Height falls along the coast of
British Columbia are expected to reverse our surface pressure
gradient by the afternoon leading to a change in wind direction.
The east or northeast winds of Monday and Tuesday will transition
to our more typical south or southwest winds (5 to 15 mph range) by
Wednesday afternoon. Smoke will likely be the most concentrated
along the East Slopes of the Cascades and the Okanogan Valley with
our expected wind regime on Wednesday. By the evening, increasing
onshore flow should promote westerly winds through the Cascade
gaps which may push smoke into the Columbia Basin and northeast
Washington during the evening and overnight hours.

Thursday: The medium range models continue to forecast a big
pattern change Thursday into the weekend. An upper level trough is
forecast to form over western Canada leading to several days of
cooler onshore flow. Thursday will be a transition day with high
temperatures in the mid to upper 80s for most lowland areas. West
or southwest winds should increase into the afternoon and early
evening with 10 to 20 mph winds across the Palouse, West Plains,
and Columbia Basin. Gusts will likely peak during the evening in
our typical Cascade Gap spots like Wenatchee, Vantage, and Entiat
(25 to 30 mph).

Friday through Monday: The GFS and ECMWF continue to forecast
cooler and breezy weather Friday through the weekend. Higher
humidity will also accompany the trough as marine air spills
across the Cascades into eastern Washington and north Idaho. Air
quality should be much improved courtesy of "cleaner" west winds.
Keep your fingers crossed. The GFS and ECMWF are forecasting a
deep and slow moving low in the Sunday/Monday time frame.
Hopefully mentioning rain won`t jinx things, but the models are
wet over the Cascade Crest, the mountains along the Canadian
border, and the Idaho Panhandle. Even if the low happens to miss
the Inland Northwest early next week, there will be a good chance
for rain in British Columbia where a lot of our smoke is
originating. /GKoch

&&

.AVIATION...
06Z TAFS: Visibilities should improve over the next 12 hours at
the TAF sites as northeast winds strengthen over the area. VFR
conditions are expected by about 18Z for most locations. Winds
will be strongest at KCOE and down the Okanogan valley. Winds will
quickly subside during the evening hours on Monday.  RJ


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        79  58  86  58  89  60 /  10   0   0   0   0   0
Coeur d`Alene  78  54  85  55  87  57 /  10   0   0   0   0   0
Pullman        81  53  84  55  87  56 /  30  10   0   0  10   0
Lewiston       88  60  91  61  92  62 /  40  10   0  10  10  10
Colville       82  52  90  51  91  53 /   0   0   0   0   0   0
Sandpoint      77  50  84  49  86  51 /  10   0   0   0   0   0
Kellogg        74  50  82  53  86  54 /  10   0   0   0   0   0
Moses Lake     88  59  90  56  92  57 /   0   0   0   0   0   0
Wenatchee      87  63  89  63  92  63 /   0   0   0   0   0   0
Omak           87  59  91  59  95  60 /   0   0   0   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning from 10 AM this morning to 6 PM PDT this
     evening for Northern and Central Idaho Panhandle (Zone
     101).

WA...Red Flag Warning from 10 AM this morning to 6 PM PDT this
     evening for East Washington Northern Columbia Basin (Zone
     673)-East Washington Okanogan/Methow Valleys (Zone 684)-
     East Washington Palouse and Spokane Area (Zone 674).


&&

$$


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