FXUS66 KOTX 211739

Area Forecast Discussion
National Weather Service Spokane WA
1039 AM PDT Mon Aug 21 2017

Skies should be favorable for viewing the eclipse this morning,
however there may be some smoke in the northern valleys and high
thin cirrus clouds. Tuesday and Wednesday will be quite warm with
afternoon temperatures in the upper 80s to upper 90s. A vigorous
cold front passage has the potential to produce thunderstorms
Wednesday night into Thursday, mainly over the southern Idaho
Panhandle. This will be followed by gusty west winds Thursday.
After a cool Thursday and Friday, temperatures will warm over the


Today through Tuesday night: Eclipse day is here! Satellite shows
an upper ridge centered off the coast with a low pressure system
moving into northern BC. While this system is located far to the
north...the southern fringes of a warm front will track across
Washington and North Idaho today bringing a band of high clouds.
The GFS and ECMWF show increasing cirrus through late morning over
Central and NE Washington into the North Idaho Panhandle...while
SE Washington should have slightly less cirrus. These high clouds
will be thin and shouldn't have much of an impact on eclipse
viewing. On Tuesday a weak upper ridge builds ahead of the next
weather system. This will result in a warming trend through
Tuesday with mostly 80s for high temperatures today...warming into
the lower to mid 90s for Tuesday. Hazy skies and patchy smoke
will continue to be an issue for the northern valleys and Idaho
Panhandle given closer proximity to wildfires in BC and western
Montana. The Canadian smoke model suggests hazy skies may increase
to include more of Eastern Washington on Tuesday as fire activity
increases from regional wildfires with the warming/drying air
mass. This should be short lived however with winds increasing
Wednesday into Thursday. JW

Wednesday through Sunday: Computer forecasts are still haggling
over the details of the frontal passage for Wednesday night and
Thursday. The latest forecasts have backed off on the intensity of
the front a bit. But they could easily switch back to a stronger
solution with their next version. So at this point, I backed off
slightly on the wind speeds for Thursday, but overall kept the
same theme as before.

Wednesday morning shows the potential for some elevated convection
over southeast WA and the southern Panhandle. But given the lack
of synoptic lift, I'm guessing we'll mainly just see some mid-
level Accas clouds. Temperatures on Wednesday will actually be
slightly cooler than Tuesday, as temperatures aloft start to fall.
Winds will be a bit gusty in the afternoon with hot temperatures. Later
in the day, surface- based convection will develop over eastern
Oregon and be directed to the southern Panhandle. Most of the
shower/thunderstorm activity should hold off until late in the
afternoon for that area. As Wednesday night progresses, more
elevated convection will move over the area east of a line from
Tri-Cities to Colville. I expect mainly sprinkles from this
convection along with some lightning strikes, but a few convective
cores could put down a brief downpour. All of this activity will
move into Montana by Thursday mid-morning.

Wind will be the main story for Thursday. The timing of the system
isn't ideal for a strong wind event. The frontal passage still
looks to be around 10pm Wednesday for the WA/ID border. As such,
by Thursday afternoon, the front will be well east of our area.
We'll still be windy, but just not as strong as if the timing
would be 6-12 hours slower. Humidities will be very low so fire
weather will be the concern, but temperatures will also be
markedly cooler on Thursday which will reduce the fire threat

Friday will be the coolest day of the week, before temperatures
start a warming trend through the weekend and into next week.
Long range forecasts show that summer isn't over, as hot weather
is possible next week. RJ


18Z TAFS: Some thin cirrus and light terrain driven winds
to remain at times through 18z Tuesday. Winds will be light and
generally terrain driven but may weaken or reverse briefly during
the eclipse 16-19Z. Hazy skies from smoke is expected over NE
Washington and the N Idaho Panhandle...but visibilities should
remain VFR.


Gusty winds will develop on Wednesday afternoon, coupled with hot
temperatures and low humidities. This could lead to increased
activity on some of the current wildfires in the area.

A cold front will move through the region Wednesday night,
bringing the threat of thunderstorms east of a line from Tri-
Cities to Colville. Gusty winds will develop behind the front,
especially on Thursday. There is still some uncertainty with the
wind speeds, but humidity values will be 15-20% across the region,
so critical fire weather conditions may exist on Thursday. RJ


Spokane 85 60 91 63 88 61 / 0 0 0 0 10 20
Coeur d'Alene 85 54 91 57 88 57 / 0 0 0 0 10 20
Pullman 85 52 92 57 87 57 / 0 0 0 0 10 30
Lewiston 91 61 97 65 94 64 / 0 0 0 0 20 40
Colville 87 51 91 54 90 53 / 0 0 0 0 10 0
Sandpoint 83 49 89 50 88 51 / 0 0 0 0 10 20
Kellogg 83 52 89 56 87 54 / 0 0 0 0 10 30
Moses Lake 89 54 95 59 92 57 / 0 0 0 0 10 0
Wenatchee 88 63 93 66 90 63 / 0 0 0 0 10 0
Omak 90 59 95 62 93 59 / 0 0 0 0 10 0



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