Area Forecast Discussion
Issued by NWS Spokane, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS66 KOTX 272343
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
443 PM PDT THU AUG 27 2015

.SYNOPSIS...
A cold front will approach the region tonight through Friday
night. This will result in breezy conditions Friday afternoon with
any showers expected to remain in the Cascades. Cold front passage
on Saturday will bring the potential for high winds. This will
create a situation for blowing dust with reduced visibility. Some
areas may also experience toppled trees and downed power lines. A
cooler and occasionally breezy regime with some shower activity
will persist through the next week.

&&

.DISCUSSION...

Tonight through Friday night: The region will be sandwiched
between a deep closed upper level low pressure system out at
140W/40N in the eastern Pacific and a ridge of higher pressure
over the Rocky Mtns. This will keep the region under broad
southwest flow. Satellite imagery does show a batch of moisture
pumping up on the eastern flank of the upper low, but much of this
is expected to remain west of the Cascade Mtns. The east slopes of
the northern Cascades will see an increasing chance for showers on
Friday with the best chances remaining near the crest. The rest of
the region will see increasing high clouds. Pre-frontal winds will
increase on Friday as well. This will result in breezy southerly
winds, especially up the Okanogan Valley. Temperatures will be a
little cooler compared to today with the increasing cloud cover,
but high temps will still be in the 80s for most locations.

...STRONG STORM SYSTEM TO BRING HIGH WINDS AND BLOWING DUST ON
SATURDAY...

Saturday: The low situated off the coast will eject toward the
region in the morning. This storm system will feature a strong
vorticity maximum fueled by a 120 kt upper level jet. The surface
low will track into western WA Saturday morning and then push
northeastward into southern BC through the afternoon. Models have
been consistent in showing a strong cold front passage over the
Inland Northwest. The cold front is expected to push into the
basin Saturday morning then track up to the Canadian border
between noon to 2 PM.

* Winds: Very strong winds are expected with frontal passage.
  Models show 850 mb winds of near 50 kts across the Columbia
  Basin with strong cold air advection. This is expected to result
  in good momentum transfer to the surface with 50-60 mph gusts
  possible. These stronger gusts will be most likely with frontal
  passage in the morning to early afternoon. Windy conditions will
  likely persist through the afternoon; although 50+ mph gusts
  will become less likely by this time with the front pushing
  into Canada. We will be issuing a High Wind Watch for much of
  the region; the exception will be the east slopes of the
  Cascades and the Wenatchee Area where the orientation of the
  pressure gradient will not be as favorable for high winds. High
  winds may result in pockets of toppled trees and/or downed power
  lines. Strong cross winds along Interstate 90 between Vantage
  and Sprague and Highway 2 west of Wenatchee to Spokane can be
  expected. This will create hazardous driving conditions for high
  profile vehicles.

* Blowing Dust: Strong winds are expected to pick up and blow
  around a lot of dust across the Columbia Basin. Blowing dust
  will be a concern as far east as the Spokane/Coeur d`Alene Areas
  and the Idaho Palouse. There is also a good chance for blowing
  dust on the Waterville Plateau and up the Okanogan Valley.
  Widespread visibility restrictions down to 1 mile will be
  possible and some areas could see near zero visibility at times.
  This will include the I-90 and Highways 97, 2, 395, 195 and 95
  corridors.

* Precipitation: Models have been trending the heaviest rainfall
  further west. It looks like the best chances for more
  significant rainfall of 0.25-0.50 inches will be in the east
  slopes of the northern Cascades. Areas closer to the Cascade
  crest may see rainfall totals between 0.50-1.00 inches. This
  rainfall will be stratiform in nature. This will translate into
  some pockets of more moderate rainfall at times. High intensity
  rainfall typically found with thunderstorms is not expected.
  Some minor mud flows may be possible near burn scars, but the
  risk for flash flooding looks low. /SVH

Saturday night through Thursday...General long-wave trof of low
pressure allows the jet stream to remain in close proximity which
is favorable to allow numerous shortwave passages through Eastern
Washington and Northern Idaho, and as such below normal
temperatures with above normal precipitation (but not excessive)
mark this forecast interval. Of significant note is a synoptic
scale low pressure system that nests in the large trof and digs
southward into it Wednesday and Thursday which helps to intensify
it and keep it in the area. Current timing shows the most robust
synoptic scale and smaller shortwave disturbances to move through
it and bring the best chances of precipitation to Eastern
Washington and North Idaho Sunday and Wednesday. This pattern
change won`t end the fire season for Eastern Washington and
Northern Idaho but will slow it down some. /Pelatti

&&

.AVIATION...
00Z TAFS: The region will be sandwiched between low pressure in
the eastern Pacific and high pressure over the Rookies. A cold
front will linger offshore through Friday afternoon. The
proximity of the front will promote better mixing. This is
expected to result in continued smoke improvement at the TAF sites.
However, MVFR visibility will be possible due to smoke at KGEG,
KSFF, KCOE, KPUW and KLWS as inversions set in overnight.  /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        61  84  63  80  53  72 /   0  10  10  20  30  50
Coeur d`Alene  57  84  59  81  51  71 /   0  10  10  30  20  40
Pullman        55  84  59  83  51  73 /   0  10  10  20  20  20
Lewiston       64  89  66  89  58  81 /  10  10  10  20  20  20
Colville       55  83  56  79  49  72 /   0  10  10  50  30  40
Sandpoint      51  83  54  81  48  69 /   0  10  10  40  30  50
Kellogg        55  86  56  82  48  71 /   0  10  10  30  30  30
Moses Lake     60  85  62  77  55  75 /   0  10  10  20  30  30
Wenatchee      67  83  65  74  57  73 /   0  10  20  30  40  20
Omak           61  81  62  75  51  71 /   0  10  20  30  40  30

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...High Wind Watch from Saturday morning through Saturday evening
     for Central Panhandle Mountains-Coeur d`Alene Area-Idaho
     Palouse-Lewis and Southern Nez Perce Counties-Lewiston Area-
     Northern Panhandle.

WA...Red Flag Warning until 8 PM PDT this evening for East Washington
     Central Cascade Valleys (Zone 677)-East Washington
     Northeast (Zone 686)-East Washington Northern Columbia
     Basin (Zone 673)-East Washington Okanogan Highlands (Zone
     687)-East Washington Okanogan/Methow Valleys (Zone 684)-
     East Washington Palouse and Spokane Area (Zone 674).

     High Wind Watch from Saturday morning through Saturday evening
     for Lower Garfield and Asotin Counties-Moses Lake Area-
     Northeast Blue Mountains-Northeast Mountains-Okanogan
     Highlands-Okanogan Valley-Spokane Area-Upper Columbia Basin-
     Washington Palouse-Waterville Plateau.

&&

$$


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.