Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 222325

Area Forecast Discussion
National Weather Service Spokane WA
425 PM PDT Mon May 22 2017

Tuesday will be warm with continued rises expected on local
rivers and streams in the Cascades and across the Northern
Mountains of Washington and Idaho. A strong cold front will plow
through the region Tuesday evening bringing gusty winds. Breezy
winds will usher the cooler air into the region Wednesday
knocking temperatures down almost twenty degrees from Tuesday.
Cooler and unsettled weather will likely persist through the end
of the week with a warming trend for the weekend.



Tonight through Tuesday afternoon: It will feel a lot like summer
during the next 24 hours courtesy of high pressure anchored over
the Northwestern US. Overnight lows will only be cooling into the
50s allowing afternoon highs on Tuesday to warm into the 80s to
lower 90s. Outside some thin cirrus, clouds will generally be
clear and winds will be light.

Tuesday evening through Wednesday: Models are in good agreement that a
strong cold front will plow through the region late Tuesday. This
will be a dry cold front passage so there are little concerns for
precipitation in this event. The main focus will be on winds. The
challenging aspect of this front is the timing. We are confident
that strong cold air advection will accompany the front with
afternoon highs expected to be on the order of 20-25 degrees
cooler Wednesday however the timing of the front close to dark or
later suggests lowlands may have the opportunity to decouple.
Regardless, the front looks too strong to in my eyes to remain
decoupled during and shortly after the actual frontal passage
which looks to be supported by hi-res model data.

Winds look to increase from the south late Tuesday afternoon, decouple
prior to sunset, then ramp up and swing around to the west with
the cold front passage. This could be quite a punch of winds with
this time period carrying the highest risk for strong gusts.
Following the front, the boundary layer may decouple (winds
becoming lighter) for a few hours Wednesday morning then increase
again Wednesday morning as morning inversions mix out. The front
is expected to move into Central WA and the Cascades in the
evening (7-10PM) then into Ern WA and N ID 10PM-1AM. Bufkit data
from the Wenatchee AP also suggest a weak stable layer 5-8 ft AGL
which could also pose a threat for breaking waves in and around
the Waterville Plateau. Potential wind gusts on the Cascade
ridgetops and Waterville Plateau could be upwards of 40-55 mph.
These will carry a lower threat for surfacing in the deeper
valleys along the Wenatchee and Columbia River Valleys for
reasoning mentioned above. Wind gusts across the, Okanogan Valley,
Columbia Basin and into the lower Idaho Panhandle should be
weaker but still pose a threat for speeds on the order of 35-45
mph. Winds will be breezy through the day on Wednesday but winds
aloft will be weakening and gust potential will decrease closer to
25 mph by afternoon. Temperatures by Wednesday afternoon will
only be warming into the 60s to lower 70s in the deep Basin.

The resident mild air mass will continue to cook high elevation snow
leading to increasing runoff. River basins in the Cascades and
across Northern WA/ID are experiencing significant rises. The
Okanogan and Stehekin Rivers have a good shot of rising into minor
flood Tuesday. We are also monitoring the Kettle River for
potential minor flooding. The Entiat, Methow, Moyie, and Kootenai
are or will be reaching bankfull and continue to be updated in the
Hydrologic Statement. /sb

Wednesday night through Saturday morning...The upper level low will
shift east of the Continental Divide Wednesday and take up
position over the Canadian Providences. Meanwhile High pressure
will amplify in the eastern Pacific. This will put the Pac NW in a
northerly flow. The atmosphere will slowly destabilize on
Thursday and more so on Friday. Numerous weak waves will wrap
around the parent low and move from north to south through central
Washington on Thursday and then along the ID/MT border on Friday.
These waves will have be able to tap into a little better
moisture for a chance of mainly showers on Thursday and showers
and thunderstorms on Friday across extreme eastern Washington and
the Idaho Panhandle. Precipitation amounts with any of these
showers and thunderstorms will be under a tenth of an inch. Small
hail and gusty outflow winds will be possible with any
thunderstorms. Cooler then normal temperatures on Thursday will
begin to rebound with temperatures rising into the high 60s and
lower 70s. Temperatures will bottom out on Wednesday then show a
slow rise each day. Winds will remain elevated and gusty at times
with the showers and thunderstorms. Gusty winds will linger across
the area Wednesday evening, but should become diurnal by Thursday

Saturday through Monday...The ridge of high pressure will be along
the coast on Saturday and over central Washington on Sunday and
Monday. Showers will be kept in the forecast for the Panhandle for
Saturday, but confidence is low that we will see much more then
cloud build ups. Model guidance is showing a couple of short wave
disturbances trying to under cut the ridge on Sunday and Monday
and this would be enough forcing for isolated showers over the
mountains at times. But again confidence in anything more than
cumulus build ups is low. Temperatures will rebound nicely through
the weekend with highs rising into the high 70s to near 90 for
Sunday and Monday. Winds will be light and variable and diurnally
driven. Tobin


00Z TAFS: High pressure will remain over the region through
Tuesday afternoon. Some high cirrus will move over the region at
times for some scattered cirrus. A cold front will move into the
region Tuesday night with winds expected to increase out of the
southwest after 22z Tuesday with gusts 18-25kts. Tobin


Spokane        57  85  48  64  47  65 /   0   0   0  10  10  30
Coeur d`Alene  53  83  47  62  44  64 /   0   0  10  10  10  30
Pullman        52  83  49  63  45  62 /   0   0   0   0  10  20
Lewiston       56  90  53  68  48  68 /   0   0   0   0  10  20
Colville       53  86  48  67  46  67 /   0   0   0  10  10  30
Sandpoint      48  81  44  61  41  63 /   0   0   0  10  20  50
Kellogg        48  81  43  60  41  61 /   0   0   0  10  10  50
Moses Lake     56  92  51  72  47  73 /   0   0   0   0   0  10
Wenatchee      60  90  50  69  48  72 /   0   0   0   0   0  10
Omak           57  88  49  70  48  72 /   0   0   0  10  10  10



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