Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 100004

Area Forecast Discussion
National Weather Service Spokane WA
404 PM PST TUE FEB 9 2016

Strong high pressure will persist into Wednesday, with dry and
mild conditions. A more progressive and unsettled pattern will
return late this week, bringing a chance of light rain Thursday in
the Cascades, then throughout the region Friday into the weekend.


Tonight through Thursday: The ridge of high pressure will slowly
weaken over the next couple of days as weak impulses of energy
push onshore off of the eastern Pacific. Confidence is high that
fog will redevelop across much of the same areas that had fog
earlier this morning. This included much of the deeper valleys
across the ID Panhandle, in the Cascades and northern mtn valleys.
The question remains, and where models have not been much help as
of late, is how much of the basin will see fog develop tonight.
Surface temperatures are quite warm in the mid 50s for early
February on the Palouse. This part of the region will likely
remain clear with large dew point depressions in place. Winds at
the surface will veer a bit across extreme eastern WA from out of
the northeast to out of the southeast. I think this will keep much
of the northeastern portion of the basin from saturating as that
drier air across the Palouse advects up into the Spokane West
Plains. The best potential for new fog development by Wednesday
morning will be across the southern portion of the Upper Columbia
Basin to western portions of the Moses Lake Area. Low clouds are
expected to hang around a bit longer across the northern mtn
valleys on Wednesday. This will keep high temperatures for
locations such as Omak, Republic, Colville, Metaline Falls and
Bonners Ferry in the mid to high 30s or low 40s. Warmest
temperatures will once again be across the Palouse and in the
Lewiston-Clarkston Vly with highs a bit cooler than this
afternoon, but still above normal in the upper 40s to low 50s.

A weak system for Wednesday afternoon into Wednesday evening will
increasing mid and high level clouds over the region. We will also
see a chance for some precip in the Cascade Mtns with possibly a
few drops of rain possible over the northern mtns. A wetter warm
front will begin to push in Thursday afternoon. This will result
in a better chance for precip in the east slopes of the northern
Cascades, as well as out over onto the Waterville Plateau and over
into the Okanogan Highlands. Neither of these disturbances will
bring much mixing, so the current Air Stagnation Advisory remains
valid and no changes will be made at this time. /SVH

Thursday night through Tuesday: The Inland NW transitions to a
more active pattern, with several opportunities for precipitation.
Look for a cool down into the weekend before temperatures rebound
early next week. Thursday night into Friday a warm front will be
draped across the northwest to northern CWA, while a weak mid-
level shortwave skims by late Thursday night into Friday. This
will bring a modest threat of precipitation to the Cascades
through northern panhandle, while a more transient threat comes to
southeastern WA and the central and lower panhandle with the
passing shortwave. Friday night into Saturday a cold front and
stronger shortwave pushes through the region. This will revitalize
the threat of precipitation across the region Friday night, before
the steadier precipitation shifts into the mountains and leaves
mainly hit-and-miss shower threat elsewhere Saturday. Snow levels
should be high enough to support mainly valley rain and high
mountain snow. However we will have to keep an eye out for
possible freezing rain in the overnight/morning hours especially
near the sheltered valleys near the lee of the Cascades. Winds are
expected to increase for Saturday with the passing cold front,
especially over the Upper Columbia Basin through the
Palouse/Spokane/C`dA area and Blues and over the mountains. Right
now speeds are projected to be in the 10 to 20 mph range, with
gusts to 30 mph. Precise numbers will continue to be fine-tuned.

Then from Saturday night into Sunday night the next warm front
starts to lifts in from the south with a subtropical moisture tap.
This will expand the threat of precipitation across the region
again, starting especially Sunday overnight. The threat will be
lowest in the lee of the Cascades and deeper Columbia Basin.
Cooler air may initially allow for a rain/snow mix, with snow
levels between 2.0-3.5kft Saturday night, before they rise again
Sunday. Monday into Tuesday a trough pivots into the eastern
Pacific and the flow over the Inland NW buckles and amplifies,
shifting the warm front north and the precipitation threat into
the mountains and northern counties. Models also suggest more
breezy conditions going into Monday, but depending on the
evolution of the warm front these speeds may be lower than
forecast. The precipitation through the weekend into early next
week, accompanied by some milder temperature, may lead to some
significant rises on areas waterways due to rain and snow melts.
The NWRFC indicates rises on most main-stem rivers. At this time
they are forecast to remain below any critical thresholds. However
we will have to monitor these and any smaller streams /creek for
rises and potential flooding concerns. I did raise highs slightly
on Tuesday from the previous forecast but if the warm front is
stronger and there is less cloud cover/precipitation those highs
may need to be bumped up more. /J. Cote`


00Z TAFS: Fog and stratus was observed for most of the mountain
valleys this morning and along the Spokane/Columbia
rivers...closer to water sources. The inversion will remain strong
again tonight and fog/stratus will likely form in those areas
again tonight. However the strong ridge of high pressure that has
been over the region will shift east and bend slightly overnight.
This will allow upper level clouds to move into the region
overnight as well...and this may mitigate somewhat the strong
radiational cooling. In addition the surface flow will gradually
come around to southerly through the evening and this should pile
up the moisture for the northern valleys. With the exception of
the eastern basin and the Palouse at least some fog and stratus
will be possible for the TAF sites. So KLWS/KPUW can expect VFR
conditons through 00z. At the other TAF sites current VFR
conditions will likely drop down to MVFR cigs/vsby between 12-18z
then bounce back to VFR with a thickening but high cloud deck.


Spokane        31  45  33  47  37  48 /   0   0  10  10  40  40
Coeur d`Alene  31  46  34  47  36  48 /   0   0  10  10  40  40
Pullman        38  51  40  53  40  53 /   0   0  10  10  20  20
Lewiston       38  54  42  57  42  58 /   0   0  10  10  20  10
Colville       28  40  32  41  33  43 /   0   0  10  20  60  50
Sandpoint      29  43  32  43  35  44 /   0   0  10  20  60  40
Kellogg        32  46  35  45  38  47 /   0   0  10  10  50  30
Moses Lake     29  47  34  48  38  49 /   0   0  10  10  20  40
Wenatchee      29  40  33  40  34  44 /   0  10  10  40  40  40
Omak           23  34  31  37  34  40 /   0  10  10  50  50  40


WA...Air Stagnation Advisory until 10 AM PST Saturday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.


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