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Area forecast discussion 
National Weather Service Spokane Washington
1224 am PST Sat Nov 29 2014

Update....allowed the Wind Advisory for most of the region to
expire at midnight. Continuing the Wind Advisory for the Okanogan
Valley and Waterville Plateau through Saturday evening.

&&

Synopsis...
a showery and breezy weather pattern will continue over far
eastern Washington and the Idaho Panhandle tonight, but snow
levels will remain above pass levels for motorists traveling. A
strong push of cold Arctic air will bring very windy conditions
to the Okanogan Valley tonight and Saturday. Cold conditions are
forecast for the upcoming work week, with some opportunities for
snow. The next big threat looks to come the southeast half of
Washington and Idaho later Monday into Tuesday.

A showery and breezy weather pattern will continue over far
eastern Washington and the Idaho Panhandle tonight, but snow
levels will remain above pass levels for motorists traveling. A
strong push of cold Arctic air will bring very windy conditions
to the Okanogan Valley tonight and Saturday. Cold conditions are
forecast for the upcoming work week, with some opportunities for
snow. The next big threat looks to come the southeast half of
Washington and Idaho later Monday into Tuesday.

Discussion...
evening update: the Arctic front is on the move. The main push of
colder air is making it into the Cascades and Okanogan, while it
remains mild over the southeast half of the forecast area. For
example at last report around 8 PM temperatures were in the mid-20s
near Oroville, Washington over the northern Okanogan Valley, with north
winds sustained between 20 and 30 mph; at the same time Lewiston,
Idaho was at 56 degrees, with winds around that area coming out of
the southwest at around 15 to 25 mph with gusts to 45 mph.

So those winds have been blowing down the Okanogan Valley at a
good clip already, so I went ahead and started the Wind Advisory
in that area about an hour ago (730 pm). That portion of the Wind
Advisory also includes the Waterville Plateau, but those winds
should materialize later (after about 09-12z).

The other Wind Advisory GOES through midnight (12 am) across the
upper Columbia Basin east into the Spokane area and Palouse and
l-c valley, as well as the Coeur D'Alene area (which I added at
730 PM to due to some rather strong winds reported at the surface
and indicated by radar aloft). Newest model runs support this
downward trend. These updates to the Wind Advisory are already on
the street. I did increase winds down the Purcell Trench tonight
into Saturday, as that increasing northerly gradient develops, but
these really don't appear should increase until after 09-12z).

The other issue out there is the precipitation. A modest shield
of rain continues to Rake the eastern third of Washington and north ID,
especially from the Palouse east into the portions of the central
Panhandle. All models support this precipitation gradually
decreasing from the northwest overnight. On the backside of this,
however, will be some some snow threat.

The rain changed to snow around the Okanogan Valley, per the ASOS
at omk, around 5pm and fell for a couple hours. It wasn't being
sampled well by radar and available web cams in the region did not
show much. Yet I have no reason to doubt the sensor. So this
highlights that some snow threat will be coming on the heels of
the cold front and with the cold core of the upper trough. The
snow chances will found near the Cascades through the Okanogan
the remainder of this evening and above about 5-6kft farther east
and south. However later overnight into Saturday snow levels drop
toward valley floors. Outside of the mountain the snow is not
expected to amount to much: a half inch or so over northeast Washington
and north Idaho and maybe an inch to an inch and a half toward the
Palouse. More snow is projected about the central Panhandle
mountains, where a Snow Advisory remains in place through the day
Saturday (4 am to 4 pm). The northwest flow and unstable upper
trough will help produce this threat here, while the unstable
upper trough will bring the light snow threat across the remainder
of eastern Washington and north Idaho.

The last thing to mention that some guidance suggests is a
possible Puget Sound convergence zone in the westerly flow. It is
mainly the NAM/sref which has this suggestion, which wants to show
some band of snow developing near the Chelan/Okanogan County
border overnight (after 09z) and expanding east across northern
Douglas and Lincoln County through Saturday. Typically a band of
precipitation associated with the pscz doesn't spread that far
east, so I suspect there may be some mix of the incoming upper
trough influencing that depiction. /J. Cote'

Aviation...
06z tafs: an Arctic front drops across the Washington and north Idaho
tonight, with the trailing upper trough coming through Saturday.
Look for areas of rain across the eastern taf sites to turn to
showers and dissipate overnight. The showers may mix with or turn
to snow before morning. The incoming upper trough will keep the
threat of flurries or snow showers alive across the eastern taf
sites through Saturday, before the threat wanes at night. The
western taf sites (eat/mwh) will see some the potential for a few
flurries or a brief snow shower and some increase cloud cover
during the day Saturday too, but the threat appear smaller in that
region. Winds will remain breezy to windy this evening. The
overall speeds are projected to decrease after midnight into
Saturday morning, but will still remain gusty through Saturday
before abating Saturday night.

Note: the visible sensor at eat is out of service so amendments to
visible are not scheduled. A replacement sensor is on order. Service
may return as early as Saturday, but may not be available until
the middle of next week. /J. Cote'



06z tafs: an Arctic front drops across the Washington and north Idaho
tonight, with the trailing upper trough coming through Saturday.
Look for areas of rain across the eastern taf sites to turn to
showers and dissipate overnight. The showers may mix with or turn
to snow before morning. The incoming upper trough will keep the
threat of flurries or snow showers alive across the eastern taf
sites through Saturday, before the threat wanes at night. The
western taf sites (eat/mwh) will see some the potential for a few
flurries or a brief snow shower and some increase cloud cover
during the day Saturday too, but the threat appear smaller in that
region. Winds will remain breezy to windy this evening. The
overall speeds are projected to decrease after midnight into
Saturday morning, but will still remain gusty through Saturday
before abating Saturday night.

Note: the visible sensor at eat is out of service so amendments to
visible are not scheduled. A replacement sensor is on order. Service
may return as early as Saturday, but may not be available until
the middle of next week. /J. Cote'

&&

Preliminary point temps/pops...
Spokane 12 22 12 27 18 30 / 30 0 0 20 30 0
Coeur D'Alene 11 24 12 28 18 31 / 60 0 0 20 40 0
Pullman 15 25 16 32 22 34 / 80 0 0 50 60 10
Lewiston 20 29 20 36 27 38 / 80 0 0 60 70 10
Colville 3 21 8 27 13 30 / 20 0 0 0 0 0
Sandpoint 5 21 8 26 14 29 / 70 0 0 10 20 0
Kellogg 4 22 11 28 17 31 / 100 0 0 40 50 10
Moses Lake 12 24 12 27 17 31 / 10 0 0 10 20 0
Wenatchee 14 23 12 26 18 30 / 20 0 0 10 10 0
Omak 2 18 7 24 13 27 / 20 0 0 0 0 0

&&

Otx watches/warnings/advisories...
Idaho...Winter Weather Advisory from 4 am early this morning to 4 PM PST
this afternoon for central Panhandle mountains.

Washington...Wind Advisory until 10 PM PST this evening for Okanogan Valley-
Waterville Plateau.

&&

$$

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