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Area forecast discussion 
National Weather Service Spokane Washington
405 am PST sun Dec 21 2014

Synopsis...
the active weather from the past few days will begin to wind down
today and Monday. Expect warm temperatures and very gusty winds
this afternoon. A storm system will move down from the north and impact
the region around Christmas eve. This will bring the potential
for moderate to heavy snow in the mountains and light
accumulations to the valleys. Temperatures are expected to remain
above average through early next week...before dropping down
toward normal values by Christmas day. Another winter storm may
affect the region for next weekend.



&&

Discussion...
today through Monday...a fast wave moving quickly through the
northern edge of the upper level jet will cut-off the deep
moisture tap early this morning. A cold front behind the exiting
wave will sag south pushing the moisture further south into
northern Oregon and reduce the chances for precipitation today.
Well mostly reduce the chances anyway. Strong westerly flow will
allow precipitation to slop over the Cascades crest and possibly
as far east as the Waterville Plateau for a while this morning.
And of course up-sloping flow into the Panhandle and south into
the Camas Prairie will keep pretty high pops in those location
through the evening. The remainder of the forecast area should
see drying conditions. Snow levels are up between 5000-6000 feet
for the Cascade and 4500-5000 feet for the Panhandle so
precipitation as mainly rain or wet snow. Lookout Pass on I-90
could pick up 2-3 inches of wet snow through the early morning
hours.

The other weather issue we need to address will be winds this
morning. The jet is over head and the models are showing 850 mb
winds still around 45-50 kts...with a tightening surface gradient.
However that gradient is only around 8 mb kpdx-kgpi and it usually
takes more than that. The question comes down to will there be
enough mixing with the front to get these winds to surface.
Already there have been some gusts in the mountains 45 mph and
higher so it looks there is good potential. The best chance looks
to be lower Garfield County and spilling into the Palouse and the
Lower Basin. A Wind Advisory has been issued for these areas for
winds 25-35 mph with gusts 45 mph and possibly higher. All
locations should be prepared for breezy/gusty conditions through
sunset. Very warm temperatures are also expected with highs in
the mid 40s to mid 50s.

High pressure will build off the coast tonight and then swing into
the region on Monday for further drying. Northwest flow into the
the central Panhandle and south into the Camas Prairie will
support rain and snow showers. The higher terrain of southern
Shoshone County could pick up a few inches of new snow Sunday
night and early Monday. With high pressure and a saturated
boundary layer areas of of and stratus will also be likely
tonight. Temperatures will begin to cool off on Monday by 5-10
degrees over Sunday, but still well above seasonal normals. Tobin

Monday night through Christmas eve...a ridge of high pressure
will build into the region Monday night before the next Pacific
trough takes aim on the inland northwest. Dry conditions will
prevail overnight with fog and low stratus the main weather
challenge. A warm front will bring some light precipitation to the
region Tuesday but there remains quite a bit of model spread as to
how far south the moisture will spread. The latest GFS keeps it
across our northern zones while the European model (ecmwf) brings it farther south.
The northern valleys may see some very light accumulations Tuesday
before warmer air moves in to change it over to rain.

The main weather event will be on Wednesday (christmas eve) as an
upper trough swings through the region. Models have come into much
better agreement on the timing and track of this feature so pops
have been raised across the southeast zones where trough cusp
dynamics and upslope flow will combine for the best forcing. As
mid level flow turns northwesterly Wednesday, snow levels will
fall to most valley floors late in the day and even to the Lewis-
Clark Valley by Wednesday night. Many of you asked for it, and now
it looks more likely that there will be at least a little bit of
snow for Christmas day for many locations across the inland
northwest. No promises. The southeast zones will likely see light
snow accumulations and possibly advisory amounts for the Camas
Prairie and Idaho Palouse. Traveling the passes will be
troublesome.

Christmas day through Saturday...the upper trough axis will move
east of the forecast area ans large scale northwest flow will
commence. Passing shortwave energy will maintain the threat of
snow showers into the weekend. The best chance for accumulating
snow for Friday will be in the Idaho Panhandle. Another Pacific
trough will be waiting in the wings with the potential to affect
the region by next weekend. Only minor changes made to the
extended forecast. /Kelch



&&

Aviation...
12z tafs: a cold front is sagging south into the region this
morning and is resulting in drier conditions...but also windy and
gusty southwest winds. Southwest winds 20-25 kts with gusts 25-35
kts will be possible at all taf sites except keat until sunset.
Rain and snow showers will continue to slop over the Cascades
through the morning...and also for the Panhandle mountains...the
Blue Mountains and the Camas Prairie. Otherwise mainly dry
conditions at the taf sites. The Puget Sound convergence zone is
in place and radar indicates a fire hose of moisture pointed right
at keat. This will likely result in rain/snow showers through the
morning hours and deteriorating conditions. For the remainder of
the taf sites lingering stratus will keep conditions MVFR and
locally IFR through 15-17z then conditions improve after 18z.
Tobin



&&

Preliminary point temps/pops...
Spokane 47 31 39 30 40 34 / 20 10 10 10 30 40
Coeur D'Alene 46 31 39 28 39 34 / 40 20 20 10 30 60
Pullman 50 36 43 31 43 34 / 80 50 30 10 20 40
Lewiston 52 38 47 32 46 36 / 60 50 20 10 20 40
Colville 42 28 38 27 36 32 / 20 10 10 10 40 50
Sandpoint 41 30 37 26 36 33 / 60 20 10 10 40 60
Kellogg 42 31 37 27 36 33 / 90 90 40 10 50 60
Moses Lake 51 33 43 31 42 34 / 10 10 10 0 20 20
Wenatchee 47 34 42 32 39 33 / 20 20 10 10 30 20
Omak 41 28 36 28 35 31 / 10 10 10 0 40 40

&&

Otx watches/warnings/advisories...
Idaho...Wind Advisory until 4 PM PST this afternoon for Idaho Palouse-
Lewis and southern Nez Perce counties-Lewiston area.

Washington...Wind Advisory until 4 PM PST this afternoon for lower Garfield
and Asotin counties-northeast Blue Mountains-Spokane area-
upper Columbia Basin-Washington Palouse.

Wind Advisory until 10 am PST this morning for Moses Lake area-
Waterville Plateau.

&&

$$

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