Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 312347
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
346 PM PST SAT JAN 31 2015

.SYNOPSIS...
A frontal system will bring light snow to much of the region on
Sunday. Another front is expected on Monday, and it should bring
rain and mountain snow. More warm and wet weather disturbances are
expected next Thursday through Saturday to end the nest work
week.

&&

.DISCUSSION...
Tonight through Sunday night...

...Light to moderate snow accumulations for Northeast Washington
and North Idaho on Sunday...

A large low parked in the Gulf of Alaska will send a moist frontal
system across the Inland Northwest on Sunday. Precip looks to
begin in Central and Eastern Washington early to mid
morning...reaching the Idaho Panhandle late morning. This system
has a subtropical moisture tap...which combined with increased
isentropic lift will result in widespread rain and snow...except
for possibly Wenatchee and Moses Lake where the lift will not be
as strong with westerly flow resulting in downslope off the
Cascades. With widespread stratus over most valleys holding temps
in the lower to mid 30s this afternoon...this will help keep snow
levels low initially. Then in the afternoon with no strong
surface development with this system...winds look to remain light
with little to no rise in snow levels as steady precipitation
helps keep the column cool. Wet bulb zero heights would suggest
the snow from the Waterville Plateau to Spokane to Kellogg north
to the Canadian border as well as the higher portions of the
palouse...with rain/mountain snow south of these areas. Low level
upslope flow into the higher terrain of NE Washington and North
Idaho will result in the highest accumulations around Deer Park,
Elk, Sandpoint, Coeur D`Alene and the Central Panhandle Mountains
with valleys receiving 1 to 3 inches with as much as 4 to 8 inches
in the mountains. However with afternoon temperatures in the lower
30s roads will probably become slushy...but may become slick again
Sunday evening after sunset. While amounts are marginal for an
advisory...we will issue one to heighten the winter weather
potential for those traveling for the "Big Game." JW

...More warm and wet weather is expected through the work week...

Monday through Tuesday...The models are in pretty good agreement
that weak ridging will be over the region. The resultant
southwest flow will allow another frontal passage to move through
the forecast area Monday morning with the following weak warm cold
front following Monday afternoon/evening. This will be a near
repeat of the Sunday/Sunday night event. Forcing will not be
overly impressive, but moisture will with PWAT`s over 200% of
normal. The big difference will be that the warm advection is
slightly stronger and snow levels are expected to rise. Snow
levels Monday morning will be around 4k feet across the southern
zones and 2-2.5k feet across the north, but should rise through
the day to near 5k feet south and near 3k feet across the north.
As such we expect mainly rain across the southern zones. North of
the Columbia/Spokane rivers the valleys may begin as a rain snow
mix but should turn over to rain through the morning. Snow will
prevail for the mountains above 3-3.5k feet. 24 hour snow amounts
for the northeast and Panhandle mountains will be 3-6 inches and
locally higher. For the Cascades 4-8 inches will be possible with
more possible near the crest. Drying from the west is expected
behind the cold front Monday evening for break in the weather
action. The exception will be for the Crest of the Cascades and
the Panhandle mountains where up-slope flow will keep higher pops
in the forecast.

Wednesday through Saturday...The models begin to diverge at this
point. All the medium range models show high pressure building
along the coast Wednesday and moving inland Thursday and Friday.
This keeps a warm and very moist southwesterly flow pointed at the
Pac NW. Differences show up in timing of any individual wave
moving through the flow Wednesday and Thursday and generally broad
brushed chance for precipitation through this period. Guidance is
in better agreement showing a better of precipitation Thursday
night through Saturday. Precipitation amounts to end the week
could be quite impressive. Moderate warm air advection will not
only result in warming temperatures but also big rises in snow
levels. By Friday snow levels will be 5-6k feet with snow only at
the highest elevations and rain for all of the valleys. One thing
we will have to keep an eye is the potential for freezing rain
Thursday night and early Friday as the precipitation type
transitions form frozen to liquid. At this time the greatest
potential will be for the Valleys of the east slopes of the
Cascades and to a lesser degree portions of the Okanogan valley
and the Okanogan highlands. We will have a better idea as we get
closer to the event so stay tuned.

Temperatures in the mid 30s to mid 40s on Thursday are expected
to warm into the mid 40s to mid 50s. Tobin


&&

.AVIATION...
00Z TAFS: High pressure will build back into the region this
afternoon and with light and variable winds the stratus deck that
has been around most of the day will persist through 00z.
Ceilings at most TAF sites are expected to be ovc015-020. The next
in a series of weather systems will move in from the west over
night. -SN should to develop over the Cascades by early morning
with -SN developing at the TAF sites between 15-18z with IFR and
potentially LIFR cigs. KLWS will likely stay as -RA. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        30  32  31  38  32  39 /  10 100  60  70  50  20
Coeur d`Alene  30  32  31  39  34  40 /  10 100  90  80  60  30
Pullman        30  36  34  44  37  45 /  10  90  70  70  60  30
Lewiston       34  41  37  49  39  49 /  10  60  50  50  50  20
Colville       31  34  31  35  31  36 /  10 100  50  60  40  20
Sandpoint      32  33  30  36  32  37 /  10  90  90  70  60  30
Kellogg        30  34  32  39  34  39 /  10 100 100  90  90  60
Moses Lake     34  38  31  41  33  44 /  10  40  10  50  10  10
Wenatchee      33  38  33  40  33  42 /  30  40  10  60  20  20
Omak           32  34  30  37  31  36 /  50  60  10  60  20  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory from 10 AM Sunday to Midnight PST Sunday
     Night for Central Panhandle Mountains-Coeur d`Alene Area-
     Northern Panhandle.

WA...Winter Weather Advisory from 7 AM to 7 PM PST Sunday for
     Northeast Mountains-Okanogan Highlands-Spokane Area.

&&

$$



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