Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 012345
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
345 PM PST SUN FEB 1 2015

.SYNOPSIS...
A frontal system bringing rain and snow to the region will exit the
region tonight. Another front is expected on Monday, and it should
bring mainly rain in the valleys with snow in the mountains. A
much milder and wetter pattern is expected for the middle to end
of the week.

&&

.DISCUSSION...
Tonight through Monday...Satellite imagery shows a moist frontal
system moving into the Inland Northwest. Radar composites indicate
widespread light precipitation over the area except in the lee of
the Cascades where downslope flow has resulted in very little
precipitation in Wenatchee. As of 2 pm...the back edge of the
front was crossing the Cascades with the back edge expected to
reach the Washington/Idaho border between 5-7 pm...and the Lookout
Pass area between 7pm-10pm. Although post frontal upslope flow
into the Central Panhandle Mountains will allow snow showers to
continue into the overnight hours. Snow levels are currently
ranging from about 1000-1500 feet near the Canadian border to
1500-2500 feet over southeast Washington. Weak low level winds
should result in these values not changing much through this
evening...although weak warm advection over southeast Washington
and the Lewiston area is expected to raise snow levels to
3000-4000 feet. Thus the snow that is falling will persist until
the back edge of the front tracks through, except in the foothills
of the Blue Mountains, La Crosse, and Pullman areas where snow is
expected to change to rain. Road temperatures this afternoon in
the valleys have warmed into the 32-38F range per WADOT sensors
with the coldest readings near the Canadian border. This has
limited snow accumulation on roadways with area web cams showing
mostly wet...or slushy roads. As snow increases with the front and
the sun angle gets lower through the afternoon snow may begin to
stick more efficiently to the roads. Thus will let current winter
weather advisories remain in place.

On Monday a fast moving short wave associated with the large low
in the Gulf of Alaska will cross the Cascades in the late
morning/early afternoon bringing a round of rain and snow. Snow
levels rise to 3500-5000 feet from Spokane southward but only rise
to 1500-2000 feet near the Canadian border. Models show the best
potential for light accumulations on Monday to be in the northern
mountains and Methow Valley.  JW

Monday Night through Thursday...Weak ridging over the region will
try to strengthen Monday night and Tuesday, but will get
flattened somewhat by a Clipper moving south through Saskatchewan
and Alberta Canada. By Wednesday the ridge will once again begin
to build with the ridge on or just east of the Cascades Wednesday
night and Thursday. Several weak frontal waves will move through
the ridge with the strongest and wettest progged for Thursday.
Temperatures will remain in the mid 30s to mid 40s which is on the
warm side of normal for this time of the year.

Monday night through mid-day Tuesday...A cold front will track
east across the forecast area Monday evening and be east of the
area before sunrise Tuesday. This will allow drier air to move
into the region. In addition down sloping off the Cascades will
result in a drying trend for the lower east slopes and into the
Columbia basin...reaching as far as the West Plains and Spokane by
Tuesday night. Westerly flow will keep up-sloping precipitation
for the Panhandle mountains. Precipitation will be light with
valley rain and maybe another inch or two of snow for the
Panhandle mountains.

By late in the day Tuesday another fast moving wave will track
mainly through Oregon, and just brush the southern end of the
Basin, Palouse, Blue mountains and the Camas Prairie. The models
are showing substantial timing and placement differences with the
warm front. It looks like the brunt of the energy and moisture
stays south and confidence in measurable precipitation is rather
low. That said low end chance pops were kept in the forecast
across the southern zones through Wednesday. Any precipitation
would be very light and as low elevation rain, with snow above
about 3000 feet.

Wednesday night and Thursday...The next weak wave will move across
the northern zones Wednesday evening, with a slightly stronger
frontal system following during the day Thursday. The second wave
will tap into deeper moisture and result in just about all
locations receiving measurable precipitation. Moderate warm air
advection will push snow levels up from around 3000 feet to over
5000 feet across the south. But across the northern mountains snow
levels will rise from near valley floors to only about 3000-3500
feet. So mainly rain across the south. A mix of rain/snow turning
to all rain from about I-90 north and mainly snow for the
mountains. Snow amounts will be light 1-3 inches and possibly a
little more for the Cascade crest. Tobin

Thursday night through Sunday...A rather wet forecast will affect
the Inland Northwest for the end of the work week and through the
weekend. Unfortunately for snow lovers, the white stuff will be
relegated to the high peaks. The first system will feature a tap
into deep subtropical moisture with Pwats close to an inch pushing
into the region. This will mean a good soaking for the Inland
Northwest as a warm front moves over the region Thursday night,
bringing warm moist air northward, and hanging out through late
Friday. Temperatures will not be all that cold to begin with so
most valleys will see persistent rain. The exception will be the
Cascade valleys north of Lake Chelan and perhaps the northernmost
locations along the B C border. There may be enough cold air in
those valleys for a brief period of freezing rain Thursday night
or Friday morning before the air column warms down to the surface.
The southern valleys will remain warm even overnight Friday as a
mid level jet mixes down some gusty winds. It looks like there may
be a short break in the action Saturday but more rain should be
coming our way for Sunday. Models diverge on the timing and
strength of the next Pacific trough. For now it appears to be
almost as warm but does not have quite the juicy fetch as the
precious system. All this rain will increase the flow in most area
rivers by the weekend so we will be keeping an eye on model QPF
and river forecasts. /Kelch

&&

.AVIATION...
00Z TAFS: One weather system will move through the eastern zones
this afternoon and exit to the east this evening...another will
move into the region Monday after 19-20z and slowly move east
through the afternoon. Through 01-02z around an inch of light
snow will be possible for KGEG/KSFF/KPUW and possibly as much as
1-2 inches at KCOE. The deck will rise into MVFR/IFR as
precipitation moves through the region then cigs will drop as
stratus builds back into place with conditions dropping back to
IFR/LIFR after 02-03z for the KGEG-KCOE corridor. Otherwise
expect VFR/MVFR cigs/vsby at the remaining sites. Some question
for the KMWH whether they see stratus formation and chose to drop
cigs there as well. The next system will begin to effect the
western zones after 19-20z for increased chances for -RA and
VFR/MVFR cigs/vsby.


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        30  37  32  40  30  38 /  60  70  50  30  20  20
Coeur d`Alene  30  37  33  39  30  38 /  90  70  80  30  30  30
Pullman        32  44  37  43  35  43 /  70  70  50  30  30  30
Lewiston       36  47  38  46  37  46 /  80  60  50  30  30  30
Colville       31  36  30  37  27  36 /  50  60  50  20  20  20
Sandpoint      30  35  31  36  28  36 /  90  60  90  30  20  20
Kellogg        32  37  33  38  30  38 / 100  60  90  40  30  40
Moses Lake     28  38  32  43  32  42 /  10  60  20  30  30  20
Wenatchee      31  38  32  42  33  41 /  10  60  20  30  30  20
Omak           30  35  30  36  29  37 /  10  60  30  20  20  20

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory until Midnight PST tonight for Central
     Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-
     Northern Panhandle.

WA...Winter Weather Advisory until 7 PM PST this evening for
     Northeast Mountains-Okanogan Highlands-Spokane Area.

&&

$$



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