Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 112358
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
358 PM PST THU FEB 11 2016

.SYNOPSIS...
A warm front lifts into the Inland Northwest through tonight.
This will spread a chance of rain across much of the area. Snow
will generally fall only in the higher mountains. The exception
will be in the valleys near the north Cascades. A cold front
passes later Friday, with continued precipitation chances and
slightly lower snow levels. Unsettled weather will continue
through the weekend into early next week with valley rain, high
mountain snow and breezy winds expected. Temperatures will be
quite mild on Monday with many locations seeing highs in the mid
50s to low 60s.


&&

.DISCUSSION...
Tonight through Saturday: The Inland NW will be in a wetter
pattern as a frontal wave moves through the region. Tonight a warm
front draped across southern WA and the lower ID Panhandle lifts
toward the northern mountains. Deepening and moistening isentropic
ascent will lead to broad precipitation threat across the Inland
NW this evening. However the highest risk will be along and north
of I-90 and lowest toward the Palouse into the L-C Valley.
Precipitation will largely fall as rain in the valleys, leaving
snow for the higher mountains. The main exception remains near the
Methow Valley where the warm air is not too deep and precipitation
may fall as a rain/snow mix or all snow. This may result in an
inch or so of snow through the night. Otherwise models don`t show
the precipitation to be too significant in terms of amounts, with
most areas seeing somewhere around a tenth of an inch through
Friday morning. Also, while PoPs will be relatively high, the
precipitation may be periodic, meaning it doesn`t look organized
enough to say the entire period will see steady rain. Between the
precipitation there will be the potential for fog. Yet confidence
in coverage and intensity in low, so it left as patchy.

Going into Friday the warm front lingers near the northern-tier,
while a cold front comes toward the Cascades in the afternoon. In
the morning some models show drier air across south-central and
southeastern WA and the lower Panhandle. Others are not as ready
to bring drier air in. A threat of precipitation will continue
across region, however the highest risk across the Cascades and
northern mountain zones. Between Friday afternoon and evening the
cold front crosses the Cascades and advances toward the ID/WA
border. This will revitalize the threat of precipitation The
Cascades will seeing the highest risk in the afternoon, while
chances wane there through the evening. Chances will increase
farther east through the afternoon and peak in the evening.
Between late evening and overnight the broader threat retreats to
the mountains, while the lowlands dry out. The incoming cold front
will also lead to some breezy conditions by Friday afternoon,
generally highest over south-central to southeastern WA into the
Idaho Palouse. Speeds on the order of 5 to 15 mph with gusts to 25
mph will be possible.

On Saturday an upper trough continues to migrate through the
eastern third of WA and north ID early, while the next warm front
starts to impinge on the Cascades in the afternoon. This set-up
will keep the the threat of showers alive across the region. With
the highest risk in the Cascades and the northeast WA and ID
Panhandle mountains, as well the rising terrain over the eastern
Columbia Basin. The lowest risk will be in the lee of the Cascades
and deeper Columbia Basin. Winds will be a bit stronger Saturday
afternoon, especially south-central and southeast and eastern-
central Washington into the Idaho Palouse. Speeds of 10 to 20 mph,
with gusts to 30 mph will be possible. This should allow for most
areas to come out of the Air Stagnation Advisory. The main
exception will be near the Cascade valleys/Okanogan Valley where
winds and mixing will be less. /J. Cote`

Saturday night through Thursday...The models are in relatively
good agreement through about 12z Wednesday before breaking down
Wednesday and Thursday. Zonal flow or weak ridging will be over
the region through the forecast period. The westerly flow will tap
into deep Pacific moisture with several weak waves that are
expected to move through the main flow. This will result in a warm
and fairly wet forecast through the extended period. Snow levels
Saturday night will be around 3k feet for the north and 4k feet
across the south, but rapidly increase by Sunday afternoon to 5-6k
feet and to 6-7k feet by Monday. So the higher elevations of the
Cascades and the northern and Panhandle mountains could see 3-6
inches of wet snow Saturday night, otherwise precipitation will be
as rain with high elevations snow the remainder of the week.
Precipitation amounts from Saturday night through Tuesday could
reach 0.25-0.50 for the lower elevations and 0.50-1.00 or a littlemore
for the mountains. Near the Cascade crest 1.0 to 1.5 inches will
be possible. Temperatures on Sunday will be in the 40s and 50s,
which will be about 5 degrees above normal. Then the temperatures
will increase Monday and Tuesday by another 5-10 degrees. The warm
temperatures and rain will almost certainly result in good snow
melt and rises on area rivers.

We will have to pay special attention to Monday. Temperatures are
expected to 10-15 degrees above normal and dew points will be
well into the 40s and 50s. A surface low will develop east of the
Continental Divide and with weak surface high pressure along the
coast the surface gradient will increase. In addition 850mb winds
will increase to around 35-40kts. This will result in southwest
winds 20-30 mph with gust 30-40 mph across the mountain tops, the
Columbia basin and the Palouse area. Gusty winds, warm
temperatures and high dew points will result in rapid snow melt.
The focus will be across the Waterville Plateau, some of he
mountain valleys, and across the Idaho Palouse where the low
elevation snow will likely melt at a rapid rate. Model hydrographs
show rapid rises on almost all rivers and streams, but areas of
concern will be the Palouse basin, and the Coeur D`Alene basin
where the rivers may bump up against action stage. Up on the
Waterville Plateau there is plenty of snow to melt and run off.
Palisades creek will see some significant rises. In addition snow
melt will likely cause nuisance flooding along secondary roads and
especially in area where culverts cross the road. We will issue a
hydrologic outlook to keep up with situational awareness through
the weekend.

Wednesday and Thursday...The models break down as far as
consistency goes. Some models try to bring an upper level trough
through the region late Wednesday and Thursday, while others want
to under-cut the ridge with the low going into California ans
still others have something some where in between. I chose to keep
a low end chance of rain or showers in the forecast for now with
temperatures cooling off but remaining above normal. Tobin

&&

.AVIATION...

00Z TAFS: A warm front will move north through the forecast area
tonight...deepening the moisture over the region and increasing
the chance for light rain at the TAF sites. Light rain currently
falling across the western zones will slowly track east across the
region through the evening. Conditions will be mainly VFR ahead of
and with the precipitation. Behind the rain stratus and fog
development lower cigs/vsby to MVFR and possible IFR early Friday
morning. Conditions improving back to VFR for most areas after
18z Friday. Tobin


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        38  47  34  45  35  46 /  60  50  60  40  60  40
Coeur d`Alene  37  47  36  45  34  45 /  60  60  70  60  70  60
Pullman        41  53  38  47  37  49 /  30  50  70  40  90  60
Lewiston       43  57  41  54  42  55 /  20  30  50  30  80  50
Colville       34  40  33  43  33  41 /  80  80  50  50  60  30
Sandpoint      34  40  34  41  33  40 /  80  80  90  60  70  60
Kellogg        36  42  35  39  33  40 /  70  60  90  80  90  80
Moses Lake     38  49  34  51  37  52 /  50  50  20  10  40  20
Wenatchee      34  44  33  46  33  46 /  80  40  20  10  50  30
Omak           35  42  30  41  30  39 /  80  60  20  20  40  20

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until 10 AM PST Saturday for Moses Lake
     Area-Northeast Mountains-Okanogan Highlands-Upper Columbia
     Basin-Waterville Plateau-Wenatchee Area.

     Air Stagnation Advisory until 10 AM PST Tuesday for East Slopes
     Northern Cascades-Okanogan Valley.

&&

$$


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