Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 210912
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
212 AM PDT Thu Sep 21 2017

.SYNOPSIS...
A band of light showers will move from the northern mountains
into Basin this morning, and then weaken to hit and miss showers
by afternoon with cool temperatures. Drier and warmer weather
starts Friday and persists into the weekend and possibly early
next week.

&&

.DISCUSSION...
Today through Friday: The stubborn upper level trough continues to
influence the weather over the Inland NW. Currently the main low
center is over the Canadian prairies with it`s trough axis
stretching back across wrn MT, se WA into central Oregon. Radar`s
picking up on a few upslope showers over the central Panhandle
under the light westerly flow, while the satellite fog product
shows a moist boundary layer and a low cloud deck from extreme
eastern WA into the Idaho Panhandle. Patchy fog with reduced
visibilities will be possible in sheltered spots in this areas.
Meanwhile an increasing northeast flow aloft is ushering moisture
and warming aloft. A weak disturbance on the leading edge of this
moisture band is responsible for light showers drifting from srn
BC across the Okanogan valley into the northeast WA mountains.
These showers will gradually increase and press southward this
morning, spreading from the mountains toward I-90 before weakening
and becoming more convective as low level instability increases.
The instability doesn`t look strong enough to support lightning
this afternoon, although isolated intense showers are still
possible along with snow down to near 5k ft. Winds will pick up
out of the north through the day with locally gusty winds
funneling down the Okanogan valley for the afternoon and evening.
Scattered showers are expected to dissipate this evening, while
the mid level moisture remains with the northern flow aloft. The
upper trough pinches off into a closed low over OR overnight and
slowly lifts across srn ID into sw MT. As it does moisture aloft
will thin over the region. Surface pressure gradients tighten
across the ID/MT border and north to northeast winds increase late
tonight into Friday morning with local gusts. This should help
keep the boundary drier late tonight, although sheltered valleys
across the central Panhandle may be subject to a lingering cloud
deck. Temperatures will cool into the 30s overnight and some
patchy frost is possible in cold spots. Anticipate a drier dry for
Friday with a few mountain showers near the Cascade crest and the
central Panhandle mountains, while temperatures slowly begin their
slow warm up. /rfox.

Friday night through Thursday...No major changes to the extended
forecast. The upper level low will slowly move east of the area
Friday night and Saturday. Meanwhile a flat ridge of high pressure
will nose into the region. This pattern will set up a mainly dry
northerly flow over the Inland Northwest. A few showers will be
possible in the up-sloping flow along the Idaho/Montana border
through Saturday afternoon, otherwise the forecast will remain
dry. Due to blocking across the eastern third of the country the
ridge axis will not move into central Washington until Tuesday
night or Wednesday. Model guidance indicates that a couple of weak
short wave disturbances will try to sneak over the ridge and
provide the forcing necessary for isolated showers over the higher
terrain. This will also be a period with the temperatures slowly
warming as the ridge axis slides east of the Cascades. It still
looks like temperatures in the 60s on Saturday will warm 2-3 each
day with high temperatures finally making it back to the lower to
mid 70s by Wednesday and Thursday, which is right at seasonal
highs for this time of the year. Tobin

&&

.AVIATION...
06Z TAFS: A cluster of showers will track in from north but should
weaken while reaching the terminals. Patchy fog and areas of MVFR
stratus will be possible which then becomes overrun by a band of
light rain sagging in from the north 10-17z. The band of moisture
looks to fall apart over the area btwn 17-19z then heating to
promote hit or miss showers through 02z. Drier north flow will
develop tomorrow night with clearing from north to south. /sb

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        53  39  60  41  62  42 /  50  10   0  10  10  10
Coeur d`Alene  52  36  59  37  62  38 /  50  10   0  10  10  10
Pullman        55  34  59  39  60  39 /  20  10  10  10  10  10
Lewiston       60  41  65  43  67  44 /  20  10  10  10  10  10
Colville       57  38  65  38  67  38 /  40  10  10  10  10  10
Sandpoint      51  34  59  34  60  35 /  50  20  10  10  10  10
Kellogg        49  32  54  33  57  35 /  50  30  10  10  10  10
Moses Lake     62  41  69  41  70  43 /  20  10   0  10   0  10
Wenatchee      61  45  68  46  70  48 /  40  10   0  10   0  10
Omak           61  44  68  41  71  42 /  30  10  10  10   0  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.

&&

$$


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