Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 231055

Area Forecast Discussion
National Weather Service Spokane WA
255 AM PST Mon Jan 23 2017

Snow showers will linger this morning over the extreme northeast
corner of Washington and the northern Idaho Panhandle as a weak
system begins to track out of the area. Another weak system will
likely lead to flurries late tonight and Tuesday. By midweek a
strong ridge will build over the Pacific Northwest. This will
bring dry and cooler weather with an abundance of low clouds and
fog in the valleys.


Today and tonight...Main feature of consequence this morning was
the deep upper level low off the Washington/Oregon coast, which
was slowly digging SSW. Meanwhile a weak disturbance pinwheeling
around the low was producing some light precipitation across
extreme NE Washington and the northern Idaho Panhandle. Over the
past couple hours this feature has sheared apart significantly as
it drifts farther away from the low, which has lightened with
winds resulting in weakening isentropic ascent through the area.
Although we currently have a winter weather advisory in effect for
the Okanogan Highlands until 4am, we can likely end it a little
early as the cooler top clouds are quickly leaving that area while
radar was showing very little in the way of precipitation
returns. The focus for the morning precipitation will continue to
focus over a small portion of NE Washington and far northern
Idaho. Precipitation amounts will be quite light.

While the threat of precipitation will be waning, we should see
a widespread deck of low clouds over most valley locations with
areas of fog as well. As of 2am, most of the cloud ceilings were
1000 feet or lower, however visibility conditions we all over the
board with dense fog at the Spokane Airport and 10 miles or
greater at Coeur d`Alene and Wenatchee. This will be the difficult
part of the forecast, determining where dense fog will occur. We
currently have a dense fog advisory out for the Columbia Basin,
and Waterville Plateau until 10 am , however the latest obs at
Moses Lake and Ephrata suggest visibilities are much better than
the required quarter mile. Nonetheless a few webcams across the
area, including Ritzville, Othello, and Waterville suggest there
is still some dense fog scattered about. We are quite confident
the low clouds will remain fairly persistent through the day, but
the boundary layer looks like it will get quite thick which
suggests more stratus than fog. Temperatures should show only a
small diurnal rise later today given the thick cloud cover.

For tonight, we expect the thick boundary moisture to persist,
however we will also see a weak upper level disturbance sweeping
in from the northwest. Many of the models are showing some very
light precipitation developing over the eastern quarter of
Washington and the Idaho Panhandle late this evening and
persisting into Tuesday. This should be a very light event as the
dendritic layer won`t be fully saturated, nor will there be much
ascent through this region. Model sounding data over this area
seems to paint a picture of a few flurries or light snow showers.

Tuesday through Friday...An upper ridge near 130W will result in
a cool northerly flow Tuesday and Wednesday. A weak wave dropping
down in this flow will pass through the Idaho Panhandle and
extreme eastern Washington Tuesday and Wednesday. The best chance
for minor snow accumulations will be in the Central Panhandle
Mountains and Camas Prairie. The ridge axis will then move
east...becoming firmly established over the region on Friday.
Until then the northerly flow combined with lots of stratus over
the region will result in chilly day time highs...mostly in the
mid 20s to lower 30s for the lower elevations Tuesday and
Wednesday. As the ridge moves overhead by Friday inversions will
begin to strengthen with a warming trend in the mountains...while
an abundance of stratus for most lower elevations keeps highs in
the upper 20s. Exception could be the palouse as southeast winds
may erode the stratus. JW

Saturday and Sunday: The ridge remains firmly in place to start
the weekend with the inversion strengthening as temperatures aloft
warm. This will keep the stratus around well into the weekend
before our first chance for appreciable mixing on Sunday. The GFS
is coming into agreement with the EC on bringing a shortwave
through on Sunday so have increased snow shower chances for the
mountains. If this materializes it will be a short lived respite
as a ridge again builds in on Monday. Temps won`t fluctuate much,
mainly in the low to mid 30s for highs. /bwilliams


06Z TAFS: A band of -RASN continues to lift north into NE WA and N
ID with KCOE the last to clear out of the pcpn. As the pcpn
ends...fog and stratus will fill in across most terminals with
low confidence on exact timing of when conditions will bounce
from LIFR to IFR/MVFR but general confidence is high for low
clouds and restrictions. I think we will see subtle improvement
Mon aftn with vis/cigs but to what degree...carries moderate
uncertainty and forecast is based on a very moist boundary layer
consisting of light winds. /sb


Spokane        34  24  28  19  29  19 /  10  10  20  10  10  10
Coeur d`Alene  35  24  28  20  29  20 /  20  20  40  20  20  20
Pullman        34  24  30  19  30  20 /   0  20  40  20  20  20
Lewiston       37  27  34  23  34  24 /   0  20  30  10  10  20
Colville       35  25  29  20  29  20 /  30  10  10  10  10  10
Sandpoint      35  25  30  21  29  21 /  50  10  30  20  20  20
Kellogg        33  23  29  19  28  19 /  10  20  40  30  30  30
Moses Lake     34  22  31  16  31  20 /   0   0  10  10  10  10
Wenatchee      32  24  31  17  30  21 /   0   0   0  10  10  10
Omak           33  22  30  15  30  18 /   0  10   0  10  10  10


WA...Winter Weather Advisory until 4 AM PST early this morning above
     2500 feet for Okanogan Highlands.

     Dense Fog Advisory until 11 AM PST this morning for Moses Lake
     Area-Upper Columbia Basin-Waterville Plateau.


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