Area Forecast Discussion


179 
FXUS66 KOTX 110528
AFDOTX
Area Forecast Discussion
National Weather Service Spokane WA
928 PM PST Sun Dec 10 2017
.SYNOPSIS...
Strong high pressure will persist through Thursday. The lowlands 
of eastern Washington and north Idaho will be covered by low 
clouds while the mountains remain mild and mostly clear. Chances 
for precipitation will increase Thursday night into Friday with 
unsettled weather expected through next weekend.
&&
.DISCUSSION...
Tonight through Wednesday...An upper ridge will remain in place
through Wednesday resulting in little change to the current
pattern. There will be one wave that tops the ridge and moves into
southern BC Monday night into Tuesday but given that this wave is
tracking to our north it should have little if any effect with 
our current inversion. The stratus layer will continue to lie in 
the 2500-4000 MSL elevation range giving most towns cloudy skies 
but good visibility with the stratus above the valley floors. 
Cloudy skies will limit diurnal temperature changes to 2-4F for 
most towns. The palouse, Lewiston area, and parts of the Idaho 
Panhandle continue to lie on the edge of the stratus with easterly
boundary layer flow. Continued a near persistent forecast here 
with stratus and patchy freezing fog more prevalent in the 
overnight and morning hours. JW
Wednesday night through Sunday: The upper-level ridge will continue 
to dominate our weather pattern Wednesday night and Thursday. Conditions
will remain dry and cool with widespread low clouds plugging the 
Columbia Basin and most mountain valleys. Thereafter, models 
continue to support the break down of the ridge and likelihood for
several rounds of precipitation.
The first shortwave arrives late Thursday night into the Cascades and 
spreads across Eastern WA and N ID Friday. This will be a light 
precipitation event with QPF amounts generally around 0.15" or 
lighter. Precipitation type will be quite challenging with the 
moisture falling through the inversion. Models are not capturing 
conditions under our current inversion so continued to trend 
colder than guidance within the boundary layer allowing 
precipitation type to fall as a combination of rain, freezing 
rain, sleet, and snow. Again, this will not be heavy but will have
the potential to create slick conditions. Winds look to pick up 
behind the cold front Friday afternoon/evening to help mix out 
the temperature inversions. 
A strong jet will setup across the Eastern Pacific and into the 
Northwestern US in the wake of Friday's system. This will usher 
the next rich slug of moisture and frontal system over the 
weekend. There is decent agreement that the environment will be 
cold enough to bring snow to the northern mountains and mix of 
rain and snow in the lowlands. A second system arrives early next 
week bringing another round of mountain snows and mix of rain/snow
in the lowlands. If the models continue with the current trends, 
this one will stand a better shot for lower elevation snow. /sb
&&
.AVIATION...
06Z TAFS: A layer of low stratus clouds over the lowlands and
valleys of Eastern Washington and North Idaho's aviation area will
result in MVFR to IFR conditions at times. Some areas of freezing
fog resulting in locally low IFR visibilities may occur at times
as well. The top of the Stratus deck is generally 1000 to 2000
feet AGL. /Pelatti
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane        27  31  27  31  27  31 /   0   0   0   0   0   0 
Coeur d'Alene  26  32  26  32  28  32 /   0   0   0   0   0   0 
Pullman        23  32  23  34  23  34 /   0   0   0   0   0   0 
Lewiston       25  35  25  35  25  35 /   0   0   0   0   0   0 
Colville       28  32  28  31  28  31 /   0   0   0   0   0   0 
Sandpoint      17  34  17  33  17  33 /   0   0   0   0   0   0 
Kellogg        19  29  19  31  19  31 /   0   0   0   0   0   0 
Moses Lake     30  32  30  33  30  33 /   0   0   0   0   0   0 
Wenatchee      29  32  29  32  29  32 /   0   0   0   0   0   0 
Omak           30  32  30  32  30  32 /   0   0   0   0   0   0 
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Air Stagnation Advisory until noon PST Thursday for Central 
     Panhandle Mountains-Coeur d'Alene Area-Idaho Palouse-Lewis 
     and Southern Nez Perce Counties-Lewiston Area-Northern 
     Panhandle. 
WA...Air Stagnation Advisory until noon PST Thursday for East Slopes 
     Northern Cascades-Lower Garfield and Asotin Counties-Moses 
     Lake Area-Northeast Blue Mountains-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Spokane Area-Upper 
     Columbia Basin-Washington Palouse-Waterville Plateau-
     Wenatchee Area. 
&&
$$