Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 280551

Area Forecast Discussion
National Weather Service Spokane WA
1051 PM PDT Thu Oct 27 2016

A moist frontal system will exit Eastern Washington and north
Idaho tonight. There should be a break in the wet weather on
Friday and Friday night, but more wet weather will move into
the region over the weekend and persist into next week.
Temperatures will remain relatively mild for this time of year
with no widespread freezing conditions expected.


Tonight and Friday...A moist frontal system will track from Eastern
Washington late this afternoon into the north Idaho Panhandle by
early this evening before exiting the area into western Montana.
Steady rain will continue with this feature...before decreasing to
scattered showers mainly over the mountains as a secondary wave
tracks across the region overnight. Most of the energy from this
wave will track over North Central Washington where the threat of
showers will linger into Friday morning. Then drier air aloft
overtakes the entire region by Friday afternoon.

Behind this band of rain tonight a saturated boundary layer will
remain over much of the area leading to an abundance of stratus.
Current indication from models is that the stratus will be deep
over NE Washington into the Idaho Panhandle which should keep fog
patchy in nature. Better chance of breaks in the clouds will be
over the Columbia Basin where areas of fog...possibly dense...may
develop. Models show this stratus will continue Friday morning
before retreating to the northern mountains and along the East
Slopes while areas further south...especially south of I-90 should
see some clearing skies. JW

Friday night through Sunday night...The dry weather that will
begin on Friday is expected to continue through most of Friday night
as the shortwave ridge continues to reside over the area. The
stratus which is forecast Friday will slowly ease through the
evening and this could lead to a clear beginning to the evening
and the possibility of it reforming rapidly overnight. However
that is far from a given as the next system is expected to wrap
around the perpetual offshore trough. At a minimum it will result
in increasing high clouds from the southwest overnight, and if it
comes early enough it will stop the stratus and fog from
reforming. Looks like the best odds of reformation will occur over
NE Washington and the northern Idaho Panhandle however the low-
level winds will be turning to the east-northeast as high pressure
settles east of the Continental Divide. This is not a conducive
wind pattern for fog/stratus especially if speeds near 10 mph but
for now the forecast is for slightly weaker values than that.

The dry respite will come to an end on Saturday as a warm front
moves in from the south as it pivots around the offshore low. The
feature will move progressively north to south across the region,
however a portion of the associated moisture could get stuck over
SE Washington and NC Idaho as the next one comes rapidly on its
heels. Precipitation amounts will generally range from 0.10-0.20
inches with quite a bit less over the Basin and perhaps a bit more
over the SE portion of the forecast area.

The Sunday system will be the wettest portion of this forecast as
the strongest 500 mb shortwave moves in from the south. Expect the
precipitation to pick up over the WA/OR border region late in the
day and then intensify overnight as the shortwave moves NE toward
the Clearwaters. There will be a big difference in potential
precipitation amounts with the NW portions of the area receiving
less than a tenth of an inch. Meanwhile rainfall amounts between
0.5-1.00 inches are possible over the Blues, Clearwaters, and
across southern Shoshone County. Most of the precipitation in that
area will consist of rain as snow levels in that area will remain
around 7000 feet. Temperatures through this period will remain
milder than normal with highs generally in the 50s and lows in the
upper 30s and 40s. fx

Monday through Thursday...The synoptic pattern Monday afternoon
continues to be troffy (non technical term). A longwave trof is
anchored over northern Alberta/Saskatchewan. A trio of shortwaves
are rotating around the periphery including one over the northern
plains, one nearing the north California coast, and then a more
significant cut-off low near western Alaska. The California trof
is the one that will impact our weather initially. The trof axis
basically extends from northern Saskatchewan through eastern
Washington and northern California. Unsettled weather will
continue Monday afternoon thanks to this trof but will be mainly
confined to the mountains of north Washington north Idaho. At this
point, we`ve downplayed the potential for rain/showers over the
Columbia Basin with Spokane down to Pullman being right on the
cusp of the wetter weather.

The goblins and ghouls interested in the weather Monday evening
will have to stay tuned with widespread rain likely in the
mountains of Washington and most of northern Idaho; a chance of
rain elsewhere.

Beyond Monday, the trof axis shifts to the east. A large area of
low pressure strengthening south of Alaska will amplify high
pressure along the Great Divide and the Inland Northwest. This
high pressure will bring the region a brief respite from the
active/wet weather pattern mid week. The models differ greatly in
how fast this ridge breaks down and the next wave of moisture
pushed inland from the eastern Pacific. Because of the
uncertainty, have blanketed most areas with a chance of rain by
Wednesday night and Thursday of the upcoming week. /AB


06Z TAFS: The band of rain showers continues its slow eastward
track, and should be mostly in north ID by midnight. A mix of
MVFR to VFR conditions with local IFR will continue for all TAF
sites. LIFR/IFR stratus cigs and possibly fog is expected to
develop overnight tonight and continue through 18z Friday.
Cigs will likely dissipate in the morning with thinner high
clouds moving in during the afternoon.


Spokane        43  52  40  51  41  52 /  80  10   0  30  40  20
Coeur d`Alene  43  53  40  52  41  51 /  90   0   0  40  50  30
Pullman        40  57  44  54  43  54 /  70   0   0  40  70  30
Lewiston       45  58  45  59  46  58 /  50   0   0  40  60  40
Colville       42  50  38  51  40  52 /  70  10   0  40  50  30
Sandpoint      42  50  36  50  39  49 / 100  10   0  40  50  30
Kellogg        41  50  39  51  40  49 / 100  10  10  50  80  50
Moses Lake     41  56  40  55  40  55 /  20   0   0  30  20  10
Wenatchee      42  53  43  54  40  52 /  30  10  10  40  20  10
Omak           41  52  41  53  39  53 /  30  10   0  30  40  10



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