Weather Service Report


893 
FXUS66 KOTX 252106
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
206 PM PDT Tue Apr 25 2017

.SYNOPSIS...
Expect cool, breezy, and showery weather this week. The most 
widespread precipitation will occur tonight into Wednesday with 
the potential for a half inch or more of rain over portions of the
Idaho Panhandle and southeast Washington. Mountain passes could 
see a few inches of snow overnight into the morning hours. A ridge
of high pressure moves in Saturday delivering a brief dry period 
before more unsettled weather moves in Sunday and into early next
week.

&&

.DISCUSSION...
Tonight and tomorrow...Expectation is any lingering thunderstorms
still occurring in the area should diminish rather quickly this 
evening. Still showers may linger in the area slightly longer. A 
front, with a well maintained tap of moisture feeding into it, 
passes southwest to northeast through the forecast late tonight 
and keeps wet weather continuing on through tomorrow. The surface 
pressure pattern tightens up a bit with the passage of the front 
and allows for an increase in winds tomorrow. Expectation is that 
mixing and warm air advection brought about by tonight's frontal 
passage will keep overnight low temperatures on the warm side of 
climo while the lingering wet conditions will keep daytime highs 
on the cool side of normal tomorrow. /Pelatti 

Wednesday night through Friday: The Inland NW will be positioned on 
the cool, unstable side of the Polar jet which takes on a 
northwest to southeast trajectory across the northern Pacific, 
Central Oregon before nosing into northeastern Nevada. Several 
shortwaves are progged to track through the region under this 
northwesterly steering flow delivering clusters of showers each 
day and night. In between these features, persist west to 
southwest flow will fuel mountain showers along the Cascade Crest,
Idaho Panhandle, and rising terrain of NE WA. Isolated cells 
could also bubble up across the Basin with the aid of afternoon 
heating however downsloping winds off the Cascades will keep the 
greatest risk focusing to the east. Areas with the most persistent
shower activity such as the Idaho Panhandle could receive in 
excess of half an inch by Thursday evening. An additional quarter 
of a inch will be possible with shower activity between Thursday 
night and Friday. Snow will fall above 5000 feet Wednesday night 
then expect these levels to lower closer to 3000 feet on Thursday 
and perhaps to 2500 feet in spots Friday morning. After analyzing 
wetbulb zero heights and QPF via the NAM/GFS, the best chance for 
the combination of snow levels near 2500 feet while precipitation 
is falling looks to occur on Friday morning. Confidence is not 
stellar in regards to the precipitation timing and impacts are 
likely be minimal yet something we will be keeping an eye on. In 
the mountains, confidence is much higher for snow to fall and 
likely impact the mountain passes with a few inches. Greatest risk
for snow to stick on roads (ie impacts to travel) will be during 
the overnight and early morning hours with mainly wet roads by 
midday. Stevens and Lookout Passes carry the highest risk for 
accumulations with a lower threat at Sherman. Light snow could 
also fall over the higher terrain of the Camas Prairie and Blue 
Mtns impacting a few sections of US95. 

Temperatures will be cool and on the order of 10 degrees below 
normal for afternoon highs. Overnight lows will flirt with 
freezing in a few of the northern valleys, especially around the 
Cascades where clearing should be more pronounced. For the 
remaining lowlands, temperatures are expected to dip into the mid 
to upper 30s each Thursday and Friday mornings and will need to be
closely monitored for any damaging freezing temperatures. /sb

Friday Night through Tuesday: An upper level ridge will build into
the Pac NW late Friday night/early Sat morning. Showers across NE
WA and N ID will decrease through the evening, and then pick up
again Saturday afternoon. Have increased our chance of showers Sat
for the aforementioned area, but other locations across eastern WA
will remain dry. The ridge will flatten quickly as the next low
pressure system makes its way into northern British Columbia. The
bulk of the energy associated with this trough will remain north
of the US/Canadian border. However we will see another influx of
Pacific moisture into the area Sat night and Sunday. The chance of
precip will increase late Sat night into Sunday morning. Current
forecast models are showing fairly light precip amounts with this
system. The heavier amounts of a quarter inch or slightly more
would be along the Cascade crest and the mountains of the ID
Panhandle. We will stay in a west to northwest flow through the
remainder of the forecast, which will keep portions of the Cascade
valleys into the Columbia Basin mostly dry. However showers will
continue to plague portions of eastern WA and north ID...mainly in
the mountains. By next Monday the models start to diverge on a
building ridge...where the axis will be and whether the Pac NW
will be in a more unsettled northwesterly flow or will the axis
nudge a bit closer to us and keep us drier? For now have trended
toward the more unsettled weather regime. Temperatures will be
below average, especially high temperatures which will be about
4-6 degrees below average. /Nisbet

&&

.AVIATION...
18Z TAFS: Some low stratus and fog in the process of eroding and
clearing this morning with the majority of it gone by 20Z this
morning. Showers this morning will become more widespread this
afternoon and evening as a disturbance drops down from the north
and aids in firing them off. By 2Z Wednesday most of the 
convection will be finished and/or on diminished substantially. A
frontal band moving from southwest to northeast will spread rain 
over the region starting at the far western edge of the forecast 
area as early as 04Z Wednesday for the East Slopes of the North 
Cascades and to the spokane area near 08Z Wednesday. /Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        42  52  36  52  36  54 /  80  90  50  40  20  40 
Coeur d'Alene  40  51  35  50  35  53 /  80  90  80  90  30  40 
Pullman        42  50  37  50  36  51 / 100  90  60  50  20  40 
Lewiston       46  54  41  56  39  56 /  90  90  40  30  20  30 
Colville       40  53  37  53  37  56 /  60  90  50  40  20  30 
Sandpoint      38  49  36  48  36  51 /  90  90  80  90  60  40 
Kellogg        37  45  35  44  34  47 /  90 100  90  90  60  40 
Moses Lake     45  61  40  60  38  61 /  50  60  10  10  10  10 
Wenatchee      44  58  39  57  39  59 /  40  40  10  10   0  10 
Omak           43  59  38  57  38  60 /  30  70  10  10  10  10 

&&

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

$$

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Western Regional Climate Center, wrcc@dri.edu