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Area forecast discussion
National Weather Service Spokane Washington
439 PM PDT Wed Apr 26 2017

Synopsis...
expect cool, breezy, and showery weather for the rest of this
week. Mountain passes could see a few inches of snow overnight
Wednesday into Thursday morning. 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. Next Wednesday
dry conditions with average temperatures are expected.

&&

Discussion...
this evening and tonight: we are seeing a moderate amount of
sunbreaks across central Washington at this hour which will be spreading
east. As this occurs, the atmosphere will destabilize promoting
widely scattered showers and a few weak T-storms. Looking at the
current dewpoint analysis, gusty west winds are drawing drier air
from Wenatchee eastward with 20z analysis showing lower 30
dewpoints largely south of Hwy 2 and north of I-90 while areas to
the north and south still coping with the remnants of today's
shortwaves are sitting in the upper 30s to lower 40s. This wedge
of drier air will carry the lowest risk for showers while the
backside of each of the ongoing clusters of rain carries the
highest risk. After sunset, many locations will dry out overnight
however we are monitoring another disturbance tracking into northwest Washington
at this time which should cross through the area overnight. Best
chance for additional showers with this feature arrive after 10pm
and look to impact the Idaho Panhandle and far eastern reaches of
Washington. Additional precipitation amounts should be light. Despite
being on the cool side of the polar jet, persistent west to
southwest winds through the overnight hours will keep temperatures
from bottoming out with overnight lows expected to dip into the
mid to upper 30s and lower 40s in the deep basin. /Sb

Thursday through Friday night...latest models are in good
agreement with the overall weather pattern through the end of the
short term forecast. Confidence is relatively high for a continued
unsettled and cooler weather regime with the forecast area
residing to the north of the polar jet axis as a broad upper level
trough develops over the Canadian prairie and a broad upper level
ridge builds off shore. Thus increasingly northwesterly flow will
develop over the region on Thursday. Normally this is a dry
pattern for the region but satellite does indicate a few
disturbances being caught in this flow currently over the Queen
Charlotte islands and Alaska Panhandle region.

These waves will drop into the forecast area on Thursday and
Friday bringing isolated to scattered showers over the basin
and scattered to numerous showers over the orographically
favorable Idaho Panhandle and northeast Washington mountains.

Since the forecast area will reside north of the polar jet
axis...these showers will take a more early Spring character with
snow levels dropping to the 3000 to 4000 foot levels...and in the
overnight hours and early morning there is a possibility of some
non-accumulating snow to make it to valley floors and the rising
terrain of the eastern basin. Travel impacts are expected to be
minimal with the potential for an inch or two of snow
accumulation over the passes during the overnight and early
morning hours...melting off by late morning with wet surfaces
during the afternoon. The other persistent characteristic for the
next two days will be occasionally breezy west to southwest winds
across the region...particularly near the Cascade gaps as high
pressure develops under the building offshore ridge and creates an
onshore gradient across the Cascades.

Temperatures will remain cooler than normal during the day...only
in the mid to upper 50s...but the breezy conditions should keep
overnight lows above freezing except in sheltered valleys mainly
in the Cascades and Okanogan Highlands each morning. /Fugazzi

Saturday through wednesday: weak energy will exit the region
Saturday morning as a shortwave ridge builds in. Saturday will be
a fairly nice day for most locations. However the threat of
afternoon showers does exist across north Idaho and extreme NE Washington.
The ridge is quickly flattened as a trough moves into British
Columbia Sat night. Even though models agree that the bulk of the
energy will remain north of the border, there is a warm front and
decent amount of moisture that will stream in from the Pacific. A
chance of fairly light precipitation will spread across the region
late Sat night through Sunday with it moving out sun evening. The
Columbia Basin may be the one dry spot as westerly flow will
shadow them. Then another wave will move in for Monday to keep the
threat of showers going for the mountains as well as eastern Washington
and north Idaho. The models do agree on a ridge building into the
western US starting next Tuesday. We will have a slight chance of
showers Tuesday for extreme eastern Washington and north Idaho and then dry
conditions after that, for a possible 24+ hr dry period with
warming conditions! Temperatures Saturday through Tuesday will be
below average and then Wednesday we could see average temperatures
for this time of the year...60s to around 70. /Nisbet

&&

Aviation...
00z tafs: showers and isolated thunderstorms will continue into
the evening hours with radar trends supporting the most focused
activity over the northern mountains...and between kgeg and kpuw.
Thus for most of the taf sites vcsh was utilized with storms not
expected to impact any of the taf sites. Breezy winds will also
continue this evening especially keat with gusts around 30 kts
possible. Overnight the boundary layer moistens slightly with
latest models keeping the best chances for IFR/MVFR stratus over
the Idaho Panhandle and the Palouse and thus restrictions are
expected at kcoe/kpuw. There will be a decrease in shower activity
overnight before increasing again Thursday afternoon with daytime
heating. Jw

&&

Preliminary point temps/pops...
Spokane 37 51 36 54 37 56 / 40 50 40 30 10 10
Coeur D'Alene 36 49 35 52 34 55 / 40 70 60 40 20 20
Pullman 37 50 36 52 36 56 / 50 40 50 30 10 10
Lewiston 42 55 39 57 39 61 / 30 40 30 20 0 0
Colville 37 52 37 56 36 57 / 70 60 30 40 20 20
Sandpoint 38 47 36 50 34 53 / 90 70 60 60 20 30
Kellogg 36 43 34 46 33 51 / 70 70 70 50 30 30
Moses Lake 39 61 37 62 37 62 / 0 10 10 10 0 0
Wenatchee 40 58 39 60 38 59 / 0 10 10 10 0 0
Omak 39 59 38 62 37 59 / 10 20 20 10 10 0

&&

Otx watches/warnings/advisories...

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