310
FXUS66 KOTX 290905
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
205 AM PDT Mon Apr 29 2024

.SYNOPSIS...
Today will be windy with snow in the Cascade mountain passes
through this morning and rain to much of the rest of the region.
Temperatures will trend cooler with areas of frost returning
Tuesday morning. Unsettled conditions return for the remainder of
the week, especially to the mountains.

&&

.DISCUSSION...

Today through Tuesday Night...As the trough advances inland, we
will see an increase in westerly winds today. While much of the
area will see the increase in winds, the strongest will be over
the Waterville Plateau with gusts up to 40 mph. Everywhere else,
gusts of 25 to 35 mph are expected. Blowing dusts is also possible
over the Columbia Basin as the winds increase in the afternoon.
Along with the winds, showers will increase late this morning over
the Cascades, eastern third of WA and the ID Panhandle. These
showers could contain steady rain and/or graupel with amounts
above a tenth of an inch, with a quarter inch or more over the
higher terrain. A few lightning strikes withing the strongest
showers is possible as there is some instability in the
atmosphere.

With the cooler temperatures over the Cascades, precipitation
will fall as snow through the morning. A Winter Weather Advisory
is in effect through 2AM Tuesday for elevations above 3500 feet in
the Cascades. Snow will continue through the morning hours, with
the likelihood of snow melting off the road in the afternoon due
to the high sun angle. Models are indicating of snow banding
occurring later this evening, with an additional few inches of
snow, before decreasing overnight. Above, 3500 feet, expect snow
totals of 4 to 7 inches with Stevens Pass receiving 8 to 10 inches
of snow. Snow is also likely to fall over Lookout Pass but
amounts of 1 to 3 inches are anticipated.

Another shortwave will slide through the region Tuesday with a
return of showers and/or graupel by Tuesday afternoon, along with
a slight chance of thunderstorms not out of the question during
the afternoon and evening. Winds will also be a bit breezy, but
will not be as high as what is seen today. As we move into Tuesday
night, the threat of showers will decrease

High temperatures will hover around 50, with lows dipping into
the low to mid 30s, leaving a heightened risk of frost across the
area. Those with sensitive plants should take precautionary
measures, particularly as temperatures flirt with freezing. /KM

Wednesday to Sunday: The Inland NW will remain in an active
pattern, but model agreement continues to falter toward next
weekend. Wednesday the area remains under the influence of an
upper trough. The area will be cold enough in the morning to bring
potential frost from the Upper Columbia Basin to the northeast WA
and north ID valleys, including some of the Spokane area. Rain
and snow shower chances will continue around the Cascades and
Idaho Panhandle, with slight chances near the WA/ID border. These
will be most numerous in the afternoon hours and decrease after
dark. Thursday another sharp shortwave drops into the region.
Frost will remain possible in the morning over eastern WA and ID,
though coverage looks less over eastern WA compared to Wednesday
morning. The trough itself will bring higher and broader shower
chances to the region, compared to Wednesday. There is a little
CAPE (near 100 J/kg) so some isolated embedded t-storms cannot be
ruled out, but overall they are not expected to be a big impact.
Going into Thursday night models start to diverge in terms of how
quickly to move this shortwave out. Some wrap a deformation axis
back into southeast WA and lower ID, providing a focal point for
moisture and better precipitation potential. So the details will
warrant more fine-tuning.

A weak ridge builds in Friday, with shower chances lingering over
the region. Then heading into the weekend another shortwave
trough digs into the West, but here models either show it tracking
south and bringing very limited precipitation chances to the
region or tracking it directly into the region with broader and
higher precipitation chances. About 70% of the solution suggest a
pattern still dominated by a trough, but 40-50% show a stronger
trough. Overall this will continue to support precipitation
chances through the weekend, but some of that weekend could be
much wetter if some solutions verify. Confidence is low at this
point.

Expect a warming trend into Saturday. Yet by Saturday and Sunday
there is a broader range of possible temperatures, with as much a
15 degree spread in the 25-75 percentile by Sunday. This is the
difference of highs in the upper 50s or highs near 70. Expect some
breezy conditions Wednesday and Thursday and again possibly
toward the weekend. Speeds are nothing that appears would
necessitate any highlights but still noticeable with gusts near
15-20 mph. /Solveig

&&

.AVIATION...
06Z TAFS: A cold front coming in overnight into Monday morning
will bring an increase in showers over the region especially over
the Idaho Panhandle and eastern third of Washington. Snow levels
fall to near 3000 feet resulting in rain showers for most airports
across the region, with wet snow mixing in as low as 2500 feet
which is near the elevation of KGEG/KPUW. There atmosphere will
destabilize in the afternoon with a 20% chance of thunderstorms
for the eastern third of WA including Colville, Spokane, and
Pullman as well as Lewiston. Given low confidence in precise
timing and limited coverage of thunderstorms did not include for
these sites. North Idaho has a slightly better potential so
included a PROB30 group for Coeur d`Alene. The showers will
moisten the boundary layer with areas of MVFR conditions
developing Monday morning between Pullman and Spokane and into the
Idaho Panhandle.


FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
There is about a 30% chance of blowing dust across the Columbia
Basin Monday afternoon, including MWH. Confidence in visibility
dropping below 7 miles is low so did not include mention in TAF.
JW

-----------------------

Confidence descriptors:
Low - Less than a 30 percent chance
Moderate - 30 to 70 percent chance
High - Greater than a 70 percent chance

For additional probabilistic information for NWS Spokane airports,
please refer to the Aviation Dashboard on our webpage:
https://www.weather.gov/otx/avndashboard

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        51  31  50  34  59  36 /  80  30  30  10  10  10
Coeur d`Alene  47  30  47  33  54  34 / 100  40  40  20  20  10
Pullman        46  31  46  32  53  34 /  90  40  60  20  30  10
Lewiston       54  36  53  37  59  38 /  90  30  60  30  20  10
Colville       50  26  51  30  60  33 /  80  40  30  10  10  10
Sandpoint      47  30  45  34  51  36 /  90  60  60  20  40  10
Kellogg        43  31  42  34  49  35 / 100  60  70  30  50  20
Moses Lake     57  33  56  34  66  38 /  40   0  10   0   0  10
Wenatchee      54  37  55  38  63  41 /  40  10  10   0   0  10
Omak           56  32  55  35  65  40 /  30  10  10   0  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Winter Weather Advisory until 2 AM PDT Tuesday for Western
     Chelan County.

&&

$$