041
FXUS66 KOTX 292354
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
454 PM PDT Mon Apr 29 2024

.SYNOPSIS...
Scattered showers through Tuesday. Winds decreasing tonight with
the potential for frost expanding across the mountain valleys
through Wednesday morning. A warming trend through the rest of the
week into the weekend. Weather conditions will remain unsettled
for the rest of the week with a weather system moving in off of
the eastern Pacific on Thursday and another one over the weekend.

&&

.DISCUSSION...
Tonight through Wednesday night: A cold upper level trough of
lower pressure will reside over the Inland Northwest. Scattered
showers will dissipate this evening, but then reform over much of
the region on Tuesday with diurnal heating. Showers will persist
however across the Cascade crest where additional light snow is
expected over Washington Pass and Stevens Pass. Showers are
expected to be more steady over Stevens Pass where an additional
1-3 inches is expected and a winter weather advisory remains in
effect through 2AM tonight. Snow is less likely to accumulate over
Washington Pass tonight. Best instability of 100-200 J`kg of CAPE
will be over extreme southeast Washington and into the southern
to central Idaho Panhandle where a 15% chance for thunderstorms is
expected. We will see a 10-15% for thunderstorms over the higher
terrain of the Northeast Mountains into the Northern Panhandle as
well. Thunderstorms will be weak and only develop long enough to
spit out a lightning strike or two before collapsing onto itself.
Graupel showers will also continue to be likely with convection
tomorrow.

The trough will be pulling away to the east on Wednesday. This
will result in warmer temperatures closer to seasonal normals with
highs in the mid 50s in the Idaho Panhandle to the mid 60s in
eastern Washington. Showers on Wednesday will primarily be
confined to the Idaho Panhandle into northeast Washington on
Wednesday as well. Graupel showers will be less likely by
Wednesday with the warmer temperatures. Tuesday and Wednesday
mornings will be chilly. There should be enough cloud cover
tonight that I am less concerned for frost development for zones
in their growing season (Wenatchee Area, Moses Lake Area, and
Lewiston-Clarkston Valley). Wednesday will also be on the chilly
side, but also doesn`t look to get cold enough to warrant a frost
advisory. /SVH

Thursday through Sunday: Model consensus is still a little fuzzy
toward the end of the week. Thursday a shortwave trough will move
through, increasing chances for showers regionwide. Thursday morning
will be a couple degrees warmer than the temperatures we`ll see in
the morning on Tuesday and Wednesday, but frost will still be a
threat in some of our colder spots including mountain valleys in
northeastern WA and the ID panhandle. A minimal amount of CAPE
Thursday afternoon could allow a few isolated thunderstorms to pop
up with Thursday`s showers, but any thunderstorms that develop would
be non-impactful.

The shortwave`s time over our area will be brief. It is expected to
move out sometime Thursday night, though the exact timing of its
exit is still uncertain. Weak ridging will take its place on Friday.
Showers will linger, but will be confined mainly to the mountains
through Friday night until another shortwave moves in for the
weekend, bringing returning shower chances regionwide. How much
precip we`ll get is unknown at this point, as precip amounts will
depend on the track of the shortwave, and models are showing lots of
variability in the track at this point.

As for temperatures, a gradual warming trend will be in place over
the entirety of the forecast period. How warm temperatures will get
by the weekend is another thing that will depend on the track of the
weekend shortwave, so the range of possible temperatures is still
quite large. Models are showing anywhere between the upper 50s and
low 70s by Saturday and Sunday. Daytime heating and mixing of the
atmosphere combined with the couple of waves expected to pass
through will produce breezy winds, particularly in the afternoons.
Gusts will generally be in the range of 15 to 20 mph. /Fewkes

&&

.AVIATION...
00Z TAFS: A weather system passing through into the early evening
will continue to promote scattered showers and gusty west winds.
Heavier showers will continue to produce small hail or graupel
along with an isolated lightning strike. This evening with the
loss of daytime heating shower will dissipate along with the gusty
winds. On Tuesday another round of showers will develop as the
atmosphere destabilizes but less in coverage compared to today.
Isolated thunderstorms may also develop, but the main threat will
be over the higher terrain of SE Washington (Blue Mountains), and
up over NE Washington around Republic and Colville. Mainly VFR
conditions are expected, except for KPUW/KCOE from near 12-18z
Tuesday with the HREF showing near a 60% chance of MVFR
conditions.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
There is about a 30% chance of blowing dust across the Columbia
Basin into the early evening, including at MWH. Confidence in
visibility dropping below 7 miles is low so did not include
mention in TAF. Confidence is also low that thunderstorms will
impact terminals through early this evening and also Tuesday
afternoon. 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        31  53  34  58  36  60 /  30  20  10  10  10  20
Coeur d`Alene  30  50  33  55  36  59 /  60  30  20  30  10  20
Pullman        31  48  32  53  34  57 /  50  40  20  30  20  30
Lewiston       36  56  37  61  39  62 /  30  40  30  20  10  30
Colville       25  54  30  61  33  61 /  60  40  10  20  10  30
Sandpoint      31  50  34  53  36  58 /  40  40  20  50  20  40
Kellogg        32  45  34  48  36  56 /  60  50  30  70  20  40
Moses Lake     34  59  34  66  38  62 /  20  10   0   0  10  20
Wenatchee      38  57  38  63  41  59 /  10  20   0   0  10  20
Omak           32  58  35  66  41  64 /  10  20   0   0  10  20

&&

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

&&

$$