438
FXUS66 KOTX 172207
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
307 PM PDT Fri May 17 2024

.SYNOPSIS...
Gusty winds will decrease this evening and subside overnight. Cooler
and unsettled weather will continue through the weekend. Tonight
will be quite chilly with the potential for frost in our sheltered
valleys of north Idaho and northeast and north central Washington. A
wetter low pressure system is expected on Wednesday and will keep
temperatures below normal.

&&

.DISCUSSION...
Tonight through Sunday Night: The upper level trough moved through
earlier today and is already into western Montana. A boundary has
set up across the Palouse and into the southern ID Panhandle where
some showers are occurring. Earlier today around noon there were a
few lightning strikes, but nothing since. The extensive cloud
cover across NE WA and the north ID Panhandle has inhibited
convective showers, but clouds appear on satellite to be
thinning, and that area could see more pop up showers and an
isolated strike through sunset. The showers are moving toward the
southeast.

Winds continue across the Cascade gaps, Wenatchee/Waterville
Plateau, Columbia Basin and onto the West Plains, Palouse,
Lewiston/Clarkston area and the Camas Prairie. Winds are not as
strong as they were yesterday. Winds ramped up again around 8 am
and continued through the morning, but have been slowly
decreasing this afternoon. Have cancelled the advisories as
criteria is no longer being met.

Clouds will decrease tonight and with dry air in place in wake of
the trough, we could see come pretty chilly temperatures Saturday
and Sunday morning. Have higher confidence of near or below
freezing temperatures Saturday morning than Sunday morning, as
Sunday there will be some thicker clouds across the region as the
next trough moves through the region. The `typical` sheltered
northern valleys of Washington and Idaho will see frosty
conditions. Locations include but are not limited to: Colville,
Newport, Usk, Deer Park, Priest Lake, Green Bluff area, Republic,
parts of the Methow Valley. Actions should be taken to protect
sensitive plants and vegetation if you live in sheltered valley
that can typically get cold.

Saturday we are between systems, but 500 mb temperatures remain
cold enough for a 20-30% chance of thunderstorms. The same is true
for Sunday as a trough moves into the region. So the weekend is
looking to be cooler with temperatures in the upper 50s and 60s
and a 30-50% chance of showers for portions of the Inland
northwest. Probabilities are less than 10% for central WA into
the Moses Lake area, and are 60% or higher for the northern WA and
ID counties. Winds will be less than what has been seen the last
day, but Cascade gap winds will pick up each afternoon and evening
with gusts 20-30 mph. /Nisbet

Monday through Friday: A longwave trough of lower pressure will
settle over the west next week. Ensembles are in good agreement with
shortwave trough digging over the region around Wednesday. There is
some uncertainty with how deep this shortwave will get, but 50-60%
of the ensemble members indicate a closed low forming over the
Northwest region. Another 25% of the ensemble members keeps the wave
open and more progressive, while 20% of the members has a weaker
reflection of a shortwave pushing across. There is high confidence
that temperatures will remain cool and below normal with high
temperatures cooling into the 60s Wednesday into Thursday. A closed
low will also result in a conditionally unstable air mass with
unsettled conditions. Showers will be most prevalent during the
afternoon hours as surface heating destabilizes the lower levels of
the atmosphere. A cold pool overhead will also steepen mid level
lapse rates with the potential for afternoon thunderstorms. Ensemble
members diverge heading into the Memorial Day weekend period. Some
members are slower in moving the upper level low out of the region
off to the east. The general consensus is for the long wave trough
to remain with temperatures warming slight but remaining below
normal. /SVH

&&

.AVIATION...
18Z TAFS: A shortwave descending from B.C. is increasing winds
into the 15 to 25kt range with gusts 25-35kts or more at all TAF
locations thru 03Z. Numerous showers will also accompany the
passage of the shortwave across eastern WA and the ID Panhandle.
PROB30 and TEMPO groups have been included in the GEG/SFF/COE/PUW
TAFs. Chances for lightning has been expanded to include
Stevens/PDO/Spokane and Whitman counties as well as Latah county
northward in Idaho. Confidence is low in a thunderstorm going over
or approaching a TAF location, and short term TAF amendments will
handle any thunderstorms.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Blowing dust
limiting visibilities to 3 miles for a few hours at Moses Lake
and Spokane on Thursday with winds gusting in the 45 to 55 mph
range. There should be less dust today since winds won`t reach
that magnitude over the source region of the dust around Moses
Lake. However, the last 10 days has been quite dry so recently
worked fields that happen to be near an airport could produce
visibility reductions.

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

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        39  62  39  61  40  68 /  10  30  30  40  10  10
Coeur d`Alene  38  59  39  57  40  65 /  30  40  50  60  10  10
Pullman        37  60  37  56  39  63 /  10   0  30  30  10  10
Lewiston       44  70  44  65  46  71 /  20   0  30  30  10  20
Colville       31  62  34  62  35  70 /  20  80  70  80  20  20
Sandpoint      37  57  39  55  37  64 /  50  50  60  80  20  30
Kellogg        39  57  40  52  41  61 /  50  40  40  70  20  40
Moses Lake     40  68  40  69  43  75 /   0  10  10  10   0   0
Wenatchee      45  64  43  66  45  73 /   0  10   0  10   0   0
Omak           39  66  40  70  42  77 /  10  40  30  20  10   0

&&

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

$$