510
FXUS66 KOTX 282127
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
227 PM PDT Sun Apr 28 2024

.SYNOPSIS...
Monday will be windy with gusts 30 to 40 mph. A cold front will
bring snow to the Cascade mountain passes Sunday night and Monday
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...
Tonight through Tuesday Night: Breezy to windy conditions with
gusts 20 to 30 mph this afternoon will decrease after sunset.
Speeds will remain elevated through the night, but gusts will
generally be 20 mph or less. Showers have popped up again this
afternoon across northeast WA and the ID Panhandle. Instability
isn`t as good as it was yesterday, and the potential for
thunderstorms is decreasing quickly. Have removed mention of
thunder for Washington and have it confined to the ID
Panhandle through 7pm.

The trough will begin to move onshore late tonight. Rain will
change to snow across the Cascade mountains after sunset and begin
to accumulate towards midnight. Will continue with the winter
weather advisory above 3500 ft. For Stevens Pass there is a 75%
chance of 4 inches of snow and a 30% chance of 6 inches. Snow will
continue through the morning hours at the pass, but by 10ish or
after it will become increasingly difficult for snow to accumulate
on the roads given the sun angle and temps warming above freezing.
Periods of snow will continue in the mountains through Tuesday,
though accumulations will be minor.

As the trough moves inland Monday we will see an increase in
westerly winds. Strongest winds will be across the Waterville
Plateau with sustained winds to 25 mph with gusts up to 40 mph. As
you head onto the Columbia Basin, Palouse and West Plains winds
will be sustained winds 15 to 20 mph with gusts 25 to 35 mph. Have
kept the patchy blowing dust in the forecast for portions of
Grant, Lincoln and Adams counties from 3 to 7pm.

These strong westerly winds will shadow out portions of the
Wenatchee/Waterville Plateau and Columbia Basin around Moses Lake.
Otherwise there is a 60% chance or greater of the rest of the
region seeing rain showers Monday. During the morning, some higher
bench locations like the West Plains could see snow briefly mixed
in with the rain. No accumulation is expected on the roads.

As the low moves through in the late morning and afternoon hours
there is a 15 to 25 percent chance of thunderstorms. Have the
eastern third of Washington...mainly east of a line from Walla
Walla to Ritzville to Republic and areas eastward into Montana
highlighted for thunderstorm potential. Impacts from thunderstorms
would be gusts to 40 mph, graupel and lightning.

Tuesday morning temperatures will dip to near freezing or below
for a large portion of the lower elevations of the Cascade
Valleys, northeast WA, the Spokane area, Palouse and ID Panhandle.
Have mention of frost for these areas.

Showers continue Tuesday as a secondary trough moves into the
region. Tuesday there is a 15-20% chance of thunderstorms across
southern WA and onto the Palouse and southern ID Panhandle.
/Nisbet

Wednesday through Saturday: Wednesday will be another day of
unsettled conditions with showers and isolated thunderstorms mainly
isolated over the Cascades and Shoshone County. Afternoon winds will
still be a bit breezy with gusts of 15 to 20 mph.

Most of the region will see temperatures drop near freezing Tuesday
night into early Wednesday morning, and a few locations in the
mountain valleys and the northern Basin may drop below freezing.

Heading into the second half of the week starting Wednesday night,
we start to see divergence in model solutions. Around 70 percent of
models suggest a ridge will move in, taking the place of the trough
that will be over us through the first half of the week, and warming
our temperatures back into the 60s by next weekend. The other 30
percent of ensemble members want to keep us in a troughing pattern,
which would result in temperatures staying in the 50s through the
end of the week.
/Fewkes

&&

.AVIATION...
18Z TAFS: Showers are expanding once again across the ID Panhandle
and will develop in the mtns of NE WA as well. Cigs will continue
to improve at GEG, but under showers cigs to 3000 feet will be
possible. Otherwise, winds will increase region wide with a
general south to southwest direction. Gusts around 30-35 mph will
be possible in the Okanogan Valley, Columbia Basin, and near the
Blue Mountains. A potent cold front tonight into Monday will
bring more widespread precipitation to the Idaho Panhandle and
Eastern third of WA. Rain will transition to wet snow for
elevations around 2500 feet and higher which includes Pullman,
Spokane, and Coeur D Alene. Higher confidence for GEG to see snow
mix in and have that in the TAF, but not for PUW/COE because of
lower confidence. Confidence is moderate for little to no
accumulations with steady winds keeping temperatures above
freezing during this time. Winds will become gusty Monday from the
west as well with potential for brief gusts around 40-45 mph.


FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
A lightning strike or two will be possible again in Northeastern
WA and North Idaho. The threat is lower than Saturday but tough to
rule out completely.

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

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        38  52  32  53  35  59 /  20  70  10  20  10  10
Coeur d`Alene  38  47  31  50  34  56 /  40  90  30  50  20  20
Pullman        36  46  31  49  32  53 /  20  90  30  50  30  20
Lewiston       43  55  37  56  37  61 /  10  70  10  40  20  20
Colville       33  50  26  54  29  61 /  30  80  10  30  10  10
Sandpoint      38  47  31  49  34  54 /  50  90  30  60  20  40
Kellogg        38  44  33  45  34  49 /  50 100  50  70  30  50
Moses Lake     38  58  34  59  35  66 /  10  20   0  10   0   0
Wenatchee      38  55  37  57  38  64 /  10  10   0  10   0   0
Omak           36  57  32  59  34  66 /  10  30   0  10   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Winter Weather Advisory from 11 PM this evening to 11 AM PDT
     Monday for Western Chelan County.

&&

$$