742
FXUS66 KOTX 152149
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
249 PM PDT Sat Jun 15 2024

.SYNOPSIS...
Gusty winds along with thunderstorm outflow winds and rain
showers into this evening. Snow will be possible down to 4000
feet by Sunday morning. Temperatures will trend cooler into the
start of early next week with the potential for frost in colder
pockets Sunday and Monday morning. Showers and thunderstorms,
mainly in the mountains will be possible each afternoon through
midweek with gradual warming by late week.

&&

.DISCUSSION...

Tonight through Sunday night: Showers and thunderstorms will develop
into the early evening. Thunderstorms will be more isolated in
nature over northeast Washington into the Northern Panhandle. A
convergence zone extending from around Yakima to the Central
Panhandle Mountains will be a source of more substantial
convection that forms with thunderstorms more scattered in nature
on the Palouse. This convection will wane through the evening with
the loss of daytime heating. One area of concern will be for
travel over Stevens Pass as the Puget Sound Convergence Zone
(PSCZ) will result in more intense precipitation over the pass.
Snow levels will be right around pass level and more intense
precipitation under the convergence zone may result in heavy wet
snow with slippery travel. Total snow accumulation over Stevens
Pass is expected to be between 1 to 3 inches, but there is a lot
of uncertainty. Warm road temperatures should limit the amount of
snow that accumulates, but heavier intensity snow could over come
the warm road temperatures. The National Blend of Models indicates
a 10% chance for over 4 inches of snow. Winds will also remain
breezy into the early evening hours. A wind advisory will remain
in effect until 8 PM, but its likely that winds will be just shy
of advisory criteria at 20-25 mph sustained and gusts up to 35-40
mph over much of the area.

Clouds look to clear out over much of the region aside from over the
Cascades and right near the Canadian border. Dry air mixing down
with winds weakening will result in good radiational cooling. Low
temperature over much of the upper basin into the Spokane Area,
Palouse, and northern mountain and Panhandle valleys are expected
to drop down into the lower to mid 30s. A frost advisory remains
in effect. People with sensitive vegetation should cover their
plants to protect from frost damage.

An area of deformation over southern British Columbia will move
south into the northern mountain zones by Sunday morning. Snow
levels will be down around 4000 feet with light snow expected
over Washington Pass and Sherman Pass. Snow looks to get going
late enough in the day at Sherman Pass that it may have a hard
time accumulating. Sunday will be a cool and showery day over the
northern mountains and into the Cascades. Precipitation amounts
will be light, but it will be welcomed precipitation for an area
that is seeing moderate drought conditions. There will also be a
15-20% Chance for thunderstorms on over the mountains as the
deformation band breaks up and weakens with sun breaks warming up
the surface and destabilizing lower levels of the atmosphere. /SVH

Monday through Saturday: The broad upper level trough will dip
through the Northern Rockies Monday and head southeast. The Inland
Northwest will be left in a deformation zone, prime for unsettled
cloudy conditions especially in the higher terrain areas. Monday and
Tuesday temperatures will remain below normal under the cold air
aloft, and then Wednesday into next weekend the warming trend will
settle in as daytime temps climb back into the 80s. Speaking of
Monday and Tuesday, the cold air aloft and cooler profile (850mb
temps 2-4C), there is some ensemble guidance suggesting up to 3-4"
of snow in the far north Cascade mountains along the crest. These
values are at the 90th percentile, with only up to 1-2" for the
forecast mean. Needless to say, it will be difficult to accumulate
anything on roads this time of year.

Midweek through late week, the flow aloft will shift more zonal
versus northwest as we maintain a broad yet weak trough pattern
across the Northwest. A rather weak ridge will begin to build by
late week, which will aid our daytime heating to settle into a
warming trend through the week ahead. Little to no weather hazards
are expected during the workweek at this time, outside of some
terrain driven showers early in the week. /Dewey

&&

.AVIATION...

18Z TAFS: Windy with pop up shower and thunderstorms today.
Sustained winds of 15-23 kts, with gusts to 28-35 kts are forecast
over the region. There is a 30-50% chance of thunderstorms over
Northeast Washington into the Idaho Panhandle, with a 10-20%
chance across the Columbia Basin down into the LC Valley and
Palouse. Chances for thunderstorms for KDEW-KGEG-KSFF-KCOE will be
highest through early afternoon (around 21-22Z). Showers with
embedded thunderstorms will be more likely around mid afternoon after
20Z near KPUW along a west to east boundary. Convection will come
to an end after sunset with loss of daytime heating, with
decreasing winds as well.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
There is high confidence in continued VFR conditions through
Sunday morning. One potential caveat is for low ceilings and MVFR
ceilings to develop at KPUW between 15-18Z. /SVH

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

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        40  64  40  67  43  71 /  20  10  10  30  10  20
Coeur d`Alene  38  61  39  64  43  66 /  20  10  10  30  30  30
Pullman        36  60  39  61  40  68 /  20  10  10  30  20  10
Lewiston       44  68  48  69  48  76 /   0  10  20  40  20  10
Colville       32  59  32  66  36  68 /  40  50  40  50  30  50
Sandpoint      37  58  38  63  42  62 /  40  30  20  50  50  60
Kellogg        40  58  42  58  45  63 /  30  10  20  50  40  40
Moses Lake     40  69  43  73  44  77 /   0  20  30  10   0   0
Wenatchee      45  66  47  71  48  76 /  10  30  30  10   0   0
Omak           41  64  44  73  45  76 /  10  30  30  20  10  20

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Frost Advisory from 1 AM to 8 AM PDT Sunday for Central
     Panhandle Mountains-Idaho Palouse-Northern Panhandle.

WA...Frost Advisory from 1 AM to 8 AM PDT Sunday for Northeast
     Mountains-Okanogan Highlands-Spokane Area-Upper Columbia
     Basin-Washington Palouse-Western Okanogan County.

     Wind Advisory until 8 PM PDT this evening for Lower Garfield and
     Asotin Counties-Moses Lake Area-Spokane Area-Upper Columbia
     Basin-Washington Palouse.

&&

$$