180
FXUS66 KOTX 202349
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
449 PM PDT Mon May 20 2024

.SYNOPSIS...
Showers will quickly diminish this evening with a short break
between weather systems into early Tuesday. Then a wet low
pressure system is expected to move in the latter half of Tuesday
into Wednesday, and linger into Thursday. Another weather system
will move in on Friday. The week and into the Memorial Day weekend
will be cool, unsettled with thunderstorms each day, especially
over the higher terrain.

&&

.DISCUSSION...

Tonight: Convective showers this afternoon are much more subdued
compared to this time yesterday. The low pressure trough axis has
swung through into western Montana leaving the Inland Northwest
on the back edge with cumulus build ups from differential heating
combating subsidence aloft with higher heights moving in. There
is still a 20% chance for a lightning strike or two with stronger
updrafts, thunderstorm potential overall will be less compared to
what we saw yesterday evening. Skies will then quickly clear out
overnight. There will be the potential for a redevelopment of fog
in the mountain valleys of northeast Washington and in the Idaho
Panhandle tonight as the surface radiates out. Fog coverage is
expected to be less and more so confined in the mountain valleys
instead of extending out into the Spokane Area like it did earlier
this morning.

Tuesday into Tuesday night: Tomorrow will start out dry, but a
warm front will quickly move into the region ahead of a robust low
pressure system that drops south across BC. The warm front will a
shot of increased precipitable waters from around 0.45 inches to
around 0.75 inches. The combination of good dynamics with the
front drawing in ample moisture off of the Pacific Ocean will
bring an increasing chance for rain through the afternoon and into
the overnight hours. Light rain is expected to begin in the
Cascades by noon, and then push east of the Cascades into the
basin and Okanogan Highlands/Valley by mid afternoon. The
thickening clouds and rainfall will subdue our warming through the
day with high temperatures generally in the 60s.

Precipitation will become enhanced in the evening as it continues
its march into the Idaho Panhandle by the late evening hours.
Steady precipitation into Tuesday night will result in soaking
rains in the lowlands across much of the region. The exception
will be in the lee of the Cascades where downsloping will result
in less accumulations with places like Wenatchee, Quincy, and
Ephrata struggling to receive at least a tenth of an inch of
precipitation. Snow levels will be lowering late in the night into
Wednesday morning as the cold front quickly catches up the warm
front. /SVH

Wednesday through Sunday: Widespread rain is expected throughout the
day Wednesday as the low continues to trek eastward. The forecast
continues to be on track with the rain totals. Over the
mountains, totals will be upwards of 0.5 inches to over an inch,
with a quarter to half an inch in the lower elevations. The
Columbia Basin will miss out on much of the rain with less than
0.05 inches expected. Snow will be limited to the highest terrain,
with one to two inches forecasted at Washington Pass, and Stevens
Pass will remain mainly as rain, with the possibility of a few
snowflakes mixed in. This rain, along with additional snowmelt
from the mountains will lead to a slight rise in creeks and
rivers, but should remain below action stage. During the day on
Wednesday, an isolated lightning strike is possible but don`t
expect to see any. Wednesday`s temperatures will be the coolest of
the week, with high temperatures in the 50s as the system passes
through. In areas that receive limited rain could see breezy winds
with gusts up to 25 mph mainly in the Columbia Basin and
Waterville Plateau.

For Thursday through the weekend, scattered showers will continue,
especially in northeast WA and ID Panhandle. Another low arrives
late Friday into Saturday, with additional rain to the area.
Temperatures will conintue to stay slightly below normal for this
time of year. Ensembles are hinting that by Monday, a ridge will
begin to build, warming temperatures. /KM

&&

.AVIATION...
00Z TAFS: The Inland Northwest is on the back edge of an exiting
upper level trough of lower pressure. Scattered showers will
persist over the region through 03z with the highest focus over
Northeast Washington into the Idaho Panhandle. There is a 15-20%
chance of thunderstorms as well mainly east of a line from
Colville to Spokane to Rosalia. These may include brief heavy
downpours, small hail, and gusty outflow winds. Skies will clear
out with loss of surface heating through the evening. A wet low
pressure system will make its entrance on Tuesday with increasing
clouds expected overnight.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is a 15-20%
chance of thunderstorms at KGEG, KSFF, and KCOE through 03z this
evening. Patchy fog is forecast 9-15z Tuesday in the mountain
valleys of Northeast Washington and the Idaho Panhandle. This
includes KCOE, but confidence is low given the expected patchy
coverage.

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

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  63  45  55  41  62 /  20  30  80  90  30  30
Coeur d`Alene  41  62  45  54  41  60 /  30  10  90  90  40  30
Pullman        38  61  44  52  39  57 /  10  10  90  90  50  30
Lewiston       45  70  50  60  46  65 /   0  10  90  90  50  30
Colville       41  63  40  55  36  64 /  20  40  80  90  40  50
Sandpoint      36  61  45  52  41  60 /  40  20  90 100  60  50
Kellogg        41  60  46  50  43  57 /  40  10  90 100  70  50
Moses Lake     45  67  45  62  44  72 /  10  40  50  60  20   0
Wenatchee      48  64  47  60  46  70 /   0  40  30  40  10   0
Omak           39  65  45  62  44  72 /  10  40  50  70  20  10

&&

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

$$