996
FXUS66 KOTX 231211
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
411 AM PST Sun Feb 23 2025

.SYNOPSIS...
Rain will arrive this weekend as high temperatures warm
into the 40s and low 50s. Runoff from rain and melting snow will
lead to increased flow and minor flooding across southeast
Washington and the central and southern Idaho Panhandle.
Another weather system Monday into Tuesday will bring more rain and
stronger winds.

&&

.DISCUSSION...

Today and Tonight: A pair of moisture-laden shortwaves will
produce widespread precipitation in the next 24 hours. The first
will be exiting the Idaho Panhandle around sunrise this morning.
We are closely monitoring rain amounts through the early morning
hours and the response of Paradise Creek running through Moscow,
Idaho as it is forecast to climb above flood stage prior to
daybreak. The second shortwave will deliver another round of
widespread rain late in the day and into the evening as this
disturbance shoves a warm front across Washington and north Idaho.
The plume of moisture directed into the Pacific Northwest has
sufficient Integrated Water Vapor Transport (IVT) to be classified
as a "moderate" strength atmospheric river. The precipitation
delivered to the region combined with runoff from melting snow
will not only produce rises on Paradise Creek and the Palouse
River, but other small streams across the eastern third of
Washington and the Idaho Panhandle will experience rises. There
will also be a heightened risk of field flooding and rock slides
in the steep terrain of north Idaho. Areal Flood Watches have been
replace with Areal Flood Warnings for Whitman, Latah, and Benewah
counties with the expectation of of an additional three-quarters
to inch an a half of rain Sunday morning through Sunday night.
This is on top of 1 to 3 inches of snow water equivalent across
much of Latah and Benewah counties. Areal Flood Advisories are now
in effect for the north Idaho Panhandle, Spokane/Coeur d`Alene
area, the Central Idaho Panhandle, the L-C Valley, and Lewis
county Idaho.

Monday and Tuesday: Our final round of widespread rain will occur
Monday afternoon into Tuesday as a vigorous low pressure system
drives into northwest Washington and southern British Columbia.
The easterly flow ahead of this low will likely be sufficient to
drive snow levels down to the floor of the Methow Valley Monday
night. A couple inches of wet snow accumulation will be possible
overnight into early Tuesday morning before west winds increase
and scrub the cooler air from the valley east of the Cascade
Crest. The National Blend of Models (NBM) gives Stevens Pass a 60
percent chance of a foot or more of snow accumulation Monday into
Tuesday. For north Idaho, snow levels aren`t expected to fall
below 4000 feet until the passage of the cold front Tuesday
morning. The NBM generates a 50 percent chance of 6 inches of
accumulation Tuesday into Tuesday night. With much of that snow
occurring during the day Tuesday with temps in the 30s, low
accumulation efficiency may limit the impact at Lookout Pass. Post
cold front winds on Tuesday will have the potential to be a more
significant impact. The ECMWF ensembles produce average maximum
wind gusts of 40 to 45 mph for the eastern third of Washington and
adjacent portions of north Idaho including Spokane, Pullman and
wind prone areas near Coeur d`Alene. We will be keeping a close
eye on Tuesday for the potential for future Wind Advisories.
/GKoch

Wednesday through Sunday: Above average temperatures in the 40s
and 50s continue through the end of the week as upper level height
rises dominate the period. A weak wave on the northwest branch of
the ridge in SW BC will bring the chance (30-50%) for high
elevation snow (above 4000 feet) and valley rain to the Cascades
and ID Panhandle Thursday. A second ridge forms offshore Thursday
night and shifts into the Inland NW Friday, so most of the day
Friday will be dry. As the ridge axis shifts east in western
Montana Friday night, precipitation chances increase thanks to a
low pressure headed toward the Kenai Peninsula in southern Alaska.
A deep subtropical moisture plume will be aimed at Washington. The
north-south orientation of the plume suggests this will not be a
very long winded event, but precipitation chances continue through
late next weekend. Snow levels will be around 4500-5500 feet
through the event. Not anticipating a significant hydrologic event
from this late week system. /Butler

&&

.AVIATION...
12Z TAFS: Rounds of rain will impact the Inland NW over the next
24 hours. One round shifts out early in the TAF period, but
additional rain develops overnight into early Sunday, followed by
a brief lull before another round develops later Sunday PM. Look
for MVFR conditions, with periodic IFR conditions possible with
fog/stratus between those rounds of rain. Additionally wind shear
is expected as the atmosphere remains mixed, until this afternoon
to evening when some gusty winds are possible, especially at KPUW.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate
confidence in timing and location of upcoming precipitation.
Ceilings expected to degrade to MVFR with lower confidence for
IFR overnight. Moderate to low confidence of wind shear values
being greater than 30 knots difference. Timing confidence in LLWS
shear vs gusty winds making it to the surface is low.

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

Confidence descriptors:
Low - Less than a 30 percent chance
Moderate - 30 to 70 percent chance
High - Greater than a 70 percent chance

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        49  36  49  39  47  33 /  90 100  50  90  40  30
Coeur d`Alene  47  35  48  36  45  31 / 100 100  30 100  60  50
Pullman        49  37  46  37  45  31 / 100 100  60 100  50  50
Lewiston       53  39  52  40  52  34 /  90 100  40  90  40  40
Colville       46  30  45  35  45  29 /  40 100  40 100  40  30
Sandpoint      43  35  45  37  43  32 / 100 100  30 100  80  70
Kellogg        45  37  47  37  40  33 / 100 100  40 100  80  80
Moses Lake     52  34  49  37  54  31 /  60  60  70  50  10   0
Wenatchee      46  33  42  35  47  32 /  50  60  80  70  30  10
Omak           45  31  44  35  47  31 /  20  90  60  90  20  10

&&

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

$$