976
FXUS66 KOTX 211801
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1001 AM PST Fri Feb 21 2025

.SYNOPSIS...
Warmer temperatures and rain will arrive this weekend as high
temperatures warm into the 40s. 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
possibly stronger winds.

&&

.DISCUSSION...

Friday: Southwest flow directed into the Pacific Northwest due to
a weak ridge over the western US combined and troughing over the
northeast Pacific will set the stage for the next several days as
a series of systems pass through the region. The first system
will arrive Friday afternoon into the evening as a surface low
moves into the southern Alaskan Panhandle and the associated
frontal boundary shifts into the Inland Northwest. Temperatures
will be cool enough and snow levels will be low enough for light
snow across the northern valleys (Methow Valley, Republic, Deer
Park) and upper Columbia Basin between Wilbur and Davenport
overnight. Higher benches around Spokane and Coeur dAlene through
Bonners Ferry may also experience a mix of rain and non-
accumulating snow.

Saturday and Sunday: Two systems are progged to impact the Pacific
Northwest between Saturday afternoon and Sunday and bring a
moderate to strong atmospheric river into the region. Models
continue to be in relatively good agreement with the ridge over
the Western US to progressively flatten as the systems ride
overtop. The first system will arrive Saturday afternoon and
evening as a warm front lifts north across the Inland Northwest.
There still remain differences in the onset of precipitation and
exact amounts. The highest precipitation totals with this first
round of precipitation will be across the Cascades, far eastern
Washington, and north Idaho as strong westerly flow aloft favors
orographic enhancement. That being said, the lee of the Cascades
will not be completely shadowed initially with the warm front.
Snow levels will be on the rise through the day on Saturday with
precipitation falling mostly as high mountain snow and lowland
rain. The exception will be for the Methow Valley where colder air
looks to support a wintry mix overnight.

A second surge of widespread precipitation will occur Sunday as
deterministic models show a more compact low to move through the
northwest. Notable differences in the precipitation amounts
between models stemming from the strength and timing of this low.
The deterministic GFS has been trending much wetter with a
stronger, slower moving low allowing the moisture axis to persist
into the region, while the deterministic ECMWF depicts a weaker
low with a quicker moving upper level shortwave and lower rainfall
totals. The ensemble means are more similar to each other, with a
large spread between the 10th and 90th percentile values. Our
current forecast leans closer to the wetter forecast with 48 hour
totals between 0.80 to 1.25 inches for the lowlands of far eastern
Washington and 1.5 to 2.5 inches over the mountains.

IMPACTS: The combination of warmer temperatures, rain, and breezy
winds will result in rapid snowmelt across the lowlands where
recent observations show around 4 to 9 inches of lowland snowpack.
Several observations across the Spokane County and the Washington
and Idaho Palouse are showing 1.3 to 1.8 inches of liquid within
the snowpack. If the wetter scenario verifies, rises in our
flashier creeks and streams will be common across Spokane County
and through the Washington and Idaho Palouse. Ponding of water in
urban areas with poor or clogged drainage and field flooding will
be of concern. It is advised to take proper precautions to
mitigate flood impacts. Paradise Creek at Moscow is currently
forecasted to reach minor flood stage by late Sunday morning. The
South Fork Palouse River at Pullman, Hangman/Latah Creek at
Spokane, and Little Spokane River at Dartford are all forecasted
to rise near bankfull conditions Sunday night into Monday.

Monday: Deterministic models have been coming into better
agreement with a deepening surface low to slide northward along
the Pacific Northwest coast on Monday. There are still differences
in the exact details, but this would bring another round of
precipitation and possibly stronger winds Monday night into
Tuesday. /vmt

Tuesday through Friday: An early morning trough will be pushing
through the Inland Northwest on Tuesday. It is expected to be
the end of the wet weather pattern for the region. It will
continue to bring lowland rain and mountain snow into Tuesday
afternoon before moving into Southern BC. Portions of the Basin,
Southwest WA, and Lower ID Panhandle can expect gusty winds with
the passage. 850mb wind speeds reach into the upper 30 to 50 knots
range. There is currently a near 30% probability of wind gusts of
35 MPH or above. Best chance is Southeast Washington and Lower ID
Panhandle as these reach a 50% probability. As the wave exits
warm, dry air fills in behind it. It will bring a taste of Spring
to the region with highs reaching into the mid 40s to 50s.
Overnight lows will be be in the 30s. The dry pattern will bring a
gradual decline to flood/hydro concerns for the Inland Northwest.
Starting over the weekend, a zonal flow pattern will bring a
general cool, wet pattern for the start of March. /JDC

&&

.AVIATION...
18Z TAFS: Local MVFR/IFR cigs in low stratus will persist through
the morning, though surface visibilities are improving for most
locations as the cloud deck continues to lift. As a storm system
moves into the area, rain and snow will begin impacting the region
later today and into Saturday. This precipitation could be a mix
of rain and snow for area TAF sites. Areas of fog are expected to
return early Saturday as well, with widespread MVFR to IFR
conditions anticipated overnight.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate
confidence in timing and location of upcoming precipitation.
Moderate confidence on the return of IFR for tonight. /KD

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

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        39  36  43  40  48  39 /  20  70  40 100  90  70
Coeur d`Alene  41  34  44  39  47  38 /  20  70  50 100  90  80
Pullman        37  34  41  38  45  38 /  10  50  30 100 100  90
Lewiston       42  36  48  42  52  42 /   0  40  20  90  90  80
Colville       39  33  43  38  46  33 /  40  80  70 100  80  70
Sandpoint      39  34  41  39  44  38 /  30  80  80 100  90  90
Kellogg        42  36  43  41  44  41 /  20  60  60 100 100  90
Moses Lake     41  31  48  40  55  37 /  20  30  20  70  60  30
Wenatchee      38  34  42  38  48  38 /  20  40  50  70  70  40
Omak           39  34  42  36  46  35 /  30  50  50  90  60  50

&&

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

$$