704
FXUS66 KOTX 130738
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1238 AM PDT Sun Sep 13 2026

.KEY MESSAGES...
- Widespread rain returns late Saturday night through Sunday.
  Most of the Inland Northwest has a 50-90% chance of receiving
  half an inch or more of rain with this system.

- Risk for debris flows and rock slides in Central Washington
  near sensitive burn scars and steep terrain.

- Isolated thunderstorms Saturday night into Sunday, especially
  for Eastern Washington and North Idaho.

- Gusty winds across the broader basin areas from Sunday morning
  through evening.

- Warming and drying trend Monday through Friday with
  temperatures rebounding into the 70s-80s by the end of the
  week.

&&

.SYNOPSIS...
Rain will begin moving in late Saturday night from the southwest,
then will spread through the entire region by early Sunday morning.
These widespread rain chances persist through the day Sunday,
accompanied by isolated thunderstorm chances, hydrology concerns,
and gusty winds. Conditions trend warmer Monday through Friday as a
ridge of high pressure builds over the Inland Northwest.

&&

.DISCUSSION...
Sunday through Monday morning: A strong low pressure system is
starting to move inland, with the center of the low crossing over
the Washington/Oregon border. The main frontal passage looks to take
place Sunday morning, and will bring widespread rains to the Inland
Northwest. There are high chances (70 percent and above) for the
entire forecast area to see at least 0.5 inches of rain. The
heaviest rainfall looks to be in the Cascades and Wenatchee to the
Spokane area and northward, alongside the northern Idaho Panhandle.
While mid and long range models were initially struggling with
precipitation totals due to the track and speed of the low,
uncertainty has decreased somewhat now that high-res models can
capture the event. There is still a good amount of spread in
precipitation totals, with differences of up to a quarter inch
between the 25th and 75th percentiles through the areas that are due
to see the highest rain totals. The bottom line, though, is that the
majority of the Pacific Northwest will receive 0.5 inches of rain or
more through Sunday afternoon.

With the highest rainfall totals expected across much of central,
north-central, east-central, and northeast Washington, hydrologic
concerns will increase through the morning and afternoon. Hourly
rainfall rates through these areas are projected to reach 0.2 to 0.3
inches, particularly in the morning hours. Excessive runoff from
these rains could bring a chance for debris and ash flows over burn
scars in steep terrain, alongside rockslides. Additionally, urban
areas with poor drainage could see minor flooding, and storm drains
and ditches may become clogged with debris. For these areas, a Flood
Watch has been issued from 1 AM Sunday through 8 PM Sunday. A more
focused Flash Flood Watch has also been issued for the Old Trails
and Autumn Lane burn scars in Spokane County from 2 AM through 4 PM
Sunday due to these elevated rainfall rates. Make sure to keep an
eye on the weather and have ways to receive additional alerts should
they be necessary.

Alongside this rainfall, chances for isolated thunderstorms increase
as the low moves through. There is a 10 to 20 percent chance of
thunderstorms as the frontal system moves northward through the day.
For the early part of Sunday, the thunderstorm threat is in the
southern portion of the forecast area. For Sunday afternoon and
evening, the threat is for the northern portion of the forecast
area. Models show CAPE values around 200-400 J/kg, alongside 3-6km
lapse rates of 7-8 degC/km. With multiple soundings showing very
saturated mid and low level relative humidities (80 percent and
above), as well as PWATs 0.5 inches and above, the main risk with
these thunderstorms will be isolated heavy rainfall rates that could
contribute to debris flows or flooding.

Gusty winds will accompany this rainfall as a north-south pressure
gradient tightens across the northern part of Washington. Wind gusts
throughout the Waterville Plateau, basin, and Okanogan Valley are
already gusty ahead of the frontal passage with wind gusts 20-25 mph
expected through the morning. Wind gusts in the basin will increase
to 25-30 mph later in the morning with the frontal passage, and will
relax by Sunday evening. As flow turns westerly after the front has
passed, an east-west gradient will set up along the Cascades,
bringing gusty winds to the Cascades, northern mountains, and Idaho
Panhandle mountains through Monday morning.

Monday afternoon through Wednesday: As the low moves out of the
area, broad northwest flow will prevail as heights rise downstream
of a strong ridge along the Alaskan coast. This will result in
temperatures starting to warm. On Tuesday, another weaker low moves
through the area, which will result in light rainfall and isolated
thunderstorm chances in the northern mountains and in the
northern ID Panhandle. Elsewhere, expect dry and warming
conditions.

Wednesday through Saturday: By Wednesday, 90 percent of clusters
show high pressure strengthening over the area and persisting
through the weekend, resulting in a warming and drying trend.
Temperatures will increase back into the mid-70s by Thursday, which
is a few degrees higher than normal for this time of year. Long
range guidance indicates temperatures reaching 80 throughout the
basin by next weekend, showing increasing confidence in a drying and
warming pattern following the active weekend. /AS

&&

.AVIATION...
06Z TAFS: Rain is spreading into the region from the south with
the arrival of a robust low pressure system. The air mass will
moisten with 50-70% chance for MVFR ceilings to develop. Rain
intensities for KGEG-KSFF-KCOE-KEAT will have a 50% chance or
greater to become moderate at times which has potential to drive
down visibilities. Steady rain will linger over KEAT-KOMK
through much of the day but a dry slot moving into Ern WA and N
ID will deliver breaks in the precipitaiton. Sunshine in the
afternoon will bring a 10-20% chance for convective cells and
thunderstorms. Greatest risk will be around KLWS-KPUW and 10-15%
chance KGEG-KSFF-COE. Probabilities were too low to include in
the TAF issuance at this time. As the system tracks east Sunday
evening, rain will taper off in Central WA and increase near the
ID/WA border. Favorable winds will increase the risk for
lowering cigs again with 60% chance or greater for MVFR
conditions. Winds will be gusty at times 06-11z KEAT-KMWH-KLWS
and through much of the TAF period at KPUW-KGEG. Marginal LLWS
for KGEG-KCOE-KSFF 06-10z with a brief 30kt easterly jet around
2000 ft AGL.


FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence
for rain at all terminals. Lower confidence for precise hours of
moderate rain and how this will impact visibilities. Confidence
also low for thunderstorm to move over terminals in the
afternoon but any storms could enhance wind gusts toward 40 mph
and briefly lower vis/cigs. Moderate to high confidence for rain
to increase again along the ID/WA border in the evening.


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

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        58  45  66  45  66  45 / 100  60   0   0  10  10
Coeur d`Alene  57  45  63  44  65  44 / 100  90  20   0  10  10
Pullman        58  47  64  41  66  41 /  90  90   0   0   0  10
Lewiston       66  48  72  49  72  50 /  90  70   0   0   0  10
Colville       59  46  66  39  68  38 / 100  70   0  10  30  10
Sandpoint      55  46  59  41  62  41 / 100  90  40   0  10  10
Kellogg        54  43  59  44  64  45 / 100 100  50   0   0  10
Moses Lake     59  44  69  44  69  44 /  80  50   0   0   0  10
Wenatchee      61  49  69  52  69  53 / 100  20   0   0  20  10
Omak           63  47  71  49  69  47 / 100  50   0  10  40  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch through this evening for Central Chelan County-
     Moses Lake Area-Northeast Mountains-Okanogan Highlands-
     Okanogan Valley-Upper Columbia Basin-Waterville Plateau-
     Wenatchee Area-Western Chelan County-Western Okanogan
     County.
     Flash Flood Watch through this afternoon for Spokane Area.
ID...None.

&&

$$