Harrington, Washington Weather Forecast Discussion

335
FXUS66 KOTX 301147
AFDOTX
Area Forecast Discussion
National Weather Service Spokane WA
447 AM PDT Tue Sep 30 2025
.KEY MESSAGES...
- Areas of haze and smoke impacting air quality, especially in
  and near the east slopes of the Cascades.
- Unsettled weather pattern this week with multiple chances for
  showers.
&&
.SYNOPSIS...
A cooler and wetter pattern persists through the week with temperatures
near seasonal normals and multiple chances for showers. Recurring
breezy southerly winds through the workweek in the afternoon
and evening hours. Drier conditions is expected early next week.
&&
.DISCUSSION...
Today through Saturday night: A longwave trough of lower pressure
will remain over the western portion of the U.S. with a series of
shortwave disturbances keeping the weather unsettled. The first in
the series is moving through early this morning. Scattered showers
with light precipitation will continue through the morning primarily
over extreme eastern Washington and into the Idaho Panhandle.
The atmosphere looks to destabilize in the afternoon over far
southeast Washington into the southern Idaho Panhandle where
isolated thunderstorms will be possible. Otherwise, a bit breezy
into this afternoon with south to southwesterly winds and gusts
up to 20-30 mph particularly up the Okanogan Valley. The
backing wind profile with southerly winds will be in response to
the next shortwave that is set to push across Tuesday night.
This second shortwave disturbance will be very similar to the
one exiting this morning. It will bring widely scattered
showers, but rain accumulation will be light. The low pressure
trough will bring cooler temperatures cooling to the upper 60s
today, and then cooling further into the mid 60s by Wednesday.
The cooler temperatures will help slow down fire activity, and
specifically so with our large active fires in the Cascades.
Rain that we receive from showers won`t be very wetting though.
The atmosphere looks marginally more unstable for Wednesday
afternoon with a 20-25% chance for thunderstorms over northeast
Washington and in the Idaho Panhandle. Instability parameters
are rather paltry though with surface based CAPEs only up to
100-200 J/kg. This is enough for a couple of lightning strikes
from storm cells, but will likely quickly collapse with the lack
of instability.
The longwave trough will shift inland off of the eastern Pacific
Thursday into Friday. The Inland Northwest will be conditionally
unstable under the trough. There is uncertainty though with where
the best dynamics will track with the trough. Latest model
guidance off of the ensembles suggests that the bulk of the
dynamics will dive south into northern California. Drier air in
northerly flow on the back edge of the trough looks to move in
fairly quickly by Friday. Thursday will continue with showers,
especially with diurnal heating and over the more favored higher
topography. Chances for showers decrease into Friday. Although
temperatures will be cooler, they only cool to near normal for
early October. A shortwave disturbance looks to graze across
the northeast portion of the region on Saturday. This will bring
the potential for showers primarily for the Northeast Mountains
and in the Idaho Panhandle, but this comes with low confidence.
Sunday through Tuesday: Early next week looks to be a dry period
with temperatures rebounding with a ridge of high pressure nosing
into the region off of the eastern Pacific. Highs will warm above
normal with temperatures in the upper 60s to low 70s. This doesn`t
necessarily mean warmer temperatures overnight though. The
northerly flow will bring in drier air with dew points dropping
into the 20s to low 30s. Longer nights with clear skies should
result in effective radiational cooling and lows becoming chilly
in the values. This will be especially so in the sheltered
mountain valleys where multiple mornings of temperatures at or
near freezing is expected. Inversions will strengthen and the
fires in the Cascades may continue to be active and producing
smoke. An increase in prescribed fires east of the Cascades will
also be potential producers of smoke. This smoke may become
trapped under the inversion with more hazy to smokey skies
possible early next week. /SVH
&&
.AVIATION...
12Z TAFS: A shortwave trough of lower pressure will swing
through tonight with passing scattered showers. Most of these
showers will be shifting out of eastern Washington through the
morning on Tuesday. Covective showers will continue to pop up
into the afternoon near KPUW and KLWS. Ceilings will lower with
showers tonight, but not enough moisture to see low clouds
forming and VFR conditions prevailing. The passing disturbances
will bring increased southwesterly winds. Sporadic gusts up to
20 kts may come with showers tonight. The a bit breezy in the
afternoon Tuesday with gusts up to 15-20 kts across the Palouse
and Spokane Area. Southerly winds will be breezier up the
Okanogan Valley with gusts up to 20-25 kts at KOMK. Cooler
temperatures will subdue fire activity somewhat, but hazy skies
is expected to continue near the Cascades.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
Moderate to high confidence for VFR conditions. There is a
chance for ceilings to lower below 3,000 feet agl over northeast
Washington into the Idaho Panhandle with a 10-20% chance for
MVFR conditions at KGEG-KSFF and around a 30% chance at KCOE
Tuesday morning. /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:/weather.gov/otx/avndashboard
&&
.Preliminary Point Temps/PoPs...
Spokane        69  49  65  45  65  42 /  30  60  50  40  20  10
Coeur d`Alene  68  50  64  46  64  43 /  60  70  70  60  30  10
Pullman        67  46  64  43  62  40 /  60  60  60  60  20  10
Lewiston       72  55  71  51  68  49 /  70  40  50  70  30  10
Colville       68  39  64  35  63  31 /  50  60  80  50  50  20
Sandpoint      64  44  60  42  61  38 /  80  80  90  70  50  20
Kellogg        65  50  62  48  61  45 /  80  80  90  80  50  20
Moses Lake     71  49  67  43  67  39 /   0  30  30  10  20   0
Wenatchee      69  51  67  47  65  47 /  10  50  30  20  30  10
Omak           71  48  68  44  66  42 /  10  40  30  20  20  10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
WA...Air Quality Alert until 1 PM PDT this afternoon for Central
     Chelan County-Okanogan Valley-Waterville Plateau-
     Wenatchee Area-Western Chelan County.
ID...None.
&&
$$

NWS OTX Office Area Forecast Discussion