Diamond, Washington Weather Forecast Discussion

632
FXUS66 KOTX 020804
AFDOTX
Area Forecast Discussion
National Weather Service Spokane WA
104 AM PDT Thu Oct 2 2025
.KEY MESSAGES...
- Unsettled weather pattern through Thursday with breezy
  south/southwest winds and multiple chances for showers.
- Dry with chilly overnight lows falling into the 30s by Sunday
  and continuing into early next week.
&&
.SYNOPSIS...
A cooler and wetter pattern persists today with showers and
isolated afternoon thunderstorms over the Idaho Panhandle.
Drier conditions expected over the weekend into early next week
with chilly overnight lows and areas of frost.
&&
.DISCUSSION...
Today through Sunday: A trough of low pressure will move in across
the western U.S. over the next couple of days. The trough axis today
will remain just offshore and there is a shortwave disturbance that
will round the trough and push up across extreme eastern Washington
into the Idaho Panhandle for the late morning and afternoon hours.
Dynamics with this shortwave will be rather weak with scattered
showers expected. Diurnal heating will also result in weak surface
based instability from the Blue Mountains into the southern to
central Idaho Panhandle where isolated thunderstorms are expected in
the afternoon.
By Friday, the trough axis will be shifting through the Inland
Northwest. Drier air will begin to get introduced into the area and
this will decrease chance for showers. A closed low pressure
circulation also looks to form over California into western Nevada.
Moisture that rounds this low will stream northward across Idaho,
but drier air moving in from the north looks to counter any moisture
trying to nudge in across the southeast portion of the region. The
added moisture from rain that fell yesterday evening will
result in fog forming in the mountain valleys. Fog in these same
mountain valleys of northern Washington and the Idaho Panhandle
will continue to be possible overnight Friday and Saturday.
Model guidance also shows a shortwave trough of low pressure
diving south along BC Friday into Saturday. This will bring a 30
percent chance for showers in the Panhandle on Saturday, but
eastern Washington looks to remain dry. The disturbance will
however increase the northern gradient with an increase in drier
north winds down the Okanogan Valley and Purcell Trench.
Temperatures Sunday morning will drop into the lower 30s across
the northern mountain valleys. These temperatures will cool
even further for Sunday night into Monday morning where lows at
or below freezing will be more common across these northern
mountain valleys. Monday morning in particular looks to be quite
frosty across much of the region including cold pockets in the
northern Columbia Basin.
Sunday night through Friday: There is good agreement in the model
ensembles for a ridge of high pressure to build in over the region
early next week. This will result in temperatures rebounding a bit
with highs climbing back into the upper 60s to low 70s Monday
through Wednesday. Low temperatures will continue to be chilly
as a lack of cloud cover results in good radiational cooling.
Overnight temperatures will see moderation though later in the
week. Ensembles diverge considerably around the middle of next
week. The ECMWF ensemble shows a deep closed low pressure area
forming over the Northwest with snow levels dropping down to
around 4,500 feet over the Cascades. The GEFS on the other hand
continues to show weak ridging of higher pressure. The Canadian
ensemble favors the ECMWF. This could be our first appreciable
snowfall over the Cascade passes for Wednesday night into
Thursday morning. /SVH
&&
.AVIATION...
06Z TAFS: Rain showers will shift into the Idaho Panhandle into
the early morning hours Thursday. Decreasing mid to high level
clouds across eastern Washington with small dew point
depressions of 2-4 degrees will set up the potential for patchy
fog to form. KPUW-KGEG-KSFF-KCOE will see the potential for MVFR
to IFR conditions by 10-12Z overnight into Friday morning. Low
clouds are expected to lift between 15-17Z with a 30-60 percent
chance for additional showers developing into the afternoon.
Light winds are expected through Thursday.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
Moderate confidence for fog to develop at KGEG-KSFF-KCOE-KPUW
overnight. Fog development will depend largely on how much
higher level clouds dissipate overnight. /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        63  43  68  42  66  40 /  20  20   0   0   0  10
Coeur d`Alene  64  47  67  44  66  40 /  30  20   0   0   0  10
Pullman        63  43  61  40  61  36 /  30  30  10   0   0  10
Lewiston       68  53  68  49  67  44 /  30  40  10   0   0  10
Colville       63  33  69  32  66  30 /  20  10   0   0   0  10
Sandpoint      61  45  66  43  64  36 /  40  20   0   0  10  20
Kellogg        63  47  64  46  61  43 /  40  30  10   0  20  20
Moses Lake     64  41  69  43  70  41 /  20  10   0   0   0   0
Wenatchee      64  46  69  45  68  46 /  10  10   0   0   0   0
Omak           67  44  71  43  71  41 /   0   0   0   0   0   0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
WA...None.
ID...None.
&&
$$

NWS OTX Office Area Forecast Discussion