Lewiston, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

219
FXUS66 KOTX 251737
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1037 AM PDT Sat Apr 25 2026

.KEY MESSAGES...

- Chilly overnight temperatures with sensitive vegetation
susceptible to frost and freeze damage through this weekend.

&&

.SYNOPSIS...
Aside from a few mountain showers, dry conditions and partly cloudy
skies will prevail through the weekend. Temperatures will be chilly
at night with frost expected across much of the region over the
weekend. Temperatures then start to slowly moderate into next week.
Weak weather disturbances will early next week will bring scattered
showers primarily over extreme eastern Washington and the Idaho
Panhandle Monday into Tuesday. Warmer and dry through the remainder
of the work week.

&&

.DISCUSSION...
Today through Wednesday night: A deep upper level low pressure
system will remain over central Canada this weekend. The low
begins to shift northeast towards the Arctic region early next
week, but the western to central U.S. will continue to be
influenced by a broader area of a trough that this low resides
in. A continuation of a flux of drier air out of British
Columbia today will limit precipitation to the mountains over
the Idaho Panhandle. These showers will be very weak and little
accumulation is expected. Much of the this drier air will come
with northerly winds down the Okanogan Valley. The northerly
push will be weaker today compared to the previous couple of
days. Winds down the Okanogan Valley are expected to gust up to
around 20 mph primarily for the morning to early afternoon
hours.

A weak shortwave disturbance rotating around the upper level
low over Canada will brush across the Idaho Panhandle on Sunday.
This disturbance interacts with a little bit more moisture that
advects in off of the Pacific. There will be an increased
chance of up to around 30% for showers in the Idaho Panhandle
for Sunday afternoon. Diurnal heating will destabilize the
atmosphere slightly; enough for convective showers, but CAPE
values barely up to 100-200 J/kg doesn`t look to be enough for
much in the way of deeper convection to produce thunderstorms.

Chances for showers increase a bit more Monday into Tuesday.
The primary reason for the increase up to 40-50% chance is due
to an increase in moisture. Moisture increase will be modest
with P-Wats increase from a very dry 0.25 inches on Friday up to
around 0.50 inches for Monday and Tuesday. Additional weak
disturbances in the north to northwest flow pattern will help to
generate showers, but forcing will continue to be dominated by
buoyancy from differential heating. As such, the mountains
during peak heating hours will see the better chance for
showers. Instability parameters over southeast Washington into
the Idaho Panhandle will be a bit more favorable for at least
isolated thunderstorms with surface based CAPE up to 200-400
J/kg and equilibrium levels up to 18 kft. This is very low end
for thunderstorms, but at least a small threat.

We also see a return of a westerly push of winds through the
Cascades on Monday. The operational 00Z GFS run is on the higher
end of wind gusts through the Cascade gaps with the potential
for 20-25 mph gusts through the Wenatchee River Valley. Other
model guidance doesn`t indicate as strong of a westerly push
though. It`s a sign of a reversal of winds at the very least
form easterly to westerly and bring back a maritime air mass
into the Northwest. Instability decreases Tuesday into Wednesday
as the upper level trough begins to pull away. Tuesday will see
more showers over the same areas as Monday (generally the
eastern half of the forecast area), and Wednesday will see even
less in the way of shower activity primary just over the Idaho
Panhandle.

Temperatures will be chilly again tonight and similar to Friday
night into Saturday morning. Additional frost/freeze messaging
may be needed for the Wenatchee Area, Moses Lake Area, and the
Lewiston-Clarkston Valley. How cold temperatures get for
Saturday morning will give us a good idea of the potential for
temperatures to cool off Sunday morning. Increased moisture into
the region for Monday into Wednesday will moderate the
overnight lows a bit, but we will continue to see freezing
temperatures over at least the colder northern mountain valleys.

Thursday through Saturday: A ridge of high pressure builds in
for the end of the week. Subsidence will increase under the
ridge with dryer weather in store. Temperatures will also see a
warming trend with highs increasing from the 50s and 60s at the
beginning of the week into the 70s at the end of the week. Model
ensembles hint at the potential for a disturbance to push
through the ridge around Saturday, but very little confidence in
this. If anything, it looks like any energy that moves through
would be rather weak. /SVH

&&

.AVIATION...
18Z TAFS: VFR conditions expected. A northerly flow on the
backside of a low will continue to promote some cloud
development through the afternoon, with spotty shower chances
mainly near the mountains. These dissipate with the loss of
heating of the day. Otherwise look for variable cloud cover.
Winds will be breezy down the Okanogan Valley, near KOMK, with
gusts of 15-25kts possible. Winds elsewhere will generally be
less than 10kts.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
High confidence for VFR conditions.

-----------------------
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        55  31  57  33  60  39 /   0   0  20   0  10  10
Coeur d`Alene  55  30  55  33  57  38 /   0   0  30  10  20  10
Pullman        53  30  55  32  57  38 /   0   0  10  10  20  10
Lewiston       58  35  60  37  61  41 /   0   0  10   0  20  10
Colville       59  28  59  28  62  36 /  10   0  20  10  10  10
Sandpoint      53  30  52  32  55  38 /  10  10  50  10  20  20
Kellogg        53  30  53  32  55  38 /  20  10  60  20  40  20
Moses Lake     61  31  65  36  67  41 /   0   0   0  10   0   0
Wenatchee      60  37  64  40  67  45 /   0   0  10  10   0   0
Omak           62  34  63  35  66  42 /   0   0   0   0  10   0

&&

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

&&

$$