Lewiston, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

457
FXUS66 KOTX 072132
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
232 PM PDT Sun Jun 7 2026

.KEY MESSAGES...

- Frost expected across the Northern Valley`s tonight into Monday
  morning.

- Rain moves in Monday night with an 80% chance of at least a
  tenth of an inch over much of extreme eastern Washington and
  into the Idaho Panhandle. Precipitation turns showery on
  Tuesday with a 10- 30% chance for thunderstorms.

- Trending drier Wednesday into next weekend with high
  confidence for above normal temperatures by Friday. There is
  a 30-50% chance for temperatures in the upper 80s to low 90s
  by next Sunday and widespread minor to moderate HeatRisk.

&&

.SYNOPSIS...
Showers with isolated thunderstorms will dissipate late this evening
with clearing skies. This will set up an additional night of frost
for the northern valley locations. A wetter storm system widespread
rain moves in across the region Monday evening into Tuesday morning.
Breezy with showers Tuesday afternoon with the threat for isolated
thunderstorms. The rest of the week will be drier with warming
temperatures. Widespread 80s to low 90s for highs by the weekend.

&&

.DISCUSSION...

Rest of this afternoon through Monday morning: The Inland Northwest
is on the back edge of an upper level low pressure system with a
cold pool of -25 Celsius extending across the eastern half of the
forecast area. Diurnally forced showers will continue into the early
evening hours. These showers are expected to die off quicker that
yesterday as warmer air moving in ahead of a warm front will erode
the cold pool over the region and have a stabilizing effect on
the atmosphere. Before this happens however, I do expect
isolated thunderstorms to pop up where we have roughly 100-300
J/kg of skinny CAPE across the Northeast Mountains into North
Idaho and along the Panhandle/Montana border. Thunderstorms will
be relatively weak and pulse type growing just enough to spit
out a lightning strike or two before collapsing. Convection will
wane between 8-10pm with skies clearing out rather effectively
and this will set up the potential for another chilly night
across the northern mountain valleys. Dew points will be in the
lower 30s and may drop below 30 for some colder pockets with as
moisture frosts out of the atmosphere. I see a better potential
for frost for the Methow Valley, around Republic, Deer Park,
Springdale, Chewelah, Colville, Priest River, Metalline Falls
and other cold pockets in this part of the region and have
issued a frost advisory that is in effect for tonight through
early Monday morning. Make sure to cover sensitive vegetation or
bring them indoors to protect from frost damage.

Monday through Wednesday night: The next weather maker is already
walking up to the doorstep. An upper level low pressure system
spinning in the Gulf of Alaska will direct a robust P-Wat plume
of 1.0-1.5 inches into the west coast. This moisture plume is
taking shape across the North Pacific between 40-50N latitude
riding a 140 mph jet streak at 250 mb. Moist isentropic ascent
with the warm front will increase across the region from late
afternoon on Monday into Monday evening. All areas will see the
potential for wetting rains as our typical rain shadow areas in
the lee of the Cascades will be absent with southerly to
southeasterly flow will actually result in favorable upslope
across the east slopes of the Cascades. There is an 80% chance
for wetting rains (at least a tenth of an inch) over the
Columbia Basin into the Wenatchee Area, and near 100% chance
everywhere else. There is pretty good agreement among the ECMWF
Ensemble and GEFS members for a surface low to track into
southwest Washington Monday evening and then into north-central
Washington around midnight. The low fills in pretty quickly as
it tracks inland, but this track is favorable for southerly flow
across the Columbia Basin with the northern mountains across
eastern Washington likely to do well with ringing out moisture,
and then than trend continue across extreme eastern Washington
into the Idaho Panhandle as the trailing cold front tracks
across during the overnight into early morning hours on Tuesday.
The Northeast Mountains and Idaho Panhandle will see a 90% and
higher chance for receiving over a quarter of an inch of
precipitation. Those probabilities are a little less into the
Spokane Area and Palouse at 70-90% chance; for over a half of an
inch of precipitation, there`s a 60-75% chance and 30-40%
chance respectively, and the North Idaho has a 10% chance for
seeing at least an inch of precipitation. Snow levels do drop
down to around 6,000 feet by early Tuesday morning over the
Cascades with light wet snow expected at the highest peaks;
otherwise, it will be rain everywhere else. There will be some
pockets of more moderate rainfall especially as the cold front
pushes through and creeks and small streams will see rises, but
rain will overall be a beneficial sight for an area experiencing
drought conditions. This storm system will be the last
significant rain that many areas will experience for some time
and we could use it as our climatologically driest time of the
year, a.k.a summer is coming up.

We transition to showery precipitation in the afternoon on Tuesday
and the morning rainfall will prime the pumps for convection with
just a little bit of diurnal heating. The atmosphere will become
conditionally unstable with a modest cold pool of -21 degrees
Celsius at 500 mb. Thunderstorms are expected to begin developing
pretty early in the day across much of the region, but higher
probabilities in the 20-30 percent chance being across the Palouse,
Spokane Area, Okanogan Highlands, Northeast Mountains, and the Idaho
Panhandle. Thunderstorms will be pulse type storms featuring
occasional lightning, heavy downpours, and brief small hail.
Pressure gradients will tighten as well with breezy westerly winds
for the afternoon. Winds will be strongest across central Washington
in the lee of the Cascades from Wenatchee/Chelan into the western
Columbia Basin with gusts up to 30-40 mph expected. Locally stronger
wind gusts with a 20-40% chance of seeing gusts up to 45-50 mph
will be possible in the lee of the Cascades around Chelan,
Wenatchee, and the Waterville Plateau.

Cloud cover remains over extreme eastern Washington into the Idaho
Panhandle on Wednesday with just some lingering showers and
winds remaining a little breezy. Temperatures will be below
normal through Wednesday, but that will quickly change heading
through the latter half of the week.

Thursday through Sunday: There is good consensus from the model
ensembles for a ridge of high pressure to be pumped up over the
eastern Pacific Ocean. This means high confidence in the far
extended portion of the forecast for temperatures warming above
normal. Some uncertainty remains with where the ridge axis will set
up and this will play a part in how warm we get. There is a 30%
chance for moderate HeatRisk to be a factor by next weekend though
with a 30-50% chance for widespread 90 degree temperatures by next
Sunday into the beginning of the following week for the Columbia
Basin, in the Lewiston- Clarkston Valley, at Wenatchee, and in the
Okanogan Valley. /SVH

&&

.AVIATION...
18Z TAFs: The Inland Northwest will be on the back edge of a
cold upper level trough of lower pressure today. There will be
enough instability across far northeast WA and north Idaho to
support a 15-20% chance of lightning. Showers with towering
cumulus will be spotty around KGEG, KSFF, KCOE with the better
chances and a 30% probability of a passing showers impacting
KCOE this afternoon. Lightning activity is expected to remain
north and east of the Spokane/Coeur d`Alene corridor. Breezy
west-southwest winds into the afternoon with gusts 20 to 25
kts, then decline after 02-04Z.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
High confidence VFR conditions at all TAF sites. Low confidence
in shower or thunderstorm developing over a given TAF site. /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:/www.weather.gov/otx/avndashboard

&&

.Preliminary Point Temps/PoPs...
Spokane        41  71  47  64  43  65 /   0   0  90  90  40   0
Coeur d`Alene  41  70  49  59  44  62 /   0   0  80 100  70  10
Pullman        39  69  45  59  41  60 /   0   0  90 100  50  10
Lewiston       45  76  53  68  48  69 /   0   0  80  90  40   0
Colville       35  71  41  64  36  68 /   0   0  80 100  80  20
Sandpoint      39  68  46  57  42  61 /   0   0  70 100  90  30
Kellogg        39  71  48  57  43  58 /   0   0  60 100  90  50
Moses Lake     41  72  45  71  41  73 /   0  20  90  40   0   0
Wenatchee      48  69  52  68  49  71 /   0  30  90  20   0   0
Omak           40  72  48  70  42  73 /   0   0  90  80  10   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
WA...Frost Advisory from midnight tonight to 8 AM PDT Monday for
     Northeast Mountains-Okanogan Highlands-Western Okanogan
     County.
ID...Frost Advisory from midnight tonight to 8 AM PDT Monday for
     Northern Panhandle.

&&

$$