Area Forecast Discussion
Issued by NWS Spokane, WA

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443
FXUS66 KOTX 211006
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
306 AM PDT Sun Jul 21 2024

.SYNOPSIS...
Very hot temperatures continue through Monday, with widespread
triple digits value. A significant pattern change arrives Tuesday
with a dry cold front. Temperatures cool to near average values
by Thursday. Breezy winds and dry conditions each afternoon will
result in elevated fire weather concerns.

&&

.DISCUSSION...
Sunday through Monday: A high amplitude upper level ridge is
centered over northern Alberta as a closed upper level low slowly
inches toward the British Columbia coast. Resultant deep southerly
flow aloft has allowed elevated monsoonal moisture to stream
northward as a shortwave slides along western Oregon. Current
radar imagery shows scattered thunderstorms across western Oregon
early this morning. As the shortwave progresses northward into
Washington, elevated moisture and thunderstorm chances will
increase across central Washington this afternoon and evening.
Overall lift does not look very supportive of widespread
thunderstorms, but the elevated moisture combined with orographic
enhancement over the Cascades will bring a 10 to 15 percent chance
of isolated shower and thunderstorm activity. Any showers or
thunderstorms would increase the risk for lightning caused fires
and breezy outflow winds.

As the deep low approaches the British Columbia coast on Monday,
moisture and high level clouds will spread eastward into the rest
of eastern Washington and north Idaho ahead of an approaching
cold front. The threat for thunderstorms will also spread eastward
as this mid level moisture increases elevated instability.
Currently the best chances will be across the north Cascades, the
northeast mountains, and north Idaho with a 10 to 20 percent
chance.The return of strong onshore flow will tighten the cross-
Cascade pressure gradient with breezy winds through the Cascade
gaps and central Washington Monday evening. Winds look to pick up
around sunset on Monday as a cold front moves into western
Washington. Despite a slight increase in minimum relative
humidities on Monday, these winds will elevate fire weather
concerns.

With regard to temperatures, widespread triple digits are expected
across the Inland Northwest today. Widespread smoke and haze from
area wildfires may dampen high temperatures a couple degrees, but
it will still be very hot regardless with many spots forecasted to
break their daily high temperature record. The return to onshore
flow as the low moves onshore will slightly cool the air mass on
Monday, but it will still be very hot. Everyone who is exposed to
the heat is at risk for heat related illnesses. Please consider
canceling outdoor activities. Warm overnight low temperatures will
result in little to no relief overnight. If you have access to air
conditioning, use it, or find a location that does. Even a few
hours in a cool location can lower risk for illness. /vmt

Tuesday to Saturday: An long-wave upper trough gradually shifts
inland through this week to bring a relative cooling trend,
periodic breezy conditions which might sync up with some low RH
values to bring near critical fire weather conditions, and some
very limited shower chances. Tuesday and Wednesday continue to
see above normal temperatures, but a shortwave pivoting into the
region Wednesday will bring a few more cloud and some passing
shower chances. The main shower chances will be found near the
southeast periphery of the CWA and near the northeast mountains.
Some guidance (particularly the Canadian model) show broader
shower chances with this incoming wave, but 66% of the models
are drier. Still this will be monitored. Most of the convective
instability sits east/southeast of our region, so I don`t have any
thunderstorms in the forecast.

More notable on Wednesday and continuing into Thursday will be
increased winds. Speeds around 10-20 mph (with higher gusts of
25-40 mph) will be possible, particularly near the lee of the
Cascades across the Waterville Plateau to the West Plains of
Spokane county and the Palouse. Afternoon minimum RH values will
be near critical values, so this will be monitored for fire
weather concerns. However temperatures are forecast to cool
slightly below normal by Thursday. Friday continues to feature
slightly below normal readings, before warming closer to normal
Saturday. The forecast remains dry for the end of the week and bit
breezy, but not as breezy as Wednesday and Thursday. /Solveig

&&

.AVIATION...
12Z TAFS: An upper level ridge will allow VFR conditions to
continue through the period. The only exception will be some hazy
conditions from smoke near wildfires that may reduce visibilities.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: With the
exception of smoke near wildfires, confidence is high for
continued 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       104  69 100  63  93  60 /   0   0  10  10   0   0
Coeur d`Alene 102  68  98  62  91  59 /   0   0  10  10   0   0
Pullman       102  63  95  57  89  57 /   0   0  10   0   0   0
Lewiston      110  75 105  70  99  69 /   0   0  10  10   0   0
Colville      102  61  99  54  91  50 /   0   0  20  10   0   0
Sandpoint      99  65  96  59  90  52 /   0   0  20  10   0   0
Kellogg       100  72  98  66  91  65 /   0   0  20  10   0   0
Moses Lake    107  68 101  58  94  58 /   0  10   0   0   0   0
Wenatchee     105  74 101  64  95  64 /  10  10   0   0   0   0
Omak          107  73 106  64  98  61 /   0  10  10  10   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Excessive Heat Warning until 8 PM PDT Monday for Central
     Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-Lewis
     and Southern Nez Perce Counties-Lewiston Area-Northern
     Panhandle.

WA...Excessive Heat Warning until 8 PM PDT Monday for Central Chelan
     County-Lower Garfield and Asotin Counties-Moses Lake Area-
     Northeast Blue Mountains-Northeast Mountains-Okanogan
     Highlands-Okanogan Valley-Spokane Area-Upper Columbia Basin-
     Washington Palouse-Waterville Plateau-Wenatchee Area-
     Western Okanogan County.

     Red Flag Warning from noon today to 10 PM PDT this evening for
     East Portion of North Cascades National Park/Lake Chelan
     National Recreation Area (Zone 697)-East Washington Central
     Cascades (Zone 696)-East Washington North Cascades (Zone
     698)-Foothills of Central Washington Cascades (Zone 705)-
     Methow Valley (Zone 704).

     Heat Advisory until 8 PM PDT Monday for Western Chelan County.

&&

$$