Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 170957
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
257 AM PDT Wed Aug 17 2022

.SYNOPSIS...
Temperatures today through Friday will climb well into the 90s
and triple digits. The forecast for the weekend into early next
week should be a few degrees cooler with afternoon temperatures in
the 90s.

&&

.DISCUSSION...

...EXCESSIVE HEAT WARNINGS AND HEAT ADVISORIES ARE IN EFFECT
WEDNESDAY THROUGH FRIDAY EVENING FOR CENTRAL AND EASTERN
WASHINGTON AND PARTS OF THE IDAHO PANHANDLE...

Today: Our next round of temperatures in the upper 90s and triple
digits begins this afternoon and will likely persist into Friday.
As of 2 AM, readings are generally 3 to 8 degrees above where they
were 24 hours ago and indication of warming under an increasingly
strong high pressure ridge. With the axis of the high pressure
ridge squarely over Washington, Oregon, and Idaho today, skies
will be mainly clear through the day and into the overnight. With
plenty of sunshine, there is very little spread in the ensemble
temperature output. In other words, we are confident that most
locations will be within a couple degrees of the forecast. As we
get into Friday and the uncertainty of cloud cover and rain
showers will complicate high temperatures.

Thursday and Friday: Thursday continues to look like the hottest
day of this heatwave. As this upper ridge axis migrates east of
the Cascade crest, 850mb temperatures will likely reach 28C to
29C. We will be watching increasing clouds spreading toward our
region from Oregon during the afternoon on Thursday. As mentioned
in previous discussions, it looks like the arrival of clouds will
be late enough in the day to not hinder heating. Some records on
Thursday look to be out of reach. Records like Lewiston`s 111
degree record set in 1940 and Pullman`s 101 set in 1903 should be
safe. But other records like Omak and Wenatchee at 104 will be
threatened. National Blend of Model probabilities give Spokane a
36 percent chance of tying the 1967 record of 101 degrees at the
airport.

A small chance of afternoon and evening thunderstorms has been
retained for the northern and central Washington Cascades
Thursday. NAM surface dewpoints and CAPE values are running
significantly higher than values from the GFS and ECMWF. High
values from the NAM are probably driving SREF probabilities for
thunderstorms, but a few convective cells capable of generating
lightning can`t be ruled out across the high terrain around
Leavenworth, Lake Chelan, and the upper Methow Valley. The influx
of mid-level moisture overnight Thursday will likely keep
temperatures quite warm. Lows in the 70s will be common across
central Washington and the L-C Valley. Downtown Spokane may also
remain above 70. Folks without air conditioning will struggle to
cool their homes Thursday night during an unusually warm night.

The potential for clouds and light rain showers on Friday will
complicate the high temperature forecast. The operational ECMWF
forecasts 850mb temperatures Friday afternoon to be similar to
Thursday. If this solution verifies, and there are frequent breaks
in the clouds we can expect another afternoon of widespread upper
90s and triple digit temps. However, other models including the
GFS and NAM generate a good deal more cloudiness and suggest
Friday will be 3 to 5 degrees cooler than Thursday. /GKoch

Saturday through Tuesday: Lots of uncertainty in the forecast for
this period. Ensembles continue to be split on if a low will
strengthen as it moves onto the Pacific coast early Saturday. The
ridge appears to break down but depending on how deep of a low
forms, could change our current forecast (meaning we could see
cooler temperatures than forecasted). Normals for this time of year
are in the mid 80s.

Models continue to bring an offshore low into the PacNW Sunday into
Monday , which would continue to keep temperatures slightly above
normals but cooler. This could also bring a chance of showers and
thunderstorms in the Idaho Panhandle but this remains at a slight
chance due to the uncertainty in the low.

Looking farther out into the middle of next week, models are
building another ridge over the west coast which could yet again,
heat daytime temperatures back up well above normal. Enjoy the brief
cool-off because it looks like we will warm back up for at least a
couple days. /KM

&&

.AVIATION...
06Z TAFs: VFR conditions will continue through Wednesday, with
mainly light diurnally driven winds. The exception could be
slightly stronger winds draining through the COE area in the
morning. Smoke from area wildfires should largely stay aloft
and/or away from TAF sites. A potential exception will be near EAT
as some Cascade wildfire smoke could bring brief MVFR conditions.
However confidence is low. /Cote`


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        98  63  99  69  97  65 /   0   0   0   0  10  10
Coeur d`Alene  97  61  98  66  96  63 /   0   0   0  10   0  10
Pullman        96  59  96  63  93  59 /   0   0   0   0  10  10
Lewiston      103  68 103  73 100  70 /   0   0   0   0  10  10
Colville       98  55 101  60  97  56 /   0   0   0   0   0  10
Sandpoint      93  58  96  61  93  59 /   0   0   0   0   0  10
Kellogg        94  67  96  69  93  67 /   0   0   0  10   0  10
Moses Lake    102  65 103  69 100  63 /   0   0   0   0  10  10
Wenatchee     101  74 103  76  99  69 /   0   0   0   0  10  10
Omak          103  67 105  71 101  66 /   0   0   0   0  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Heat Advisory from noon today to 11 PM PDT Friday for Coeur
     d`Alene Area-Idaho Palouse-Lewis and Southern Nez Perce
     Counties-Lewiston Area-Northern Panhandle.

WA...Excessive Heat Warning from noon today to 11 PM PDT Friday for
     Central Chelan County-Moses Lake Area-Okanogan Valley-Upper
     Columbia Basin-Waterville Plateau-Wenatchee Area.

     Heat Advisory from noon today to 11 PM PDT Friday for Lower
     Garfield and Asotin Counties-Northeast Blue Mountains-
     Northeast Mountains-Okanogan Highlands-Spokane Area-
     Washington Palouse-Western Chelan County-Western Okanogan
     County.

     Red Flag Warning from 11 AM this morning to 10 PM PDT Thursday
     for East Washington Central Cascades (Zone 696).


&&

$$


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