Wildfire in Idaho, August 18 to 31, 2022

Area Forecast Discussion
National Weather Service Spokane WA
252 AM PDT Thu Aug 18 2022

.SYNOPSIS...
Most of central and eastern Washington will climb into the triple
digits this afternoon. Some places like Omak and Ephrata will have
a good shot of setting record highs today. Friday through the
weekend will remain quite hot with widespread 90s. Monday and
Tuesday will feature the chance for showers and thunderstorms.
Temperatures for the second half of next week are expected to be
well into the 90s which is quite a bit above average.

&&

.DISCUSSION...

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

Today: This afternoon will feature the hottest temperatures of
the week across the Inland Northwest. Our hot dome of high
pressure will be firmly planted over Idaho and eastern Washington.
Temperatures aloft will be a degree or two warmer than yesterday
with 850mb temperatures expected to be between 27C and 29C.
Without much significant cloud cover anticipated until mid to late
afternoon, highs will climb into the mid to upper 90s across the
northern and central Idaho Panhandle. Look for widespread triple
digits for the majority of central and eastern Washington. If our
forecast of 106 for Omak verifies, it will break the 2020 record
of 104. Our forecast for Ephrata of 105 also breaks the 1977
record of 104. Spokane (record of 101), Wenatchee (record of 104),
and Pullman (record of 101) will be within a degree or two of
records as well. By the afternoon our most significant increase in
cloud cover is expected over central Washington up the spine of
the Cascades. The influx of mid-level moisture is sufficient to
retain a 20 percent chance of showers for the high terrain around
Leavenworth, upper Lake Chelan, and the upper Methow Valley late
this afternoon into the evening. Instability appears to be
marginal for lightning, but a small chance of thunderstorms has
been retained as well for the northern and central Cascades.
Increasing clouds region-wide tonight will keep overnight lows
quite warm with much of central Washington warmer than 70 degrees
for an overnight low.

Friday and Saturday: Temperatures will slowly trend down Friday
and Saturday as a weak upper trough gradually makes a dent in our
formidable hot ridge. Friday will feature more clouds ahead of the
incoming trough. The amount of cloud cover for Friday and how much
clouds will influence our temperature is a very tricky forecast.
In general, we have taken up to a couple degrees off the National
Blend guidance, and it is possible that readings could end up
being a couple more degrees cooler in places. At this time,
chances for showers and thunderstorms has been limited to areas
around Wenatchee, Leavenworth, Chelan, Omak, and the Methow Valley
Friday afternoon into the night, but a light shower or sprinkles
could occur about anywhere in the Inland Northwest on Friday. Some
runs of the NAM and GFS over the last day or two have drawn a
weak shortwave over eastern Oregon into the Idaho Panhandle. By
Saturday, our hot ridge will be displaced far enough into Montana
that Pacific air will begin to bleed east of the Cascades.
Saturday will still be 10 degrees or more above average, but low
to mid 90s will be noticeably less hot. /GKoch

Sunday through Thursday: This is why we encourage folks to check
the forecast each day; because forecasts change. After the
potential showers for the first half of the weekend, Sunday looks
much drier, and actually warmer than Saturday by a few degrees.
Can't entirely rule out a stray mountain shower in the afternoon,
but not enough evidence to include it in the forecast. But things
start to possibly unravel after that. The computer models are
coming into agreement on a potential Pacific wave that will move
onshore Monday. This wave is currently way out at 155W and we're
talking 4-5 days out, so there's still lots of time for the
forecast to continue to change. But suffice to say, the potential
is there for a decent event early next week, so keep an eye on the
forecast over the coming days.

At this point, a Pacific wave would impact a still rather hot and
unstable atmosphere, along with about 1" of precipitable water.
This set up could bring any number of impacts starting Sunday
night. Lightning could be bad for potential numerous fire starts.
But the moisture content of the atmosphere may be wet enough to
mitigate the fire aspect. If it's wet enough, we could be looking
at potential hydrology concerns from wet thunderstorms. And if
things are just right with timing and intensity, severe
thunderstorms (hail and wind) aren't out of the question either.

The forecast gets a little more strange as we move into the middle
of the week. Instead of the Pacific low moving on through our
area, it stalls over the Inland NW for Tuesday and Wednesday. The
deterministic models all agree on this. The ensemble means are
going to naturally wash out this detail, but they also agree on
troughing rather than ridging. Granted, the 500mb heights are
still above normal, so it will still be warmer than normal. But if
these model forecasts verify, we could see afternoon/evening
mountain thunderstorms each day.  RJ

&&

.AVIATION...
06Z TAFs: VFR conditions are expected to prevail for the next 24
hours as strong high pressure lingers over the aviation area. An
exception will be some smoke and haze from local and regional
fires. Winds will generally be light and diurnally driven through
Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane       100  69  97  66  93  63 /   0   0   0  10  10  10
Coeur d'Alene  99  65  95  63  92  60 /   0   0   0  10  10  10
Pullman        99  64  94  60  90  57 /   0   0   0  10  10   0
Lewiston      106  72 100  71  97  68 /   0   0   0  10  10  10
Colville      102  62  98  58  94  54 /   0   0   0  10  10  10
Sandpoint      95  61  94  61  89  58 /   0   0   0  10  10  10
Kellogg        96  67  94  68  89  65 /   0   0   0  10  10  10
Moses Lake    105  70 100  64  96  60 /   0   0  10  10   0   0
Wenatchee     103  75  97  69  95  66 /  10  10  10  20  10   0
Omak          106  74 100  67  98  65 /  10  10  10  20  20  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Heat Advisory until 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 until 11 PM PDT Friday for Central Chelan
     County-Moses Lake Area-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

     Heat Advisory until 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 until 10 PM PDT this evening for East
     Washington Central Cascades (Zone 696).

&&