376
FXUS66 KOTX 061751
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1051 AM PDT Sat Jul 6 2024

.SYNOPSIS...
Weather conditions are expected to be hot and dry the next seven
days. Northerly winds will be breezy on Saturday, otherwise light
through next Tuesday. Next threat for increased winds will
be Wednesday next week.

&&

.DISCUSSION...

...SIGNIFICANT HEATWAVE TO IMPACT THE INLAND NW THIS WEEK...

Today through Friday: A significant heatwave is poised to impact the
Inland Northwest this week delivering widespread triple digit
heat. Confidence remains high in the upcoming forecast with very
little spread in the models. The upper-level ridge responsible for
the upcoming heat wave remains centered off the Western US Coast
but will make the trek inland beginning Sunday and remain anchored
overhead through midweek. Given its placement this morning, one
last shortwave is dropping down its eastern flank into Western MT
and skirting far North Idaho. This has resulted in some shower
activity in proximity of Bonners Ferry eastward into Troy, MT.
While no precipitation has been reported, breezy northerly winds
from the rain cool air are being felt in the northern Purcell
Trench. A few lightning strikes have also been observed in NW MT.

Much of the region will contend with light to locally breezy north to
northwest winds today in the wake of this system. The breeziest
winds will channel down the Okanogan Valley with speeds of 10-20
mph. The good news is these winds will peak before midday then
begin to weaken during the warmest and driest part of the day,
thus no fire weather highlights are anticipated. Another area that
will be breezy, especially in the afternoon will be far SE WA and
into the L-C Valley. The light gradient winds will align with the
typical diurnal winds of this direction resulting in speeds near
15 mph at times with gusts up to 25 mph. Temperatures today will
be within a degree of those experienced on Friday topping out in
the 90s for most communities; a few low 100s in the deep Basin and
upper 80s in the cooler northeastern valleys. The airmass will
remain very dry with afternoon RH values in the teens.

As the ridge migrates inland Sunday into early next week, increasing
subsidence will result in a net warming of the air mass with
850mb temperatures surging from 23C on Saturday to nearly 30C Tue-
Wed. This will equate to 3-4 degrees of warming each consecutive
day and widespread triple digit heat. Overnight lows will follow
suite and struggle to cool out of the 60-70s. This compounding
effect will result in moderate to major heatrisk with some areas
likely coping with extreme conditions. At this time, Tuesday and
Wednesday look to be the peak of the heat wave as for the hottest
temperatures however the reprieve will be dismal Thursday-Saturday
with temperatures only backing off into the 90s.

Please consider those vulnerable to the heat (elders, children, pets)
and check on them frequently. Be sure to take proper precautions
when working in the heat such as taking frequent breaks, staying
hydrated, and finding times to cool off in air condition when
applicable. The incoming heat will also result in increased fire
danger with dry fuels becoming extremely volatile to ignition.
Although winds will be light, the hot and unstable weather
conditions could allow for rapid fire spread, especially where
sloped terrain plays a role.

Current models are indicating the first blow to the upper-ridge coming
around Wednesday. If this comes to fruition, this will be the
first concern for increased winds and potential for critical fire
weather conditions. There is a lot of uncertainty on the magnitude
of these winds but any winds when it is 100 degrees with RH
values in the teens will be a major concern. Would not rule out
some local breeziness bleeding through the Cascade Gaps prior to
the more widespread breeziness. Once the ridge begins to flatten,
winds will become a more common nuisance for the Cascade Gaps and
when the next shortwave arrives, on a more widespread basis. Fire
danger indices will be on a new level following this incoming
heat wave.

At this time, there are little to no signs of precipitaiton throughout
the next week. There is a ghost of a chance for an isolated
t-storm to form in the higher terrain in the N Cascades SUN-MON
coming with a 5% chance. The next threat for any lightning would
be around the Blue Mountains WED-THU yet this only has support
from around 15% of a 100 member ensemble and remains out of the
forecast at this point.

The latest National Blend of Models gives Spokane International a 12%
chance for hitting 108F or warmer on WED. The current all time
record is 109F set back in the June 29th heatwave of 2021. /sb

&&

.AVIATION...
18Z TAFS: VFR conditions will prevail. Hazy conditions are
forecasted for the Lake Chelan and Waterville Plateau area and
onto portions of the Columbia Basin. Have mention of FEW200 for
hazy skies around MWH and EAT at times. Haze will not reduce
surface visibility and will remain elevated.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in
VFR conditions. Low confidence for localized visibility
reductions due to smoke.

-----------------------

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        92  62  97  65 100  66 /   0   0   0   0   0   0
Coeur d`Alene  89  61  92  64  96  66 /   0   0   0   0   0   0
Pullman        88  58  93  61  96  62 /   0   0   0   0   0   0
Lewiston       99  67 102  70 105  71 /   0   0   0   0   0   0
Colville       89  54  94  57  98  60 /   0   0   0   0   0   0
Sandpoint      88  56  91  57  95  61 /   0   0   0   0   0   0
Kellogg        84  62  89  65  92  68 /   0   0   0   0   0   0
Moses Lake     98  64 102  67 105  68 /   0   0   0   0   0   0
Wenatchee      99  69 102  71 105  74 /   0   0   0   0   0   0
Omak           99  65 102  68 105  70 /   0   0   0   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Heat Advisory from noon Sunday to 10 PM PDT Friday for Central
     Panhandle Mountains-Northern Panhandle.

     Excessive Heat Warning from noon today to 10 PM PDT Friday for
     Coeur d`Alene Area-Idaho Palouse-Lewis and Southern Nez
     Perce Counties-Lewiston Area.

WA...Heat Advisory from noon Sunday to 10 PM PDT Friday for Northeast
     Mountains-Okanogan Highlands.

     Excessive Heat Warning from noon today to 10 PM PDT Friday for
     Central Chelan County-Lower Garfield and Asotin Counties-
     Moses Lake Area-Northeast Blue Mountains-Okanogan Valley-
     Spokane Area-Upper Columbia Basin-Washington Palouse-
     Waterville Plateau-Wenatchee Area-Western Okanogan County.

     Heat Advisory from noon today to 10 PM PDT Friday for Western
     Chelan County.

&&

$$