512
FXUS66 KOTX 151135
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
435 AM PDT Sat Jun 15 2024

.SYNOPSIS...
Breezy to gusty winds along with isolated thunderstorms and rain
showers are expected Saturday afternoon and evening. Snow will be
possible down to 5000 feet. Temperatures will trend cooler into
early next week with the potential for frost in colder pockets
Sunday and Monday morning. Showers and thunderstorms, mainly in
the mountains will be possible each afternoon through midweek.

&&

.DISCUSSION...
Today through Sunday Night: Closed low over Vancouver Island will
track east across northern Washington and southern British
Columbia today. Cooling aloft associated with the low (500mb temps
dropping to near -28C), combined with afternoon heating will
destablize the atmosphere. Surface based CAPE increases to 200-400
J/KG over the region, except 400-700 J/KG over NE Washington into
the Idaho Panhandle where the best chances for thunderstorms will
be found. Another story for today will be the wind. A well mixed
atmosphere and cold air advection will promote breezy to windy
conditions regionwide, with the strongest gusts (30-40 MPH) found
across the Columbia Basin into the West Plains and Palouse.
Localized gusts to 45 MPH will be found in the windiest prone
areas include the Waterville Plateau and Alpowa Summit. Added
boost to the gusts will also be found near thunderstorms. Finally,
850mb temperatures drop to near 0C along the Cascade crest this
morning and near 2C in the Okanogan Highlands. This will support
snow levels near 4500 feet along the crest and 5500-6000 feet in
the Okanogan Highlands. This will support light snow over
Washington Pass, with a rain/snow mix at Stevens and Sherman
Passes. A persistent Puget Sound Convergence Zone will be aimed at
near Stevens Pass this afternoon and evening producing moderate
rain, with snow possibly mixing in at times.

For tonight models continue to advertise clearing skies and
decreasing winds for cooler temperatures. Areas of frost are
expected for the northern mountain valleys, and across the
Upper Columbia Basin, West Plains, and Palouse. There are a couple
wildcards though. Cloud cover associated with a deformation zone
could hold lows up near the Canadian border. And southwest winds
around the Upper Columbia Basin into the West Plains may not
completely decouple making it more difficult for temperatures to
drop into the mid 30s for frost formation. Frost advisories are in
place though given at least patchy frost is likely where winds
decouple and skies clear.

On Sunday another closed low develops over the region for hit and
miss showers. The cold advection comes to an end and pressure
gradients are much lighter equating to much less wind. High
temperatures will make into the 60s for most areas, although cloud
cover over the northern valleys and mountains from a deformation
area may mean temperatures don`t even get out of the 50s in some
spots such as Colville and Republic. JW

Monday through Friday: The Low from Sunday will continue to exit the
region through Monday. Ongoing shower activity is expected over
Northeast Washington and the Idaho Panhandle. Amounts are not
forecast to be more than an additional few hundredths. Weak
convection could bring an isolated lightning strike from these
showers. High for the day will be in the 60s to low 70s.

For the rest of the week, a broad trough will set up over Western
Conus. Weak waves of moisture periodically pass through the Pacific
Northwest bringing spotty showers chances to the Inland Northwest.
The best chances are generally over the mountains. Weak afternoon
convection from daytime heating has around a 20-30% chance of
generating an isolated thunderstorm. The pattern will allow
temperatures to moderate to near normals. Highs will start in the
70s and climb into the 80s and low 90s by the weekend. Overnight
lows will start in the 40s and climb into the upper 50s and 60s for
Friday night. /JDC

&&

.AVIATION...

12Z TAFS: Winds will increase this morning, with windy west-
southwest winds for all TAF sites today. Sustained winds of 15-23
kts, with gusts to 28-35 kts are forecast over the region. A low
pressure system moving into the area will also destablize the
atmosphere with increasing showers through the day. There is also
a 30-50% chance of thunderstorms over Northeast Washington into
the Idaho Panhandle, with a 10-20% chance across the Columbia
Basin down into the LC Valley and Palouse. KGEG/KSFF are on the
fringe of the highest probabilities for thunderstorms with not
enough confidence to include in a PROB30 group. Convection will
come to an end after sunset with loss of daytime heating, with
decreasing winds as well.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
There is high confidence in continued VFR conditions through 12z
Sunday at the TAF sites. Increased boundary layer moisture into
the Central Panhandle Mountains this morning due to rain showers
leads to a 60% chance of MVFR conditions around Kellogg (HREF
guidance) between 15-18z. JW

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

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        64  40  64  40  67  44 /  50  20  20  20  30  20
Coeur d`Alene  61  38  62  39  64  43 /  80  20  20  20  30  30
Pullman        60  36  60  38  61  40 /  50  20  20  20  30  20
Lewiston       71  44  70  46  70  48 /  30   0  20  20  30  20
Colville       62  32  58  34  67  37 /  90  40  50  30  50  30
Sandpoint      59  37  58  38  62  41 /  90  40  40  20  50  50
Kellogg        55  40  58  41  58  44 /  90  30  20  20  50  40
Moses Lake     69  40  68  44  73  45 /  10   0  20  20  10  10
Wenatchee      65  45  66  47  72  47 /  10  10  20  20  10   0
Omak           68  41  62  43  73  45 /  60  10  40  20  20  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Frost Advisory from 1 AM to 8 AM PDT Sunday for Central
     Panhandle Mountains-Idaho Palouse-Northern Panhandle.

WA...Frost Advisory from 1 AM to 8 AM PDT Sunday for Northeast
     Mountains-Okanogan Highlands-Spokane Area-Upper Columbia
     Basin-Washington Palouse-Western Okanogan County.

&&

$$