149
FXUS66 KOTX 031031
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
331 AM PDT Mon Jun 3 2024

.SYNOPSIS...
A vigorous cold front will seep across the Inland Northwest today.
Thunderstorms will be possible along the front this morning into
the afternoon. This will be followed by windy conditions
regionwide. Wind gusts may become strong, especially late this
morning into the afternoon. A weaker weather system on Tuesday
will keep winds breezy and bring additional light showers. A
significant warming trend will then commence mid week into the
weekend. Very warm temperatures in the mid 80s to mid 90s is
expected Friday into the weekend.

&&

.DISCUSSION...

...MORNING AND AFTERNOON THUNDERSTORMS AND WINDY CONDITIONS TODAY...

Today into Tonight: Strong cold front passage today! Water vapor
satellite imagery early this morning at 2:30 AM shows a vigorous
shortwave trough of lower pressure pushing into the Northwest with a
150-160 kt jet streak diving down on the backside of the shortwave.
The upper level jet is rounding the trough and being directed across
northern Oregon and up across extreme southeast Washington into the
southern and central Idaho Panhandle. The shortwave trough will push
across with a negative tilt, favor left exit region of the jet
streak, and strong positive vorticity advection across the Inland
Northwest: all indicative for strong vertical upward motion on the
synoptic scale this morning into this afternoon. At lower levels, a
cold front will sweep across the region crossing the Cascades within
the next 3-6 hours (5-8 AM) and into the Idaho Panhandle by 11AM-1PM
later today. This is a strong cold front with strong lift along the
front congruent with the lift being supplied aloft. Water vapor
satellite imagery also shows a good drying aloft indicative of a dry
slot and subsidence behind the cold front about to move into the
coastal locations of Washington.

We will continue to see precipitation within the warm sector of this
weather system. The Atmospheric River will mainly be directed south
of the region through the rest of the day. The PWat plume also looks
to weaken as it migrates south as well. Another inch or so of
precipitation is anticipated along the Cascade crest with an
additional 0.25-0.75 inches of rain expected over the Idaho
Panhandle. Much of the higher end of this additional rainfall over
the Idaho Panhandle will be spotty and generally reserved for
windward westerly aspects. Lee side locations will see downsloping
and this will cut into the amount of rainfall that is observed: this
includes areas such as Bonners Ferry, Silver Valley, and Lewiston-
Clarkston Valley to the Camas Prairie. There hasn`t much of a
response to creeks and small streams with the rain that has fallen
already, and I don`t expect much if any impacts from rain moving
forward. The Flood Watch for Shoshone County and Lewis County has
been cancelled. There will be the possibility for minor rock slides,
but even this risk looks to be on the low side.

Snow levels dropping over the Cascades will result in a transition
to snow above 4500 feet. Expect light snow over Washington Pass with
2-4 inches expected.

The primary impacts expected moving forward will be (1) strong winds
and (2) convection along the cold front.

* Winds: Widespread winds of 20-30 mph with gusts of 40-50 mph is
  expected today across much of the region. Exposed areas in the lee
  of the Cascades, across the basin, Spokane/Coeur d`Alene areas,
  Palouse, Lewiston-Clarkston Valley, Camas Prairie, and lower
  Asotin and Garfield County are expected to see the higher end of
  these winds with sustained speeds more in the range of 25-30 and
  gusts 45-50. There is also potential for isolated areas with
  sustained wind speeds of 35 mph with gusts of 50-60 mph on the
  Waterville Plateau, and from the Northeast Blue Mountains down
  onto the southern portion of the Palouse. These stronger winds
  will more likely come with the cold front passage late this
  morning into the early afternoon. There is also the potential for
  mountain wave activity to draw down stronger wind gusts in the lee
  of the Cascades through the afternoon into the early evening as
  the jet aloft migrates north over this area.

* Thunderstorms: Convective Allowing Models (a.k.a. CAMs) have
  consistently shown convection developing along the cold front.
  The focus for convection looks to be from the Moses Lake Area
  to the Okanogan Valley/Highlands starting around 800 AM this
  morning. Then pushing eastward very quickly through the morning
  reaching Spokane/Coeur d`Alene and Colville/Chewelah as early as
  900 AM - 1000 AM; and then into the Idaho Panhandle by 1100 AM
  into the early afternoon. Chances for thunderstorms across these
  areas is between 20-30%. Isolated thunderstorms will also be
  possible further south along the front with a 15% chance for
  places like Lewiston and Pullman/Moscow. Instability will be a
  limiting factor, but strong dynamics should be enough to
  overcome this limitation. Convection will be moving quickly, and
  will feature the potential for strong downdraft winds, along
  with infrequent lightning strikes. There will be about 40-50 kts
  of 0-6 km of bulk shear to go along with 200-500 J/kg of
  surface based CAPE. This may be enough for organization.

* Impacts: There is a moderate risk for impacts to life and
  property due to winds today. Thunderstorms will be capable of
  producing strong downdraft winds today, particularly with
  morning convection along the cold front. How impactful
  thunderstorms become will be dependent on available CAPE. There
  may not be enough energy for thunderstorms to become strong and
  organize, but shear profiles are there and the cold front will
  supply amble lift. It won`t take much for strong winds to mix
  down to cause damage. Winds on the synoptic scale along and
  behind the front today will be enough for the risk of moderate
  wind impacts as well. Isolated tree damage and scattered power
  outages will be possible. Strong cross winds will make driving
  very difficult, particularly for high profile vehicles.

Tuesday and Tuesday night: A second punch of moisture will move
across the region with a an occluded front. The parent low for this
system will be well off to the northwest moving into northern BC off
of the Gulf of Alaska. This will result in much weaker dynamics with
precipitation having a harder time being squeezed out. Precipitation
will be light with accumulations mostly reserved for the
mountains. A hundredth at best can be expected for locations out
in the basin. Winds will continue to be breezy, but not to the
level of what is expected today. Wind speeds on Tuesday are
expected to be on the order of 20-25 mph with gusts of 30-40 mph
possible. /SVH

Wednesday through Sunday: Amplifying ridge of high pressure allows
for a warming and drying trend with temperatures peaking Saturday.
As early as Friday, but maxing out Saturday, the warmer/hot
temperatures allow NWS Heat Risk to increase to moderate level
(impacting most individuals sensitive to heat, especially those
without effective cooling and/or adequate hydration). The ridge
moves to the east Sunday and the resulting upper level southwest
flow looks moist enough to allow for clouds to invade the sky from
west to east and and a slight chance mention of showers and
thunderstorms along with slightly cooler temps and increased wind
and possible gusts, which would also include outflow from any
showers or thunderstorms that form. /Pelatti

&&

.AVIATION...
06Z TAFS: Periods of light to moderate rain will persist across
Washington and north Idaho through the night ahead of cold front.
Strong westerly flow aloft will shadow airports in central
Washington like Wenatchee and Chelan while persistent rain fall at
Spokane, Coeur d`Alene, Sandpoint, Kellogg, and Pullman. The
arrival of the cold front between 15-18z will a significant
increase in west winds region-wide as well as the potential for
thunderstorms capable of brief heavy rain and localized wind
gusts up to 55 mph. From 18-00z precipitation will be mainly
limited to scattered convective showers with 30 to 60 percent
coverage across the mountainous terrain of north Idaho and far
northeast Washington. Post frontal west winds of 20 to 30 mph with
gusts to 45 mph will be common from 18z to 03z from Wenatchee to
Moses Lake, to Spokane and Pullman before gradually decreasing
Monday evening.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Visibility and
ceilings will vary at Spokane, Coeur d`Alene, and Pullman as
conditions change during light to moderate rain through 15z. Once
the cold front passes, strong west winds will sweep low clouds out
of our airports. Wind may be strong enough to generate localized
blowing dust in places that are shadowed from rain. Confidence is
low that there will be enough dry fields to generate visibility
reductions, but it will be something to watch. /GKoch

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

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        61  43  66  42  70  45 / 100   0  30   0   0   0
Coeur d`Alene  58  41  62  44  68  45 / 100  10  50  10   0   0
Pullman        57  41  61  44  67  45 / 100  10  40  10   0   0
Lewiston       67  49  72  53  77  52 / 100  10  30  10   0   0
Colville       61  35  63  35  70  39 /  90  10  50  10   0   0
Sandpoint      56  40  58  41  66  42 / 100  30  70  40   0   0
Kellogg        55  43  57  46  66  46 / 100  20  70  40   0   0
Moses Lake     68  48  74  44  76  47 /  60  10  10   0   0   0
Wenatchee      63  48  68  46  75  50 /  60  20  20   0   0   0
Omak           68  44  73  42  75  46 /  80  10  20   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory from 9 AM this morning to 7 PM PDT this evening
     for Northern Panhandle.

     Wind Advisory from 8 AM this morning to 11 PM PDT this evening
     for Central Panhandle Mountains-Coeur d`Alene Area-Idaho
     Palouse-Lewis and Southern Nez Perce Counties-Lewiston Area.

WA...Wind Advisory from 9 AM this morning to 7 PM PDT this evening
     for Northeast Mountains.

     Wind Advisory from 8 AM this morning to 11 PM PDT this evening
     for Lower Garfield and Asotin Counties-Moses Lake Area-
     Northeast Blue Mountains-Spokane Area-Upper Columbia Basin-
     Washington Palouse-Waterville Plateau-Wenatchee Area.

&&

$$