Dust Storm Warning 7, NWS Spokane, WA

Area Forecast Discussion
National Weather Service Spokane WA
1059 AM PDT Sun Sep 29 2024

.SYNOPSIS...
A strong cold front will push through the area this morning,
bringing gusty winds through this afternoon. These winds will
result in blowing dust and critical fire weather conditions across
much of the Inland Northwest. Temperatures will be very chilly
Monday morning with frost and freeze conditions. Another cold
front on Tuesday will bring breezy winds Tuesday afternoon through
Wednesday.

&&

.DISCUSSION...
Sunday: Today is shaping up to be an impactful late morning and
afternoon with critical fire weather conditions and blowing dust
the primary concerns. Water vapor and nighttime satellite
products showing a band of clouds and light showers associated
with a mostly dry cold front moving through central Washington as
of 2 AM PDT. A trailing upper level trough moving across southern
British Columbia will support showers post frontal showers across
north Idaho this afternoon.

* FIRE WEATHER: In response to the rising pressure behind the
  front, a +8.7 mb pressure gradient between SEA and EAT is
  bringing breezy winds through the Cascade gaps early this
  morning. As the front pushes through eastern Washington and
  north Idaho this morning, efficient boundary layer mixing and a
  tight pressure gradient will support windy conditions across
  much of the region with sustained winds 20 to 30 mph and wind
  gusts up to 45 mph. Extremely dry air behind the front will
  allow precipitable water values to plummet with relative
  humidity values dropping into the upper teens and low 20s.
  Despite the cooler temperatures this afternoon, the strong winds
  combined with the very dry conditions will result in a rapid
  spread of any new wildfires.

* DUST: These winds will also be capable of lofting dust across the
  Waterville Plateau, Columbia Basin, Palouse, and Spokane area
  near recently worked fields. Very little rain over the last
  couple months combined with peak planting season in these areas
  will support visibilities between 2 to 5 miles and localized
  visibilities down to 1 mile will be possible later this morning
  through the early evening. Use caution while traveling today. If
  you encounter dense dust while traveling, pull off the road as
  far as you can, turn off your lights, put your car in park, and
  set your emergency brake.

Monday and Tuesday: Winds will become calm Sunday night into
Monday morning. Strong radiative cooling will result in a very
chilly Monday morning. There is a high probability (90 to 100
percent chance) for temperatures below freezing Monday morning for
locations within the northeast Washington and north Idaho
valleys. Places in the Washington and Idaho Palouse will see
temperatures near freezing with a 30 to 60 percent chance to drop
below freezing.

The flow aloft becomes more zonal by Tuesday as a low pressure
system nears the northern British Columbia coast and weak upper
level ridging amplifies from the south. Modest warming will be felt
across the Inland Northwest for Tuesday although the northern
valleys will dip to near freezing early in the morning. Winds will
become breezy Tuesday afternoon from the south-southwest ahead of
the front with wind gusts up to 20 to 30 mph in the afternoon. /vmt

Wednesday through Saturday: Shortwave ridging will once again be
suppressed by a weather system moving across southwest Canada and
dipping into the Northwest corner of the States midweek. This
midweek weather disturbance will bring another reinforcing shot of
breezy and dry conditions as well as keeping temperatures right
around seasonal normal for early October (mid 60s during the
day/low to mid 40s overnight). The dry conditions will continue
into the weekend when the next chance for moisture arrives.

* Wind & Dry: Precipitable water readings in the 40% of normal
  range and surface dew points back in the 20-30F range will
  once again produce elevated concerns for fire weather on
  Wednesday. Differences among the National Blend of Models and
  the low- resolution global ensembles vary for wind speeds on
  Wednesday (see below). PWAT values will slowly climb above
  50-60% of normal by next weekend with another shortwave feature
  moving through the region.

- NBM: 40-60% probability of winds 15+ mph Wednesday.
- Other ensembles (ECMWF, GFS): 10-15% probability of winds 15+
  mph Wednesday.

* Uncertainty: The ensemble cluster of models from WPC has almost
  an equal split of 30/30/30 percent for the solution of where
  the weather system will align for Wednesday with none of these
  options showing a strong difference in placement. The varying
  probabilities in wind speed would indicate uncertain placement
  of the upper level and surface conditions.

* Impacts: Another round of dry and breezy conditions Wednesday
  will keep the near critical fire weather conditions at the
  forefront of the messaging. As winds relax and moisture values
  rise later in the week, this concern will decrease. Temperatures
  will be on the cooler side, but the wind and dry conditions
  will be of concern for any new fire starts or fire spread.
  /Dewey

&&

.AVIATION...
18Z TAFS: Gusty winds will continue across eastern Washington and
north Idaho through the afternoon. Local gusts of 35 to 45 mph
will lead to visibility reductions due to blowing dust, with the
best chances at KEPH and KMWH. Slight chances for showers in
extreme northeast WA and north ID through 00Z Monday. Winds
decrease after 03-06Z Monday.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate
confidence in visibility reductions in blowing dust this
afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        64  34  63  39  71  45 /   0   0   0   0   0   0
Coeur d'Alene  63  34  63  38  70  45 /  10   0   0   0   0   0
Pullman        60  32  61  36  70  46 /  10   0   0   0   0   0
Lewiston       70  41  68  43  78  54 /  10   0   0   0   0   0
Colville       65  26  64  31  69  31 /   0   0   0   0   0   0
Sandpoint      63  32  61  35  66  40 /  20   0   0   0   0  10
Kellogg        59  37  59  42  68  48 /  10   0   0   0   0   0
Moses Lake     66  33  65  38  73  44 /   0   0   0   0   0   0
Wenatchee      62  41  65  46  76  49 /   0   0   0   0   0   0
Omak           68  36  68  43  72  43 /   0   0   0   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning from 11 AM this morning to 7 PM PDT this
     evening for Northern and Central Idaho Panhandle (Zone 101).

     Freeze Warning from 1 AM to 8 AM PDT Monday for Central
     Panhandle Mountains-Idaho Palouse-Northern Panhandle.

     Frost Advisory from 1 AM to 8 AM PDT Monday for Coeur d'Alene
     Area-Lewis and Southern Nez Perce Counties.

WA...Red Flag Warning from 11 AM this morning to 7 PM PDT this
     evening for Colville Reservation (Zone 702)-Eastern
     Columbia Basin  -Palouse  -Spokane Area (Zone 708)-
     Foothills of Northeast Washington (Zone 701)-Lower Palouse
      -Snake River (Zone 709)-Okanogan Valley (Zone 703)-
     Waterville Plateau (Zone 706)-Western Columbia Basin (Zone
     707).

     Freeze Warning from 1 AM to 8 AM PDT Monday for Northeast
     Mountains-Okanogan Highlands-Washington Palouse.

     Frost Advisory from 1 AM to 8 AM PDT Monday for Moses Lake Area-
     Okanogan Valley-Spokane Area-Upper Columbia Basin-
     Waterville Plateau.

     Blowing Dust Advisory from 9 AM this morning to 7 PM PDT this
     evening for Moses Lake Area-Spokane Area-Upper Columbia
     Basin-Washington Palouse-Waterville Plateau.

&&