Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 091201

Area Forecast Discussion
National Weather Service Spokane WA
501 AM PDT FRI OCT 9 2015

Today will be unseasonably warm with most of the Inland Northwest
warming into the 70s. Saturday will also be quite warm with breezy
winds developing in the afternoon. A fast moving cold front will
bring a good chance of light rain to the region Saturday night. It
will also be windy Saturday night behind the front. Mild and
mainly dry weather is expected to return for the early to middle
part of next week.




Today and Tonight: An unseasonably warm day is in store for the
Inland Northwest today. Our region will be under the influence of
deep southerly flow ahead of a strong cold expected to arrive on
Saturday evening. Ahead of the front today, a shortwave high
pressure ridge will amplify over the western U.S. providing enough
subsidence to bring more sunshine than yesterday. South or
southwest winds in the 10 to 15 mph range will provide enough
mixing to push temperatures into the 70s. Late in the afternoon
and into the evening, a shortwave trough well ahead of the main
cold front will produce rain over the Cascade crest and spread
clouds into north central Washington. The models have trended
drier tonight as this shortwave moves through eastern Washington
and north Idaho, and precipitation chances have been decreased
below 20 percent.

Saturday and Sunday: A deep surface low is expected to move inland
on Saturday morning along the central British Columbia coast. A
tight southerly surface pressure gradient will develop by mid day
as the surface low moves through B.C. into Alberta. Look for
increasingly mild and breezy conditions Saturday afternoon ahead
of the cold front. Rain chances should peak with the passage of
the cold front Saturday evening, and our winds will likely peak
Saturday evening as well. By Sunday, the front will be well east
of the area. Winds should subside as pressure gradients relax
through the day.

* Winds: On Saturday afternoon, sustained south or southwest winds
  of 15 to 20 mph will be common over the Columbia Basin, West
  Plains, and Palouse with late day gusts to 30 mph. The NAM and
  GFS are in good agreement that the cold front will cross the
  Cascades during the early to mid evening hours as the surface
  low emerges east of the Canadian Rockies in central Alberta. The
  southwesterly gradient will likely favor the windiest conditions
  over the West Plains and Upper Columbia Basin in the evening and
  spread over the Palouse through the night. The tightest pressure
  gradient and best momentum aloft won`t arrive until after
  sunset, so we may not mix the 40-50kt winds from 850-800mb to
  the surface. However, exposed terrain above 2500 feet around
  Spokane and Pullman could experience gusts of 45 mph or more
  Saturday evening/night. Any convective downdrafts from showers
  could produce strong gusts over the Idaho Panhandle as well.

* Blowing Dust: The light rain we received on Thursday over the
  Columbia Basin, Palouse, and West Plains may limit our blowing
  dust potential. Warm temperatures today may dry the soil
  somewhat, so we may need to add some dust to the forecast
  Saturday evening. Fortunately, the strongest winds will not
  arrive until the evening hours. Cooler evening temperatures and
  the tendency for humidity to rise overnight should minimize the
  impact of blowing dust.

* Precipitation: The strong westerly component of the low/mid-
  level winds with the frontal passage will limit precipitation
  amounts with this frontal system. The front will also be moving
  quickly. The rain shadow east of the Cascades will likely limit
  rain amount to a few hundredths for our burn scar areas in
  central Washington. The mud slide threat looks very low at this
  time. In general, this front will bring a quarter to a half inch
  of rain to the Cascade crest with less than a tenth of an inch
  elsewhere. The mountains of Shoshone county may be the exception
  Saturday night...especially if convective showers develop along
  the front.

Sunday night through Thursday: Next week looks to be relatively
dry and mild. An upper level ridge will rebound across the Inland
Northwest late Sunday and into Monday, although it will be dirty
with Pacific moisture streaming in as the ridge gradually flattens
aloft. Could see some sprinkles or light precipitation near the
Cascade crest and far northern mountains as a weak warm pushes
north across southern B.C. Temperatures will be mild especially
across the southern portions of the forecast area meanwhile
thickening cloud cover may limit the diurnal heating across the
north. A disturbance will race across southern BC Monday night
into Tuesday and push a weakening cold front across the region.
The flow aloft will continue to flatten. Again mainly light
precipitation is expected across the northern mountains, but
breezy westerly winds will kick up from the lee of the Cascades
into the Columbia Basin. Drier air will arrive by Tuesday as
temperatures rise slightly. By Wednesday, the upper ridge axis
would have have retrograded into the Pacific near 130W, while
another round of Pacific moisture gets entrainined into the flow.
Expect filtered sunshine to mostly cloudy skies for Wednesday and
Thursday with the increase of high and mid level clouds, although
the chance of precipitation looks meager at this time. The storm
track shifts across southern BC with any activity just brushing
across the Canadian border. Temperatures are forecast to continue
about 5-10 degrees above normal. So expect more dry conditions and
unseasonably mild temperatures for mid October. /rfox.


12z TAFS: Patchy fog will be possible through 17z in the sheltered
valleys around Sandpoint, Bonners Ferry, Omak, and Winthrop. A
ragged stratus deck between 2000-3000 feet will be banked against
the Cascades around Wenatchee and Chelan. The stratus should also
dissipate by 18z. Elsewhere VFR conditions are expected for the
next 24 hours under a warm high pressure ridge. /GKoch


Spokane        74  55  74  48  64  44 /   0  10  20  60  10  10
Coeur d`Alene  74  53  74  47  64  41 /   0  10  10  60  10  10
Pullman        76  52  76  48  65  40 /   0   0  10  30  10  10
Lewiston       80  56  81  53  72  46 /   0   0   0  30  10  10
Colville       73  50  71  44  64  40 /   0  10  20  70  10  10
Sandpoint      70  51  71  47  65  36 /   0  10  20  70  10  10
Kellogg        74  49  71  46  60  41 /   0  10  10  70  30  10
Moses Lake     73  53  74  47  70  43 /   0  10  10  20   0  10
Wenatchee      70  55  73  48  70  50 /  10  10  20  20   0  10
Omak           70  49  71  43  67  46 /  10  10  40  40   0  10



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