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Forecast Discussion for Spokane, WA

000
FXUS66 KOTX 201211
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
511 AM PDT Fri Oct 20 2017

.SYNOPSIS...
Showers and gusty winds can be expected today and tonight as a low
pressure system swings through the area. There will be a low end
chance for lightning up across the northeast mountains
this afternoon. After a brief break in the active weather tonight,
the next storm system will arrive Saturday morning and will exit
Sunday night. This storm will also be warm, wet, and windy. Drier
conditions are expected for much of next week as high pressure
moves into the region.

&&

.DISCUSSION...
Today and tonight...The active weather will continue through
the weekend as one storm system moves through the region today
and another follows quickly on Saturday. Satellite imagery is
pretty clear showing an upper level low moving into the region
this morning, but with slower timing then previous thinking. The
cold front is still moving through the eastern zones, but should
be east of the region right around 12z. As the cold upper level
low moves through in today broken skies will allow surface
heating and increase lapse rates over the area. This will support
showers across the Cascades and the Idaho Panhandle mountains
through the afternoon. Some convection will likely build back as
far west as the eastern Basin and the Palouse. There may be
enough instability to support a chance of thunderstorms across the
northeast zones this afternoon. This will be highly dependent on
cloud cover but low end chances were added to the forecast from
the Spokane-Coeur D`Alene corridor north and east towards
Republic. Temperatures will be down 4-7 degrees today behind the
front. 30-40 mph 850 mb winds this afternoon will have an easy
time mixing to the surface so we expect southwest winds to
increase to 20-30 mph with gusts 30-40 mph through the Basin, the
Palouse, and up near the Spokane-Coeur D`Alene area through
sunset. Showers will linger through the evening hours in up-
sloping flow across the Panhandle mountains, but will be on the
decrease. Snow levels around 6k feet this morning will decrease to
around 4K feet this evening.

Saturday...There will only be at best a 12-24 hour break in the
weather as the next storm system moves into the region from the
southwest Saturday morning. Another atmospheric river will
increase moisture above 200 percent of normal again by mid-day
Saturday. Isentropic lift along the 295-300K surface looks better
with this system then the one Wednesday and Thursday. Snow levels
will start out around 3K feet and increase to between 3500-4000
feet by afternoon. This will result in snow down to pass levels or
below for the Cascades. Through the day 4-7 inches will be
possible above about 3500 feet. Tobin

Saturday night and Sunday: An atmospheric river will be over the
region Saturday night bringing widespread precipitation with
rising snow levels as a warm front passes. Snow levels will
quickly rise above all pass levels except Washington Pass and
Sherman Pass which may see significant accumulations before
changing to rain overnight. Models continue to show windy
conditions developing in the warm sector Saturday night for the
Upper Columbia Basin, Palouse, Spokane area, the foothills of the
Blue Mountains, and in the mountains as 850mb winds increase to
45-60 kts and pressure gradients begin to increase. Mixing
potential in the warm sector shouldn`t be sufficient for high
winds to mix to the surface although the UW-WRF GFS continues to
show gusts near 60 mph for Alpowa Summit. The moisture plume
shifts south over far SE Washington and Oregon on Sunday which is
a little faster than previous runs. Drier air aloft moves in along
with strong downslope flow east of the Cascades. 850mb winds of
35-40 kts during the late morning and early afternoon combined
with increased atmospheric mixing will promote breezy to windy
conditions for much of the area. The downslope flow should yield a
dry day for much of Central and Eastern Washington with showers
limited to mainly the Cascades, southeast Washington, and the Idaho
Panhandle.

Sunday night through Tuesday: An upper ridge builds in bringing a
drying and warming trend.

Tuesday night through Thursday: Models are coming into better
agreement of a cold front dropping in from the northwest Tuesday
night into Wednesday. This will bring an increase chance for
showers except in Central Washington where downslope flow should
result in dry conditions. The northwest flow will favor the
Cascade crest and Idaho Panhandle. POP`s have been increased.
Winds will also increase. The latest 00z runs of the GFS and ECMWF
show the potential for breezy to windy conditions over much of the
area. Although with the Canadian and some of the GFS Ensembles
not as strong with the front did not indicate winds as strong as
the GFS/ECMWF would suggest. Winds may need to be further
increased depending on what future models show. After this front
passes cooler and drier air moves in for Thursday.  JW

&&

.AVIATION...

12Z TAFS: Showers will linger across the eastern zones through
16-18z as the cold front moves out of the region. Precipitation
will linger over the Panhandle mountains through 18-20z with mtn
obscurations. The atmosphere will destabilize 18-01z and support
-shra for the eastern TAF sites. There will be a low end chance
for -tsra 20-23z across the northeast areas and these may effect
the KGEG-KCOE corridor. Then skies clearing after 03z KMWH-KEAT
will see mainly mid and high clouds through the 12z. Winds will
be on the increase through the morning with widespread sustained
winds southwest 15-20kts and gusts 25-30kts. Winds not likely to
decrease until after 06z. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        50  35  46  44  59  40 /  20  10  90 100  40   0
Coeur d`Alene  48  35  45  42  57  40 /  50  10  70 100  70  10
Pullman        48  35  48  44  58  43 /  40  10  90 100  80  40
Lewiston       55  38  52  47  64  46 /  30  10  80  90  70  10
Colville       52  33  45  40  57  36 /  20  10 100 100  30   0
Sandpoint      48  34  43  39  53  36 /  80  10  70 100  70  10
Kellogg        43  34  43  38  50  39 /  80  30  70 100  80  30
Moses Lake     57  37  50  47  66  40 /   0   0 100  80  10   0
Wenatchee      54  36  46  42  63  41 /  10  10 100  80  50  10
Omak           55  32  45  40  62  35 /  10   0 100  80  10   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.

&&

$$

NWS Spokane, WA (OTX) Office Area Forecast Discussion

Discussion Script by Ken True at Saratoga Weather - WFO Script by SE Lincoln Weather