Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 201225

Area Forecast Discussion
National Weather Service Spokane WA
425 AM PST Mon Nov 20 2017

Expect wet and mild weather as a series of storm systems brings
several rounds of precipitation this week. Snow levels will be
quite high Tuesday, Wednesday, and Thursday allowing motorists to
travel over mountain passes on wet pavement. Snow levels will
begin to lower just as travelers are heading home Friday into the


Today through Tuesday night...The forecast over the next day or
two will start out wet and get wetter. As of 2 AM a warm front
moving/sagging into the region form the west in response to an
area of low pressure out around 130W off Vancouver Island. We will
likely see a short break in the precipitation across the
northwest and northern zones early this morning as the front
shifts east. However, by mid morning the low off the coast is
expected to close off as it moves inland and this will bring
another shot of the precipitation to to the area. The 00z models
are pushing the moisture a little further north than previous runs
and that was added to the forecast. We then expect drying from
the west starting early in the afternoon as the following cold
front tracks east across the area. The drying will be short lived,
however, as another warm front will move into the region after
06z tonight and very slowly move across the forecast area Tuesday
and Tuesday night. This will be the wettest period in the short
term forecast. Temperatures will be in the lower 40s to lower 50s
and 4-6 degrees above seasonal normals. Winds behind the front
this afternoon will increase to southwest 10-20 mph with gusts
20-30 mph, mostly across the basin and the Palouse.

* Precipitation: The area will get a decent shot of precipitation
  today, but much more Tuesday and Tuesday night. Rain shadowing
  off the Cascades will keep amounts in the low lands pretty
  light. But the eastern portion of the forecast area where the
  warm front lingers through the day will see from a half inch to
  possibly over three quarters of an inch of water through this
  evening. The second surge of precipitation will be wetter.
  Amounts from a quarter to almost three quarters of an inch will
  be possible outside of the mountain zones. An inch or slightly
  more is likely for the northeast and Panhandle mountains. The
  Cascades could see 1-2 inches before all is said and done.

* Precipitation type: This is a more tricky forecast, at least
  through this morning. Snow will be likely this morning for the
  higher Cascades and above 3500 feet for the northern mountains,
  but amounts are not expected to be very much. The St Joe and
  Clearwater mountains could see 4-7 inches above about 4000 feet.
  The area of concern will be the Methow valley. That area has a
  hard time mixing out the cold air at times and could easily see
  another inch of snow this morning before the snow turns over to
  rain. Some clearing is expected across the Cascades today and
  this evening. This may result in decent radiational cooling and
  temperatures in the valleys dropping back below freezing. With
  the warmer air moving in aloft there will be a slight chance of
  localized, light freezing rain from Leavenworth up to Plain and
  Winton, Possibly up near Lucerne, and for the Methow valley.
  Confidence in the skies clearing out enough for the cooler
  temperatures is low, but this will need to be monitored closely

* Hydro impacts: Warm rain over an above normal snow pack will
  increase runoff and result in rapid rises on area streams and
  small rivers through most of the week. No flooding is expected
  at the time. An area of concern will be Paradise Creek that runs
  through Moscow. That stream is very responsive to moderate rain
  and snow melt and may see some high flows as early as tonight.

Wednesday through Sunday: A wet and active pattern will continue
for the rest of the holiday week with the mid-week highlighted by
well above normal temperatures. The models are in good agreement
of this upcoming pattern, although the timing of the later
features begins to digress by the weekend. The main feature is an
atmospheric river that bombards the Pacific NW coast this week
with pwats near an inch reaching east of the Cascades Wednesday
into Thursday. A strong warm front lifts through the region on
Wednesday with increased southern winds. The Inland NW remains in
the warm sector Wednesday night into Thursday with snow levels
above 8k ft regionwide. Then a cold front arrives Thursday
afternoon as the rain ends and breezy winds develop. This will
also encourage good mixing and anticipate Thanksgiving day to have
the warmest temperatures of the week. In fact, it has the
potential to be warmest Thanksgiving day on record. This warmup
will lead to increased runoff and the potential for rises on
rivers and streams, especially in the Cascade basins.
Temperatures and snow levels begin to fall Thursday night into
Friday, with snow reaching the mountain passes. Aside from the
mountains, Friday into Saturday looks to have the driest weather
of the week with daytime highs in the 40s. The moist southwest
flow aloft reloads another weather disturbance late Saturday with
more rain and mountain snow for Saturday night into Sunday to top
off the weekend. The lowlands should be mild enough to experience
rain while the mountains receive the bulk of the snow. The
exception would be be a few sheltered northern spots, such as the
Methow valley, Republic and Priest Lake that could see a little
snow by this weekend. Overall expect temperatures trending above
normal for late November. /rfox.


12Z TAFs: After a short break in the rain and mountain snow across
the northern zones early this morning, precipitation will
increase again from southwest to northeast as a cold front moves
towards the region. The cold front will track across the region
through the afternoon and bring drying conditions from west to
east. Another weather system will follow closely Tuesday and
Tuesday night and we expect a wet work week. CIGS/VSBY will be
mainly VFR/MVFR the next 24 hours. Tobin,


Spokane        45  36  47  44  54  45 /  70  10 100 100  70  50
Coeur d`Alene  45  35  45  42  54  44 /  90  20 100 100  80  50
Pullman        46  39  49  46  58  47 / 100  20 100 100  70  30
Lewiston       53  42  53  47  60  48 / 100  20  80  80  50  30
Colville       44  33  41  37  47  40 /  60  10 100  90  60  70
Sandpoint      41  32  41  39  48  41 /  80  20 100 100  90  80
Kellogg        41  34  42  40  50  43 / 100  50 100 100  80  50
Moses Lake     50  35  45  40  53  42 /  50  10 100  90  50  40
Wenatchee      47  35  41  37  49  40 /  40  10  90  40  60  30
Omak           44  34  42  38  48  43 /  50  10  90  60  60  40




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