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Area forecast discussion
National Weather Service Spokane Washington
251 PM PDT Mon Oct 16 2017

Synopsis...
a wetter and windier weather pattern is expected starting Tuesday.
Unsettled weather will continue Wednesday and Thursday however
with relatively mild temperatures for the season. A cold front
late in the week will cool the region down again to more seasonal
temperatures with the return of mountain snow.

&&

Discussion...

..windy tomorrow afternoon and evening...

Tonight through Wednesday night: jet stream remains within very
close proximity to the north, if not directly overhead, at
times over eastern Washington and northern Idaho as an upper level
Flat Ridge of high pressure remains in place for most of this time
interval. As such disturbances moving through the flow have
potential to bump some of the jet steams upper level winds down to
the surface with their passage. Such passages are expected to occur
Tuesday afternoon and evening and to a lesser degree Wednesday
afternoon and evening. A Wind Advisory was issued earlier and later
expanded to address the Tuesday afternoon and evening winds. This
jet stream positioning will favor snow levels high enough to limit
any snowfall to the higher mountain terrain generally near or above
5000 feet mean sea level. Cooling trend in temperatures through this interval
will allow daytime highs to run closer to seasonal average values
while overnight lows will be slightly on the warmer side given the
suggested mixing and cloud cover inhibiting overnight radiational
cooling this jet positioning should be able to provide. Similar
reasoning suggests a significant rain shadow to the east of the
Cascade crest should keep much of the Columbia Basin and good amount
of lowlands from receiving anything other than extremely light
rainfall. The usual exceptions to this will be portions of
northeast Washington and the north Idaho Panhandle where the terrain
allows the incoming disturbance to run upslope, so pops and qpf
there area higher Tuesday and even higher still on Wednesday.
/Pelatti

Thursday through Monday...
beginning Thursday, the upper trof that is the cause for the
active weather will finally approach the pacnw coast. As it
approaches, the inland northwest will again be in the warm sector
so temperatures will rebound into the upper 50s to lower 60s while
snow levels increase to over 7000 feet. The cold front associated
with the trof will bring another round of wind and rain to the
region and drop snow levels substantially by Friday night. One of
the changes made to the forecast was to increase the chance of
precipitation and rain amounts with this frontal passage. Thursday
is looking like it will be a very wet day except for the Lee of
the Cascades that should down slope. Precipitation will last
through much of Thursday night into Friday morning before finally
drying out. Again, this is quite the change from previous model
solutions that had much less rain through this 24 hour period.

Winds during this time will remain breezy but nothing like the
Tuesday event. As the trof moves overhead Friday, there is
potential for another breezy day in addition to plenty of
convection. Snow levels will be down to 3000-4500 feet across the
region so scattered valley rain and mountain snow showers are
likely Friday afternoon.

That doesn't last long as the next wave kicks the trof to the
east and another plume of moisture streams out ahead. This is
another change to the forecast; adding higher chances for rain
Saturday through Saturday night again with breezy winds. It's not
until Sunday night and Monday where the models are finally drying
out the region under a building ridge of high pressure. Long range
models are indicating that this could be the beginning of a
period with above average temperatures and dry conditions. Some
models show snow levels above 11000 feet by mid next week!/Ab

&&

Aviation...
18z tafs: Flat Ridge of high pressure over the aviation area
will allow for middle and high clouds to stream overhead today and
tonight at times with the expectation that VFR conditions will
prevail. Tuesday the jet stream will be overhead of the aviation
area and a disturbance rippling through it will allow windy
conditions with gusty winds to mix down to the surface Tuesday
afternoon and evening. The winds are not likely not to mix down
to the surface in the early morning hours so have opted to put in
a mention of low level wind shear between 15-18z Tuesday to
account for this. /Pelatti

&&

Preliminary point temps/pops...
Spokane 43 59 41 59 47 59 / 0 60 20 50 50 70
Coeur D'Alene 42 60 39 59 45 60 / 0 70 20 60 50 70
Pullman 43 63 44 64 48 64 / 0 50 50 40 30 40
Lewiston 46 70 48 71 50 71 / 0 10 20 30 20 10
Colville 38 58 35 55 42 57 / 10 50 20 50 60 70
Sandpoint 36 55 34 54 41 56 / 10 80 30 60 70 80
Kellogg 40 58 39 55 43 59 / 0 60 60 60 50 50
Moses Lake 39 65 39 65 45 63 / 0 10 10 30 30 40
Wenatchee 45 62 40 61 47 59 / 0 20 10 30 40 40
Omak 40 63 34 60 42 59 / 10 20 10 40 60 70

&&

Otx watches/warnings/advisories...
Idaho...Wind Advisory from 1 PM to 8 PM PDT Tuesday for central
Panhandle mountains-northern Panhandle.

Wind Advisory from 1 PM to 8 PM PDT Tuesday for Coeur D'Alene
area-Idaho Palouse.

Washington...Wind Advisory from 1 PM to 8 PM PDT Tuesday for east slopes
northern Cascades-northeast mountains-Okanogan Highlands-
Okanogan Valley-Wenatchee area.

Wind Advisory from 1 PM to 8 PM PDT Tuesday for lower Garfield
and Asotin counties-Moses Lake area-Spokane area-upper
Columbia Basin-Washington Palouse-Waterville Plateau.

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