Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Spokane Washington
536 am PDT Sat Oct 10 2015
today will be quite warm with very windy conditions developing in
the late afternoon and lasting into the night. A fast moving cold
front will bring a good chance of rain to the region tonight.
The wind will decrease on Sunday, and precipitation will move out
of Washington and Idaho on Sunday as well. Mild weather is
expected to return for much of next week.
..becoming windy this afternoon through tonight...
Today and tonight: wind advisories remain in effect from Moses
Lake and the Waterville Plateau through eastern Washington and
the Idaho Panhandle. Winds are expected to peak along and behind a
strong cold front which will cross the Cascades late this
afternoon. The cold front will also bring showers and the
potential for embedded thunderstorms with the best potential for
thunderstorms along the Canadian border.
* Winds: our forecast for wind speeds this afternoon into tonight
hasn't changed much. The NAM and GFS have remained fairly
consistent with the late afternoon/early evening timing of the
cold front. Pre-frontal south winds will increase by mid
afternoon. Look for sustained south winds of 15 to 25 mph this
afternoon with gusts to 35 mph over the Columbia Basin, West
Plains and exposed mountain ridges of central Washington. As the
cold front races across eastern Washington and north Idaho
between 5 PM and 8 PM, we expect to become westerly and increase
into the 20 to 30 mph range with gusts of 40 to 50 mph. The open
wheat country from the Waterville Plateau to Spokane and Pullman
will likely experience the most widespread windy conditions.
Mountain ridges over the Idaho Panhandle will also experience
windy conditions well through the night under stiff cold
advection accompanied by winds of 35 to 45 mph in the 850-700mb
* Thunderstorms: isolated thunderstorms have been added to north
central and northeast Washington and the far northern Idaho
Panhandle late this afternoon into the evening. The NAM progs
several hundred j/kg of surface based cape in places like
Republic, Colville, Spokane, and Bonners Ferry. We are certainly
out of our peak thunderstorm season, but vigorous frontal
forcing combined with rapid mid-level cooling may produce some
widely scattered thunderstorms. Convective downdraft could have
the potential to enhance our already windy conditions. Gusts
exceeding 55 mph could be possible given the momentum above
700mb and steep lapse rates.
* Impacts: patchy blowing dust has been added to the forecast.
Conditions in central and eastern Washington are not as
favorable as they were a month ago. We have had some rain
recently, and we are further removed from the planting season
for winter wheat. However, blowing dust could still become a
localized issue by early evening over the Columbia Basin,
Waterville Plateau, West Plains and Palouse. Other wind impacts
will be hazardous cross winds for high profile vehicles, and
localized power outages. We may also see a higher risk for
downed trees in our areas burned by Summer fires.
* Rain amounts: the fast frontal movement and the strong mid-level
westerlies tonight should produce a rain shadow over central and
eastern Washington. Our highest rain amounts will likely occur
over the Cascade crest with up to an inch and a half of rain in
the high terrain. A secondary rain Max with amounts up to a half
inch possible for the mountains along the Canadian border of far
northeast Washington and extreme northern Idaho. Our vulnerable
burn scars in Okanogan and Chelan counties will probably receive
a tenth of an inch of rain or less. The burn scar flooding
threat looks very low.
Sunday and monday: much drier air will follow the passage of
Saturday night's cold front. Rain chances will be limited to the
extreme eastern portion of Shoshone County on Sunday morning. The
wind should decrease Sunday morning as the surface pressure
gradient relaxes with the departing front. The mention of rain has
been dropped from all but the Cascade crest for Monday. The latest
model runs shunt deep layer moisture into northern and central
British Columbia...well north of our region. It still looks like
Monday will be mostly cloudy with temperatures in the upper 60s to
low 70s. /Gkoch
Monday night through saturday: a weakening and shearing cold front
will be on the exit Monday night. This will result in a decreasing
trend of cloud cover and precip on Tuesday. Models are all in
good agreement that a strong ridge of high pressure will then
build in over the region for the remainder of the work week. This
will result in a warming trend with temperatures around 15
degrees above normal by Thursday and Friday. Models look to break
the ridge down at the end of this period some time around next
12z tafs: winds ahead of a cold front are expected to increase
through the afternoon at most airports in the region. Gusts will
likely peak in the 02z-06z time frame along and behind the fast
moving cold front. Localized blowing dust could impact Moses Lake
and Spokane. Since it has rained a bit in the last couple of days,
confidence is low that visibility will be restricted, so we will
handle blowing dust on a Nowcast basis. Rain showers and isolated
embedded thunderstormw will also accompany the front late this
afternoon and evening. The best instability will likely be from
Spokane northward. Convective downdrafts up to 55 mph may
accompany thunderstorms. /Gkoch
Preliminary point temps/pops...
Spokane 73 47 64 43 67 48 / 20 60 0 0 0 0
Coeur D'Alene 73 47 64 39 67 46 / 10 60 10 0 0 0
Pullman 76 48 65 41 70 45 / 10 50 10 0 0 0
Lewiston 80 53 72 44 74 51 / 0 30 10 0 0 0
Colville 71 44 64 37 64 43 / 20 70 10 0 10 10
Sandpoint 69 48 65 34 64 42 / 20 60 10 0 10 10
Kellogg 71 46 60 37 66 45 / 10 70 30 0 10 0
Moses Lake 74 48 70 40 71 47 / 10 30 0 0 0 0
Wenatchee 71 49 70 45 69 54 / 20 20 0 0 0 10
Omak 71 44 67 42 65 49 / 50 30 0 0 10 10
Idaho...Wind Advisory from 2 PM this afternoon to 1 am PDT Sunday for
Coeur D'Alene area-Idaho Palouse.
Wind Advisory from 2 PM this afternoon to 5 am PDT Sunday for
central Panhandle mountains-northern Panhandle.
Washington...Wind Advisory from 2 PM this afternoon to 1 am PDT Sunday for
lower Garfield and Asotin counties-northeast mountains-
Spokane area-Washington Palouse.
Wind Advisory from 2 PM this afternoon to 5 am PDT Sunday for
northeast Blue Mountains.
Wind Advisory from 2 PM this afternoon to 11 PM PDT this evening
for Moses Lake area-upper Columbia Basin-Waterville Plateau.