Scientific Forecaster Discussion
fxus66 kotx 261120
Area forecast discussion
National Weather Service Spokane Washington
420 am PDT Tue Sep 26 2017
drier and warmer weather will return to the inland northwest today
through Friday under mild high pressure. Thursday will feel a bit
like Summer with afternoon temperatures in the upper 70s to low
80s. Temperatures will fall dramatically Friday night into
Saturday with the arrival of a strong cold front. The weekend will
be chilly, breezy, and showery.
Today through Wednesday night: positively tilted ridge shows
amplification and transition to a more neutral north to south non
tilt through this interval. This amplification and reorientation of
the ridge axis should push the path for any clutter of moisture
and/or disturbances fluxing through it further away to the north and
thus result in not only a dry forecast but one with not much in the
way of significant cloud cover. Forecast temperatures on the warm
side of what would be considered normal for this time of year.
Thursday and friday: little has changed regarding the forecast for
Thu and Fri. Afternoon temperatures on Thu will climb into the
upper 70s to low 80s under clear skies. On Fri high clouds will be
on the increase in the afternoon ahead of an approaching cold
front. There may be enough cloud cover to hinder warming in
central Washington and highs for places like Wenatchee, Omak, and
Chelan have been lowered a couple of degrees into the mid 70s.
Prefrontal south winds will also increase Fri afternoon across the
Columbia Basin and open wheat country of the Palouse and West
Plains. Look for 10 to 15 mph with late day gusts up to 20 mph.
Friday night through sunday: the forecast for the weekend has been
changed considerably. Precipitation chances have been increased
Fri night through sun. The evening models have trended deeper,
wetter, and cooler.
The most significant swath of rain will likely occur Sat morning
along the cold front. The central and southern Idaho Panhandle
could receive a quarter inch of rain with localized amounts up to
a half inch. Behind the cold front, Saturday afternoon promises to
be cool, breezy, and showery. If the evening model runs verify, a
500mb cold pool (-21c to -25c) will track across Oregon and
Washington yielding showers with snow levels falling into the 5500
to 6500 ft range. Afternoon temperatures in the upper 50s to mid
60s will be accompanied by 10 to 20 mph winds with gusts up to 25
mph across the Columbia Basin, Palouse, and West Plains.
There may be fewer showers Sunday over central Washington as the
cold 500mb trough migrates into Montana, but the GFS and European model (ecmwf)
suggest wrap around rain and High Mountain snow for the Idaho
Panhandle and possibly the eastern third of Washington. Afternoon
temperatures will again be below average with more breezy west
Monday: the medium range models diverge into a mess of different
solutions by Mon and Tue. The European model (ecmwf) and Canadian share some
similarities early next week with the arrival of another wet
frontal system. The GFS trends drier with a cool northerly flow.
With little to hang our hat on, we kept a chance of showers in the
forecast with below average temps. /Gkoch
12z tafs: clouds should continue to decrease as the ridge of high
pressure over the aviation area shows amplification. Some late
night and early morning fog possible producing spotty MVFR
conditions primarily north of kgeg, ksff and kcoe. Otherwise after
the morning when the fog dissipates VFR conditions will prevail.
Preliminary point temps/pops...
Spokane 70 50 75 51 79 51 / 0 0 0 0 0 0
Coeur D'Alene 70 46 74 48 78 48 / 0 0 0 0 0 0
Pullman 69 46 75 48 78 49 / 0 0 0 0 0 0
Lewiston 75 50 78 52 81 52 / 0 0 0 0 0 0
Colville 73 44 78 45 82 46 / 0 0 0 0 0 0
Sandpoint 68 42 73 43 76 44 / 0 0 0 0 0 0
Kellogg 67 45 72 46 76 48 / 0 0 0 0 0 0
Moses Lake 76 47 80 48 82 48 / 0 0 0 0 0 0
Wenatchee 75 53 79 54 80 54 / 0 0 0 0 0 0
Omak 77 48 79 49 81 49 / 0 0 0 0 0 0