Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus66 kotx 162340 
afdotx

Area forecast discussion
National Weather Service Spokane Washington
440 PM PDT Mon Sep 16 2019

Synopsis...
cool, wet Fall weather will persist through mid week as a pair of
weather systems slowly make their way across the inland northwest.
As the rain decreases this evening, a wetter storm will arrive
Tuesday with widespread rain and continued showery weather into
Wednesday. Aside from a few showers over the Idaho Panhandle,
drier, breezy and more seasonal weather is expected Thursday
through Saturday. A return of to unsettled is expected by Sunday.

&&

Discussion...
tonight through tuesday: cool and unsettled weather will continue
for the next 24 hours. A slow moving cold front will gradually
exit the region tonight. Radar shows a band of steady rain,
producing a tenth to two tenths of an inch of rain which will
shift from the Spokane area and Palouse into north Idaho this
evening while temperatures hover in the mid 50s to lower 60s. This
band is expected to weaken and shear apart overnight, leaving
plenty of cloud cover and scattered showers behind over the Idaho
Panhandle. In the wake of the front, instability has been on the
increase with cold air aloft due to the upper trough swinging into
the region. Satellite shows more convective clouds and spotty
showers across north central Washington from Wenatchee to Omak.
Some of these showers have produced heavy downpours, especially
across the Waterville Plateau. There is a small chance of a
thunderstorm over the northern Cascades late this afternoon into
the early evening. Anticipate this convection to weaken this
evening. Should see a brief clearing overnight across central and
eastern Washington. Lingering low level moisture may lead to
patchy fog in the northern valleys into early Tuesday morning.
High and mid level clouds will be on the increase from the west as
the next frontal band and upper trough swings into the region.
The timing of next front seems a bit slower than previously
forecast with a band of stratiform rain over the Cascades and
central Washington through early afternoon, and reaching eastern
Washington by late afternoon. Anticipate more cool temperatures,
with overnight lows in the 40s and daytime highs again in the
60s. /Rfox.

Tuesday night through Thursday night...models are in good agreement
showing the next closed low currently moving south along the b.C. Coast
will be off the Washington coast by Tuesday afternoon. The low
will move east-southeast through the Pacific northwest and will be
east of the Continental Divide by Friday morning. Plenty of
moisture will be associated with this deep low. Pwats are almost 3
Standard deviations above normal for Tuesday night and Wednesday.
We are expecting widespread stratiform rain Tuesday night and
Wednesday morning as the deep moisture wraps into the Cascades and
slowly shifts east. The cold core will move over the inland
northwest Wednesday afternoon. This will allow the atmosphere to
destabilize and support deep enough convection for scattered to
numerous showers and thunderstorms through sunset Wednesday night.
Precipitation amounts for the 36 hour period from Tuesday evening
through Thursday morning will be impressive. The deep basin will
likely see a tenth of less otherwise most places will see
0.25-0.50 with some of the mountain locations as much as 0.75.
Temperatures will be mainly in the 60s with a few low 70s at our
warmer locations both days. High pressure noses into the region
from the west late in the day Thursday. Some isolated to scattered
showers will be possible for the up-sloping areas of the Idaho
Panhandle and possibly the Blue Mountains, otherwise there will be
a warming and drying trend. Tobin

Friday and saturday: following a wet and cool week, Friday and
Saturday will be drier as a ridge builds over the Pacific
northwest. Moisture may still be present with best chances of any
rain in the higher elevations of the Cascades and Idaho Panhandle.
The peak of the week's warming trend will be this weekend with
high temperatures back in the upper 60s and low 70s. While this is
warmer, temperatures are still below seasonal normal.

Sunday and monday: the models show poor consistency in the arrival
of an incoming trough as the ridge moves out of the region. Too soon
for specifics, but the next chance of precipitation looks to be on
Sunday or Monday, with the earliest models showing morning
precipitation in the Cascades on Sunday. Low confidence at the time
being. Js

&

Aviation...
00z tafs: a narrow band of rain will move through the
kgeg/ksff/kcoe/kpuw and klws sites this evening. Cigs will lower
to MVFR with this rain band, with a slight chance of IFR cigs at
kgeg/ksff. Overnight, cigs should actually rise up a bit. But
around sunrise the cigs at kgeg/ksff/kcoe could actually lower
back down to IFR conditions for the morning before lifting a bit
for the afternoon hours. The next weather system will move across
the Cascades on Tuesday, bringing rain and MVFR cigs to keat. Kmwh
should stay VFR through this forecast period, but they do have
small chance of some IFR fog around sunrise. Rj

&&

Preliminary point temps/pops...
Spokane 45 63 46 62 43 65 / 20 20 80 60 40 10
Coeur D'Alene 46 63 46 60 42 65 / 30 20 70 60 40 10
Pullman 42 64 44 61 41 62 / 40 20 70 60 40 30
Lewiston 49 69 53 67 51 67 / 50 10 70 70 40 30
Colville 39 64 40 65 36 72 / 30 70 90 70 40 0
Sandpoint 45 61 45 60 41 64 / 20 30 70 70 30 20
Kellogg 47 61 50 58 46 61 / 40 10 60 70 40 30
Moses Lake 44 63 44 68 43 72 / 0 60 60 30 20 0
Wenatchee 50 60 50 65 50 70 / 0 80 70 40 10 0
Omak 45 61 49 65 45 70 / 20 90 90 50 10 0

&&

Otx watches/warnings/advisories...
Idaho...none.

National Weather Service Glossary of Abbreviations