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fxus66 kotx 190543 
afdotx

Area forecast discussion
National Weather Service Spokane Washington
1043 PM PDT Fri Oct 18 2019

Synopsis...
the weekend will be wet and raw with locally heavy snow in the
mountains. The most significant slug of precipitation is expected
to occur on Saturday morning with locally heavy rain over
southeast Washington and the southern Idaho Panhandle. Another
round of locally heavy rain will be possible in the Monday and
Tuesday time frame before a drier and more stable pattern arrives
for the second half of next week.



&&

Discussion...
the first wave of High Mountain snow and valley rain moved across
the Cascades this evening. Snow levels look to be above 4000 feet
as Stevens Pass picked up a quick few inches. The next round of
precipitation on the West Coast will move in late tonight along
with a developing surface low that will concentrate more rain
moving into the Central Basin progressing north and east into the
Idaho Panhandle by 8 am Saturday morning. At this time it still
looks like snow will stay in the higher elevations although there
could be some rain mixed with snow down around 2500 feet for
a while Saturday morning on the West Plains west of Spokane but
little accumulation is expected. The surface low will concentrate
heavier precipitation on its perifery and rith now the south and
eastern third of Washington and central Idaho Panhandle look to get
some pockets of moderate rain early Saturday tapering off by
late Saturday afternoon on the Washington side and taking
longer until late night to move out in the Idaho panhanle.
We'll keep the advisories running for the Cascades and central
panhanle. Tc

&&

Aviation...
06z tafs: moisture will continue to increase over the region
as a dynamic low pressure system moves into the area.
More widespread limited ceiling and visible conditions will impact the eastern
taf sites kgeg,ksff, kcoe and kpuw after roughly 10z. IFR ceilings are
now forecast for more sites now at kgeg,kcoe,ksff and kpuw for Saturday
morning into at least early saturdayafternoon. Toward 00z there will
be marked improvement in conditions and winds will pick up gusting
to 25 mph from the southwest near keat and kpuw as drier
air moves in. However it will take longer at kcoe to improve. Tc




&&

Previous discussion... /issued 504 PM PDT Fri Oct 18 2019/

Synopsis...
the weekend will be wet and raw with locally heavy snow in the
mountains. The most significant slug of precipitation is expected
to occur on Saturday morning with locally heavy rain over
southeast Washington and the southern Idaho Panhandle. Another
round of locally heavy rain will be possible in the Monday and
Tuesday time frame before a drier and more stable pattern arrives
for the second half of next week.
The weekend will be wet and raw with locally heavy snow in the
mountains. The most significant slug of precipitation is expected
to occur on Saturday morning with locally heavy rain over
southeast Washington and the southern Idaho Panhandle. Another
round of locally heavy rain will be possible in the Monday and
Tuesday time frame before a drier and more stable pattern arrives
for the second half of next week.

Discussion...

Tonight: clouds will continue to increase tonight ahead of the
arrival of a wet frontal system Saturday morning. Periods of
light precipitation are expected to become heavier over the
Cascades overnight. By the early morning hours snow levels are
expected to fall to 4000 feet bringing snow to Stevens, Blewett,
and Loup Loup passes in the north Cascades. The heaviest
accumulations in the Cascades are expected to occur prior to
sunrise through the morning hours on Saturday. Further east, bands
of rain are expected to develop overnight and increase during the
early morning hours as a compact surface low moves inland.

Saturday: as our cool upper level trough spreads precipitation
across eastern Washington and north Idaho, a compact surface low
is expected to emerge east of the Cascades. Fast flow regimes
often give the models fits, and this case is no exception. We have
struggled to determine the track of the surface low as it deepens
in the Columbia Basin and through eastern Washington into the
Panhandle. Precipitation amounts and localized bands of snow
embedded with the rain are the main concern Saturday morning.

*Precipitation type: the 12z GFS, 12z ECMWF, and 18z NAM are in
fair agreement that the surface low will form between Moses Lake
and Tri Cities around 4 am and track along the Spokane/Whitman
County line during the mid to late morning hours and through
Kootenai and Shoshone counties in the afternoon. Strong upward
vertical motion along and north of the low track may be enough to
cause rain to change to snow above 2000-2500 feet for a few
hours Saturday morning across the West Plains, South Hill, and
hills around couer d'alene. At this time, it looks like the best
chances for the change to snow will occur during the daytime
hours which is a good thing. With temperatures expected to be the
mid to upper 30s, snow will probably have a hard time sticking
to anything.

*Mountain snow: winter weather advisories are in effect for the
north Cascades, the mountains of the central Idaho Panhandle, and
the Blue Mountains. The heaviest accumulations are expected to
occur above 4000 feet. Big game hunters and other outdoor
enthusiasts may encounter difficult driving conditions on back
roads especially on ridges of 5000 feet or higher. I-90 at
Lookout Pass (elevation 4700ft) may also experience periods of
accumulating snow on Saturday and Saturday evening.

*Rain concerns: some creeks and streams on the Palouse are
notoriously flashy. Fortunately, rain amounts the last several
days haven't been enough to saturate the soil. However, we are
still concerned that sharp rises will occur on Paradise creek in
Moscow on Saturday. With another round of significant rain
possible Monday and Tuesday, we will be watching Paradise creek
again and possibly other streams on the Palouse since the ground
will be wet and more prone to yield runoff.

Sunday: the polar jet will begin to migrate north on Sunday
emerging out of southern Oregon and retreating toward Canada by
late Sunday. It looks like another shortwave will move inland as
the jet lifts northward bringing another round of rain and High
Mountain snow to Washington and Idaho. At this time, it looks like
the best chances for widespread rain will be in the afternoon and
evening. We will be keeping a close eye on precipitation amounts
over the Palouse and the headwaters of the Stehekin River in the
Cascades. These basins are our most prone to quick rises during
rain events this time of year. /Gkoch

Monday through friday: with the arrival of a warm front on Monday,
subtropical moisture will bring more precipitation to the region.
Models are varying significantly in timing of both monday's warm
front and a following shortwave, but favor a concentration of the
precipitation occurring in the Idaho Panhandle and Cascades. Snow
levels begin at an elevation of 3500-4000 ft Monday morning and rise
drastically through the day. Currently, Monday and tuesday's
precipitation is looking like it will be mostly rain with snow in
the high elevations and some passes. Still low confidence in the
timing and intensity, but a decent portion of the region will begin
with a wet week. The shortwave is likely to bring stronger winds and
potentially gusty conditions to areas such as the eastern Cascades,
blues, and Palouse. The models have an inconsistency in timing and
intensity, but the strongest winds are looking to occur overnight
Monday into Tuesday. These will be conditions we are going to keep a
close eye on. Temperatures will begin mild, near-normal with highs
in the 50s and 60s. The remainder of the week will bring drier
conditions. Temperatures look cooler in the latter half of the week,
but still time to change. Js

Aviation...
00z tafs: moisture will continue to increase over the region
as low pressure moves into the area. More widespread MVFR
conditions will impact mainly the eastern taf sites kgeg,ksff,
kcoe and kpuw after roughly 10z. IFR ceilings are forecast at kgeg
mainly for the mornign hours Saturday. Toward 00z there will be
marked improvement in conditions and winds will pick up gusting
to 25 mph from the southwest as drier are moves in. Tc

00z tafs: moisture will continue to increase over the region
as low pressure moves into the area. More widespread MVFR
conditions will impact mainly the eastern taf sites kgeg,ksff,
kcoe and kpuw after roughly 10z. IFR ceilings are forecast at kgeg
mainly for the mornign hours Saturday. Toward 00z there will be
marked improvement in conditions and winds will pick up gusting
to 25 mph from the southwest as drier are moves in. Tc

&&

Preliminary point temps/pops...
Spokane 38 45 34 46 36 50 / 80 100 20 60 40 30
Coeur D'Alene 39 42 35 44 36 47 / 90 100 30 60 50 40
Pullman 39 48 35 46 37 50 / 50 100 30 50 50 40
Lewiston 45 54 42 54 44 57 / 40 100 30 50 50 40
Colville 36 46 30 49 30 51 / 70 70 10 60 40 40
Sandpoint 39 41 36 43 35 46 / 90 90 20 60 60 50
Kellogg 39 39 37 42 38 45 / 90 100 60 70 70 60
Moses Lake 42 57 36 54 37 57 / 70 70 0 40 20 20
Wenatchee 41 57 39 51 40 55 / 70 60 10 50 30 40
Omak 40 53 34 49 36 51 / 60 60 0 60 30 40

&&

Otx watches/warnings/advisories...
Idaho...Winter Weather Advisory from 5 am Saturday to 8 am PDT Sunday
for central Panhandle mountains.

Washington...Winter Weather Advisory until 5 PM PDT Saturday above 4000 feet
for east slopes northern Cascades.

Winter Weather Advisory from 2 am Saturday to 2 am PDT Sunday
above 4500 feet for northeast Blue Mountains.

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