Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Spokane Washington
446 am PDT Friday Apr 18 2014

Synopsis...
today will be a brief break in the Pacific storm train. A weaker
front will bring mainly windy conditions Saturday afternoon and
night with some showers across the north. Easter Sunday should be
mild and mainly dry. After a warm and dry Monday, temperatures
will cool for the remainder of the week as another Pacific storm
moves into the area.

&&

Discussion...
today and tonight: the cold front is now just beginning to push
into the Idaho Panhandle at around 2:30 am. This is producing some
showers along the front. There is also some showers popping up
behind the front in an increasingly unstable air mass. These
showers, at the moment, are concentrated over the Okanogan
Valley/Highlands and will continue on their eastward progression
through the rest of today. Much of the shower activity associated
with the upper level disturbance will remain across the northern
mtns with the Spokane area possibly seeing an isolated shower on
the southern fringe through this morning. Much of the forcing is
a bit too far out ahead of the weak instability to see much of a
chance for any thunderstorms this morning. The cold pool aloft
will begin to exit the region this afternoon before we reach our
maximum heating, so I don't see much of a risk for thunderstorms
today either.

Pressure gradients behind the cold front are tightening
considerably this morning with windy conditions picking up across
the basin. Our strongest winds are still expected through this
morning with generally breezy conditions through the afternoon
hours. Some spots across the upper Columbia Basin, into the
Spokane area and down onto the Palouse will see near to Wind
Advisory level winds; however, it will be borderline enough that
I do not anticipate having to issue a highlight. Sustained wind
speeds of up to 25 to 30 mph with gusts to around 40 mph still
looks valid through this morning. These winds will slacken off a
bit in the afternoon as pressure gradients begin to weaken.

Winds will become light overnight with a substantial amount of
drier air filtering into the region. Dew point temps at Wenatchee
and Moses Lake have already plummeted down into the low 30s early
this morning. This dry air will continue to spread across the
region today. Sky conditions will be clearing through the
afternoon with some thin cirrus beginning to enter into the region
tonight. There will be a risk for freezing temps across the Moses
Lake area and across the lower portions of the upper Columbia
Basin. These areas are considered to be in their growing season
and a highlight may be needed; however, confidence is not quite
high enough at this time.

Saturday: a weak cold front will enter the region off of the
eastern Pacific. Due to the drier air in place, we will likely
only see increasing high and mid level clouds with this front. I
went ahead and added some sprinkles to the forecast, but
measurable precip is not really expected. Good mixing and
increasing milder air into the region will result in warmer temps
with highs slightly above normal. /Svh

Saturday night through tuesday: as the cold front moves through
the area late Saturday, gusty winds will develop. These winds
should last through the night and subside on Sunday, just in time
for Easter. The timing for winds is a bit more favorable than the
front currently moving through our area, since the frontal passage
will be in the late afternoon hours and we won't have a lot of
rain cooled air ahead of it. Gusts to 40 mph still look possible.

Easter Sunday continues to look dry with just a few mountain
showers. There should be some clouds moving through the area, but
by no means a cloudy day.

Then the attention turns to a large-scale Pacific trough system.
The models have been backing off a bit on the timing of this
storm, and Monday now looks like it will be dry and rather warm
with temperatures in the 60s to lower 70s. We'll see a drop of
about 15 degrees for Tuesday as the trough pushes onshore and rain
develops over much of the area. Since the models have been
adjusting their timing with this system, I didn't go whole-hog
with the precip chances at this point. At this point, this front
does not look as wet as the one that moved through our area on
Thursday. Rj

Tuesday night through saturday: the large scale trough will be
traversing the region for the middle portion of the work week.
While the trough crossing the region is in agreement with the
extended models, there is some disagreement in how fast it moves
into the northern plains. The GFS/dgex would suggest it take a
more meandering approach across Montana, with wrap-around moisture
keeping thick cloud cover and higher precipitation chances over
far eastern Washington into the Idaho Panhandle into Wednesday
night. The European model (ecmwf) would suggest the trough continue moving east. With
the previous forecast already having higher pops for the east,
went ahead and gave a nod to the wetter solutions, while not going
too high. This really isn't much higher, but more of a trend in
that direction. Brief shortwave ridging will give way to yet
another storm system toward the latter part of the work week.

As far as temperatures go, most areas will remain below normal for
this time of year. With the trough bringing in colder air aloft,
snow levels will have to be watched over the Idaho Panhandle. If
the wrap around precipitation does occur, 850 mb temperatures are
going to be near or even below zero for Wednesday and Thursday
mornings. This would bring snow down below pass levels, and even
into some valleys. Still a lot of time to look at this so will
keep a more mountain Snow/Valley rain for now. TY

&&

Aviation...
12z tafs: a cold front is sliding east of the region early this
morning with windy conditions developing behind the front. Expect
strongest winds to continue through the early afternoon hours with
gusts up to between 30-40 mph possible. These winds will gradually
weaken through the late afternoon hours before decoupling in the
evening. Showers will continue to linger into the afternoon,
mainly across the northern mtns and in the Idaho Panhandle. Considerable
amount of dry air behind the front will keep cigs above 5 kft agl
with VFR conditions prevailing through 12z Saturday. /Svh



&&

Preliminary point temps/pops...
Spokane 55 33 64 36 58 40 / 20 0 10 20 0 10
Coeur D'Alene 54 31 63 37 57 39 / 40 10 0 20 10 10
Pullman 53 33 66 35 57 41 / 10 0 0 10 0 10
Lewiston 60 37 72 41 64 45 / 0 0 0 10 0 10
Colville 61 31 67 33 64 36 / 40 10 10 30 10 10
Sandpoint 53 29 62 36 57 36 / 60 20 0 30 10 10
Kellogg 51 31 63 36 56 37 / 60 10 0 30 10 10
Moses Lake 63 31 69 38 66 43 / 0 0 10 10 0 10
Wenatchee 61 39 65 42 66 47 / 0 0 10 10 10 10
Omak 62 30 66 35 65 40 / 10 0 10 10 10 10

&&

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

$$