Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Spokane Washington
255 am PDT sun Apr 20 2014

Synopsis...
Easter Sunday should be mild and dry. After a warm and dry
Monday, a cool and unsettled weather pattern will return Tuesday
and linger through much of the week.

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Discussion...
eastern sunday: the inland northwest will be between weather
systems from Easter Sunday into Monday. The cold front from
yesterday will be well east of the region today with shortwave
ridging of higher pressure building in. This will promote more
stable mid level lapse rates with clearing skies behind the front.
However, we will see some mid to high level cloud cover enter the
region off of the Pacific. Current satellite imagery at 2:00 am
shows increasing clouds moving toward western Washington along a weak warm
front boundary. These clouds will ride up over the ridge and
generally impact the northern two-thirds of the forecast area
through this afternoon into this evening. The good news is that
precip is not expected along this warm front, so Easter
festivities are expected to see dry conditions with temperatures
right around normal.

Tonight through monday: the next weather system is set to begin
to impact the region on Monday. All model guidance shows
increasing moisture steaming up out ahead of the cold front at
this time. This front can be located on satellite imagery between
140-150w and 35-45n with darkening on water vapor imagery
indicating the back edge of this front. A 150 +kt jet steak on the
back side of the upper level trough will act to dig this energy,
which will effectively orientate the front more meridionally with
time. This will slow down the front and hang it up just off the
western coastline. Moisture will increase over the region in an
increasingly more southerly and mild flow pattern. This moisture
will result in increasing cloud cover during the day, but any
precip will likely hold off closer to the Cascade mtns until
better forcing with the front moves further east after this
period. 850 temperatures will increase substantially across the
eastern half of the forecast area. Warmer temperatures aloft will
result in a general warming trend into Monday, but we will also
see quite a bit of cloud cover that will temper this warm up a
bit. /Svh

Mon nt through Wed nt: the fcst challenges remain the same.
Namely...pcpn amnts and temps well below normal for tues through
Wed (leading to low snow levels and Spring snow accumulations)
for NE WA and the Idaho Panhandle, as well as gusty winds and
thunder chances tues. Though model guidance concerning the above-
mentioned challenges has not dramatically changed, our confidence
level remains low concerning the specifics...especially with snow
levels and accumulations tues nt. The initial band of pcpn tues
morning may be enhanced by elevated instability with the mid-level
front. We continued with a broad-brush approach to this pcpn
threat and did not add thunder attm. We did however keep thunder
in the fcst for tues afternoon across the nrn mtn zones. With the
upper trough directly over the pac NW tues through Wed morning,
not only will the pcpn be highly convective, but snow levels will
fall markedly, leading to a significant snow and/or graupel
accumulation threat. The area of most concern is the Idaho
Panhandle Wed morning under a developing trowal and Post- frontal
upslope. In addition, small- scale vort maxes within the upper
trough are notorious for producing localized heavy bursts of
pcpn...the locations of which will be very difficult to nail down.
It's likely that valley locations will see some snow or graupel with
this scenario. We increased the gusty west winds for tues, but
still below advsy thresholds. Bz

Thursday through sunday: unsettled weather will remain for much of
the extended forecast, as a trough of low pressure slowly moves
overhead. Precipitation chances will exist each day, with almost
all areas carrying at least some chance of rainfall (or mountain
snowfall). The trough does begin to move east sometime during the
weekend, but it will remain close enough that showers would still
be possible in the afternoon. And looking further into the future,
yet another trough may affect the inland northwest the following
week.

Cooler than normal temperatures are expected each day with
expected widespread cloud cover and associated precipitation.
Readings will be 5 to 8 degrees below normal Thursday, with only a
slow moderation into the weekend. TY

&&

Aviation...
06z tafs: an exiting cold front is taking most of the light
showers and/or sprinkles out of the aviation area overnight along
with a gradual decrease in the gusty/breezy wind conditions...otherwise
VFR conditions expected at all forecast sites through 06z Monday.
/Pelatti



&&

Preliminary point temps/pops...
Spokane 57 39 65 44 54 36 / 0 0 0 50 70 50
Coeur D'Alene 57 37 65 46 54 36 / 10 0 0 40 70 70
Pullman 57 39 66 44 52 36 / 0 0 0 50 70 60
Lewiston 64 42 73 49 57 39 / 0 0 0 40 60 50
Colville 62 35 68 41 59 36 / 10 0 10 50 60 40
Sandpoint 56 35 65 43 53 36 / 10 0 0 20 70 80
Kellogg 56 35 67 41 51 34 / 10 0 0 20 80 90
Moses Lake 66 42 68 46 62 39 / 0 0 10 60 40 20
Wenatchee 66 46 66 48 60 38 / 0 0 20 60 30 20
Omak 66 39 67 44 60 36 / 0 0 20 60 40 20

&&

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

$$