Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 161146
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
446 AM PDT WED APR 16 2014

.SYNOPSIS...
Another weather system will bring more showers to the Inland
Northwest today. A stronger system will result in widespread rain
Thursday and Thursday night. At this time the Easter Weekend
looks to be mild and dry. Showers return to the forecast for the
first part of next week.

&&

.DISCUSSION...
Today and Tonight: An upper level shortwave disturbance will push
across the region this morning into this afternoon. There will be
a couple main forcing mechanisms that will help generate light
rain and mountain snow this morning. One will be a 120 kt jet
streak oriented NW to SE across western WA. This will place
eastern WA and the ID Panhandle in the more favorable left exit
region. We will also see some weak isentropic ascent across much
of the eastern two-thirds of the forecast area. The one factor
that will inhibit precip is relatively dry air near the surface.
Dew point temps remain in the low to mid 20s across much of the
region early this morning. It will take some time for the
atmosphere to moisten through the morning hours before any precip
is observed at the surface. Light rain and mountain snow is
expected to fill in across the region after about 9:00 AM this
morning. At first I think we will see mainly stratiform precip,
but should transition to more of a convective regime through the
afternoon with the focus of precip gradually shifting more into
the ID Panhandle into tonight.

Thursday Morning into Thursday Afternoon: A much wetter weather
system will enter into the region during this period. This system
will feature stronger isentropic ascent in the warm sector with
widespread stratiform precip across much of the region. Snow
levels will increase to above 6,000 feet with mainly rain for all
areas. Overall, Thursday will be a cloudy and increasingly rainy
day. High temperatures both Wednesday and Thursday will be below
normal topping out in the 50s to low 60s for most valley locations.
/SVH

Thursday night through Saturday: Well-defined cold front will move
through the area Thursday night. The short wave aloft that
accompanies this front has a nice negative tilt to it as it moves
through the Inland Northwest. This would typically favor
thunderstorm development. But in this case, the timing is off, as
the trough moves through overnight instead of during the peak
heating. The 500mb cold pool also moves over on Friday morning,
again, not ideal for convection. However, the model timing has
been changing over the past few runs. The GFS has been
consistently trending slower, and the 00Z ECMWF was slower than
the 12Z run. If that trend continues, then things may line up
better for convection Thursday night as well as Friday afternoon.

The models all agree on a fairly impressive moisture tap for this
front. Precipitable water values are about two times normal for
mid-April. So we should see some decent rainfall amounts from this
system, in contrast to the past several fronts.

The other issue with this system is the wind potential for
Friday. The slower GFS has the strongest winds. But again, given
the less- than-ideal timing of this system, I kept the winds in
the 10-20 mph range. RJ

Sunday through Wednesday: The flow pattern over the Inland
Northwest will become more southwest, or even south, with time as
we head into next week. This means more active weather for most
areas, eventually. The transition periods between Sunday and
Monday morning look to stay mostly dry outside of the Cascades as
a large trough gets closer to the Pacific Northwest coastline.
There are still some timing and placement issues with regards to
the trough moving inland, but right now it looks like this will
take place sometime Monday night or Tuesday. This forecast
continues the trend of precipitation chances peaking during this
time frame, and then trailing off for Wednesday (becoming more
showery). Temperatures were adjusted slightly, but still look to
be at or above normal by a few degrees. However, if clouds hold on
longer or the rainfall is more prolonged, temperatures may
struggle to reach normal. ty

&&

.AVIATION...
12Z TAFS: A weak weather system this morning will result in
lowering cigs and light rain across the region. Cigs will
generally remain above 3 kft agl, but MVFR conditions cannot be
ruled out. Light stratiform rain will become more convective this
afternoon with rain showers possible at the KGEG, KSFF, KCOE,
KPUW and KLWS TAF sites. Cigs will improve this evening with
showers limited mainly to the mountains. /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        54  42  54  41  56  35 /  70  20  70 100  40   0
Coeur d`Alene  53  40  53  41  55  32 /  70  40  70 100  50   0
Pullman        53  43  57  42  53  32 /  60  20  60  90  30   0
Lewiston       59  44  64  45  59  38 /  40  20  30  90  20   0
Colville       59  41  57  42  61  31 /  70  30  80  90  30   0
Sandpoint      53  39  53  42  54  30 /  70  30  70 100  60  10
Kellogg        50  39  52  40  53  36 /  80  40  50 100  60  10
Moses Lake     63  48  61  43  64  35 /  30  10  60  40  10   0
Wenatchee      63  45  61  41  62  41 /  30  20  70  30  10   0
Omak           61  41  60  39  62  33 /  50  20  70  40  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&

$$




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