Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 171959

Area Forecast Discussion
National Weather Service Pocatello ID
159 PM MDT Sun Sep 17 2017

.SHORT TERM...Tonight through Tuesday night. Weak shortwave
crossing region today, with generally only a few high clouds to
spoil sunny and mild day. Much stronger shortwave approaching
PacNW coast associated with deep low off BC Canada coast. Valley
rain/mountain snow spreads across the region beginning in the
central mtns by late morning, and continuing into the eastern
portions of the region by evening. Cold front slides through as
well, with sfc gradient and mid level support sufficient for winds
near or above 25 mph many places. A wind advisory may be necessary
for portions of the Snake Plain. Showers continue, mainly over
higher elevations into Tuesday. Snow levels remain above valley
floors. Winds continue to be strong into Tuesday with even better
support for winds above 25 mph, and could be the better day for
wind advisory in the Snake Plain. Temps cool down quite a bit
Monday into Tuesday behind the front. DMH

.LONG TERM...Wednesday through Sunday. Pattern continues to be
cool and wet through the remainder of the work week as upper low
deepens over the PacNW states. Second significant cold front of
the week swings through the region late Wednesday. Snow levels
continue to slide toward, but remaining above, valley floors.
Wednesday also likely breezy to windy again. Upper low opens but
trough lingers into Friday. Precipitation gradually weakens and
dissipates as upper trough slowly shifts east into Saturday.
Expect temperatures to remain cool into the weekend, but drier as
northerly flow slowly shifts into the region behind the trough.


.AVIATION...Weak upper trough passing through the region today is
bringing only broken mid-clouds. So VFR conditions should persist
through 18Z tomorrow. Concern will be for KSUN in the 18/18Z-19/00Z
(tomorrow afternoon) timeframe when the next Pacific system makes
its way to the Central Mountains. Winds across the Snake Plain may
begin to increase late tomorrow morning as we mix out. Hinsberger


.FIRE WEATHER...Another deep upper low is heading towards Idaho
tomorrow, promising to bring strong winds and plenty of moisture.
This upper low will begin to move into BC Monday night, while a
strong shortwave swings through Idaho bringing the first wave of
winds and precip. Winds will increase late Monday morning with the
precip band going west to east through the evening/overnight hours.
Expect a brief break in the precip on Tuesday, but winds will still
be strong--possibly stronger than Monday. Another strong upper
trough will dig into the PAC NW Wednesday bringing another round of
showers and strong winds. With a deep upper trough over us,
temperatures should continue to remain well below normal. Humidity
will be high enough to curtail any fire weather headlines. The upper
trough will remain over the region through Friday, and begin lifting
out of the area by Saturday. Hinsberger



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