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Area forecast discussion 
National Weather Service Pocatello Idaho
155 PM MDT Wednesday Sep 17 2014

Short term...tonight through Friday. A low pressure trough was
positioned off the Pacific coast early this afternoon with a well
defined short-wave feature rotating through the base accelerating
toward the northwest California coast. This wave is expected to rotate
through northern California overnight with attending convection
developing across NE Nevada early this evening which eventually
spreads north-northeast into south-central Idaho tonight. As the ejecting wave
spreads inland Thursday we should see an increasing potential for
showers and thunderstorms spreading from west to east across southeast
Idaho. A developing surface frontal boundary is also expected to
push through the region around noon helping to boost convective
activity ahead of the front. The models are showing some fairly
decent shear developing from MacKay to Dillon which may support more
robust thunderstorm activity Thursday afternoon. Trailing short-wave
energy advancing into central California Thursday night will promote
the development of a closed low circulation over south-central
California late Friday afternoon. As the wave sets up across central
California Thursday evening...a second wave of convection is
expected to develop over NE Nevada lifting into southeast Idaho overnight.
A drier northwest flow eventually overspreads southeast Idaho Friday as the northern
branch of the developing split trough finally pushes through the
area. Huston

Long term...Friday night through next Wednesday. Both the GFS and
European model (ecmwf) show the cut-off low over south-central California drifting NE
into Nevada early Sunday. Attending precipitation is expected to
spread into/across southeast Idaho Sunday afternoon through Monday night. A
dry SW flow follows Tuesday as the next Pacific trough sets up off the
northwest coast. The associated precipitation shield with this next trough
is expected to spread into the region late Wednesday into Thursday.

Aviation...moisture continues to advance into Idaho ahead of a deep
upper trough. Radar showing isolated showery activity across the
central mountains. Expect this to intensify later this afternoon as
surface heating destabilizes the low levels. Models intensify
boundary layer southerly flow in the early morning hours ahead of a
surface cold front. NAM bufr soundings indicate 25 to 30 kts around
2000 feet above ground level...not quite strong enough to include low-level wind
shear but close. Cold front should pass late tomorrow morning with
winds shifting southwesterly in the snake plain and showers
continuing through tomorrow afternoon. Hinsberger

Fire upper disturbance will lift out of the deep
trough off the California coast overnight bringing with it
increasing moisture. We should see showers spreading across
southeast Idaho overnight with thunderstorms possible around
sunrise. Higher elevations could see a quarter to a half inch of
rainfall with locally higher amounts possible tomorrow afternoon. At
the surface...a weak cold front will move through bringing a sudden
wind shift. Will see showers lingering into Friday over the
southeastern Highlands and drying heading into the weekend. An upper
low will lift out of the Pacific trough and through the Great Basin
early next week and may produce more showers and thunderstorms
mainly over the southern Highlands. Hinsberger

Pih watches/warnings/advisories...none.


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