Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 120907

Area Forecast Discussion
National Weather Service Pocatello ID
207 AM MST Tue Dec 12 2017

.SHORT TERM...Today through Friday. Blocking pattern remains in
place with upper ridge nearly overhead this morning. WV imagery
reveals a shortwave riding atop the ridge into British Columbia.
Models suggest the shortwave will begin to flatten the ridge
somewhat on Wednesday as moisture trails in behind it. GFS
supports the idea of moisture over the Yellowstone NP area just
on our border, but opted for a drier forecast in agreement with
the NAM. Ridging will work its way through again Wednesday night
and Thursday, but we will begin to transition into a more active
pattern as a modest upper trough works its way into the forecast
area as early as Friday afternoon. This should signal an end to
our stagnant low-level inversion pattern plaguing our valleys over
this past week. Finally! Hinsberger

.LONG TERM...Friday night through next Monday. A little sharper
trough appears to be coming into Idaho Friday evening and crossing
the central Rockies Saturday. this is effectively shifting
precipitation from Sunday in the previous runs to more Saturday in
the latest model runs. This also slows the forecast winds in the
Snake Plain over the weekend and lowers temperatures a couple of
degrees at the same time. RS

.AVIATION...Loosing the low stratus in the Snake Plain and Eastern
Magic Valley yesterday seems to have opened the door for a little
more diurnal westerly shift to the winds. A little fog/stratus has
moved back into the Burley area where LIFR conditions are
persisting. The inversions increased a bit as well with the upper
ridge more overhead. GFS Lamp is favoring this fog lasting until
18Z. The RAP is trying to shift winds NNE which could help reduce
the fog a couple hours earlier. Observed winds so far have become
calm, but not shifted NNE yet. Light northerly winds are trying to
prevail at KIDA, but go variable every so often and a little fog off
the river that seems to drift into the field. At KPIH, may have a
little touch of industry effect near sunrise 12-14Z. RS

.AIR QUALITY...Inversions continue to hold and reduce air quality,
particularly for Franklin County where an Air Stagnation Advisory
remains in effect. Wednesday afternoon, the NAM12 model increases
winds from the north which could help scour the valley out some. RS



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