Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 090907

Area Forecast Discussion
National Weather Service Pocatello ID
207 AM MST Sat Dec 9 2017

.SHORT TERM...Today through Tuesday. Blocking upper high continues
to be the dominant feature for the short-term period. Surface
weather will be most influenced by the surface inversion. Fog and
stratus will continue to be the norm under these conditions. MODIS
nighttime microphysics imagery very similar to 24 hours ago with
fog/stratus trapped in the Snake Plain and adjacent valleys.
Freezing fog is present at a couple observation sites, but road
conditions have not responded as yet. Thus holding off on any
headline issuance for freezing fog. Main strategy for temps/RH was
to incorporate some persistence and carry it through Tuesday.

.LONG TERM...Tuesday night through next Friday. High pressure ridge
will continue to support inversion conditions through next Thursday
night. Models are then showing support and agreement on finally
breaking down the ridge and letting disturbances come in off the
Pacific, the first being Friday afternoon or night. Until then, will
continue to favor colder temperatures in the Snake Plain and some
valley areas, with potential for some fog and low stratus. RS


.AVIATION...Inversions continue to be problematic with low stratus
and areas of fog. KBYI is still on the edge of the stratus and has
the best potential for clouds scattering out in the afternoon. The
other location where skies may well remain VFR is KDIJ. Confidence
in low stratus at KDIJ in the early morning hours is marginal. The
NAM12 model continues to support the development of easterly winds
at the surface and in the boundary layer tonight and Sunday morning.
The inversion has been pretty strong, but this could transport some
of the status towards the west side of the state. RS


AIR STAGNATION...Inversions continue to hold and reduce air quality,
particularly for Franklin County where and Air Stagnation Advisory
remains in effect. Saturday night and Sunday morning, looking for
development of more persistent easterly winds at the surface and
near the top of the low level stratus in the Snake Plain. Both the
NAM and GFS models have supported this idea the past two days. It
probably will not get rid of the inversion completely, but it can
transport some of the low stratus out of the Snake Plain and
towards the west side of the state. RS



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