Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 112053

Area Forecast Discussion
National Weather Service Pocatello ID
153 PM MST Mon Dec 11 2017

.SHORT TERM...Tonight through Thursday. A ridge of high pressure
will remain anchored over the region through Tuesday then retrograde
westward off the coast Wednesday and Thursday as weak Pacific
impulses top the ridge and dig SE into the Dakotas. Daytime temps
have been gradually warming due to increased sunshine and thus have
tried to carry this trend through the short-term. And of course, the
overnight inversions will remain the dominant factor and thus have
tried to hang closer to persistence than anything else. The next
incoming storm looks to arrive Friday afternoon/evening which you
can read more about below in the Long Term section. Huston

.LONG TERM...Thursday night through next Monday night. The strong
upper level ridge is expected to break down during this period due
to storms coming in from the Pacific. The first one will cloud up
Fri afternoon in eastern Idaho, with a slight chance of some
precipitation as early as that afternoon, but it is more likely to
arrive Fri night and last into Sat, bringing snow and possibly a
rain and snow mixture to lower elevations. Windy conditions continue
into Sat night and Sun as a second storm pushes through. This storm
has even warmer air with it, and will likely change over to rain for
many elevations, even possibly places like Stanley. Sky cover clears
somewhat for Mon, allowing stronger warming for that day with
afternoon temperatures likely to be in the 40s. Both the GFS and
ECMWF are very similar in timing, with only minor differences in
precipitation amount. The bigger differences are in the degree of
warming, with the ECMWF staying cooler. This will obviously have a
tremendous effect on snowfall amounts. Messick

.AVIATION...Fog monster was reduced in effect by this morning to
KBYI and KPIH. Expect diminished severity, but not sure that fog is
completely done in the Snake River plain. Light wind continues, and,
outside of the morning hours at KIDA, KPIH, KBYI, CIG and VSBY
should be unlimited. Messick

.AIR QUALITY...Inversions continue to hold and reduce air quality,
particularly for Franklin County where an Air Stagnation Advisory
remains in effect. The upper level ridge of high pressure will move
more directly overhead of southern Idaho Tuesday morning. This will
increase the strength of the near surface inversion conditions. RS


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