Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 220851

Area Forecast Discussion
National Weather Service Pocatello ID
251 AM MDT Mon May 22 2017

.SHORT TERM...Today through Wednesday night. Wave of low pressure
will race southward through Wyoming today, with the far NE corner
of Idaho close enough to warrant mention of an isolated shower or
thunderstorm from Island Park south through Palisades from this
afternoon through early evening. NE winds on Sunday over-achieved
across the Snake Plain in terms of their strength. Winds are
expected to have more of a westerly component (primarily blowing
from the NW) across the Snake Plain today, until turning more
northerly and increasing by evening in response to the wave
passing through Wyoming. Northerly winds are expected to be
stronger through the day over the Eastern Highlands (15-25 mph),
and some chop on waterways is possible, but conditions don`t
currently appear favorable for a Lake Wind Advisory for American
Falls. Expect slowly climbing temperatures today and Tuesday.

The highest impact day of the short-term period currently appears
to be Wednesday, when a strong but mainly dry cold front swings
through the area as a strong closed low scampers through the
southern Canadian Provinces. Winds are forecast to sharply
increase Wednesday after the frontal passage and become W-SW in
the 20-30 mph range with gusts to 45 mph. This may create areas of
blowing dust and difficult travel, particularly for high profile
vehicles on north-south routes such as I-84 from Burley to the UT
border. The afternoon timing of the front and associated dry air
should promote ideal mixing -- so confidence is increasing in a
Wind Advisory type event. Do not currently think winds will be
strong enough for a High Wind Watch -- but will need to monitor
trends as this event grows nearer. Ribbon of moisture along the
front may be adequate for an isolated shower or thunderstorm along
the Southern Highlands Wed Eve and overnight, but lack of
moisture looks to be a limiting factor for significant, widespread
precipitation with this cold front. AD/GK

.LONG TERM...Thursday through Monday.
An upper trof will move through Idaho and bring cold and showery
weather Thursday through Saturday.  Temperatures will be well below
late May normals Thursday through Saturday.  Expect some drying and
moderating temperatures back closer to normal Sunday and Monday but
kept some mainly mountain showers in the grids.


.AVIATION...Expect VFR conditions throughout today.  The only
potential showers will be near Driggs but any ceilings expected to
stay in VFR category.  Winds generally expected to stay in the 10
knot or less range today but some northerly winds may increase
toward sunset especially at IDA.


.HYDROLOGY...A warming trend to above-average temperatures today
and Tuesday should quicken high-elevation snowmelt which will mean
an increase in runoff. This will result in rises in river levels
and flows and their tributaries through mid-week. Rises are
expected to resume on the Big Wood River and tributaries across
Custer and Blaine counties. The Big Wood River is forecast to
once again approach flood stage by Wednesday. It is also possible
that Valley Creek at Stanley may exceed bankfull as well. The Bear
River at border is expected to largely remain steady through the
week. The exception to the rising trend is for those basins where
high-elevation snowpack has largely melted off, such as the
Portneuf at Pocatello, which is expected to fall below flood
stage sometime Tuesday. AD/GK



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