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fxus65 kpih 112130 

Area forecast discussion
National Weather Service Pocatello Idaho
230 PM MST Wed Dec 11 2019

Short through Friday night. Fast moving shortwave
drove broad region of light snow with minor travel impacts through
east Idaho today. Satellite imagery shows broad area of moisture
pushing through Oregon this afternoon on nose of strong Pacific
jet. Westerly orographics favor development of moderate to heavy
snowfall over portions of the central mountains and eastern
Highlands beginning tonight and continuing into Friday morning.
Blended model spreads still favor generally 4-10 inches of snow in
locations such as Stanley and Sun Valley, with higher amounts
focused over the ranges just west along the forecast area border.
In the eastern Highlands, ensemble spreads are similar for the
higher elevations with slightly lesser amounts of 4-7 inches in
the somewhat protected valley locations such as Driggs and Island
Park. The snake plain should be warmer, especially during the
daytime hours, and somewhat shadowed in the northern portions of
the snake plain (arco desert). That said, areas such as Rexburg
and St. Anthony could fall under the fun for potential advisory
headlines as well, along with higher elevations south of I-84/86.
Have updated all previously issued watches to warning, but also
included the Idaho Cache Valley and Bear Lake Valley in advisories
for higher snow amounts and expected travel impacts there. Frontal
boundary drives through late Thursday into Thursday night.
Guidance more bullish on the increase in winds overnight Thursday
night into Friday morning. Have kept winds below guidance for now
with the expectations that the ongoing precipitation tends to
mitigate the maximum wind potential. That said, guidance does push
winds well into advisory criteria after midnight Thursday night,
and briefly approaches high wind criteria. If the trend in the
guidance continues, this may be an additional Point of concern.

There should be a break in the snowfall for higher elevations
during the day Friday, though eastern Highlands may remain under
the gun given the westerly flow. Models are consistent in bringing
the next round of precipitation into east Idaho late Friday into
Friday night. Temperatures should be colder behind the front, so
even lower elevations should see snow. The models are trending
toward focusing the band of precipitation into the southern
Highlands for the next round, though the eastern Highlands take
another big hit Fri night. At this point in time, the expectation
is that advisory level snows are expected to continue, at least
for most higher elevation zones. Dmh

Long term...Sat to next Wed night. The trend for Sat over the last
three days has been for more snow, with 0.5 to 2 inches in the Snake
River Plain on Saturday. The snow is mostly south and east of the
Snake River, with much of the northern zones drying out quickly. Sat
night appears to only have some residual moisture, but the northwest
flow continues bringing cold air and it has the right angle to
continue light snow in the southern and eastern Highlands. Another
embedded trough moves through the mean northwest flow on Sun night,
keeping the snow going in the same places: southern Highlands,
eastern Highlands, and southeast side of the Snake River Plain and
southern side of the Magic Valley. This phenomenon continues until
finally on Tue an upper level ridge is pushed over eastern Idaho due
to the next upstream low approaching the coast, which doesn't arrive
until beyond the 7-day period. Messick


Aviation...first impulse will clear during the mid- to late
afternoon, but until then will bring brief IFR conditions to kida
and kdij which are still in its sights. The break is just a brief
interlude before a very moist and warm air mass slides into eastern
Idaho tonight. The deep layer of warming will hopefully mean no
fzra, but will start out everywhere except ksun and kida as rain or
rasn. This will have less severe impacts to vsby, but expect IFR due
to ceiling for kpih kida and ksun. Kdij will be hardest hit and the most
likely to be closed Thu morning as temperatures keep snow until Thu
afternoon. Ksun will be borderline closed for most civil aviation.
Wind will not be much of a factor in this warm sector of the storm.


Pih watches/warnings/advisories...
Winter Storm Warning from 5 am Thursday to 11 am MST Friday for

Winter Storm Warning from 11 PM this evening to 5 am MST Friday
for idz071>073.

Winter Weather Advisory from 5 am Thursday to 8 am MST Friday
for idz059-061.

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