Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 102050

Area Forecast Discussion
National Weather Service Pocatello ID
150 PM MST Sat Dec 10 2016

.SHORT TERM...Tonight through Tuesday. Early afternoon satellite
imagery was showing a broad upper trough over the Gulf of Alaska
which was resulting in a moist nearly zonal flow across the NW
states. Embedded disturbances were also visible rotating through the
cyclonic flow. One such disturbance was making its way through
Oregon and the Idaho panhandle with the back edge of the associated
moisture plume advancing into SW Idaho. The regional radar depiction
was clearly showing a distinctly drier airmass shifting east into
and across SE Idaho much as the models had predicted. Numerical
models show the Pacific moisture plume settling south across Nevada
and Utah this evening with rapidly decreasing shower activity across
the ERN highlands. Thus the current Warnings will remain in place
until 5 PM. A moist WNW flow develops over the region Sunday and
continues through Monday with minor disturbances embedded in the
flow helping to accentuate precipitation and snowfall totals across
the NW facing upslope regions of the Sawtooth, Targhee and Caribou
Mountain Ranges during that time frame. Snow accumulations generally
fall just shy of Advisory levels over the 2-day period and thus have
opted to let the forecast speak for itself. By Tuesday, a low
settling south off the NW coast will drive Pacific moisture west-
northwestward across the Great Basin and into SE Idaho for an
enhanced area of snowfall along the Nevada and Utah border regions.
Temperatures remain seasonal throughout the period. Huston

.LONG TERM...Tuesday night through next Saturday. Persistent wet
period in the middle and end of next week with abundant moisture
streaming through with continuous waves to lift it. Wednesday into
Thursday will be the wettest days with persistent snow showers
forecast through Thursday afternoon. If there is any hope of a break
in the precip it looks to come late Thursday evening into early
Friday, and this would only be for portions of our area including
the Eastern Magic Valley, Lower Snake River and Southern Highlands.
Potentially the Central Mountains could get a break too, but this is
a very big maybe. Forecasting temperatures Thursday and Friday is
going to be tough with much variation between guidances. The latest
guidances bring temperatures warmer than previously suggested, which
would affect the precip type for Thursday. If we keep what we were
thinking previously it will snow, but if we raise our temperatures
much higher, as some guidance suggests, it will easily rain in the
Snake Plain. A low pressure trough sweeps through on Friday, though
this is not expected to be a great snow (or rain) maker, except in
portions of the Eastern Highlands. Long range forecast models
indicate a cold front passing the region early Saturday with precip
(hopefully) clearing out behind it. NP/MH

.AVIATION...Trailing edge of precip is expected to push through this
afternoon along a surface cold front. This should clear KSUN early
afternoon, then the Snake Plain terminals around mid-afternoon, and
finally KDIJ by early evening. Soundings indicate a saturated low-
layer, but breezy post-frontal winds should inhibit fog. However,
stratus could be present anywhere within that moist layer.
Additionally, soundings indicate the potential for seeder-feeder
action for KBYI, KPIH, and KIDA for a few hours between 06Z and 12Z
tonight, but models are not indicating any substantial snowfall.

Winter Storm Warning until 5 PM MST this afternoon for IDZ019-022-

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