Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 162010

Area Forecast Discussion
National Weather Service Pocatello ID
110 PM MST Thu Feb 16 2017

.SHORT TERM...Tonight through Saturday night. Current storm system
moving thru the Pac NW today is producing areas of low elevation
rain and mtn snow this aftn. The majority of the snow will fall in
the central mtns where the moist southwest flow interacts with the
terrain. Snowfall amounts are expected to range from 6 to 10
inches before tapering off toward Fri morn. The upper Snake
Highlands should see around 2 to 4 inches by Fri morn. Upper
ridging will end most of the precip on Fri...but another Pac storm
system quickly moves in from the southwest Fri night. This system
looks wetter. Snow is expected to become heavy by Sat morn across
the southern parts of the central mtns and the upper Snake
Hghlands. These are the areas most impacted by moist southerly
flow. In contrast...the rest of the fcst area receives less precip
due to the downslope effect off the southern highlands. Over a
foot of snow is possible in the central mtns by Sun eve...with up
to a foot along the Divide. On Sun...the heavy snow decreases in
the upper Snake Highlands and shifts more to the central mtns as
upper flow becomes more westerly. Therefore...a winter storm watch
will be issued for the central mtns and along the Divide late Fri
night thru Sun. Elsewhere...the low elevations can expect mainly
rain. A rain/snow mix is possible across the northern portions of
the Snake River Plain...but not expecting significant
accumulations at this time. Hedges

.LONG TERM...Sunday through next Thursday. Dynamics involved with a
lifting shortwave trough will start off the long-term period with
widespread chances of precipitation. The chances diminish as the
shortwave continues northeastward, but moisture transport ramps up
again Monday morning. GFS shows another slight break in the precip
Tuesday night, though the ECMWF hints at mountain precip around the
same time. Troughing will continue to develop over the West
throughout the day Wednesday, and moisture will again target Idaho
as a wave rotates around a developing upper low. Differences emerge
in the models as to the location of the upper low. The GFS
positioning is over the Great basin, while the ECMWF slides an upper
low along the coast and drops it into a deepening upper trough. Both
solutions produce ample moisture with warm temperatures Monday-
Tuesday, though a cold front will pass through Tuesday leading to
rain changing over to snow possibly to the valley floor. Another
dynamic system will bring us to the extended periods as the GFS
slides the Great Basin low eastward into a favorable 700mb
positioning to be a potential heavy snow producer, though there is
still a good deal of uncertainty in dealing with this upper feature.


.AVIATION...Dynamic upper trough with attendant cold front lifting
through California and will trigger some showers this
afternoon/evening across the forecast area. Expect terminals in the
Snake River Plain to remain VFR until tomorrow morning. Models are
keeping some modest low-level moisture in the post-frontal airmass
tomorrow morning, and will mainly impact KIDA with fog/stratus where
statistical guidance strongly supports near-minimum conditions.
Winds will be gusty as the cold front passes, but no strong
indications of gusts greater than 25kts. Hinsberger


.HYDROLOGY...A series of Pacific storm systems will roll thru the
region well into next week. Rainfall amounts over the weekend
could add up to a half to one inch across much of the area. Too
early to project precip amounts next week...but the indications
are that they will be significant. This means more flooding issues
for the next several stay alert even if not in
traditionally flood prone areas. Hedges


Winter Storm Watch from late Friday night through Sunday
afternoon for IDZ018-019-031.

Winter Weather Advisory until 5 AM MST Friday for IDZ018-031.


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