Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 260943

Area Forecast Discussion
National Weather Service Pocatello ID
243 AM MST Sat Nov 26 2016

.SHORT TERM...This could be the last 50 degree readings seen in
eastern Idaho this year. The upper level ridge dominating weather
the previous two days has peaked in its magnitude and is starting
to break down as two low pressures approach: one from the west and
one from the south. The southern one arrives here first, spreading
moisture by late tonight into the eastern third and southern
quarter of the forecast area. By Sun, this has spread northward,
affecting all of the forecast area, though the chance of
precipitation remains relatively low. The approach of the second
low from the west has a much bigger impact on central and eastern
Idaho. Mainly, it will back a greater wind, with a wind advisory
possibly necessary in the eastern Magic Valley and lower Snake
River plain. Both of these storms will bring snowfall down to the
Snake River plain level, with some partial melting in each
corresponding afternoon. Right now, snowfall amounts for each
storm appear to stay in the 3 to 6 inch range for the mountains
and highlands, with only extreme high elevations, above 8500 ft,
getting heavier than that. For each storm, valley floors should
see anything from a skiff in the eastern Magic Valley to more than
half an inch in the upper Snake River plain. After today, daily
highs will be closer to normal, with the cloud cover keeping
overnight lows warmer than normal.  Messick

.LONG TERM...Tuesday through Saturday. GFS and ECMWF showing some
feature differences, mainly with respect to timing and position.
Both agree however on unsettled period through the extended.
Remnants of early week system linger into Tuesday with a few showers
over higher elevations. Transitory ridge for Wednesday but fast
moving low pushes into PacNW region, dropping over Idaho mainly
Wednesday night into Thursday. Timing differences between models
leave some uncertainty on onset of precip. ECMWF track of low also
directly over coast while GFS remains closer to coast. These
differences continue through remainder of period with upper low
developing into amplified split Thursday into Friday. GFS drops low
along CA coast while ECMWF holds center much further northeast over
UT. Differences manifest in wildly different solutions for
precipitation, therefore have opted for a blend with climo for
Thursday and Friday. Upper low does drop far enough south in both
models to fold over a ridge late Friday into Saturday for drier
conditions. DMH


.AVIATION...Expect VFR conditions to persist through the day.
Southerly flow amplifies across the region late today into tonight
with moisture pushing into the region by 03Z mainly along and east
of I-15. Some shadowing likely at KPIH given the strong south flow
aloft but will maintain VCSH mention for now at most terminals with
trend toward MVFR ceilings. DMH



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