Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 302105

Area Forecast Discussion
National Weather Service Pocatello ID
205 PM MST Wed Nov 30 2016

.SHORT TERM...Tonight through Saturday...Current radar and
satellite depictions showing light snow across Idaho Falls
to Bancroft and eastward with another broad area of activity
west of Ketchum. Moisture from this new plume is expected to work
its way south of the Lower Snake Plain while a trough of low
pressure digs southeast across Idaho. Expect increasing snow
chances this evening from American Falls eastward. A weak cold
front then pushes through Thursday morning and enhances precip
production across Upper Snake/Eastern Highland areas. This has
resulted in an increased pop forecast in the overnight hours and
for the Upper Snake/Upper Highland areas and an increased QPF/snow
forecast. Expect the majority of snow to fall overnight and
Thursday morning into the early afternoon of 2 to 4 inches with up
to 6 inches possible. As driving conditions are likely to be
difficult a WINTER WEATHER ADVISORY FOR SNOW has been issued.
Additionally, a WINTER WEATHER ADVISORY FOR SNOW is in effect for
the Snake Plain including Pocatello and Idaho Falls for 1 to 3
inches of overall snowfall amounts that may make your Thursday
morning commute hazardous. Allow extra time for your travels

By late Thursday, activity will be gradually improving across the
Central Mountains and from the west. And by Friday morning, the
snow showers will be greatly improving in their intensity for the
remainder of the region. However, much colder early morning
temperatures can be expected for Friday and Saturday. Saturday may
also bring light snow to the mountains. NP/Messick

.LONG TERM...Sat night through next Wed night. one major winter
storm during this time. The timing is still somewhat up in the air,
with the GFS predicting Sat night/Sun, and the ECMWF more Sun/Sun
night. Also, the ECMWF has kept the precipitation at much less
amounts and focuses on the northern half of the forecast area. The
GFS has widespread heavy amounts nearly everywhere. The GFS also
brings this low through with some powerful wind. An additional
trouble is that both guidance product suites have stood their
grounds for the past two days, so it is difficult to say who is
correct. So have continued preferring the GFS solution so as to
not make too many changes. Beyond this weekend storm, a north to
northwest flow in the upper levels brings in an arctic air mass
and below zero temperatures for many heavily populated areas, once
the skies clear Tue and Wed nights. Have avoided Bias-Corrected
grids for this period, as this is such a severe change in air
mass. There is a chance for some light precipitation with some
weak impulses, but there is little timing agreement between the
GFS and ECMWF. However, precipitation is not the screaming message
for the Mon night through Wed night period; the cold air is.


.AVIATION...Showers in the north end of the valley have affected
both KIDA and KDIJ, so have kept TEMPO groups in these airdrome
forecasts. Otherwise, an incoming storm tonight should bring the
three eastern airports to IFR or worse by opening. KSUN may go
marginal VFR, but the new field minimums should not be breached.
KBYI is the farthest removed from the storm center and has the best
chance of staying VFR, although it could be marginal VFR for a
while. Winds not really affected strength-wise by this storm, but
directions are somewhat crazy for KSUN. Messick


Winter Weather Advisory from 8 PM this evening to 5 AM MST
Friday for IDZ019>021-023-025.


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