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Area forecast discussion
National Weather Service Pocatello Idaho
206 am MDT Mon Mar 27 2017

Short through Wednesday. Little change in overall
forecast as another developing split flow scenario emerges out of
the Pacific. As the upper pattern splits, models are driving most
of the heaviest precip into Utah, but some moisture remains
associated with the northern branch and its associated surface
front. Gradient tightens as a result this afternoon and evening,
but models keep wind speeds below advisory levels. Negative Lis
suggest the potential for thunder, and given sufficient lift
associated with upper dynamics, have included ts for this
afternoon. As upper system drives to the east tonight, pops
dwindle except over the southeastern Highlands where precip
chances persist into tomorrow morning. Ridging should be in place
tomorrow and into Wednesday, but may shift eastward enough to
allow precip over the central mountains by Wednesday afternoon.

Long term...Wednesday night through Monday.

Models show a strong low pressure system originating out of
southwest Oregon, tracking through northern Nevada and into central
Utah. This system has a lot of moisture with it and confidence is
growing for high elevation snow and low elevation rain. Looks like
precipitation will gradually overspread the region Wednesday night
with excellent chances Thursday and Thursday night. Snow levels will
begin above 6500 feet but as the low moves into Utah, we expect
colder air to work into the system. There's a possibility that we
could see enough cold air that rain could change over to some light
snow for the valley floors late Thursday night into early Friday
morning. Looks like the central Idaho mountains have the best chance
for accumulating snow with up to 6 inches possible. Rain/snow mix
is current forecast for the lower valleys, Magic Valley and snake
plain and really too early to talk about amounts if any. Could
easily remain all rain in the valleys, but this track is typical of
a heavy snow setup for the snake plain and Magic Valley. If this
were to remain all rain, we'd be looking at around half an inch of
liquid with this system. Expect precipitation to come to an end
Friday afternoon or evening. Saturday looks dry across the region,
but models differ greatly for Sunday and Monday with the timing of
the next system. European brings this system through on Sunday
whereas the GFS brings this system in on Monday.



Aviation...another weak system will roll through the region today.
A few showers and isolated thunderstorms are possible this
afternoon. Expect primarily VFR ceilings today, but MVFR will be
possible near showers.



Hydrology...areal Flood Watch remains in effect, as well as a
number of advisories. The Portneuf gage in Pocatello remains in
minor flooding and is forecast to go into moderate flooding early
Friday morning. The Bear river at the Wyoming border gage is in minor
flooding as well and is holding steady. Finally, the Snake River
at Blackfoot remains in bank-full, but holding steady just shy of
minor flooding. Hinsberger

Pih watches/warnings/advisories...
Flood Watch through this afternoon for idz017>019-022>025-031-

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