Local Forecast Discussion

FXUS65 KPIH 220909

Area Forecast Discussion
National Weather Service Pocatello ID
209 AM MST Thu Feb 22 2018

.SHORT TERM...Today and Tonight...Snow showers, moderate or even
heavy at times, are expected across the Wood River Valley this
morning continuing through the afternoon. A line of snow showers
are expected to develop in advance of strong westerly winds behind
it this morning, with impacts expected in the Magic Valley area
this morning and early afternoon with the line progressing
eastward, reaching Pocatello later this evening. Snow amounts
across the west and north Central Mountains, including the Wood
River Valley range from 2 to 4 inches today at valley floors with
up to 8 inches at mountain tops. Those traveling across mountain
summits should be prepared for accumulating snow and icy/snowy
conditions. As a result of these expected conditions, a Winter
Weather Advisory has been issued until this evening. Blowing and
drifting snow is a risk, primarily after the snow has fallen later
this evening.

The band of snow continues eastward into the overnight hours
through the Bear Lake region. Snow showers are also expected for
the Upper Snake Plain and Upper Snake Highlands, with ligher
snowfall amounts (including Idaho Falls). Some forecast models,
for example the NAM, was showing a slower progression of the line
by about 6 to 9 hours, which would bring heaviest impacts to the
Magic Valley around the evening rush hour, reaching Pocatello by
tomorrow morning.

Friday through Saturday...Gradual dissapation of the overall line
is anticipated early Friday across eastern Idaho with clearing to
the west. By Saturday a new upper trough will meander its way into
Idaho and increase snow chances once more. Winter will not lose
its grip now that it has begun here. Expect robust scattered snow
showers across the region Saturday. NP/Huston

.LONG TERM...Sunday through next Thursday. The operational GFS,
ECMWF, and GFS ensembles remain in good agreement regarding the
progression and strength of the next incoming Pacific disturbance
Sunday and Monday as it shifts SSE into the NW states with
attending moisture overspreading SE Idaho. Estimated storm total
snowfall from this system looks to support warning level
accumulation in the mountains and advisory levels within the Lower
Snake River Plain and Eastern Magic Valley. Beyond Tuesday, the
models fall out of phase with dramatically opposing solutions. The
ECMWF appears to favor an upstream ridge off the NW coast with a
cut-off low developing over California which slowly shifts east
Wednesday and Thursday as Pacific energy tries to undercut the
ridge. The GFS on the other hand is showing another Pacific
disturbance shearing into the NW early Wednesday and continuing
through Thursday with a concomitant increase in snow across SE
Idaho. Splitting the difference for now until we can get better
optics on this evolving system. Statistical guidance continues to
support warming temps through Monday and then remaining steady but
below climatological norms through the remainder of the week.


.AVIATION...The next upstream pacific disturbance was digging south
through Washington and Oregon early this morning with attending snow
and lower CIGS spreading east into WRN Idaho. Numerical models show
the main low drifting into SW Idaho today with periodic waves
ejecting NE across the region tonight as the trough slowly weakens
and shifts east. As the low takes shape near Boise, KSUN will likely
see predominant IFR CIGS with periods of snow resulting LIFR CIGS
and VIS which will significantly restrict airfield use this
afternoon and evening. KBYI, KPIH, and KIDA will see lowering VFR
CIGS through the day with temporary IFR CIGS and VIS in snow tonight
as the low advances east. KDIJ is expected to enjoy VFR CIGS
throughout most of the day with lower MVFR CIGS late this afternoon
and evening and temporary IFR CIGS and VIS tonight in snow as the
low shifts east. Huston


Winter Weather Advisory from 5 AM early this morning to 6 PM MST
Friday for IDZ018-031.



NWS PIH Office Area Forecast Discussion