FXUS65 KPIH 111004

Area Forecast Discussion
National Weather Service Pocatello ID
304 AM MST Mon Dec 11 2023

.SHORT TERM...Today through Tuesday night. Drastic change from
previous forecast in terms of model trends, with some difficult
decisions made on headlines. Satellite and radar imagery show
band of light precipitation extending from Eastern Oregon
southeast toward the Bear Lake region. Area web cams indicate very
light snow could be falling as far north as the Island Park
region, though some fog and pockets of freezing drizzle/mist may
be occurring as well. 00Z model runs as well as recent runs of
the HRRR continue to keep main band of precip across the Eastern
Magic Valley southeast to the Bear Lake region. Very light
precipitation still expected to occur elsewhere, but overall
amounts of both QPF and Snow have trended significantly less than
prior forecast. Additional concerns are nose of warm air aloft
riding in, mainly north, allowing for pockets of freezing rain or
freezing drizzle through the day. Followed previous shift lead and
blended a composite max of latest HREF for QPF to try to force
higher amounts toward the upper probabilities. Main impact was to
fill in some areas with light precip missing from NBM, but trend
remains the same: a quarter to half of previous snow amounts
through tonight, which fall well below threshold concerns for
advisories. There is expectation of snow impacting the morning
commute for I-84, I-86, and I-15 from the Utah border north to
Blackfoot, possibly Idaho Falls. But amounts during this time are
expected to be well below an inch through the evening. Moving into
tonight, shortwave trough axis drops southeast out of
Washington/Oregon into Nevada, taking whatever meager QPF is
available with it. There is a slightly better chance for fog
overnight tonight, but overall would think any clearing potential
on Tuesday would lead to even better fog chances Tuesday night as
low sages south toward Las Vegas and upper ridge begins to tilt
over through the PacNW into East Idaho. DMH

.LONG TERM...Wednesday through Monday. Models transition to a
ridge parked over the western US for almost the entirety of the
extended period. Temperatures are expected to warm into the
weekend, and may approach records if the NBM values manifest.
Deep low in the Pacific is progged by both GFS and ECMWF
deterministic runs to spin off a vigorous shortwave into the
coastal states by Monday, so early to mid week next week looks to
be the next active period for East Idaho. DMH


.AVIATION...For the 12Z TAFS through 12Z Tuesday.
As an upper-level shortwave trough continues to work through the NRN
Rockies, low clouds and a wintry mix of precipitation will continue
to bring a mix of MVFR/IFR CIGS/VIS to SE Idaho ahead of drier
conditions returning for Tuesday. Precipitation will remain
predominantly snow with this event with a slight chance of a wintry
mix at times. Early morning radar imagery shows a wide swath of
precipitation across SRN/CNTRL Idaho moving east with isolated to
scattered snow showers expected through the day. For tonight, a
secondary boundary working south out of Montana will continue to
support snow showers through the overnight hours as a progressively
drier airmass also builds in out of the north. During the overnight
hours, breaks in the clouds, lingering low-level moisture, and
continued light winds through will support the development of patchy
dense freezing fog. Predominant VFR and dry conditions will return
throughout the day Tuesday with lingering areas of low stratus.