Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 161000

Area Forecast Discussion
National Weather Service Pocatello ID
300 AM MST Mon Jan 16 2017

.SHORT TERM...Today through Wednesday night. Forecast is status
quo for today and tomorrow as upper ridging keeps things quiet
for us. Low-level stratus should remain present in the valleys,
and is depicted this morning on VIIRS spectral imagery over the
Eastern Magic Valley. Temperature profile supports ice nucleation
within the stratus layer, and is resulting in light flurries in
some areas. This should end late this morning. The upper ridge
will pass Tuesday night opening us up to increasing moisture
transport from the Pacific. Models are a bit out of sync with the
timing of the onset of precipitation, but generally the best
chances will be Wednesday afternoon. Models are suggesting a warm
layer developing over the Eastern Magic Valley possibly extending
to Pocatello throughout the day Wednesday. Temperature profiles
support the potential for freezing rain during this period. Low to
moderate confidence levels for freezing rain at this time. Snow
accumulation will begin for the Central Mountains Wednesday
afternoon, and we have better confidence on snow intensity, though
timing may vary over the course of the next few model runs.

LONG TERM...Thursday through Monday. Medium range models in good
agreement this cycle. Amplified shortwave trough deepens across
PacNW and intermountain region during the day Thursday, spreading
precipitation across Idaho. Weak cold front slides across Idaho,
with temp profiles supportive of snow all areas. Break break
Thursday night behind front. Models start to diverge somewhat with
southern stream supporting faster shortwave feature undercutting
slower and slightly retrograding northern stream. Thus weakest
confidence in precipitation, with both GFS and ECMWF in relative dry
but cooler period Friday through Sunday. Flow consolidates over
Pacific again with deep trough off west coast. Both models, with
some agreement with GFS ensembles, indicating next significant
feature rotating around trough to reach coast and spread inland by
Monday. Details remain fuzzy thus kept to broadbrush blend late in
the period. DMH


.AVIATION...IFR conditions in place early this morning in region
stretching from KIDA to west of KBYI, and including many valleys
south of the Snake River. Stratus layer lies within favored temp
zone for snow, and seeing light snow continue in some locations so
will keep temp conditions for snow going until after sunrise. Ridge
remains intact with inversions so will keep persistent forecast with
brief afternoon improvement to VFR then a return to marginal or
worse conditions after sunset as inversions strengthen and
stratus/fog return for overnight. DMH


All current flood headlines remain in place this morning:

An Areal Flood Advisory will remain in effect for Cassia and
southern Minidoka county through the weekend. Floodwaters on roads
has frozen over and several county roads remain closed.

A Flood Warning continues at Antelope Creek in Darlington due to an ice
jam on this creek along with runoff from early-week rainfall and
snowmelt has resulted in some homes being flooded in Darlington.

The Flood Advisory for the Challis River Bridge south of Challis
will continue at the request of the BLM and local law enforcement.
Citizens are urged to avoid this area.

Dry conditions remain forecast through Tuesday. Frozen flooded areas
continue to pose a threat to drivers. Ice jams will remain a threat
with sub-zero lows in many areas through Tuesday morning, and ice
build-up already present in many river channels. Another storm
system arrives mid week. This system is expected to bring a warm-up
to near or just above freezing to Cassia, Minidoka, Power and Oneida
counties, where frozen flooded areas exist. At least partial melting
of these areas is possible, along with the added concerns of
additional precipitation which could fall as rain in lower
elevations. Current headlines are expected to be evaluated again
during daylight hours, in consultation with emergency management
officials. DMH



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