Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 192018
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
218 PM MDT Sun Mar 19 2017

.SHORT TERM...Tonight through Wednesday. A broad trough of low
pressure is slated to steadily strengthen off of the PacNW coast
before coming ashore Wednesday. As a result, moist SW flow will
remain in place across SE Idaho into early Wednesday before the
trough closes off near Vegas late Wednesday. As a result, odds
favor active weather as multiple embedded disturbances slide
through the region. The first wave slides across the region this
evening bringing a round of showers (and perhaps an isolated
thundershower) across much of the Snake Plain. The next wave is
then expected to trigger widespread showers and mountain snow
(mainly above 7,000 ft elevation) across the Sawtooths/Central
Mountains eastward across the Divide and towards Island Park
extending southward across the Arco Desert, with activity more
showery/sporadic elsewhere. After this widespread activity
departs, the expectation is more isolated showers/thunderstorms
until more widespread activity begins to roll into the region by
Late Tuesday into Wednesday.

Temperatures are expected to remain well above average across the
region through Tuesday, then slowly begin to fall back towards
average on Wednesday. Therefore, continued snowmelt is expected
for those areas with extensive snowcover, and additional rain and
rain on snow will continue to increase runoff, allowing for
continued rises on area streams, creeks and rivers. AD/DMH

.LONG TERM...Wednesday night through Sunday. Wet and continued warm
period continues through most of the extended. Good agreement
between GFS and ECMWF early in the period with split trough shifting
through the intermountain west. Precipitation ends west to east
through Thursday as trough axis shifts past the state and transitory
ridge builds. Ridge axis shifts east through the day Friday, with
next trough pushing precipitation inland and toward Idaho late
Friday. Saturday night through Sunday remain wet as trough works
across the state. Cold front passage timed for Saturday night, with
snow levels falling mainly Sunday. DMH


&&

.AVIATION...Showers starting to develop across the region per radar
and satellite imagery. Winds across upper Snake Plain west of KIDA
also quite windy this afternoon, with winds slightly stronger than
anticipated this afternoon. Have continued to trend showers
impacting the East Idaho terminals this afternoon and evening.
Airmass weakly unstable so would not be surprised to see a lightning
strike here or there but very low confidence that this happens at
any particular location so kept out of terminals. If so, KIDA and
KDIJ would be closest to inclusion. Kept shower activity going
overnight into Monday morning at both KSUN and KDIJ but believe
Snake Plain locations will dry out for much of the night. Showers
redevelop either late tonight or early Monday. Reintroduced VCSH for
all areas by morning, but latest model solutions leaning toward that
being a lower confidence event for KIDA/KPIH/KBYI. Expect ceilings
to remain VFR throughout, except for potential IFR ceilings within
showers for KSUN/KDIJ. DMH


&&

.HYDROLOGY...Flood advisories continue for lower Blaine county,
western Bingham county, northeast Caribou county, eastern Oneida
county and low elevations of Bear Lake county with a Flood Watch
continuing for northern Lincoln and Minidoka counties, Upper Snake
Highlands and southeast and east Highlands. River flood warning in
effect for the Portneuf River at Pocatello and this river is
expected to rise to near Moderate stage (10ft) by Thursday, with
the Bear River near the WY border and Snake River at Blackfoot
approaching flood stage. With continued above average temperatures
through early week with additional rainfall, changes to current
flood watches, warnings and advisories are possible tomorrow --
with the potential for new areas to be added. The Salmon River
valley near Stanley saw around 0.40 inches of rain in the last 24
hours along with record high temperatures yesterday, and we`re
starting to see a response with some rises at Valley Creek in
Stanley as the extensive snowpack there is beginning to be
converted to runoff. AD/DMH


&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Monday morning for IDZ017-019-021>025-031.

&&

$$



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