489
FXUS65 KPIH 282001
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
201 PM MDT Sun Apr 28 2024

.SHORT TERM...Tonight and Monday
Afternoon satellite imagery shows more sunshine in place across
the region compared to yesterday. Temperatures are warmer
accordingly with the increased sunshine, although still running on
the cooler side of normal. Winds have been breezy across the
lower Snake Plain and into the Magic Valley as well. More of this
to come... Have seen a few showers develop across the upper Snake,
upper Snake highlands and into the eastern Highlands as well. Hi-
res CAMs show this as the primary focus area for the remainder of
the day. Things should dry out later this evening and throughout
the overnight.

Things become a bit more active as we start the workweek however
as an upper low moves into the Pacific NW during the day tomorrow
and moves quickly into western Montana late tomorrow. The
pressure gradient will tighten significantly across the region
tomorrow which will lead to a windy day for much of eastern Idaho.
The Wind Advisory remains in place as is as not much as changed
with the previous forecast thinking. In addition to the winds, as
a cold front moves through the region, we will have some showers
(perhaps some thunderstorms) to content with as well. CAMs are
lightning up the central mountains and eastern highlands as the
most likely areas to see this activity. But at least low end PoPs
are in place throughout the forecast area. Cooler temperatures
will move in behind the front as skies should quickly clear out
into Tue AM. Temperatures will likely drop below freezing
throughout the forecast area, even in the valleys, so any linger
precip late Monday evening into Tue AM would likely be in the form
of snow showers. McKaughan

.LONG TERM...Tuesday through next Sunday
As another closed low moves onshore, it will merge with the
departing low to our northeast and the associated trough will
shift through Idaho on Wednesday. Zonal flow ahead of the trough
will result in breezy westerly winds on Tuesday, although lighter
than those forecast Monday. The Arco Desert and mountain peaks
will likely observe advisory-level sustained winds, with
widespread gusts 30 to 40 mph. Colder, below normal temperatures
will return for Tuesday and Wednesday, with daytime highs running
in the low 50s and cooler across all of Southeast Idaho and
morning lows below freezing areawide. As for precipitation,
amounts will be light with QPF generally 0.15" or less across the
mid and high elevations and locally higher totals in the
mountains. The majority of precipitation will fall as snow, with
only half an inch to around 2.5 inches currently forecast Tuesday
afternoon through Wednesday evening. Deterministic models show a
transitory ridge building in behind the trough on Thursday before
the next Pacific Northwest low moves over Idaho on Friday. Models
feature another weak ridge building in for the weekend timeframe,
although the deterministic GFS shows a Canadian trough flattening
the ridge and bringing chances for precipitation to SE Idaho,
while the ECMWF keeps the Canadian system further east and
maintains dry conditions over eastern ID throughout most of the
weekend. By the very end of the extended, models feature the next
low situated along the west coast but its location dramatically
different from model to model. As to be expected, 500 mb ensemble
clusters depict increasing and impactful differences amongst
models beginning late Thursday, resulting in a low confidence
forecast during the latter half of the extended. Cropp


&&

.AVIATION...
VFR conditions forecast areawide with much drier conditions today.
Chances for showers will continue in the vicinity of KDIJ through
around 03z this evening, with a non-zero possibility of another
shower further west near KIDA. Winds will be breezy through
tonight, with HREF ensemble maximum winds gusts ranging 20 to 30
kts at KPIH, KIDA, and KBYI. Winds will increase further on
Monday, beginning around 14z and peaking early evening as a cold
front passes. Sustained winds will range 20 to 30 kts at the
aforementioned three terminals with gusts to around 45 kts. KSUN
and KDIJ will likely observe winds more on the order of 30 kts or
less. Cropp

&&

.HYDROLOGY...
Water levels remain elevated on the Portneuf River from Pocatello
to Chesterfield Reservoir where River Flood Warnings remain in
effect until further notice. Minor to moderate flooding is ongoing
in this area with both the Pocatello and Topaz river gauges
forecast to crest this weekend into early next week before
dropping slightly heading into midweek next week.

Further north and west along the Snake River, water managers have
increased releases from upstream reservoirs leading to high flows
in excess of 10,000 cfs downstream from Palisades to Milner. The
Snake River near Heise and Snake River at Lorenzo gauges have
reached action stage as a result and are expected to be at that
stage until further notice. Water managers have also increased
releases from Blackfoot Reservoir which is leading to increased
flows across the Blackfoot River with the river gauge up Wolverine
Canyon having reached action stage this weekend but is still
about half a foot below minor flood stage.

Willow Creek below Tex Creek above Ririe Reservoir and the
Blackfoot River above Blackfoot Reservoir both also continue to be
in action stage since earlier in the week with no other major
impacts seen elsewhere in our CWA as of Sunday afternoon. MacKay

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from noon Monday to midnight MDT Monday night for
IDZ051>057-067-068-075.

&&

$$