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336
FXUS65 KPIH 172230 CCA
AFDPIH

Area Forecast Discussion...CORRECTED
National Weather Service Pocatello ID
Issued by National Weather Service Salt Lake City UT
430 PM MDT Mon Jun 17 2024

.SHORT TERM (Through 12Z Wednesday)...
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Unseasonably cold conditions
have settled in throughout southeast Idaho behind a powerful cold
front. Temperatures have generally been in the 50s for valley
locations, roughly 20F cooler than normal. Synoptic forcing will
diminish through the evening, with rain and snow tapering off for
many locations. Upslope orographic enhancement will bring more
rain and snow, especially near the Wyoming border into Tuesday.

As conditions clear, temperatures will fall to near or slightly
below freezing Tuesday morning for most valley locations. A Frost
Advisory remains in effect, with lows ranging from roughly 30-35F,
including the Snake River Plain.

The longwave trough will lift through Tuesday. Winds will be
light through the day. Isolated afternoon rain and mountain snow
showers are likely, especially near the Montana and Wyoming
border.

.LONG TERM (After 12Z Wednesday), Issued 257 AM MDT...We will see a
significant transition from the unseasonably cool and unsettled
conditions on tap for early this week to much warmer and drier
conditions by late week into the weekend. EPS and GEFS ensemble
means are in good agreement showing the upper low responsible for
the active weather in the short term filling and shifting well
northeast of the area by early Wednesday, leaving the region in a
weak southwest flow aloft between a remnant weak trough axis along
the West Coast and expansive ridging over the Eastern CONUS. The
main impacts of this forecast period may come at the onset with
another unseasonably cool morning on tap Wednesday morning, although
not as cold as the previous night. Still it appears that
temperatures may again dip into the mid 30s in parts of the Snake
Plain primarily north and east of Pocatello, potentially yielding
one more round of frost concerns. Current NBM probabilities show a
40-60% chance of temperatures falling below 36F Wednesday morning in
these areas. Beyond Wednesday morning, a notable warming trend will
commence under progressively rising heights amid a continued weak
southwest flow aloft. High temps will climb 8-10 degrees Wednesday
and another 8-10 degrees Thursday, putting values some 5-8 degrees
above normals by Thursday, quite the swing from the 20 degree below
normal values expected today. This warming trend will continue into
the weekend as shortwave ridging amplifies ahead of a system
approaching the BC coast, likely pushing lower valley highs into the
lower 90s and higher elevations into the 70s and 80s. Current NBM
probabilities suggest a roughly 50-70% chance of highs in the
Interstate corridor from Burley to Pocatello to Idaho Falls
eclipsing the 90F mark by Sunday. WPC cluster analysis shows fairly
strong agreement for this pattern, although by early the following
week toward the end of this forecast period we start to see some
differences emerge with the strength of the upper low skirting east
along the Canadian border. About 40% of the cluster membership shows
a stronger system, which would support cooler temps toward the end
of the period, while the other 60% advertise a weaker system and
resultant warmer temps. A stronger system passing to our north would
also lead to stronger winds Sunday/Monday. Precipitation chances
appear minimal through the long term period, although a few light
showers cannot be ruled out with weak shortwave impulses riding
through the flow. Friday across the Eastern Highlands currently
looks most favorable for any such light shower activity. Overall, a
pronounced warming trend and primarily dry conditions will be the
theme from mid-week into the weekend.
KB
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&&

.AVIATION...
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We continue to have showers and possible thunderstorms
around and will into this evening. We continue with VCSH, VCTS, or
-SHRA VCTS in the TAFs. We should be VFR overall with brief
reductions in visibility and/or ceiling with stronger cells that
move over a particular airport. Gusty winds will also persist with
gusts of 20-35kts through sunset. The only site that could see
showers after midnight is DIJ and we have VCSH in the forecast
there through mid morning.
Keyes
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&&

.FIRE WEATHER...
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A steady warming trend will begin Tuesday as a
low pressure system weakens and shifts northeast of the area. Cold
overnight lows can be expected the next couple of nights, falling
into the 30s even at low elevations. Some light precipitation
will linger into Tuesday primarily from the Central Mountains east
along the Divide into the Eastern Highlands on the backside of
the upper low. Dry conditions then return for Wednesday, along
with warming temperatures climbing above average by late week.
Temperatures continue to climb into next weekend, reaching the low
90s in lower valleys. We may see increasing winds again by late
next weekend as a low pressure system passes to the north.
KB
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&&

.HYDROLOGY...
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Water levels for the Teton River near Driggs remain
high with continued lowland flooding. Will continue the river
flood warning for the Teton River near Driggs until flooding drops
off. Water levels have dropped today and are forecasted to drop
even more, down to 3-6 feet, by Wednesday. Much cooler
temperatures and a diminishing snowpack are causing river flows to
drop off.
TW
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&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 8 PM MDT this evening for IDZ051>054.

Frost Advisory from 2 AM to 9 AM MDT Tuesday for IDZ051>055.

&&

$$