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111
FXUS65 KPIH 250905
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
305 AM MDT Tue Jun 25 2024

.SHORT TERM...
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Today through Wednesday Night.
Early morning satellite imagery shows a H5 ridge axis beginning
to shift east into Idaho as moisture across the SW CONUS begins to
lift NE across the NRN Great Basin. As a result, hot, dry, and
breezy conditions will continue as we remain under the influence
of a broad H5 ridge of high pressure. High temperatures today will
be 3-6 degrees warmer than Monday with highs reaching the mid 80s
to mid 90s, which is around 10-15 degrees above normal for late
June. Associated with that moisture working overtop this ridge
feature, this will help to introduce a 5-15% chance of showers and
thunderstorms south of the Snake Plain this afternoon and evening
with those chances increasing regionwide for Wednesday to 20-40%
as a warm front lifts NE out of the Great Basin.

This warm front is associated with an approaching H5 low in the
NE Pacific which is expected to move onshore late Wednesday into
Thursday to the PacNW. While the bulk of shower/storm activity
today will center around virga and very isolated chances further
south, stronger storms will be possible on Wednesday as that
aforementioned warm front works through our region throughout the
day. The latest 0Z HREF model guidance shows 400-800 J/kg of
SBCAPE, 25-35 kt 0-6 km shear, and 7-8 degree/km 700-500 mb lapse
rates. This convective environment will support stronger storms
being able to produce wind gusts in excess of 40-50 mph, brief
heavy rain, and small hail. Given PWATs climbing up to around
0.75-1.00" on Wednesday, we may see some localized heavy rain at
times but conditions overall will remain predominantly dry outside
of any convection. The latest timing for stronger storms will
center around 2-10 PM MDT with isolated to scattered showers and
storms expected outside that timeframe, of which will shift NE
for Thursday as a cold front passes through SRN Idaho.

Given increased cloud cover on Wednesday, highs will be slightly
cooler than Tuesday, but still in the 80s to low 90s. Synoptic
winds and sufficient daytime mixing with support continued breezy
conditions peaking each afternoon, with wind gusts both Tuesday
and Wednesday afternoon up to around 25-45 mph. These winds will
be slightly less than what we saw on Monday. MacKay

.LONG TERM...Thursday through next Tuesday.
With a H5 low centered over Washington and NRN Idaho for Thursday
morning, this will drive a cold front across SRN Idaho on
Thursday which will lead to strong winds and a 20-50% chance of
showers and thunderstorms across the ERN CNTRL Mountains, Upper
Snake Plain, and ERN/SRN Highlands. Some stronger storms will also
be possible Thursday with an emphasis on stronger storms
producing strong outflow winds. As soon as the sun rises on
Thursday, expect strong daytime mixing to ramp winds up quickly,
with winds peaking during the afternoon hours around 25-40 mph
with gusts to 40-65 mph. As a result, WIND ADVISORIES will likely
be needed with the potential for HIGH WIND WARNINGS across the
Upper Snake Plain and Arco/Mud Lake Desert region. In that area,
the NBM shows a 40-60% chance of wind gusts in excess of 55 mph
which would be more in line with warning criteria for Thursday.

As that cold front progresses east into Wyoming Thursday night,
dry conditions will return regionwide as a colder, drier air mass
settles in place for Friday. As a results, highs on Thursday and
Friday will drop down to the 70s to low 80s which is near normal
to slightly below for late June. While we may see a 5-15% chance
of showers and thunderstorms around Island Park and Yellowstone NP
on Friday, look for dry conditions to continue into the start of
the weekend as a H5 ridge of high pressure quickly fills in behind
Thursday`s exiting trough. For Saturday, highs will climb around
8- 12 degrees into the 80s to low 90s as breezy winds persist with
gusts both Friday and Saturday afternoon around 25-40 mph.

For Sunday, the latest ECMWF/EPS and GFS/GEFS models show a
secondary Pacific trough moving onshore which will support a
return to isolated to scattered showers and thunderstorms into
Monday. Winds will also see an increase for Sunday and Monday
given this trough passage with gusts peaking around 40-55 mph.
Behind that second system, drier, cooler, and zonal flow will
keep temperatures near normal through Tuesday ahead of warming
temperatures through Independence Day as dry conditions persist.
MacKay
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.AVIATION...
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For the 18Z TAFS through 18Z Wednesday.
Predominant VFR and dry conditions will continue for Tuesday under
mostly clear skies as moisture begins to lift north out of the Great
Basin this afternoon and evening. This will support around a 5-15%
chance of isolated showers and thunderstorms south of the Snake
River Plain later today, with those chances increasing to 20-40%
regionwide on Wednesday as a warm front lifts NE. Breezy winds will
also continue through Wednesday given with winds peaking each
afternoon around 10-20 kts with gusts to 20-30 kts. MacKay
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&&

.FIRE WEATHER...
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Seasonably warm and very dry conditions will continue today as
moisture begins to lift NE out of the Great Basin, associated with
an approaching H5 trough in the NE Pacific. This will help to
introduce a 5-15% chance of showers and thunderstorms (primarily
virga) south of the Snake Plain today with those chances
increasing to a 20-40% chance regionwide on Wednesday as a warm
front lifts NE. Strong thunderstorms will be possible on Wednesday
with wind gusts in excess of 40-50 mph, heavy rain, and small
hail possible. Breezy winds will continue each day given strong
daytime mixing with winds peaking on Thursday as a cold front
moves through SRN Idaho. Cooler conditions are then expected on
Thursday and Friday before a ridge of high pressure moves back in
for Saturday. A secondary Pacific trough then remains on track to
move in Sunday/Monday with another cold front and isolated to
scattered showers and thunderstorms. Behind that second system,
drier, cooler, and zonal flow will keep temperatures near normal
through Tuesday ahead of warming temperatures through Independence
Day as dry conditions persist. MacKay
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&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$