462
FXUS65 KPIH 190800
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
200 AM MDT Tue Aug 19 2025

.KEY MESSAGES...

- High pressure this week will bring hot and overall very dry
  conditions, with the heat peaking today and Wednesday.

- Near record to record warmth is expected today, with highs in
  the upper 80s to upper 90s.

- Monsoonal moisture building in mid to late week will lead to
  low shower and thunderstorm chances Wednesday and Thursday,
  before an uptick in activity regionwide Saturday into Sunday.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 200 AM MDT Tue Aug 19 2025

Early morning satellite imagery shows a broad ridge of high
pressure building in out of the south, leading to clear skies
and light winds regionwide. Today is shaping up to be one of the
hottest days we have seen so far this year with afternoon highs
climbing into the upper 80s to upper 90s with around a 5-15%
chance of reaching the low 100s across our lowest elevations.
With highs today running about 8-14 degrees above normal for
this time of year, near record to record warmth is expected at
all of our official climate sites. Overnight lows tonight will
also fittingly be above normal in the 50s/60s for most outside
of our typical colder mountain basins in the 40s. Highs for
Wednesday will cool a few degrees for most but will still remain
above normal in the upper 80s to mid 90s.

Later today, a closed mid/upper-level low moving in from the
Pacific into British Columbia and Alberta will eject a series of
weak shortwave troughs that will work over the northern Great
Basin and Rockies tonight into Wednesday. Given very limited
moisture transport with these shortwaves, we are not expecting
much precipitation but these passing waves will support around
5-15% chance of virga/showers with a very dry airmass in place
to overcome at the surface. This lack of moisture will also
suppress much if any thunderstorm development, however we can`t
rule out around a 10-15% chance of mostly dry thunderstorms
Wednesday afternoon. Have added the mention of these isolated
chances to the forecast early this morning. Overall, conditions
will remain hot and very dry today into Wednesday with winds
peaking each afternoon around 10-20 mph with gusts to 20-35 mph.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 200 AM MDT Tue Aug 19 2025

Hot and overall very dry conditions will continue for Thursday
and Friday under the continued dominant influence of a broad
ridge of high pressure centered over the Four Corners region.
Weak monsoonal moisture advecting northeast out of the Great
Basin into eastern Idaho for Thursday will support around a
5-15% chance of showers and thunderstorms primarily east of I-15
along the Wyoming border region. Those chances will drop to
less than a 10% chance on Friday as drier zonal flow builds in
out of the PacNW associated with a mid/upper-level low continues
its track east across Canada.

As that system continues its progression east over the Great
Lakes Region on Saturday, this will add increased weight to on
the east side of our broad ridge of high pressure overhead,
allowing for the ridge axis to build further north into eastern
Idaho. What this means for us will be a more organized push of
monsoonal moisture also lifting north beginning Saturday and
especially Sunday as isolated to scattered showers and
thunderstorms return regionwide to finish out the weekend and
continue through Monday and next Tuesday. This push of moisture
and cloud cover will lead to cooling temperatures starting
Sunday with highs returning the 70s/80s, near normal to below
normal levels for late August for a change. During this
timeframe, storms will be capable of producing gusty winds,
hail, and heavy rain as PWATs amongst GEFS and EPS ensemble
models surge to 150-170% of normal for late August. This is
looking like one of the stronger monsoonal moisture signals we
have seen so far this season, so we will be keeping a close eye
on the track of this moisture fetch throughout the week. Any
rain will certainly be much appreciated out here at our office
at Pocatello Regional Airport, as yesterday marked the 45th
consecutive day of no measurable precipitation. This marks the
8th longest stretch in recorded history since 1939. With the
GEFS/EPS ensembles showing near unanimous agreement on
widespread precipitation early next week, this streak just may
ultimately come to a close as we finish out the month of August.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1029 PM MDT Mon Aug 18 2025

Expect VFR conditions with mostly clear skies and overall light
winds under high pressure through the period.

&&

.FIRE WEATHER...
Issued at 200 AM MDT Tue Aug 19 2025

Under the continued influence of high pressure through the rest
of the week, hot and overall very dry conditions will prevail
with above normal temperatures and afternoon RHs in the single
digits and teens. Following near record to record warmth today
with widespread RHs in the single digits in the single digits, a
weak shortwave trough passing overhead on Wednesday will
support a 5-15% chance of isolated showers throughout the day
with a very dry airmass in place to overcome at the surface.
This lack of moisture will also suppress much if any
thunderstorm development, however we can`t rule out around a
10-15% chance of mostly dry thunderstorms Wednesday afternoon.
Have added the mention of these isolated chances to the forecast
early this morning. Any isolated showers/storms will shift east
of I-15 on Thursday along the Wyoming border region, with dry
conditions expected regionwide back on Friday.

As a mid/upper-level low in Canada continues its progression
east over the Great Lakes Region for Saturday, this will add
increased weight to on the east side of our broad ridge of high
pressure overhead, allowing for the ridge axis to build further
north into eastern Idaho. What this means for us will be a more
organized push of monsoonal moisture also lifting north
beginning Saturday and especially Sunday as isolated to
scattered showers and thunderstorms return regionwide to finish
out the weekend and continue through Monday and next Tuesday.
This push of moisture and cloud cover will lead to cooling
temperatures starting Sunday with highs returning the 70s/80s,
near normal to below normal levels for late August for a change.
During this timeframe, storms will be capable of producing
gusty winds, hail, and heavy rain as PWATs amongst GEFS and EPS
ensemble models surge to 150-170% of normal for late August.
This is looking like one of the stronger monsoonal moisture
signals we have seen so far this season, so we will be keeping a
close eye on the track of this moisture fetch throughout the
week.

&&

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

&&

$$

SHORT TERM...MacKay
LONG TERM...MacKay
AVIATION...TW
FIRE WEATHER...MacKay