Debris Flow in Idaho, August 26, 2025

Area Forecast Discussion
National Weather Service Pocatello ID
242 PM MDT Tue Aug 26 2025

.KEY MESSAGES...

- A flood watch is in effect for all of eastern Idaho. Slight
  risk that rainfall will exceed flash flood guidance with some
  chance of flash flooding possible, especially near burn scar
  areas.

- Cooler temperatures, increased humidity, and measurable
  rainfall is expected for the next few days.

- Drier and gradually warming as we move towards the holiday
  weekend

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 240 PM MDT Tue Aug 26 2025

Afternoon satellite imagery shows widespread clouds in place over
the area this afternoon in association with a deep push of monsoonal
moisture from the south. Showers with embedded thunderstorms are
slowly becoming more numerous across the area and this trend is
expected to continue into the evening and overnight as hi-res
CAMs unanimously show widespread precipitation across the
entire area through much of the day tomorrow. As such, have
issued a Flood Watch for the entire forecast area as 48 hr
rainfall amounts are generally in the 1-2 inch range regionwide.
Precipitation is expected to be mainly stratiform in nature and
rain rates will not be overly high but amounts will slowly add
up throughout the day. That being said, there will be embedded
thunderstorms within the rain shield, especially during the
afternoon hours today and tomorrow, and these will serve as the
primary threat for any flooding concerns, be it of the
urban/small stream variety or flash flooding and this is what
will need to be closely monitored over the next day or so. Temps
today have struggled to warm much with all the clouds and
precip around and Wednesday will be no different, most places
will struggle to get out of the 60s tomorrow.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 240 PM MDT Tue Aug 26 2025

Thursday looks continued wet and cloudy with things gradually
improving however by the latter half of the day. The deeper
moisture will be well removed from the region by Friday with
PWATs returning closer to normal values for this time of year.
We won't see precip chances disappear entirely on Friday but
they will primarily be focused across the higher terrain, will
become more scattered in nature, and will transition more
towards a mix of wet/dry storms. It does look like PoPs will
leave the forecast for the holiday weekend and into Labor Day
itself as a drier, warmer pattern takes hold. This should allow
temps to return to the 80s in the lower elevations for the
holiday weekend but low to mid 80s at best, allowing us to avoid
the 90s, at least for now, as the calendar shifts into
September.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1124 AM MDT Tue Aug 26 2025

Main impact through Wednesday morning will be continued
monsoonal flow with periods of showers and thunderstorms at all
TAF sites. Went with prob 30 thunderstorms after 20Z all sites
with predominant showers as well this afternoon and overnight.
Think there is at least a chance of MVFR ceilings as more
sustained rains set in overnight and went with 2500 foot
ceilings at all sites after 10Z. Not expecting significant wind
impacts with only some 20 to 30 mph gusts near thunderstorm
outflow.

&&

.FIRE WEATHER...
Issued at 240 PM MDT Tue Aug 26 2025

Monsoonal moisture with deep southerly flow aloft will persist
through Thursday.  Expecting a near 100 percent chance for wetting
rains throughout the entirety of all fire weather districts today
through Thursday evening.  Heavies rain today through Wednesday
night in the southern districts generally 410 to 411 and south with
heavier showers pushing north through 475 and 476 through the day on
Wednesday into Thursday.   Temperatures will be quite cool through
Thursday with very high minimum humidity and recovery humidity at
100 percent most areas as well.  Will begin to see drying Friday
through Sunday with only isolated showers and thunderstorms expected
at worst.

&&

.AIR QUALITY...
Issued at 240 PM MDT Tue Aug 26 2025

An air quality advisory is in effect for Teton County due to
degraded air quality from wildfires to the east.  The Air Quality
Index is forecast to be Unhealthy for Sensitive Groups.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Wednesday evening for IDZ051>075.

&&

SHORT TERM...McKaughan
LONG TERM...McKaughan
AVIATION...GK
FIRE WEATHER...GK
AIR QUALITY...GK