886
FXUS65 KPIH 201945
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
145 PM MDT Mon Jul 20 2026

.KEY MESSAGES...

- Will see many 100 degree temperatures this afternoon with
  slight cooling expected Tuesday. Heat risk highest today,
  especially across the Magic Valley, Snake River Plain, and
  South Hills.

- Monsoon moisture increases beginning this evening. More
  widespread storms later evening through mid-week. Wednesday
  should be most widespread day of showers and thunderstorms
  with cooler temperatures.


&&

.DISCUSSION...
Issued at 121 PM MDT Mon Jul 20 2026

Main impact today remains heat advisory in effect until 8 pm for
much of southeast Idaho. Temperatures will reach 100 in many
locations late this afternoon. Expect isolated thunderstorms
mainly over the southern hills once again this afternoon and do
expect nocturnal showers overnight again mainly in high
elevations. It will remain hot Tuesday but will cool a couple of
degrees and convective activity will be more widespread. By
Wednesday an embedded short wave moving through Idaho should
enhance significantly the shower and thunderstorm coverage with
significantly cooler temperatures with many low elevation highs
down to the upper 80s. Expecting much drier conditions Thursday
through next Monday with only isolated mountain storms expected.
Hot temperatures return with low elevations mainly in the 90s
Friday through Monday and mountains in the 80s.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1219 PM MDT Mon Jul 20 2026

VFR conditions generally expected through the period. Monsoonal
moisture will be on the increase over the next 24 hours allowing
for more mid/high level clouds later this evening and into
Tuesday. Hi-res models continue to show some potential for some
overnight/early morning shower activity which could impact all
terminals. Given the dry air, these will likely be of the dry
variety but could have some gusty outflow winds. For now,
maintained VCSH given the uncertainty on timing and location but
more widespread shower/storm coverage looks possible tomorrow
just beyond the current 18Z forecast period. Winds will remain
light outside of any influence from the aforementioned
convective activity.

&&

.FIRE WEATHER...
Issued at 414 AM MDT Mon Jul 20 2026

Excessive heat peaks today with many valley locations warming to
around 100 degrees, although heating could be inhibited in areas
where extensive cloud cover develops. Monsoonal moisture will
support daily shower and thunderstorm chances through mid to late
week. High resolution models show activity primarily concentrated
across Fire Weather Zones 475 and 476 this evening with development
further east across 410 and 413 during the late night and overnight
hours. Widespread Min RH today will range 13 to 16 percent across
Fire Weather Zones 410 and 425, but Min RH will raise to 25 percent
and higher beginning Tuesday as monsoonal moisture lifts northward.
Isolated, mostly dry storms today will trend wetter and more
scattered heading later into the week with locally heavy rainfall
possible and outflow winds of 40 to 50 mph. Certainly possible for
Red Flag conditions on Wednesday but cloud cover could limit
instability and overall tstm coverage so this will be something to
monitor and coordinate. Things look to dry out later in the week and
into the weekend with above normal temperatures expected to linger
over the region.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM MDT this evening for IDZ051>059.

&&

$$

DISCUSSION...GK
AVIATION...McKaughan
FIRE WEATHER...McKaughan