Sun Valley

000
FXUS65 KPIH 221718
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
1118 AM MDT Sat Aug 22 2026

.KEY MESSAGES...

- Scattered thunderstorms return to all of southern Idaho.
  Thunderstorms continue through the next seven days for many
  locations in southern Idaho.

- Red Flag Warnings in place for scattered thunderstorms today
  for all of Central Idaho Dispatch area, Southern Idaho
  Dispatch area, and portions of the Eastern Idaho Dispatch
  area.

- After record heat the past two days, clouds and precipitation
  will cool afternoon highs significantly today, then continue a
  weak overall cooling trend through Friday.

&&

.DISCUSSION...
Issued at 211 AM MDT Sat Aug 22 2026

Long wave ridge will allow a weak shortwave to move through the
mean southwest flow over the Gem State. This will enhance the
thunderstorm activity in the already moist and unstable air over
the forecast area. SPC has put nearly the entire forecast area
in a marginal threat of severe thunderstorms (except a small
wedge in Bear Lake County at the border with Utah. Thunderstorm
threat is as high as 40 percent in the southern and eastern
highlands. Could easily get G50KT for thunderstorm outflow. 

The increased moisture will mean more clouds and rainfall can
cause evaporative cooling to bring the record temperatures of
Thu and Fri down some 3 to 8 deg F. The cooling continues into
Sun and Mon, but at a slower rate, with temperatures still in
the upper 80s to around 90 on Sun and Mon. Overnight lows
continue mild with the cloud cover. 

Wind stays weak today, but Sun will see 14 to 24 mph wind in the
central Idaho mountains and the northwest side of the Snake
River plain. Wind of this strength does not show up again until
perhaps Thu. 

For other items in the extended (Tue through Fri), the strong
upper level ridge is finally beaten down in some of the
clusters on either Thu or Fri, but still only affects the
forecast area in about 53 percent of the solutions. Upper level
flow appears more southwest than south, which should cut down
significantly on thunderstorm coverage during the extended
period.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1115 AM MDT Sat Aug 22 2026

Expect more showers and thunderstorms to potentially impact any
of TAF sites through this evening. Gusts to or exceeding 45kts
are possible with any given storm or outflow boundaries. We
should see a lull overnight, but some of the higher resolution
models have another round or two moving through early tomorrow
morning. Chances are low enough that we will not include any
mention (even PROB30) during that period. That may need to be
adjusted later on. Expect VFR weather unless a heavy downpour
directly impacts a TAF site or we see some blowing dust.  

&&

.FIRE WEATHER...
Issued at 211 AM MDT Sat Aug 22 2026

An influx of moist and unstable air, including the possibilities
of outflow from a thunderstorm hitting 58+mph, will reach nearly
everywhere in the Fire Weather Forecast area. Coverage of
thunderstorms this afternoon and evening peaks at 25 percent to
45 percent, so Red Flag Warnings were issued yesterday for
abundant lightning. Thunderstorm coverage lowers considerably
for Sun, but then may be up again on Mon. 

Fortunately, the moist air is pushing humidity readings up. Most
readings will stay well above the 15 percent threshold for
critical fire weather criterion. Cloud cover helps, as the high
temperatures that lately have been setting records will be
solidly cooler. The cooling and more humid trend continues
through Mon. One offset to this is that the cloud cover will
keep temperatures warmer at night, so recovery may not be as
good, unless some wetting rains occur. 

Wind will be up on Sun, mainly over the central Idaho mountains
and the Snake River plain/eastern Magic Valley. It should be
enough to meet critical fire weather speeds, but the humidity
should be too high for any sort of critical fire weather
situation. More wind develops Thu afternoon, but temperatures
should be even cooler than this weekend, which bodes will for
humidity readings.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening for IDZ410-422-
425-427-475-476.

&&

$$

DISCUSSION...Messick
AVIATION...Keyes
FIRE WEATHER...Messick