Idaho Falls, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

222
FXUS65 KPIH 180344
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
944 PM MDT Sun Aug 17 2025

.KEY MESSAGES...

- Convection is mostly over for the evening. There are lingering
  isolated showers and thunderstorms in the Island Park area.

- Hot and drier conditions return Monday and persist for the bulk of
next week, with the heat peaking Tuesday/Wednesday with near record
temperatures.

- Isolated thunderstorm chances return from the south Wednesday
into Thursday, gradually expanding north by the weekend.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 135 PM MDT Sun Aug 17 2025

Forcing ahead of a shortwave trough embedded in southwest flow
aloft, along with diurnal heating/enhanced orographic forcing, has
acted on a mid-level plume of Pacific moisture to generate another
round of showers and thunderstorms this afternoon. The atmosphere
has moistened up slightly today with PWATs in the 0.7-0.9 inch
range, but overall the environment remains similar to yesterday. A
dry sub-cloud layer evidenced by DCAPE values upwards of 1000-1200
J/kg will continue to support strong outflow winds with
stronger storms. HREF probabilities show a 50-70 percent chance
of gusts over 35 mph with storms this afternoon/evening, with
strongest storms capable of producing gusts in the 50-60 mph
range. Also could see some locally heavy downpours and small
hail with the stronger storms, aided by stronger flow aloft
edging in from the northwest, increasing deep layer shear over
northern/western fringes of the CWA to around 30 kts. Similar to
previous days, thunderstorm activity will dissipate after
sunset this evening, with perhaps a few isolated sprinkles/virga
showers lingering overnight. The increased moisture and cloud
cover today is helping to hold temps down a touch, with
afternoon highs forecast to hold in the 80s at lower elevations
and 60s/70s in the mountains.

High pressure will quickly build northwest over the region on Monday
with the ridge becoming centered over the Four Corners by Monday
night. Things quickly warm up and dry out locally in response, with
Monday afternoon highs climbing roughly 5 degrees in most locations
from today. The large majority of the area will remain void of
showers/thunderstorms on Monday under influence of the building
ridge. The lone exception may be northern fringes of the forecast
area, where just enough moisture looks to linger on the northwest
periphery of the building ridge to support a few isolated afternoon
showers/storms (10-20% chance) from the Lost River and Lemhi Ranges
in eastern Custer County east along the MT Divide.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 135 PM MDT Sun Aug 17 2025

Forecast through the extended remains mainly unchanged. Very warm
temperatures return for Tuesday and Wednesday. Ensemble temperatures
reach into the mid to upper 90s, and NBM blend following the trend
with a little bit of a rise compared to previous runs. This would
now put several areas in the running for potential triple digit
highs mid week, approaching records. In addition to the warm
temperatures, there is increasing confidence in moisture rotating
around the strengthening Four Corners high for thunderstorm
potential beginning Wednesday. That said, chances of precipitation
still remain generally isolated and confined to the southern
portions of the forecast area Wednesday through Friday. Chances
increase headed into the weekend as northern Pacific low transitions
inland into Canada, weakening the ridge of high pressure. There
are some differences in the ensemble clusters this far out, but in
general point to differences in the amplitude of the trough as it
shifts inland. There should be some decrease in daytime highs into
the weekend, but NBM blend still keeps 90s across the region.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 941 PM MDT Sun Aug 17 2025

Convection is over for all TAF sites for this evening. There
are lingering isolated showers and thunderstorms in the Island
Park area but will be out of Southeast Idaho in the next hour.

High pressure builds in tonight into tomorrow bringing overall
clear skies and lighter winds. Winds will gust to around 20 kts
for IDA, PIH and DIJ tomorrow afternoon. Expect light winds and
clear skies by early tomorrow evening.

&&

.FIRE WEATHER...
Issued at 135 PM MDT Sun Aug 17 2025

Red Flag Warnings remain in place for all Fire Weather Zones (410,
411, 413, 422, 425, 427, 475, 476) through 9 PM MDT this evening for
critical fire weather conditions from scattered thunderstorms.
Despite some increase in mid-level moisture today, low levels of the
atmosphere remain dry, so wind gusts in excess of 35 mph will be a
concern with any storm, with gusts up to 50-60 mph possible with the
strongest storms. A brief heavy downpour and small hail may also
accompany the stronger storms. Similar to the past few days, look
for showers and storms to dissipate after sunset, although can`t
rule out a few isolated light showers or virga lingering overnight.

As an upper-level ridge of high pressure quickly builds northwest
into the region on Monday, a pronounced warming and drying trend
will ensue. Temperatures rebound roughly 5 degrees in most locations
from today`s slight "cool down", and relative humidities
decrease considerably, with minimum RHs falling back to 10-20
percent across all areas except the higher ridges. With high
pressure building in, wind gusts are forecast to primarily
remain below critical speeds, peaking in the 20-25 mph range in
most areas, slightly higher in the 20-30 mph range along the
Montana Divide in Zone 411. Hence widespread critical fire
weather conditions are not expected on Monday, precluding the
issuance of any Red Flag Warnings. That being said, some areas
will see near critical conditions during afternoon peak
heating/winds but overall not seeing the overlap of stronger
winds with critical relative humidities. Shower and thunderstorm
activity will be greatly reduced on Monday, with only portions
of Zones 411/475/476 seeing just enough lingering moisture to
support a slight chance (10-20%) of a few afternoon
showers/storms.

Conditions continue to heat up and dry out Tuesday, with this
currently looking like the hottest day of the week with the lowest
relative humidities (minimum values in the single digits to teens).
Winds again look to remain weak enough to preclude widespread
critical fire weather conditions as gusts peak in the 20-30 mph
range, but will see some areas of near critical conditions and
perhaps a few local pockets of critical conditions in the
afternoon. It remains hot through the rest of the week into the
weekend, but some monsoon moisture tries to gradually work north
around the upper ridge. Hence isolated shower and thunderstorm
chances return to primarily southern zones (413, 427) Wednesday
through Friday, gradually increasing and expanding to all areas
by the weekend.

&&

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

&&

$$

SHORT TERM...KB
LONG TERM...DMH
AVIATION...TW
FIRE WEATHER...KB