618
FXUS65 KPIH 221938
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
138 PM MDT Thu May 22 2025

.KEY MESSAGES...

- Shower and storm chance generally north of a line from Sun
  Valley to Idaho Falls to Driggs today.

- Another rain/storm chance on Saturday.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 308 AM MDT Thu May 22 2025

Satellite and radar checks this morning shows plenty of cloud
cover moving through the Central Mountains and some more clouds
throughout Eastern Idaho and while more organized showers remain
well to our west in eastern Oregon, this activity will move
eastward today. We`ve got a shortwave and weak cold front
passing through today which will bring the best rain and storm
chances to areas north of a line from Sun Valley to Idaho Falls
to Driggs. It really will be the northern portion of the
Sawtooths/Central Mountains, upper Snake River Plain, and Island
Park area with about a 30 to 50 percent chance of thunder
today. Around Idaho Falls, that chance drops to closer to 10 to
20 percent. That said, the NAM 3 km is definitely the more
aggressive of the CAMs as it shows one main storm popping up
near Idaho Falls/Rexburg this afternoon. In contrast, the HRRR
keeps the Snake River Plain almost completely dry this
afternoon. Both models do agree on showers and storms from the
Stanley area tracking northeast through Challis and out of our
CWA today. For our severe weather parameters today, model
soundings from RAP and NAM Nest both agree on ample 0-6 km shear
of some 50 to 70 kts and 700-500 mb lapse rates ranging from
8.5 to nearly 10 deg C/km, but there are some discrepancies on
how much CAPE we have to work with. The NAM Nest ranges from
about 600 to 800 J/kg while the RAP ranges from 300 to 500 J/kg.
The RAP shows better DCAPE values of almost 900 J/kg near the
Idaho Falls area, so based off all of this if we can get a storm
in this environment, strong wind gusts would likely be the main
threat. The latest HREF shows max wind gusts up to about 50
mph, though there is a small area of up to 60 mph near Challis
this afternoon. In general, it will be a bit breezy this
afternoon even outside of thunderstorms, with gusts around 30 to
35 mph in the eastern Magic Valley, South Hills, and Snake
River Plain. We are near Lake Wind Advisory criteria on American
Falls reservoir, but look to stay just shy of it or only reach
the 20 mph sustained winds for an hour or two. We do have a
Frost Advisory in effect out across the Arco Desert/Mud Lake
area until 9 AM, but once temperatures get to warming we will be
heading into the 70s this afternoon. Highs will be nearly a
repeat on Friday even behind the weak cold front passing through
with the shortwave today.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 138 PM MDT Thu May 22 2025

The holiday weekend looks mostly pleasant across the region as
troughing on Sunday looks to give way to weak ridging, or at least
split upper flow, over the area which should keep things mostly dry.
An isolated shower or storm is possible on Saturday across the
eastern highlands but the rest of the area will remain dry. By the
time we get into Sunday, it appears that there won`t be enough
moisture to support much in the way of clouds, or precip, so ample
sunshine is expected. Still seeing models struggle a bit with the
amplitude of the aforementioned ridge so temps have come down a bit
for Sunday with mid to upper 70s now forecast vs. the lower 80s from
a few days ago. Still running slightly above seasonal norms but a
noticeable downward trend nevertheless. Things SEEM like they want
to warm up beginning on the Memorial Day holiday and continuing into
the upcoming work week but models still show some differences in the
upper level pattern as the ECMWF continues to show a slow-moving
upper low through mid-week while the GFS shows an upper ridge
strengthening over the area through the week. NBM continues with a
middle of the road approach for now keeping temperatures in the
lower 80s for valley locations with diurnal shower/storm chances,
mainly across the high country, for much of next week and the
forecast will run with this for now with slightly lower than usual
confidence.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1150 AM MDT Thu May 22 2025

VFR conditions expected to prevail through the forecast period.
There is some potential for a shower/storm later today around
KDIJ and maybe KIDA and KSUN but hi-res models have really
backed off on this or shifted activity to areas just north of
the aforementioned locations. This will be something to watch.
Winds are expected to become a touch breezy across the valley
terminals very shortly and linger into the evening hours before
they lessen overnight and become more light and variable. Skies
will clear as well during this period with maybe just a few
mid/high clouds returning by Friday afternoon with only low
precip potential.

&&

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

&&

$$

SHORT TERM...AMM
LONG TERM...McKaughan
AVIATION...McKaughan