358
FXUS65 KPIH 162007
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
207 PM MDT Fri May 16 2025

.KEY MESSAGES...

- Showers and thunderstorms today across northern parts of the
  area.

- Frost Advisory in effect for portions of Eastern Idaho from 2
  to 8 AM Saturday.

- Another potent low pressure system expected for the weekend bringing
  more rain/storms and cold temperatures Sunday after milder
  temperatures on Saturday.

- Gradual improvement expected early next week with a warmup
  likely mid/late next week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 205 PM MDT Fri May 16 2025

Showers and thunderstorms are a bit more limited in coverage today,
but that doesn`t mean everyone is getting a break from the activity
as a weak shortwave passes through our area. While we`ve seen
showers moving into the I-15 corridor early this afternoon, the
bulk of our thunderstorms this afternoon and evening will be
confined to our northeast corner/Island Park area, or generally
north and east of Idaho Falls. Temperatures this afternoon will
be back into the low 60s in the eastern Magic Valley and lower
Snake River Plain and remain a couple of degrees cooler in the
upper Snake River Plain thanks to cloud cover and showers.
Storms today are expected to remain the "garden variety" as we
have little CAPE today (we`re talking 100-300 J/kg tops), 0-6 km
shear of 25 to 30 kts in the vicinity of Clark and Fremont
counties, and modest laps rates of 6.5 deg C/km. So, max wind
gusts today with storms would most likely be around 40. In
addition, it`s just a bit breezy in general today with wind
gusts for many around 25 to 30 mph. Temperatures tonight will
drop into the 30s and 40s area wide in our lower elevations, so
we have a Frost Advisory out for several zones where
temperatures are expected to be at or below 36 deg F early
Saturday morning. It`s a bit tricky, because there`s about a 70
to 80 percent chance temperatures will remain above that 36
degree threshold in Pocatello and Idaho Falls, but will drop
quickly as you move outside of town.

On Saturday, a strong cold front will sweep through Eastern Idaho
and bring another round of rain and storms with it. With these
storms, we will have better "ingredients" for some stronger to even
marginally severe storms. A NAMNest sounding shows around 1000-1500
J/kg of CAPE in the Snake River Plain on Saturday, around 40 kts of
0-6 km shear, and lapse rates around 8.0 deg C/km. These values are
plenty sufficient for marginally severe storms with the potential
for wind gusts up to 65 mph. We will warm up into the mid and upper
60s Saturday ahead of the cold front, but look for a sharp drop in
temperatures by Sunday. In fact, as temperatures drop we will see an
increasing chance for accumulating snow Saturday night through
Sunday morning. At this point, the bulk of the snow will fall above
pass level, but there still remains about a 50 to 60 percent chance
of at least 2 inches of snow and a 20 to 30 percent chance of at
least 4 inches of snow at Galena Summit. Overall, we`re looking at
decent QPF across the entire CWA with about a quarter of an inch of
liquid in our valley locations by Sunday morning.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 205 PM MDT Fri May 16 2025

Upper low over East Idaho during the day Sunday for continued wet
and cool conditions most of East Idaho. Another day with highs in
the 40s/lower 50s is anticipated. Snow levels drop as low as 5500-
6000 ft during the day leading to snow accumulation over higher
elevations. The greatest snowfall accumulations likely over the
Central Mountains, but the heaviest snowfall should remain confined
to high elevations so we are not thinking headlines as this point in
time. Areas along/east of I-15 look to be the warmest, and thus most
unstable with greatest chance of an afternoon/evening thunderstorm.

Beginning Monday, upper low looks to shift far enough east of the
region to see a decreasing precipitation trend through the day for
most areas. Temperatures warm over the low weekend values Monday and
beyond. Weak shortwave activity through the week could be enough for
isolated shower/thunderstorm development each afternoon Tuesday
through Friday, mainly in the northern portions of the forecast
area.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1216 PM MDT Fri May 16 2025

Satellite and radar imagery shows weak shortwave feature moving
through East Idaho today. Winds are breezy throughout the Snake
Plain, strongest at PIH with gusts approaching 30kts. Expect that
activity to decrease around sunset. Radar shows a few weak echoes
late this morning, but so far only SUN has been able to record any
precipitation. Tentatively removed VCSH from PIH and IDA as
confidence was lower that any precipitation would reach the ground.
Better chances for TSRA occurring at DIJ this afternoon, and left
PROB30 in place. Should be a break in the potential precipitation
late this afternoon through mid-evening for all terminals, followed
by VFR cigs overnight. Next shortwave drives showers into the region
during the day Saturday. Added PROB30 TSRA for SUN after 18Z, but
should be seeing more widespread SHRA all sites by late morning.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 2 AM to 8 AM MDT Saturday for IDZ051>054.

&&

$$

SHORT TERM...AMM
LONG TERM...DMH
AVIATION...DMH