653
FXUS65 KPIH 220951
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
351 AM MDT Wed May 22 2024

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT...
A closed low pressure system will track ESE across the region today
and Thu, bringing several impacts. First, winds will become breezy
this afternoon and continue right through tonight and Thu. The
strongest winds...SW 20-30 MPH gusting to 50 MPH...are forecast to
occur between 11 AM this morning and 8 PM this evening across the
Arco/Mud Lake Desert and Upper Snake Plain region, resulting in a
WIND ADVISORY for these areas. Winds may be just slightly lighter in
the immediate Idaho Falls area east to Ririe and St. Anthony. Strong
westerly winds tonight down across Cassia County and the Raft River
region may approach WIND ADVISORY criteria as well, but with lower
confidence will hold off on issuance in this area...it`s possible
impacts may be confined to the higher elevations and then the
favored downslope corridor near Malta and Idahome across I-84.
Second, winds may approach LAKE WIND ADVISORY criteria today for
American Falls Reservoir, but here too we may be a bit borderline
with the NBM exceeding criteria by a knot or two, but MOS guidance
holding just shy of what we traditionally like to see to build our
confidence. This is another area where we will need to monitor
forecast and observational trends today. Third, scattered t-storms
are forecast this afternoon. Analyzing model forecast
soundings...it`s not a wet microburst environment, and it`s not a
dry microburst environment, and it`s not really a hail environment,
yet an oddball collection of ingredients (just enough modest
instability at 200-500 J/kg SBCAPE, effective bulk shear of 35kts
and 0-6km deep layer shear over 50kts largely speed-based, and
strong low-level lapse rates) may still allow for a couple stronger
cells to produce gusty outflow winds and small hail, and the HREF
max wind gust guidance is indeed hinting at this wind potential
along with some moderately robust simulated reflectivity cores. A
few t-storms may return Thu afternoon east of I-15. Fourth, a period
of clearing skies Thu AM will help low temps to drop into the 30-36
degF range up our ern Magic Valley and Snake Plain agricultural
corridor, thus we have issued a FROST ADVISORY from 2 AM to 9 AM
Thu. Finally, temps will support snow with this system (potentially
down to valley floors Thu AM), but actual ground accumulations (2 to
as much as 7 inches for some) should remain confined to above about
7,000 feet except for perhaps the Island Park region where a coating
to 2 inches can`t be ruled out. High temps in the upper 50s to low
60s today will lose 5-10 degrees Thu holding in the upper 40s and
50s. 01

.LONG TERM...FRIDAY THROUGH NEXT WEDNESDAY...
Progressive pattern continues through the extended period with
good ensemble cluster agreement. Fri looks to be mostly dry to
start off the period as the trough remains along the coast. As a
stronger low pressure system sinks into the PacNW, it acts as a
kicker for the leading trough, spreading precipitation over the
region. Ensemble clusters show support for a blend between
operational GFS/ECMWF, though recent runs of the GFS have trended
wetter with the low center closer to East Idaho. Saturday looks
windy as well, with the NBM means already supportive of at least
Wind Advisory across the northern portions of the Snake Plain. For
the Sunday through Tuesday period, the forecast trends drier and
warmer as the early weekend system shifts east, allowing ridge to
amplify through the Great Basin. The clusters are on board,
keeping conditions dry through Wednesday, though the operational
runs slide a fast moving feature across the region late Wednesday
for weak mainly higher elevation showers. DMH

&&

.AVIATION...
Vigorous spring system brings another round of wind and showers
to East Idaho today. Winds pick up after sunrise especially for
KBYI/KPIH/KIDA, reaching peak this afternoon and early evening,
generally sustained 15-20kts and gusts around 30kts. Should see
SHRA after sunrise as well, but KSUN/KDIJ could start out mixed
with SHSN. AS frontal boundary shifts east across the region
today, TSRA will be possible at all terminals, with wind gust
potential around 45kts. Should see most of the precipitation and
wind decrease after sunset, but the northeast corner may remain
active overnight, with RA/SN possible at KDIJ into the night. DMH

&&

.FIRE WEATHER...
An active spring system will drive across the East Idaho fire
district today. Showers are expected to spread west to east across
the region, with snow possible generally over 6500 ft elevation.
Scattered thunderstorms will be possible as well, with wind gust
potential over 40 mph this afternoon and early evening. Outside of
thunderstorms, expect winds to increase through the Snake Plain,
generally 20-25 mph with gusts 30-35 mph, peaking this afternoon
and early evening. A few snow showers will remain possible through
the overnight, mainly across the Targhee NF. Expect a repeat on
Thursday, though most of the Eastern Magic Valley should be spared
as the system slowly shifts east of the region late in the day.
Friday looks mostly dry and cool, with the next system arriving
for the weekend. DMH

&&

.HYDROLOGY...
Elevated river levels continue on the Portneuf River at Pocatello
and Topaz. River levels are expected to gradually recede over the
upcoming week but will likely remain high enough to warrant
continued flood products for much of the week. McKaughan

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 2 AM to 9 AM MDT Thursday for IDZ051>055.

Wind Advisory from 11 AM this morning to 8 PM MDT this evening
for IDZ052-053.

&&

$$