Special Weather Statement, NWS Pocatello, ID

Area Forecast Discussion
National Weather Service Pocatello ID
259 AM MDT Mon May 24 2021

.SHORT TERM...Today through Wednesday night.
Main impact today will be expected wind increases in the Snake
River Plain. Have a lake wind advisory in effect for American
Falls Reservoir from 10 am through 9 pm for southwest winds of 20
mph or greater. A wind advisory is in effect for the Upper Snake
Plain including Idaho Falls and the arco desert for speeds of 30
mph from noon through 9 pm. Showers and thunderstorms will be
mainly limited to the eastern mountains today. Another Pacific
trof will move through Idaho Tuesday into Wednesday and will have
a better chance for showers and thunderstorms Tuesday through
Wednesday. Winds will be much reduced on Tuesday after the windy
conditions today. Most widespread precipitation likely to be
Tuesday night. by Wednesday expect most activity to be in the
eastern mountains again. Generally temperatures will remain cool
today with highs mainly in the 50s mountains and 60s valleys, with
slight warming ahead of next system Tuesday but in the short term
temperatures remain below seasonal normals for late May. GK

.LONG TERM...Thursday through Monday. Extended period starts out dry
with upper ridge passing overhead. Next upper trough shifts across
the region during the day Friday. Model trends have shifted the low
further north than previous runs, which introduces a drier flow
aloft. The blend has trended in this direction, but there is a
significant amount of disagreement with the ensemble clusters from
12Z, which still favor a deeper closed low solution. Interestingly,
moving into Saturday night and Sunday, both operational GFS and
ECMWF now favor a split flow closed low dropping into central or
southern California. There may be a hint of this in the clusters but
overall given the uncertainty, confidence is extremely low in the
extended period at this time, and thus stayed with the blended
solution overall.

&&

.AVIATION...East Idaho starts to see a trend toward a drier solution
beginning today as upper low has pulled well northeast of the
region. There is still a chance for a few SHRA mainly higher
elevations. Instability not very impressive today, but there is
still enough uncertainty to carry VCTS for each terminal for
daylight hours. Expect winds to pick up today, reaching 20-25kts
sustained for KPIH and KIDA, strongest 18Z-03Z. Precipitation threat
diminishes after sunset, as do the winds. Next shortwave feature
drives into the region Thursday, so SHRA a possibility for KSUN
after sunrise in the extended portion of the terminal forecast. DMH

&&

.FIRE WEATHER...Showers and a few thunderstorms remain a possibility
today, mainly higher elevations. Winds will also be a concern, with
speeds increasing especially over the northern portions of the Snake
Plain for the afternoon and early evening, though humidities still
remain high. After a brief break overnight, next feature dives into
the region beginning Tuesday for another round of showers and
thunderstorms both Tuesday and Wednesday. Thursday still looks quite
dry for East Idaho. There is some uncertainty headed into the
weekend with the next system, as the models have started trending
the system further north, which would keep East Idaho in a drier
flow and would limit precipitation potential. Confidence is low at
this time. DMH

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory from 10 AM this morning to 9 PM MDT this
evening for IDZ054.

Wind Advisory from noon today to 9 PM MDT this evening for
IDZ052-053.

&&

Special Weather Statement
National Weather Service Pocatello ID
125 PM MDT Mon May 24 2021

IDZ066-242000-
Centennial Mountains/Island Park ID-
125 PM MDT Mon May 24 2021

...LINE OF THUNDERSTORMS MOVING THROUGH ISLAND PARK AND HENRYS
LAKE THROUGH 2 PM MDT...

At 122 PM MDT, Doppler radar was tracking a line of thunderstorm
training over Island Park Village, or 8 miles southeast of Henrys
Lake, moving east at 20 mph. Folks recreating in the Island Park
area or boating on Henrys Lake or Island Park Reservoir may want to
seek shelter until the storms pass east of the region sometime after
2 PM MDT. Small hail, brief moderate rain, and wind gusts to 35 mph
are possible with these storms as they move through the region.

Locations impacted include...
Island Park Village, Macks Inn, Shotgun Village and Big Springs.

LAT...LON 4446 11155 4454 11151 4454 11146 4456 11147
      4456 11150 4458 11149 4465 11125 4462 11122
      4461 11124 4458 11123 4457 11118 4455 11117
      4453 11113 4450 11113 4449 11109 4444 11110
TIME...MOT...LOC 1922Z 257DEG 17KT 4455 11128

Huston