Special Weather Statement, NWS Pocatello, ID

Area Forecast Discussion
National Weather Service Pocatello ID
550 PM MDT Tue Jun 29 2021

.SHORT TERM...Tonight through Thursday. A quick update early this
evening as weak to modest thunderstorm activity is tracking into the
region from the NE. Some models show this activity continuing
overnight which might happen given the weak disturbance noted in
water vapor imagery shearing through Cody WY toward Idaho. Will
reevaluate that scenario a little later this evening as we see how
the current activity behaves after the sun sets. See previous
discussion below. Huston

High pressure continues to remain the dominant feature impacting
local weather over the next few days. Forecast temperatures remain
hot although not nearly as warm as what it looked like a few days
ago. Nevertheless, a heat advisory remains in place for a good chunk
of eastern Idaho. Although things have trended towards a more
marginal heat advisory felt it necessary to maintain the existing
hazards. We don't want to risk sending a confusing message to the
public that heat-related hazards are not materializing just because
the temp forecast has backed off a few degrees compared to a few
days ago. It is going to remain hot, for a long period, and
cumulative heat-related issues will be a concern across the area for
much of the week ahead and perhaps beyond.

As the aforementioned high shifts away from the area, we introduce
the potential for more widespread convective activity during the
afternoon and evening hours. Primary areas of concern for this will
be across the higher terrain where orographic lift will likely serve
as a catalyst for storm development. Wouldn't be surprised to see a
few storms try to sneak into the Snake Plain but this isn't
expressed in the forecast at the moment. Wednesday activity will be
fairly isolated in nature with coverage expected to be a bit more
scattered on Thursday. McKaughan

.LONG TERM (Friday through Tuesday)...
The trend of continued hot with daily thunderstorms continues.
Confidence is growing that there will be a decent shot of
thunderstorms all the way through the 4th and into next week. The
highest chances right now appear to through Saturday and over the
central mountains and Centennial Mountains/Island Park area. We do
suspect we may have to increase chances elsewhere as we get
closer and refine things on a daily basis. This is when some of
the higher resolution models can get a handle on storms on a much
smaller scale and determine if we might get more storms along
outflow boundaries, etc. The potential of seeing decent rain
producers is also going up and maximized during the same period.
The models are trying rebuild another ridge to our south, which
may allow for less thunderstorm coverage and push temperatures up
again a bit. We just need to see how this plays out over the
coming days. Keyes

&&

.AVIATION...
VFR to prevail through the period with mostly clear skies. Light NE
winds will continue through the evening, likely becoming more
variable overnight. After daybreak Wednesday, winds look to take on
a more E to SE direction although remaining around 10 kts or less.
McKaughan

&&

.FIRE WEATHER...
There is no doubt it will remain on the very warm/hot side of
things over the coming days. The concern now becomes the
increasing potential for thunderstorms through the holiday weekend
and early next week. The earliest we might see that is today and
this evening, but the potential is less than 10%. The most likely
places would be across portions of Zone 410, 413 and the central
mountains. These storms would definitely be dry with gusty winds.
IF something forms, look for them to move EAST TO WEST. We will
monitor trends through the rest of the day to see if anything
forms, etc. For Wednesday, we are looking for a bit better
potential for isolated thunderstorms across the central mountains
and Zones 413 and 427. Lightning potential suggests there could be
a little more concentrated (scattered coverage) in the mountains
from Stanley to west of Challis. Confidence is low and certainly
that wouldn't warrant a RED FLAG WARNING. Storms tomorrow would be
mostly dry, with a few possibly producing wetting rains. We will
need to see any outflow boundaries and produce storms elsewhere,
especially across the Snake Plain or Magic Valley. Thunderstorm
potential coverage increases Thursday through at least Saturday,
along with the chance of wetting rains. Coverage may be high
enough Thursday through Sunday across higher elevations,
especially the central mountains for RED FLAG WARNINGS. Those
trends will be monitored, and likely be tweaked daily based on
cloud cover and track of any particular wave of thunderstorms. The
risk for storms slowly decreases into next week. Keyes

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 9 PM MDT Thursday for IDZ051>059-068>075.

&&

Special Weather Statement
National Weather Service Pocatello ID
459 PM MDT Tue Jun 29 2021

IDZ062>064-292345-
Big Hole Mountains ID-Caribou Range ID-Blackfoot Mountains ID-
459 PM MDT Tue Jun 29 2021

...CLUSTER OF WEAK THUNDERSTORMS EAST OF PALISADES MOVING SOUTHWEST
INTO THE CARIBOU HIGHLANDS THROUGH 545 PM MDT...

At 454 PM MDT, Doppler radar was tracking a cluster of weak
thunderstorm near Palisades Reservoir, moving southwest at 30 mph.

Brief light rain, occasional lighting, and wind gusts to 40 mph are
possible with these storms as they move through Palisades Reservoir
and across the Caribou highlands through 545 PM MDT.

Locations impacted include...
Palisades Reservoir, Irwin and Grays Lake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If on or near Palisades Reservoir, now would be a good time to move
to shore and seek shelter until the storms pass. Gusty winds can
create hazardous waves on the lake.

&&

LAT...LON 4295 11163 4320 11180 4345 11105 4341 11104
      4322 11104
TIME...MOT...LOC 2254Z 063DEG 29KT 4328 11116

Huston

Special Weather Statement
National Weather Service Pocatello ID
607 PM MDT Tue Jun 29 2021

IDZ053-062>064-300100-
Big Hole Mountains ID-Upper Snake River Plain ID-Caribou Range ID-
Blackfoot Mountains ID-
607 PM MDT Tue Jun 29 2021

...SECOND ROUND OF THUNDERSTORMS MOVING THROUGH PINE CREEK PASS AND
PALISADES RESERVOIR THROUGH 700 PM MDT...

At 602 PM MDT, Doppler radar was tracking a line of thunderstorms
extending from 7 miles west of Teton Pass to 6 miles northeast of
Alpine to 15 miles north of Henry, moving west-southwest at 25 mph.

Brief moderate rain, frequent lightning, and wind gusts to 40 mph
are possible with these storms as they move west through Palisades
Reservoir, Pine Creek Pass and Irwin, and south of Bone through 700
PM MDT this evening.

Locations impacted include...
Swan Valley, Palisades Reservoir, Wayan, Ririe Reservoir, Irwin,
Alpine Campground, Grays Lake and Alpine Airport.

LAT...LON 4293 11145 4348 11185 4352 11109 4346 11104
      4308 11104
TIME...MOT...LOC 0002Z 078DEG 20KT 4346 11110 4322 11092

Huston