Special Weather Statement, NWS Pocatello, ID

Area Forecast Discussion
National Weather Service Pocatello ID
125 PM MDT Mon Aug 2 2021

.SHORT TERM...Tonight through Wednesday.

An upper level trough and associated surface front/dry line will
pass through central and east Idaho this afternoon. This will be the
focus for additional thunderstorms this afternoon. Precipitable
water values remain extraordinarily high, around 1.25 inches.
Surface dew points remain in the low to mid 60s. So heavy rain is
almost certain with thunderstorms once again this afternoon and
evening. Flash flood watches remain in effect for the high
country. Isolated flooding remains possible in the Snake Plain,
but mainly concerned with street flooding there, higher threat
along the bench areas.Isolated severe storms can't be entirely
ruled out with strong winds possible as well.

Models show convection ending this evening as the dry line/front
passes into Wyoming. Tuesday and Wednesday looks much drier with
lower dew points. Still moist by Idaho standards, but looking at dew
points in the upper 40s to around 50 as opposed to the current low
to mid 60s we are currently enjoying. Isolated heat of the day
variety thunderstorms are possible Tuesday and Wednesday. Wednesday
is a slightly better chance over the central mountains as a weak
upper level trough enters the region.

13

.LONG TERM...Thursday through Monday. A storm will @see across
eastern Idaho Thursday, with a better chance of showers and
thunderstorms. These storms won't be tapping into deep monsoon
moisture, but we can't rule out a few storms producing locally heavy
rain because of recent rainfall and moisture. The storm track shifts
north through the weekend. We could see some showers and storms
closer to the Montana border, but most of the area will be dry and
breezy. Keyes

&&

.AVIATION...Showers and thunderstorms will be potentially impacting
TAF sites this afternoon and evening. Just like the past few days,
we could see MVFR/IFR weather due to heavy rain and low visibility.
We should see things ending west to east overnight. At the moment,
we don't think we will have fog or stratus issues just due to all of
the recent rainfall...but it might be something we need to monitor.
Tomorrow should be VFR with no storms expected. Keyes

&&

.FIRE WEATHER...Showers and thunderstorms and the risk of heavy
rainfall and debris flows will end overnight from west to east. We
could see a few very isolated storms tomorrow across mainly the
central mountains and near the Wyoming border, but the risk is very
low (around 10% at most). There is an increasing chance in the
central mountains later Wednesday, expanding everything heading into
Thursday. These storms will be more of a mix of wet and dry, as
monsoon moisture won't be around. That said, with all of the recent
rainfall...it's possible enough moisture is there to produce a few
locally heavy rainers. The storm track shifts north heading into the
weekend. While showers and storms are possible closer to the Montana
border, the main issue may become gusty winds across most of central
and eastern Idaho with a drier airmass moving in. Keyes

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 9 PM MDT this evening for IDZ056>074.

&&

Special Weather Statement
National Weather Service Pocatello ID
435 PM MDT Mon Aug 2 2021

IDZ052-053-067-022315-
Arco/Mud Lake Desert ID-Upper Snake River Plain ID-
Beaverhead/Lemhi Highlands ID-
435 PM MDT Mon Aug 2 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN JEFFERSON AND SOUTH
CENTRAL CLARK COUNTIES UNTIL 515 PM MDT...

At 434 PM MDT, Doppler radar was tracking a strong thunderstorm near
Hamer, or 11 miles south of Dubois, moving east at 35 mph.

Winds in excess of 40 mph and small hail will be possible with this
storm.

Locations impacted include...
Dubois, Terreton, Mud Lake, Hamer, Monteview and Sage Junction.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways. Expect very low visibilities while driving through heavy
rain.

&&

LAT...LON 4376 11252 4411 11256 4419 11223 4373 11217
TIME...MOT...LOC 2234Z 261DEG 32KT 4401 11226

TW

Special Weather Statement
National Weather Service Pocatello ID
441 PM MDT Mon Aug 2 2021

IDZ066-022330-
Centennial Mountains/Island Park ID-
441 PM MDT Mon Aug 2 2021

...SPECIAL WEATHER STATEMENT...

At 438 PM MDT, Doppler radar was tracking a strong thunderstorm over
Last Chance, or 19 miles north of Ashton, moving east at 35 mph.

Winds in excess of 30 mph and small hail will be possible with this
storm.

Be cautious on area lakes. Storms will produce moderate to heavy
brief rain. Brief bonding of water is likely.

Locations impacted include...
Henrys Lake, Island Park Village, Shotgun Village, Ponds Lodge, Macks
Inn, Last Chance, Island Park Reservoir, Red Rock Pass, Big Springs,
Targhee Pass and Harriman State Park.

LAT...LON 4426 11157 4454 11172 4456 11170 4456 11159
      4454 11147 4459 11152 4464 11152 4467 11147
      4470 11149 4471 11142 4475 11137 4473 11132
      4467 11127 4465 11128 4462 11122 4461 11124
      4458 11123 4457 11118 4449 11109 4434 11109
TIME...MOT...LOC 2238Z 261DEG 32KT 4435 11142

TW

Special Weather Statement
National Weather Service Pocatello ID
444 PM MDT Mon Aug 2 2021

IDZ061-022330-
Bear Lake Valley ID-
444 PM MDT Mon Aug 2 2021

...SPECIAL WEATHER STATEMENT...

At 443 PM MDT, Doppler radar was tracking a strong thunderstorm near
Bear Lake Idaho Portion, moving east at 35 mph.

Winds in excess of 30 mph, small hail and lightning will be possible
with this storm.

Locations impacted include...
Bear Lake Idaho Portion and Fish Haven.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If on or near Bear Lake, Move to safe shelter now! Do not be caught
on or near the water. Gusty winds and choppy waves are likely.

&&

LAT...LON 4210 11140 4209 11125 4200 11128 4200 11141
TIME...MOT...LOC 2243Z 261DEG 32KT 4202 11125

TW

Special Weather Statement
National Weather Service Pocatello ID
450 PM MDT Mon Aug 2 2021

IDZ051>055-068-069-075-022330-
Eastern Magic Valley ID-Arco/Mud Lake Desert ID-
Upper Snake River Plain ID-Shoshone/Lava Beds ID-Lost River Range ID-
Wood River Foothills ID-Lower Snake River Plain ID-
Lost River Valleys ID-
450 PM MDT Mon Aug 2 2021

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL BLAINE...
SOUTHWESTERN JEFFERSON...SOUTHERN BUTTE...NORTHEASTERN LINCOLN...
NORTHWESTERN BONNEVILLE...NORTHWESTERN BINGHAM AND NORTH CENTRAL
MINIDOKA COUNTIES UNTIL 530 PM MDT...

At 449 PM MDT, Doppler radar was tracking a strong line of
thunderstorms and outflow winds from these storms.

Winds in excess of 40 to 50 mph and small hail will be possible with
this storm. Moderate to heavy rain is likely with thunderstorms.

Locations impacted include...
Atomic City, Craters Of The Moon, Central Inl, Southeast Inl,
Southwest Inl, Kettle Butte, East Butte and Big Southern Butte.

LAT...LON 4314 11378 4334 11390 4377 11278 4373 11217
      4360 11217 4329 11293
TIME...MOT...LOC 2249Z 162DEG 66KT 4360 11322

TW

Special Weather Statement
National Weather Service Pocatello ID
501 PM MDT Mon Aug 2 2021

IDZ058>062-022345-
Franklin/Eastern Oneida Region ID-Bear Lake Valley ID-
Bear River Range ID-Marsh and Arbon Highlands ID-
Blackfoot Mountains ID-
501 PM MDT Mon Aug 2 2021

...SPECIAL WEATHER STATEMENT...

At 500 PM MDT, Doppler radar was tracking a line of thunderstorm
near Oneida Narrows Reservoir, or 16 miles west of Montpelier,
moving northeast at 10 to 15 mph.

Winds in excess of 30 mph and small hail will be possible with this
storm.

Locations impacted include...
Oneida Narrows Reservoir, Thatcher and Emmigrant Summit.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.Expect low visibilities in heavy rain.

&&

LAT...LON 4210 11140 4210 11159 4227 11169 4235 11183
      4244 11186 4246 11174 4237 11150
TIME...MOT...LOC 2300Z 241DEG 7KT 4233 11162

TW

Special Weather Statement
National Weather Service Pocatello ID
505 PM MDT Mon Aug 2 2021

IDZ058-059-022345-
Franklin/Eastern Oneida Region ID-Marsh and Arbon Highlands ID-
505 PM MDT Mon Aug 2 2021

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL ONEIDA...SOUTHERN
BANNOCK AND WEST CENTRAL FRANKLIN COUNTIES UNTIL 545 PM MDT...

At 504 PM MDT, Doppler radar was tracking a strong thunderstorm over
Malad, moving west southwest at 10 to 15 mph.

Winds in excess of 40 mph will be possible with this storm.

Locations impacted include...
Malad, Pleasantview and Samaria.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways. Expect very low visibilities while driving in heavy rain.

&&

LAT...LON 4211 11238 4232 11235 4233 11218 4213 11208
TIME...MOT...LOC 2304Z 359DEG 13KT 4221 11227

TW