Severe Thunderstorm Warning 59, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
249 PM MDT Thu Aug 11 2022

.DISCUSSION...It's shaping up to be another hot afternoon across
the Northern Rockies today, and is expected to be another hot
afternoon tomorrow as well. One difference for today and tomorrow
from previous hot afternoons, will be scattered thunderstorms.
Showers and thunderstorms are already beginning to develop over
central Idaho at this hour, and more are expected. These storms
will track over Idaho and into western Montana through the evening
hours. There will be a marginal risk for some storms to become
severe over Idaho and Clearwater counties through this evening.
Most of the convection will be capable of producing 30-40 mph
outflows, with isolated gusts in excess of 50 mph. Isolated areas
will also be under the threat for brief heavy rain, potentially
leading to flash flooding in flood prone areas, such as burn
scars. Shower and thunderstorm activity is also expected to
linger through the overnight hours tonight, particularly across
northwest Montana.

As mentioned above, another hot day is expected tomorrow, along
with scattered thunderstorms. The marginal risk for severe
thunderstorms will shift further north and east into west-central
and northwest Montana, as compared to today. Atmospheric
conditions are expected to be more favorable for strong to severe
thunderstorms as well. Some of the thunderstorms Friday afternoon
and evening could produce strong damaging winds in areas along and
north of the I-90 corridor from Missoula to the Flathead valley.

A weak shortwave trough will move through the region Saturday
afternoon, that will bring breezy westerly winds and scattered
thunderstorms, mainly to western Montana. It will also bring
slightly "cooler" temperatures, but still above normal for this
time of the year.

Long range ensemble models are continuing to lean toward another
strong ridge of high pressure building over the Northern Rockies
next week. We are currently looking at the potential for record
breaking temperatures for some valley locations in western
Montana.

&&

.AVIATION...
Showers and thunderstorms are a threat today for all terminal
sites. Best time for storms at KMSO, KBTM, and KSMN will generally
be between 11/21z-12/02z. KGPI will experience a slightly later
start to the storms, with the best time being from 12/02z-12/08z.
Water vapor satellite imagery shows a stream of moisture entering
the region from the south and southwest. This moisture, combined
with moderate afternoon instability, will lead to the
thunderstorms later today. While the threat of severe storms is
low, storms will be capable of heavy downpours, lightning, and
gusty outflow winds. Wind gusts of up to 40 knots should be
expected with some of the stronger storms. Another round of
convection is anticipated Friday afternoon.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

Special Weather Statement
National Weather Service Missoula MT
410 PM MDT Thu Aug 11 2022

IDZ009-010-112315-
Eastern Lemhi County ID-Western Lemhi County ID-
410 PM MDT Thu Aug 11 2022

...A strong thunderstorm will impact portions of central Lemhi County
through 515 PM MDT...

At 407 PM MDT, Doppler radar was tracking several thunderstorms near
Shoup or 15 miles northwest of Salmon, moving northeast at 30 mph.
Also several strong thunderstorms in the vicinity of Challis, Idaho
are rapidly developing and will move into Central Lemhi county by
430 pm mdt.

HAZARD...Winds in excess of 40 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Frequent Lightning. Gusty winds could knock down tree limbs
         and blow around unsecured objects. Minor damage to outdoor
         objects is possible.

Locations impacted include...
Salmon, Lemhi, Leadore, North Fork, Gibbonsville, Carmen, May,
Leesburg, Tendoy, Patterson, Cobalt, Ellis, Williams Lake, Baker,
Shoup and Big Creek Campground.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 4449 11381 4463 11400 4526 11455 4562 11388
      4560 11381 4552 11384 4552 11377 4545 11378
      4539 11373 4533 11374 4513 11357 4506 11345
      4496 11344 4494 11350 4487 11345 4484 11338
      4479 11335 4482 11326 4481 11322 4443 11356
TIME...MOT...LOC 2207Z 239DEG 48KT 4526 11401

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH