Special Weather Statement, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
149 PM MDT Tue Jul 20 2021

.DISCUSSION...Thunderstorms have begun to trek north-northeastward
out of eastern Oregon into central Idaho. These storms have
already begun to produce lightning, and are expected to continue
to grow in strength and size through this evening as they move
into western Montana. In doing so, lightning will increase, as
will the potential for heavy downpours directly beneath storm
cores. Heavy downpours will be possible with all storms that form
today, but if you are not directly beneath the storm itself, you
may only experience gusty outflow winds, some of which could
gust as high as 40 mph. As with any thunderstorm that can produce
heavy rain in brief amounts of time, there is a low probability
that localized flash flooding may occur, particularly in Lemhi
County, Idaho in areas that are prone to flash flooding events.

A lesser chance for nocturnal storms will exist across north
central Idaho into northwest Montana tonight through early
Wednesday morning, followed by another round of afternoon and
evening thunderstorm activity (in very similar locations). Winds
out of the west will also increase across north central Idaho.
Given how dry conditions are in that area, critical fire
conditions may exist as a result through Wednesday evening.

All of western Montana and north central Idaho will experience an
increase in west-northwest winds on Thursday. At the same time,
humidity will be dropping and thus, will lead to widespread
enhanced fire danger. Various Fire Weather Watches have been
issued for Wednesday and Thursday as a result of the combination
of dry conditions and increased winds.

Friday through the weekend will see the return of hot and dry
conditions once more. Daily high temperatures will hang around
the upper 80s to upper 90s, while low temperatures will range in
the 40s and 50s. No precipitation is expected during this time.

&&

.AVIATION...A surge of monsoonal moisture will bring several
rounds of showers and thunderstorms to the Northern Rockies. The
most widespread activity will stretch from southern Idaho County,
Lemhi County, and southwest Montana initially, spreading into
west-central Montana the rest of this afternoon. The main threats
with these storms will be locally heavy rain and gusty outflow
winds, possibly approaching 45 kts. Convective coverage will be
less across Northwest Montana. However, another wave of energy is
expected to initiate nocturnal convection late tonight (after
21/0600z) across north central Idaho, possibly shifting into
portions of northwest Montana after 21/1200z. Scattered
thunderstorms will fire once again on Wednesday afternoon with
the focus across west- central and southwest Montana.

Visibility reductions will continue as local and regional
wildfires produce varying amounts of smoke. Periodic convection
will help to mix the atmosphere allowing for improved air quality
at times.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Fire Weather Watch from Thursday afternoon through Thursday
     evening Bitterroot...Deerlodge/West Beaverhead...East
     Lolo...Flathead/Glacier Park...Kootenai...Salish and
     Kootenai Reservation...West Lolo.

ID...     Fire Weather Watch from Thursday morning through Thursday
     evening Clearwater/Nez Perce.

     Red Flag Warning from 11 AM to 9 PM PDT Wednesday Palouse/Hells
     Canyon.

&&

Special Weather Statement
National Weather Service Missoula MT
314 PM MDT Tue Jul 20 2021

MTZ004>006-043-202200-
Bitterroot/Sapphire Mountains MT-Missoula/Bitterroot Valleys MT-
Lower Clark Fork Region MT-Potomac/Seeley Lake Region MT-
314 PM MDT Tue Jul 20 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL MISSOULA COUNTY
UNTIL 400 PM MDT...

At 313 PM MDT, Doppler radar was tracking a strong thunderstorm over
Lolo, or near Missoula, moving east at 25 mph.

Pea size hail will be possible with this storm.

Locations impacted include...
Missoula, Lolo, Bonner-West Riverside, East Missoula and Turah.

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.

&&

LAT...LON 4669 11420 4687 11421 4693 11376 4666 11375
TIME...MOT...LOC 2113Z 268DEG 21KT 4679 11410

Special Weather Statement
National Weather Service Missoula MT
324 PM MDT Tue Jul 20 2021

MTZ004>006-043-202215-
Bitterroot/Sapphire Mountains MT-Missoula/Bitterroot Valleys MT-
Lower Clark Fork Region MT-Potomac/Seeley Lake Region MT-
324 PM MDT Tue Jul 20 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL MISSOULA COUNTY
UNTIL 415 PM MDT...

At 324 PM MDT, Doppler radar was tracking a strong thunderstorm near
Missoula, moving east at 25 mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.
Visibility one-half mile or less will be possible.

Locations impacted include...
Missoula, Lolo, Bonner-West Riverside, East Missoula, Twin Creeks,
Clinton and Turah.

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.

&&

LAT...LON 4673 11413 4690 11416 4698 11367 4673 11363
TIME...MOT...LOC 2124Z 263DEG 20KT 4682 11404