Special Weather Statement, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
210 PM MDT Wed Jun 24 2020

.DISCUSSION...Showers and thunderstorms are forming in central
Idaho and Western Montana. On satellite we can see a line of
clouds from southwest to northeast, and that is most likely our
weak cold front. As the afternoon heats up, thunderstorms are
expected to continue forming along this boundary. The most likely
areas to see thunderstorms will be south and east of Missoula,
including central Idaho. The atmosphere is unusually moist,
therefore the biggest threat will be brief heavy rain. However,
lightning, gusty winds, and small hail are also expected. Light
showers are possible through tomorrow morning.

Friday and Saturday are still on track to be warm and breezy. Some
clouds will form along ridges, but it is unlikely showers will
move into valleys until late Saturday.

Starting Saturday evening, light showers will form in northwest
Montana, which will signal a significant change in weather. A
closed low with origins in the Aleutian Islands will drop into
Eastern Washington on Sunday. This is a cool system, and
temperatures Sunday will be 10 to 15 degrees cooler than Saturday.
In addition, winds along the Continental Divide and in northwest
Montana will turn to the northeast late Sunday. This will allow
the system to tap into moist air east of the divide and pull it
across into Western Montana. Expect a multi-day high precipitation
event for most of Western Montana.

Backcountry users need to be prepared for cool and wet conditions.
Generally, snow levels are expected to be above 9000 feet.
However, on Tuesday in areas like the Whitefish Mountains, Swan
Mountains, Bob Marshall Wilderness, and Glacier National Park,
snow levels could drop as low as 8000 feet in heavier
precipitation.

Multi-day precipitation totals in the higher terrain of northwest
Montana will range from 2 to 3 inches, with a 30% chance both
Sunday and Monday of an inch or more each day. Valleys of W.
Montana will generally receive 0.50 to 0.75 of an inch, with
locations such as the Flathead, Swan, and Glacier National Park
receiving 0.75 to 1 inch. Central Idaho will generally receive
0.50 an inch in valleys to 1 inch in the higher terrain.

Late on Tuesday, the closed low will move off to the northeast,
and the model ensembles generally agree a cool trough will remain
over the Northern Rockies. Expect continued cool and unsettled
weather through the end of the week.

&&

.AVIATION... Showers and thunderstorms are have initiated across
the northern Rockies this afternoon. A weak cold front oriented
southwest to northeast is moving through terminal KMSO at 20Z, and
is expected to continue moving southeast through the evening.
Models have been consistently showing thunderstorms ahead of this
front with some weaker storms and showers behind it. The strongest
storms are expected to affect terminal KBTM after 00Z with
storms potentially in the area until 07Z.

&&

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

Special Weather Statement
National Weather Service Missoula MT
350 PM MDT Wed Jun 24 2020

MTZ001>003-242245-
Flathead/Mission Valleys MT-West Glacier Region MT-
Kootenai/Cabinet Region MT-
350 PM MDT Wed Jun 24 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN LAKE AND SOUTH CENTRAL
FLATHEAD COUNTIES UNTIL 445 PM MDT...

At 345 PM MDT, Doppler radar was tracking a strong thunderstorm 8
miles southwest of Big Arm, or 13 miles west of Polson, moving east
at 35 mph.

Half inch hail and winds in excess of 30 mph will be possible with
this storm. Also, frequent cloud-to-ground lightning will threaten
boaters and those recreating along the shoreline of Flathead Lake.

Locations impacted include...
Flathead Lake, Polson, Woods Bay, Bigfork, Jette, Kings Point, Rocky
Point, Kerr, Big Arm, Turtle Lake, Proctor, Elmo, Finley Point,
Dayton, Lakeside, Rollins and Niarada.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Lightning will be a significant threat for boaters on Flathead Lake.
Get out of the water and seek shelter until at least 30 minutes
after lightning has ended.

&&

LAT...LON 4763 11451 4780 11460 4811 11408 4770 11380
TIME...MOT...LOC 2145Z 249DEG 30KT 4775 11445

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
429 PM MDT WED JUN 24 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0415 PM     HAIL             KILA                    48.12N 114.46W
06/24/2020  M1.75 INCH       FLATHEAD           MT   PUBLIC

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
431 PM MDT WED JUN 24 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0425 PM     HAIL             1 SSE KALISPELL         48.19N 114.31W
06/24/2020  M1.00 INCH       FLATHEAD           MT   PUBLIC

&&

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