Special Weather Statement, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
218 PM MDT Sun Jun 13 2021

.DISCUSSION...While current visible satellite imagery as of early
afternoon shows a rather clear day across the Northern Rockies,
thunderstorm activity is looking more likely for later this
afternoon. The ingredients for strong thunderstorms are lining up
for this afternoon and evening. These ingredients are strong mid-
level instability, shear, and sufficient moisture. Working
against these factors is a stable lower atmosphere. High
resolutions models are exhibiting more confidence that the low-
level stability will be overcome by a fast-moving shortwave,
giving way to storm initiation. These models are depicting storms
forming near Lost Trail Pass and moving north-northeast over the
Bitterroot Valley, the Highway 1 corridor, I-90 east of about
Superior to possibly as far east as Butte, Missoula, then moving
up through the Mission and Swan Valleys towards Glacier Park,
potentially clipping Kalispell. Storms should be east of the
Continental Divide by 9 or 10pm MDT. They will be capable of
producing strong winds, hail, brief heavy rain, and lightning.

Expect another hot day on Monday. Similar to today, ingredients
will be in place for afternoon thunderstorms. The major difference
is that there will not be a disturbance to kick start convection,
so confidence is much lower for the formation of strong storms.
Storms that are able to form will be capable of producing hail,
gusty winds, brief heavy rain, and lightning. Later on Monday
night and early Tuesday morning, a deep trough off the Pacific
Northwest will push a cold front into the Northern Rockies. If
instability lingers long enough overnight, this front could
initiate thunderstorms overnight on Monday or on Tuesday morning.
Regardless, the front will bring increased westerly winds, cooler
temperatures, and widespread rain showers to northwest Montana and
north-central Idaho on Tuesday.

Temperatures will return to seasonable for Wednesday under
westerly flow as a broad ridge begins to build over the
northwestern U.S. Some shower activity may continue over
northwest Montana in the morning. The ridge looks to persist for
the remainder of the week, bringing above-normal temperatures and
mostly fair weather. Model solutions begin to diverge over the
weekend.

&&

.AVIATION...Fair weather today will give way to a chance for
thunderstorms by this afternoon. High resolution models are
showing storm initiation taking place by about 13/2200z over the
southern Bitterroot Valley. The strongest convection looks to form
north of KSMN. Model solutions suggest storms will track from the
southern Bitterroot Valley north-northeast to Glacier Park.
Confidence is strengthening that KMSO will be affected by
thunderstorms from about 13/2300z to 14/0100z. KBTM and KGPI look
to be on the edges of the storm track. Impacts to aviation will
include brief heavy rain that decreases visibility and ceilings,
hail, gusty winds, and lightning. Terrain could become obscured
over the Bitterroot, Sapphire, Rattlesnake, Mission, and Swan
Ranges, as well as the Glacier Park Region. Storms should be out
of the Northern Rockies airspace by 14/0400z.

&&

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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
750 PM MDT SUN JUN 13 2021

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

0730 PM     TSTM WND DMG     2 E SEELEY LAKE         47.17N 113.44W
06/13/2021                   MISSOULA           MT   TRAINED SPOTTER

            REPORTED 60 FOOT PONDEROSA PINE FELL ONTO
            SHOP. 2 FEET IN DIAMETER. SECTION JACK
            FENCES WERE TIPPED OVER.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
812 PM MDT SUN JUN 13 2021

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

0720 PM     TSTM WND DMG     1 ENE CLEARWATER        47.01N 113.35W
06/13/2021                   MISSOULA           MT   DEPT OF HIGHWAYS

            LARGE TREE DOWN ALONG HIGHWAY 200, 2 MILES
            EAST OF CLEARWATER JUNCTION.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
814 PM MDT SUN JUN 13 2021

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

0730 PM     TSTM WND DMG     4 NNW CLEARWATER        47.06N 113.40W
06/13/2021                   MISSOULA           MT   DEPT OF HIGHWAYS

            ROCKS AND TREE BLOCKING NORTH BOUND LANE OF
            HIGHWAY 83, 4 MILES NORTH OF HIGHWAY 200.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
816 PM MDT SUN JUN 13 2021

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

0730 PM     TSTM WND DMG     5 SSE SEELEY LAKE       47.11N 113.43W
06/13/2021                   MISSOULA           MT   DEPT OF HIGHWAYS

            LARGE TREE BLOCKING NORTH BOUND LANE OF
            HIGHWAY 83, 9 MILES NORTH OF HIGHWAY 200.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
820 PM MDT SUN JUN 13 2021

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

0700 PM     DEBRIS FLOW      SKALKAHO PASS           46.25N 113.77W
06/13/2021                   RAVALLI            MT   DEPT OF HIGHWAYS

            ROCKSLIDE RESULTED FROM HEAVY RAIN FROM A
            THUNDERSTORM NEAR SKALKAHO FALLS BETWEEN
            MILE MARKER 22-23 ON HIGHWAY 38, ALSO KNOWN
            AS SKALKAHO ROAD.

&&

Special Weather Statement
National Weather Service Missoula MT
732 PM PDT Sun Jun 13 2021

IDZ006-140245-
Southern Clearwater Mountains ID-
732 PM PDT Sun Jun 13 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL IDAHO COUNTY UNTIL
745 PM PDT...

At 732 PM PDT, Doppler radar was tracking a strong thunderstorm 7
miles northeast of Lowell, or 26 miles east of Kamiah, moving north
at 20 mph.

Pea size hail and winds in excess of 40 mph will be possible with
this storm.

This storm will remain over mainly rural areas of north central Idaho
County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Persons in campgrounds should consider seeking sturdy shelter until
this storm passes.

&&

LAT...LON 4612 11542 4613 11554 4632 11555 4629 11528
TIME...MOT...LOC 0232Z 189DEG 19KT 4621 11548