Special Weather Statement, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
148 PM MDT Wed Jun 30 2021

.DISCUSSION...Another day of excessive, potentially record
breaking temperatures will continue across western Montana and
north central Idaho. Values well above the 100 degree mark exist
across the region, with the "cooler" temperatures ranging in the
90s. Little relief will occur tonight with overnight lows, as
those are anticipated to remain abnormally warm for yet another
night as the dominating ridge of high pressure remains locked over
the Pacific Northwest.

In addition, portions of north central Idaho (namely the southern
half of Idaho county) will see the chance for afternoon and
evening thunderstorms. Any storms that develop could produce
lightning and gusty winds, with little confidence in any
measurable rainfall.

This could change by Thursday afternoon and evening as the chance
for thunderstorms becomes more widespread, expanding in coverage
across western Montana. Areas in west central Montana and along
the ID/MT border stand the best chance of seeing storm
development, though storms could pop up further north and east as
well. Storms will have a better chance at producing isolated heavy
downpours, but will also be accompanied by lightning and gusty
winds. Lightning strikes that occur outside the wet core of some
storms could become problematic, as conditions continue to dry
out.

Another chance for thunderstorms will exist again Friday afternoon
and evening, but should remain confined to along the Divide and
over southwest Montana. These storms could be much drier, but
confidence is still low at this time.

For the Independence Day Weekend: the heat does not look to let
up much despite the high pressure ridge flattening and becoming
weaker. Temperatures will remain in the 90s during the day for
western Montana, with select valleys in north central Idaho
remaining right around the 100 degree mark. No precipitation is on
the horizon through at least the middle of next week.

&&

.AVIATION...High density altitudes will continue today as record
breaking temperatures persist across the Intermountain West.
Expect another fair flying day with afternoon terrain-driven winds
affecting most terminals until 01/0200Z. A plume of moisture will
cause showers and thunderstorms to develop over central Idaho
this afternoon and evening, but may not make it far enough north
to impact KGIC. More widespread convection is anticipated
Thursday afternoon and evening and could impact KMSO, KBTM, and
KSMN after 01/2200Z.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Heat Advisory until 8 PM MDT Thursday Bitterroot/Sapphire
     Mountains...Missoula/Bitterroot Valleys...Potomac/Seeley
     Lake Region.

     Excessive Heat Warning until 8 PM MDT Thursday Kootenai/Cabinet
     Region...Lower Clark Fork Region.

     Heat Advisory until 8 PM MDT Thursday Flathead/Mission Valleys...
     West Glacier Region.

ID...Heat Advisory until 8 PM MDT Thursday Eastern Lemhi County...
     Western Lemhi County.

     Excessive Heat Warning until 7 PM PDT Thursday Northern
     Clearwater Mountains...Southern Clearwater Mountains.

     Excessive Heat Warning until 7 PM PDT Thursday Lower Hells
     Canyon/Salmon River Region...Orofino/Grangeville Region.

&&

Special Weather Statement
National Weather Service Missoula MT
158 PM PDT Wed Jun 30 2021

IDZ006-008-302145-
Southern Clearwater Mountains ID-
Lower Hells Canyon/Salmon River Region ID-
158 PM PDT Wed Jun 30 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN IDAHO COUNTY UNTIL
245 PM PDT...

At 157 PM PDT, Doppler radar was tracking a strong thunderstorm 15
miles northeast of Riggins, or 24 miles south of Grangeville, moving
west at 15 mph.

Wind gusts of 50 to 55 mph will be possible with this storm.

Locations impacted include...
Lucile and Slate Creek.

LAT...LON 4565 11596 4547 11597 4544 11636 4571 11634
TIME...MOT...LOC 2057Z 093DEG 12KT 4557 11608

Special Weather Statement
National Weather Service Missoula MT
331 PM PDT Wed Jun 30 2021

IDZ006-007-302315-
Southern Clearwater Mountains ID-Orofino/Grangeville Region ID-
331 PM PDT Wed Jun 30 2021

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL IDAHO COUNTY UNTIL 415 PM
PDT...

At 331 PM PDT, Doppler radar was tracking a strong thunderstorm 13
miles southeast of Grangeville. this storm was nearly stationary.

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

Locations impacted include...
Grangeville.

LAT...LON 4593 11578 4575 11575 4575 11613 4597 11614
TIME...MOT...LOC 2231Z 082DEG 1KT 4583 11587

Special Weather Statement
National Weather Service Missoula MT
348 PM PDT Wed Jun 30 2021

IDZ006-008-302330-
Southern Clearwater Mountains ID-
Lower Hells Canyon/Salmon River Region ID-
348 PM PDT Wed Jun 30 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN IDAHO COUNTY UNTIL
430 PM PDT...

At 348 PM PDT, Doppler radar was tracking a strong thunderstorm 13
miles southeast of Riggins, or 24 miles north of McCall, moving
northwest at 10 mph.

Wind gusts of 50 to 55 mph will be possible with this storm.

Locations impacted include...
Riggins Hot Spring and Pollock.

LAT...LON 4548 11624 4528 11599 4514 11616 4520 11631
      4527 11634 4526 11647 4527 11648
TIME...MOT...LOC 2248Z 129DEG 7KT 4526 11617

Special Weather Statement
National Weather Service Missoula MT
612 PM PDT Wed Jun 30 2021

IDZ006-008-010130-
Southern Clearwater Mountains ID-
Lower Hells Canyon/Salmon River Region ID-
612 PM PDT Wed Jun 30 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN IDAHO COUNTY UNTIL
630 PM PDT...

At 612 PM PDT, Doppler radar was tracking a strong thunderstorm 8
miles southeast of Riggins, or 29 miles north of McCall, moving
southwest at 20 mph.

Dime size hail and wind gusts up to 50 mph will be possible with this
storm.

Locations impacted include...
Riggins Hot Spring and Pollock.

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 4545 11621 4534 11602 4517 11620 4517 11630
      4519 11630 4527 11634 4527 11646 4529 11650
TIME...MOT...LOC 0112Z 041DEG 16KT 4533 11621