508
WWUS75 KMSO 181800
NPWMSO
URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE MISSOULA MT
1200 PM MDT MON MAY 18 2026
IDZ005-006-191500-
/O.NEW.KMSO.FR.Y.0004.260519T0600Z-260519T1500Z/
NORTHERN CLEARWATER MOUNTAINS-SOUTHERN CLEARWATER MOUNTAINS-
1100 AM PDT MON MAY 18 2026
...FROST ADVISORY IN EFFECT FROM 11 PM THIS EVENING TO 8 AM PDT
TUESDAY ABOVE 3000 FEET...
* WHAT...TEMPERATURES AS LOW AS 28 WILL RESULT IN FROST FORMATION
ABOVE 3000 FEET. COLDER TEMPERATURES ARE EXPECTED IN THE HIGHER
VALLEYS.
* WHERE...SOUTHERN CLEARWATER MOUNTAINS AND NORTHERN CLEARWATER
MOUNTAINS.
* WHEN...FROM 11 PM THIS EVENING TO 8 AM PDT TUESDAY.
* IMPACTS...FROST COULD HARM SENSITIVE OUTDOOR VEGETATION. SENSITIVE
OUTDOOR PLANTS MAY BE KILLED IF LEFT UNCOVERED.
* ADDITIONAL DETAILS...TEMPERATURE RANGES: 30 TO 33 PIERCE TO
GRANGEMONT AREA, AND 33 TO 36 IN ELK RIVER. IN IDAHO COUNTY, 28 TO
33 IN POWELL, 26 TO 29 ELK CITY, AND 19 TO 25 IN BOTH DIXIE AND ELK
RIVER WHERE A HARD FREEZE IS EXPECTED.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE STEPS NOW TO PROTECT TENDER PLANTS FROM THE COLD.
IDZ007-191600-
/O.NEW.KMSO.FR.Y.0004.260519T0600Z-260519T1600Z/
OROFINO/GRANGEVILLE REGION-
1100 AM PDT MON MAY 18 2026
...FROST ADVISORY IN EFFECT FROM 11 PM THIS EVENING TO 9 AM PDT
TUESDAY ABOVE 3000 FEET...
* WHAT...TEMPERATURE RANGES BETWEEN 30 AND 32 WILL RESULT IN FROST
FORMATION ABOVE 3000 FEET.
* WHERE...GRANGEVILLE, CAMAS PRAIRIE, AND WEIPPE AREAS.
* WHEN...FROM 11 PM THIS EVENING TO 9 AM PDT TUESDAY.
* IMPACTS...FROST COULD HARM SENSITIVE OUTDOOR VEGETATION. SENSITIVE
OUTDOOR PLANTS MAY BE KILLED IF LEFT UNCOVERED.
* ADDITIONAL DETAILS...TEMPERATURE RANGES: WEIPPE 31 TO 34 DEGREES,
30 TO 32 CAMAS PRAIRIE, AND 31 TO 34 IN GRANGEVILLE.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE STEPS NOW TO PROTECT TENDER PLANTS FROM THE COLD.
IDZ010-191500-
/O.NEW.KMSO.FR.Y.0004.260519T0600Z-260519T1500Z/
EASTERN LEMHI COUNTY-
1200 PM MDT MON MAY 18 2026
...FROST ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM MDT
TUESDAY...
* WHAT...TEMPERATURES RANGING FROM 24 TO 32 DEGREES WILL RESULT IN
FROST FORMATION.
* WHERE...EASTERN LEMHI COUNTY.
* WHEN...FROM MIDNIGHT TONIGHT TO 9 AM MDT TUESDAY.
* IMPACTS...FROST COULD HARM SENSITIVE OUTDOOR VEGETATION. SENSITIVE
OUTDOOR PLANTS MAY BE KILLED IF LEFT UNCOVERED.
* ADDITIONAL DETAILS...TEMPERATURE RANGES: 27 TO 32 DEGREES SALMON
AREA AND SOUTH ALONG US-93, 26 TO 31 IN GIBBONSVILLE, AND 22 TO 28
IN LEADORE
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE STEPS NOW TO PROTECT TENDER PLANTS FROM THE COLD.
MTZ003-191500-
/O.NEW.KMSO.FR.Y.0004.260519T0600Z-260519T1500Z/
FLATHEAD/MISSION VALLEYS-
1200 PM MDT MON MAY 18 2026
...FROST ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM MDT
TUESDAY...
* WHAT...TEMPERATURE RANGES BETWEEN 30 AND 32 WILL RESULT IN FROST
FORMATION.
* WHERE...FLATHEAD/MISSION VALLEYS.
* WHEN...FROM MIDNIGHT TONIGHT TO 9 AM MDT TUESDAY.
* IMPACTS...FROST COULD HARM SENSITIVE OUTDOOR VEGETATION. SENSITIVE
OUTDOOR PLANTS MAY BE KILLED IF LEFT UNCOVERED.
* ADDITIONAL DETAILS...TEMPERATURE RANGES: 32 TO 37 DEGREES IN THE
FLATHEAD VALLEY, AND 30 TO 35 IN THE MISSION VALLEY.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE STEPS NOW TO PROTECT TENDER PLANTS FROM THE COLD.
MTZ004-191500-
/O.NEW.KMSO.FR.Y.0004.260519T0600Z-260519T1500Z/
LOWER CLARK FORK REGION-
1200 PM MDT MON MAY 18 2026
...FROST ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM MDT
TUESDAY...
* WHAT...TEMPERATURES RANGING BETWEEN 27 AND 34 WILL RESULT IN FROST
FORMATION.
* WHERE...LOWER CLARK FORK REGION, BUT NOT ALONG HIGHWAY 200 WEST OF
TROUT CREEK.
* WHEN...FROM MIDNIGHT TONIGHT TO 9 AM MDT TUESDAY.
* IMPACTS...FROST COULD HARM SENSITIVE OUTDOOR VEGETATION. SENSITIVE
OUTDOOR PLANTS MAY BE KILLED IF LEFT UNCOVERED.
* ADDITIONAL DETAILS...TEMPERATURE RANGES: 31 TO 36 DEGREES TROUT
CREEK TO PLAINS AND INCLUDING EVARO, 31 TO 35 ALBERTON, 33 TO 35
SUPERIOR, 30 TO 32 ST. REGIS, AND 27 TO 29 DEBORGIA TO HAUGAN.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE STEPS NOW TO PROTECT TENDER PLANTS FROM THE COLD.
MTZ005-191500-
/O.NEW.KMSO.FR.Y.0004.260519T0600Z-260519T1500Z/
MISSOULA/BITTERROOT VALLEYS-
1200 PM MDT MON MAY 18 2026
...FROST ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM MDT
TUESDAY...
* WHAT...TEMPERATURE RANGES BETWEEN 27 AND 32 WILL RESULT IN FROST
FORMATION.
* WHERE...LOW-LYING AREAS OF THE MISSOULA AND BITTERROOT VALLEYS.
* WHEN...FROM MIDNIGHT TONIGHT TO 9 AM MDT TUESDAY.
* IMPACTS...FROST COULD HARM SENSITIVE OUTDOOR VEGETATION. SENSITIVE
OUTDOOR PLANTS MAY BE KILLED IF LEFT UNCOVERED.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE STEPS NOW TO PROTECT TENDER PLANTS FROM THE COLD.
MTZ006-191500-
/O.NEW.KMSO.FR.Y.0004.260519T0600Z-260519T1500Z/
BITTERROOT/SAPPHIRE MOUNTAINS-
1200 PM MDT MON MAY 18 2026
...FROST ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM MDT
TUESDAY...
* WHAT...TEMPERATURE RANGES BETWEEN 25 AND 32 WILL RESULT IN FROST
FORMATION.
* WHERE...BITTERROOT/SAPPHIRE MOUNTAINS.
* WHEN...FROM MIDNIGHT TONIGHT TO 9 AM MDT TUESDAY.
* IMPACTS...FROST COULD HARM SENSITIVE OUTDOOR VEGETATION. SENSITIVE
OUTDOOR PLANTS MAY BE KILLED IF LEFT UNCOVERED.
* ADDITIONAL DETAILS...TEMPERATURE RANGES: 30 TO 32 ALONG US-12 WEST
OF LOLO, 26 TO 29 DEGREES IN THE ROCK CREEK AREA, 26 TO 28 SULA,
AND 25 TO 28 IN THE PAINTED ROCKS AREA.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE STEPS NOW TO PROTECT TENDER PLANTS FROM THE COLD.
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