325
FXUS65 KMSO 270844
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
244 AM MDT SAT JUN 27 2026
DISCUSSION
KEY MESSAGES:
- DRAMATIC SHIFT TO COLDER AND WET WEATHER TODAY INTO THE
WEEKEND, AS TEMPERATURES FALL 20-30 DEGREES.
- SIGNIFICANT HYPOTHERMIA RISK ACROSS BACKCOUNTRY AND HIGH
ELEVATION AREAS WITH SNOW AND COLD TEMPERATURES ABOVE 6,500
FEET.
A COLD FRONT TRACKED ACROSS NORTH-CENTRAL IDAHO AND WESTERN
MONTANA YESTERDAY, WITH RAINFALL TOTALS RANGING BETWEEN 0.10" TO
0.50". THE HIGHEST TOTALS WERE IN THE TERRAIN OF NORTH-CENTRAL
IDAHO AND THE ANACOND-PINTAL. CURRENT RADAR SCANS HAVE SHOWERS
RE-DEVELOPING OVER NORTH-CENTRAL IDAHO THIS MORNING THAT WILL
BECOME MORE WIDESPREAD INTO WESTERN-MONTANA THROUGH MID-MORNING'
A CLOSED LOW WILL STALL ACROSS SOUTH-CENTRAL IDAHO THIS WEEKEND,
WITH SNOW LEVELS FALLING AS COLD AIR MOVES OVERHEAD ALOFT. MODEL
GUIDANCE SUGGESTS A WIDESPREAD SHIELD OF PRECIPITATION FORMING
OVER AREAS ALONG AND SOUTH OF THE I-90 CORRIDOR, AND SNOW-LEVELS
DROPPING NEAR 6,000-6,500 FEET ACROSS LEMHI COUNTY, ID MOUNTAIN
RANGES, THE BITTERROOT, SAPPHIRE, AND ANACONDA-PINTLER MOUNTAINS,
AND ALONG THE CONTINENTAL DIVIDE THIS EVENING INTO MONDAY
MORNING. WINTER STORM WARNINGS REMAIN FOR THESE AREAS, GIVEN COLD
TEMPERATURES AND WET HEAVY SNOW BRINGING HYPOTHERMIA CONCERNS AND
DIFFICULT TRAVEL ACROSS BACKCOUNTRY AREAS. FURTHERMORE, HEAVY,
WET SNOW MAY LEAD TO DOWNED TREES, POTENTIALLY BLOCKING ACCESS TO
BACKCOUNTRY ROADS AND TRAVEL.
LOWER ELEVATIONS WILL EXPERIENCE WIDESPREAD RAIN TODAY INTO
SUNDAY MORNING AS THE UPPER LEVEL LOW SPINS ALONG AND SOUTH OF THE
I-90 CORRIDOR. LOCATIONS SOUTH OF A LINE FROM MISSOULA TO HELENA
WILL SEE THE HIGHEST RAIN AMOUNTS DURING THIS PERIOD, HAVING A
60-80 PERCENT CHANCE OF PICKING UP 1 INCH OR MORE OF RAIN BY
SUNDAY MORNING. THOSE PLANNING OUTDOOR RECREATION ON ANY SMALL
STREAMS AND RIVERS, SHOULD BE PREPARED FOR RAPIDLY CHANGING FLOWS
AND MUCH COOLER TEMPERATURES.
LOOKING AHEAD TO SUNDAY, THE CLOSED LOW WILL PICK UP SPEED,
TRACKING THROUGH WESTERN MONTANA, BEFORE SETTLING EAST OF THE
DIVIDE THROUGH MONDAY MORNING. AS THE LOW TRACKS ALONG AND EAST OF
THE DIVIDE, PRECIPITATION SHIFTS NORTHWARD IN NORTHWEST MONTANA.
THE HEAVIEST RAIN WILL FOCUS ALONG THE CONTINENTAL DIVIDE, IN
GLACIER PARK, AND ALONG THE WEST SLOPES OF THE SWAN AND MISSION
MOUNTAINS. WIDESPREAD RAIN WILL CONTINUE ACROSS NORTHWEST MONTANA
FOR MUCH OF THE DAY MONDAY, BEFORE THE LOW DEPARTS EASTWARD ON
TUESDAY. RAIN AMOUNTS HAVE CONTINUED TO TREND HIGHER FOR THESE
AREAS, WITH 24-HOUR (ENDING 6PM MONDAY) MEDIAN (MOST-LIKELY)
PRECIPITATION AMOUNTS OF 0.50-1.00 INCHES FORECAST ACROSS
NORTHWEST MONTANA NEAR THE IDAHO BORDER, WITH AMOUNTS INCREASING
TO 1.25-2.25 INCHES ALONG THE US-93 CORRIDOR FROM EUREKA, THROUGH
THE FLATHEAD AND MISSION VALLEYS. THE HIGHEST TOTALS ARE EXPECTED
ACROSS GLACIER PARK, AND THE MISSION AND SWAN MOUNTAINS, WHERE
2.00-3.00 INCHES COULD FALL. THOSE HEADING INTO GLACIER PARK
SUNDAY INTO MONDAY SHOULD PREPARE FOR COLD AND RAW CONDITIONS,
ESPECIALLY AT LOGAN PASS AND THE HIGHER ELEVATIONS.
GUIDANCE CONTINUES TO SUGGESTS UNSETTLED WEATHER WILL CONTINUE
TUESDAY INTO WEDNESDAY AS A NW PACIFIC DISTURBANCE MOVES ACROSS
WASHINGTON AND OREGON INTO THE NORTHERN ROCKIES. THESE SYSTEMS
WILL KEEP SHOWERS AND THUNDERSTORMS IN THE FORECAST.
AVIATION
A CLOSED LOW WILL STALL ACROSS SOUTH-CENTRAL IDAHO THIS WEEKEND,
WITH SNOW LEVELS FALLING AS COLD AIR MOVES OVERHEAD ALOFT. MODEL
GUIDANCE SUGGESTS A WIDESPREAD SHIELD OF PRECIPITATION FORMING
OVER AREAS ALONG AND SOUTH OF THE I-90 CORRIDOR. WIDESPREAD
RAINSHOWERS WILL PERIODICALLY IMPACT VISIBILITY AND BRING LOWER
CEILINGS FOR ALL AVIATION SITES BY MID-MORNING IN WEST-CENTRAL
AND SOUTHWEST MONTANA, AND NORTHWEST MONTANA BY THIS AFTERNOON AND
EVENING. KBTM, KSMN, AND KHRF WILL BE UNDER AN AREA OF MORE
INSTABILITY, WHERE ISOLATED THUNDERSTORMS HAVE THE ABILITY TO FORM
BETWEEN 27/2200Z-AND 28/0300Z THIS EVENING. BRIEF HEAVY RAINFALL
AND SMALL HAIL, ALONG WITH LIGHTNING WILL BE THE MAIN THREATS.
VICINITY FOG MAY BE AN ISSUE FOR KMSO AND KGPI EARLY THIS MORNING
BEFORE SUNRISE, THOUGH WIDESPREAD VISIBILITY REDUCTIONS AT THE
TERMINALS ARE NOT EXPECTED.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 9 AM MDT MONDAY
FOR BITTERROOT/SAPPHIRE MOUNTAINS...BUTTE/BLACKFOOT REGION.
ID...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 9 AM MDT MONDAY
FOR EASTERN LEMHI COUNTY...WESTERN LEMHI COUNTY.
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