124
FXUS65 KMSO 200905
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
305 AM MDT FRI JUN 20 2025
DISCUSSION
KEY MESSAGES:
- STRONG THUNDERSTORMS, WITH ISOLATED SEVERE THREAT, ACROSS WEST-
CENTRAL AND SOUTHWEST MONTANA.
- WIDESPREAD PRECIPITATION THIS AFTERNOON THROUGH THE WEEKEND.
MUCH COOLER TEMPS, HIGH ELEVATION SNOW.
- SIGNIFICANT SNOWFALL, FOR THIS TIME OF YEAR, ACROSS GLACIER
NATIONAL PARK AND THE FLATHEAD NATIONAL FOREST SATURDAY INTO
SUNDAY MORNING.
MOISTURE CONTINUES TO INCREASE ACROSS THE REGION AS AN UPPER
TROUGH MOVES IN, SUPPORTING ONGOING THUNDERSTORM ACTIVITY
OVERNIGHT. UNSTABLE CONDITIONS ARE EXPECTED TO PERSIST THROUGH
THIS AFTERNOON ACROSS RAVALLI, GRANITE, DEER LODGE, SILVER BOW,
AND LEMHI COUNTIES - AREAS MOST LIKELY TO SEE THUNDERSTORMS TODAY.
ELSEWHERE ACROSS NORTH-CENTRAL IDAHO AND WESTERN MONTANA, RAIN
SHOWERS WILL BE COMMON.
MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE DEVELOPMENT OF LOW
PRESSURE OVER NORTH-CENTRAL MONTANA, WHICH WILL WRAP PRECIPITATION
INTO NORTHWEST MONTANA, PARTICULARLY GLACIER NATIONAL PARK AND
NORTHERN FLATHEAD AND LINCOLN COUNTIES. HEAVY, WET SNOW IS
EXPECTED ABOVE 5,000 FEET, WITH POTENTIAL ACCUMULATIONS OF A FOOT
OR MORE. SNOW LEVELS MAY BRIEFLY LOWER TO NEAR 4,000 FEET LATE
SATURDAY NIGHT INTO EARLY SUNDAY MORNING, WHEN THE COLDEST
TEMPERATURES AND HEAVIEST SNOWFALL ARE EXPECTED.
THIS MAY LEAD TO RAPIDLY CHANGING CONDITIONS ALONG US-2 AND
ADJACENT VALLEYS NEAR GLACIER NATIONAL PARK. SNOW, COLD
TEMPERATURES, AND BLUSTERY WINDS COULD SIGNIFICANTLY REDUCE
VISIBILITY AND IMPACT BACKCOUNTRY TRAVELERS AND HIGH-ELEVATION
VISITORS, PARTICULARLY TOURISTS UNACCUSTOMED TO NEAR-WINTER
CONDITIONS. A WINTER STORM WARNING IS IN EFFECT FROM SATURDAY
MORNING THROUGH MIDDAY SUNDAY, WITH LATER SHIFTS TO DETERMINE THE
NEED ADDITIONAL ADVISORIES.
ELSEWHERE, WIDESPREAD VALLEY RAIN AND MOUNTAIN SNOW (ABOVE 6,000
FT) WILL LIKELY CONTINUE ACROSS FLATHEAD AND LINCOLN COUNTIES,
WITH MORE SCATTERED SHOWERS ACROSS THE REST OF THE NORTHERN
ROCKIES THROUGH SUNDAY. PRECIPITATION TOTALS MAINTAIN A HIGH-90%
CHANCE OF WIDESPREAD TOTALS EXCEEDING 0.25", AND A 50% CHANCE OF
1.5" OR MORE NORTH AND NORTHEAST OF FLATHEAD LAKE THROUGH SUNDAY
EVENING.
HIGHS SATURDAY AND SUNDAY WILL BE UNSEASONABLY COLD, WITH NEAR
RECORD COLD MAXIMUM TEMPERATURES FOR JUNE 21ST IN MISSOULA, AND
MOST VALLEYS ONLY REACHING THE MID TO UPPER 50S.
AS THE LOW EXITS EAST ON MONDAY, DRIER AIR WILL MOVE IN, BUT
TEMPERATURES WILL REMAIN COOL. MORNING LOWS WILL DIP INTO THE 30S,
WITH SUB-FREEZING TEMPERATURES POSSIBLE IN HIGHER VALLEYS
DEPENDING ON CLOUD COVER. WHILE MONDAY WILL BE DRIER OVERALL,
ISOLATED SHOWERS AND THUNDERSTORMS MAY STILL DEVELOP IN THE
AFTERNOON. A RETURN TO MORE SEASONABLE CONDITIONS IS EXPECTED
THROUGH THE MIDDLE OF NEXT WEEK.
AVIATION
SCATTERED THUNDERSTORMS THIS AFTERNOON ACROSS
SOUTHWEST MONTANA AND LEMHI COUNTY MAY CAUSE BRIEF MVFR/IFR,
OUTFLOW WINDS TO 40 KT, AND LIGHTNING. WIDESPREAD SHOWERS
ELSEWHERE WILL LEAD TO MOUNTAIN OBSCURATIONS AND OCCASIONAL MVFR
CEILINGS.
STEADIER RAIN AND TERRAIN OBSCURATION DEVELOP LATE TONIGHT INTO
SUNDAY ACROSS NORTHWEST MONTANA, ESPECIALLY NEAR KGPI, WITH SNOW
ABOVE 5,000 FT. VALLEY SITES WILL STAY RAIN-DOMINATED, BUT
VISIBILITY REDUCTIONS ARE EXPECTED. CONDITIONS IMPROVE LATE
SUNDAY INTO MONDAY.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WARNING FROM 9 AM SATURDAY TO NOON MDT SUNDAY FOR
WEST GLACIER REGION.
ID...NONE.
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