685
FXUS65 KMSO 042050
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
250 PM MDT SUN MAY 4 2025
DISCUSSION
KEY MESSAGES:
- THUNDERSTORMS POSSIBLE OVER LEMHI COUNTY TODAY
- BRIEF COOL DOWN WITH RAW BACKCOUNTRY CONDITIONS THROUGH MONDAY,
THEN BACK TO SUMMER-LIKE CONDITIONS THEREAFTER
- BREEZY THURSDAY (WESTERLY WINDS 20-30 MPH WESTERN MONTANA)
- UNSETTLED WEATHER RETURNS AT THE END OF THE WEEK
RADAR TRENDS THIS AFTERNOON SHOW THUNDERSTORMS TRACKING NORTHWARDS
INTO LEMHI COUNTY, AND GENERAL STRATIFORM RAINFALL OCCURRING FROM
NORTH-CENTRAL IDAHO INTO PORTIONS OF NORTHWEST MONTANA.
THE MAIN IMPACTS THIS AFTERNOON AND EVENING WILL BE THE CHANCE FOR
LIGHTNING AND GUSTY WINDS FROM LEMHI COUNTY EAST AND NORTH TOWARDS
BUTTE. SATELLITE IMAGERY DEPICTS AN AREA THAT HAD CLOUD COVER THIS
MORNING WHICH IS NOW EXPERIENCING SUNSHINE INCLUDING DEER LODGE
AND POINTS SOUTH. THIS AREA ALREADY HAD A COLD FRONT PASSAGE LAST
NIGHT, BUT HIGH RESOLUTION MODELS SHOW SHOWERS AND MAYBE A FEW
THUNDERSTORMS FORMING OVER SOUTHWEST MONTANA, THEN TRACKING
NORTHWARDS. THEY MAY LOSE MUCH OF THEIR INSTABILITY BY THE TIME
THEY REACH BUTTE/ANACONDA, BUT THIS MAY ENHANCE RAINFALL RATES
INTO THE EVENING HOURS. THE NBM HAS A RANGE OF 0.15 TO 0.35 OF
PRECIPITATION ALONG AND WEST OF THE DIVIDE THROUGH MIDNIGHT
TONIGHT. SNOW LEVELS WILL GRADUALLY FALL TONIGHT INTO MONDAY
MORNING. RAW MODEL SOUNDINGS SUGGEST THAT SNOW LEVELS COULD BE 500
FEET TO 1,000 LOWER THAN WHAT THE NBM HAS. THIS WOULD EQUATE TO
SLUSHY SNOW POTENTIALLY FOR UPPER BUTTE, WALKERVILLE, HOMESTAKE
PASS, GEORGETOWN LAKE AND I-15 SOUTH OF BUTTE. SOME OF THE HIGHER
ELEVATIONS ABOVE 6000 FEET COULD RECEIVE A COUPLE OF INCHES.
THE LOW PRESSURE SYSTEM WILL CAUSE GUSTY EAST TO NORTHEAST WINDS
ACROSS THE NORTHERN ROCKIES ON MONDAY, ESPECIALLY ACROSS WESTERN
MONTANA. WIND GUSTS UP TO 30 MPH WILL BE COMMON ESPECIALLY SOUTH
OF THE HIGHWAY 12 CORRIDOR. SOUTHERN LEMHI COUNTY COULD HAVE GUSTS
TO 40 MPH BY MONDAY AFTERNOON.
THE LOW CONTINUES TO MOVE OFF TO THE EAST BY TUESDAY CAUSING THE
PRECIPITATION AND WINDS TO DIMINISH ACROSS THE REGION. THEN A
RIDGE OF HIGH PRESSURE BUILDS OVER THE NORTHERN ROCKIES BY
WEDNESDAY ALLOWING TEMPERATURES TO JUMP BACK INTO THE 70S AND 80S
FOR MOST LOCATIONS.
A WEAK DISTURBANCE IS EXPECTED TO SWING THROUGH THE NORTHERN
ROCKIES ON THURSDAY WHICH WILL CAUSE AN INCREASE IN WESTERLY WINDS
ALONG WITH SLIGHTLY COOLER TEMPERATURES. THIS DISTURBANCE ALSO
HAS THE POTENTIAL TO KICK OFF A FEW SHOWERS AND THUNDERSTORM
ACROSS THE NORTHERN ROCKIES BY THURSDAY AFTERNOON.
AVIATION...THE COLD FRONT IS CURRENTLY DRAPED MAINLY OVER THE
HIGHWAY 93 CORRIDOR CAUSING WIDESPREAD LIGHT PRECIPITATION ALONG
WITH LOWERED CEILINGS. THIS FRONT WILL SLOWLY DRIFT TO THE EAST AS
A LOW PRESSURE SYSTEM CAUSES WRAP AROUND PRECIPITATION INTO LEMHI
COUNTY AND SOUTHWEST MONTANA BY THIS EVENING. KGPI, KMSO AND KHRF
WILL TRANSITION TO HIGHER CEILINGS AND VICINITY SHOWERS DURING
THE EVENING. KBTM WILL HAVE STEADY PRECIPITATION AND LOWERED
CEILINGS STARTING BY LATE AFTERNOON. SNOW LEVELS WILL LOWER ENOUGH
THAT KBTM COULD EXPERIENCE SNOW BY 05/09Z CAUSING REDUCED
VISIBILITY.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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