401
FXUS65 KMSO 290827
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
127 AM MST MON DEC 29 2025
DISCUSSION
KEY MESSAGES:
- VERY COLD MORNINGS WILL CONTINUE THROUGH THE FIRST HALF OF THIS
WEEK.
- DEVELOPING INVERSIONS WILL LIKELY LEAD TO FOG, STRATUS AND POOR
AIR QUALITY.
SATELLITE IS SHOWING REMNANT SUBTROPICAL MOISTURE ROTATING AROUND
THE RIDGE OF HIGH PRESSURE CURRENTLY BUILDING OVER THE WEST
COAST. THESE HIGH CLOUDS WILL LIKELY MODERATE EXPECTATIONS FOR A
COLD MORNING TODAY, ALTHOUGH MOST LOCATIONS WILL STILL BE QUITE
COLD. THIS WILL ALSO SLOW THE PROGRESSION OF DEEP COLD POOL
DEVELOPMENT.
THE MODELS ARE STILL ALL IN ON THE AXIS OF HIGH PRESSURE MOVING
OVER THE NORTHERN ROCKIES BY WEDNESDAY. THIS IS WHEN AN EXPANSION
OF VALLEY FOG AND LOW STRATUS CAN BE EXPECTED. WE MAY ALSO
EXPERIENCE THE BEGINNINGS OF POOR AIR QUALITY DUE TO STAGNANT
VALLEY AIR MASSES.
THIS WAS ALWAYS FORECASTED TO BE A DIRTY RIDGE, THE QUESTION NOW
IS WILL THE CLOUDS BE AT NIGHT, LIKE TODAY, AND THAT KEEPS
LOW TEMPERATURES SLIGHTLY WARMER OR ARE THE CLOUDS DURING THE DAY
KEEPING HIGH TEMPERATURES SLIGHTLY COOLER.
RIDGE BREAKDOWN IS EXPECTED BY THE END OF THE WORKWEEK, 75% OF THE
MODELS ARE IN AGREEMENT IT WILL HAPPEN BY FRIDAY EVENING. WHILE
THE REMAINING 25% SUGGEST OVERNIGHT FRIDAY. DEPENDING ON HOW STRONG
THE COLD POOLS DEVELOP, THERE COULD BE A PERIOD OF MIXED
PRECIPITATION, FREEZING RAIN, IN VALLEYS. SNOW LEVELS INITIALLY
WILL BE ELEVATED AROUND 6000 FEET AND MAY SLOWLY LOWER OVER THE
WEEKEND. BETTER DETAILS WILL COME AS COLD POOLS ARE ANALYZED MID-
WEEK.
AVIATION
TEMPERATURES WILL BEGIN TO MODERATE AS WE PROGRESS
THROUGH THE COMING WEEK, WITH THIS MORNING LIKELY BEING THE COLDEST
MORNING. AS THE RIDGE STRENGTHENS, SO TOO WILL THE VALLEY
INVERSIONS. VALLEY STRATUS AND/OR FOG WILL BECOME A CONCERN BY
TUESDAY MORNING.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page