634
FXUS65 KMSO 221911
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1211 PM MST THU JAN 22 2026
DISCUSSION
KEY MESSAGES:
- COLD POOLS REMAIN DOMINANT ACROSS THE REGION CAUSING LOW CLOUDS
AND STRATUS.
- SOME EASTERLY FLOW TONIGHT WILL HELP ERODE SOME OF THE CLOUD
COVER, BUT ULTIMATELY IT WILL REINFORCE THE COLD POOLS.
- THE UPPER LEVEL RIDGE PROGRESSES EAST SLOWLY INTO NEXT WEEK
FURTHER REINFORCING COLD POOLS AND STABLE CONDITIONS.
- THERE IS ABOUT A 20 PERCENT CHANCE OF A FREEZING RAIN PATTERN
MID NEXT WEEK.
SATELLITE IMAGERY SHOWS COLD POOLS IN PLACE OVER MUCH OF THE
REGION WITH THE STRATUS CLOUDS PERSISTING EVEN IN HAMILTON MOST OF
TODAY. WITH SOME HIGH CLOUD COVER STREAMING OVER AND WEAK WINDS
IN THE LOWER ATMOSPHERE, WE EXPECT THOSE COLD POOLS TO REMAIN
LOCKED INTO PLACE THROUGH THIS EVENING.
TONIGHT A SHORT WAVE MOVING SOUTH ACROSS THE REGION WILL HELP
SOME OF THE VERY COLD AIR EAST OF THE CONTINENTAL DIVIDE MOVE INTO
THE REGION. AS THIS IS A DOWN-SLOPE FLOW FOR MOST LOCATIONS, IT
WILL HELP ERODE SOME OF THE STRATUS CLOUDS IN THE VALLEYS OF
WESTERN MONTANA. THERE ISN'T ENOUGH UPPER LEVEL SUPPORT FOR A FULL
STRENGTH ARCTIC BLAST INTO THE REGION THOUGH, SO THE COLD AIR
WILL JUST REALLY SEEP THROUGH THE PASSES ALONG THE DIVIDE. THIS IS
VERY COLD AIR, AND ULTIMATELY IT WILL SETTLE IN THE VALLEYS AND
REINFORCE THE COLD POOLS ALREADY THERE.
THEN THE RIDGE SLOWLY STARTS TO BUILD BACK INTO PLACE OVER THE
WEEKEND. THERE WILL BE A FEW MORE SHORTWAVES THAT MOVE ALONG THE
BOUNDARY OF THE RIDGE THAT MAY AFFECT THE VALLEY COLD POOLS, BUT
IT WON'T BE ENOUGH TO WIPE THEM OUT. BY EARLY NEXT WEEK THE REGION
WILL BE FULLY UNDER THE INFLUENCE OF THE RIDGE. SO FOG AND CLOUDS
WILL CONTINUE TO BLANKET MUCH OF THE REGION.
MID TO LATE NEXT WEEK, ABOUT 20% OF MODELS CONTINUE TO PROGRESS
THE RIDGE AXIS FARTHER EAST. IF THIS HAPPENS, IT WILL POSITION US
UNDER SOME MODERATELY MOIST FLOW INTO THE RIDGE. WITH THE
ESTABLISHED COLD POOLS IN THE VALLEYS, THIS IS A RECIPE FOR LIGHT
SNOW, OR MORE LIKELY SOME FREEZING RAIN. AT THIS POINT THOUGH,
THERE IS ONLY A 1 IN 5 OR 20% OF THAT OUTCOME OCCURRING NEXT WEEK.
AVIATION
STRATUS WILL CONTINUE ACROSS THE REGION THROUGH MOST
OF THE DAY TODAY. SOME RELIEF IS EXPECTED TONIGHT AS A SHORTWAVE
MOVING NORTH-TO-SOUTH ACROSS THE REGION SUPPORTS SOME LIGHT
EASTERLY FLOW ACROSS THE CONTINENTAL DIVIDE. THAT IS GENERALLY A
DOWN-SLOPE FLOW DIRECT, AND COULD HELP ERODE SOME OF THE STRATUS
IN THE VALLEYS. IT WILL ALSO HELP TO DEEPEN THE COLD POOLS IN THE
VALLEY, WHICH WILL ULTIMATELY RESULT IN SLIGHTLY HIGHER CLOUD
BASES IN THE STRATUS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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