688
FXUS65 KMSO 220803
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
103 AM MST THU JAN 22 2026
DISCUSSION
KEY MESSAGES:
- STRATUS CLOUD COVER AND ISOLATED FOG WILL PERSIST THROUGH
TODAY IN NORTH- CENTRAL IDAHO AND NORTHWEST MONTANA.
- COLDER AIR ARRIVES BEGINNING THIS EVENING: A MODIFIED ARCTIC
FRONT WILL SLIDE INTO WESTERN MONTANA TONIGHT AND FRIDAY,
BRINGING GUSTY EASTERLY WINDS AND A DROP IN TEMPERATURES FOR
THE WEEKEND.
THE MAIN STORY FOR TODAY REMAINS THE PERSISTENT CLOUD COVER IN
NORTH-CENTRAL IDAHO AND NORTHWEST MONTANA. HIGH PRESSURE ALOFT AND
LIGHT WINDS AT THE SURFACE ARE MAINTAINING A STATUS QUO FORECAST.
WHILE A WEAK SHORTWAVE PASSING OVERHEAD MAY PROVIDE JUST ENOUGH
LIFT TO RAISE THE STRATUS DECK BY AFTERNOON, SIGNIFICANT CLEARING
IS UNLIKELY FOR THE LOWER VALLEYS.
BY FRIDAY, THE SYNOPTIC PATTERN BEGINS TO SHIFT. A POTENT ARCTIC
HIGH PRESSURE SYSTEM SLIDING DOWN THE LEE OF THE ROCKIES WILL PUSH
A COLD FRONT WESTWARD ACROSS THE CONTINENTAL DIVIDE. AS THIS
COLDER, DENSE AIR SPILLS OVER THE DIVIDE, EXPECT GUSTY EASTERLY
WINDS TO DEVELOP, PARTICULARLY IN FAVORABLE GAP AREAS LIKE
HELLGATE CANYON (IMPACTING MISSOULA) AND BAD ROCK CANYON
(IMPACTING KALISPELL) BEGINNING THIS EVENING. THIS MECHANICAL
MIXING SHOULD FINALLY SCOUR OUT THE STAGNANT VALLEY AIR.
MOISTURE IS LIMITED WITH THIS SYSTEM, CONFINING THE BEST CHANCES
FOR LIGHT SNOW TO THE GLACIER REGION AND THE IMMEDIATE CONTINENTAL
DIVIDE. VALLEYS WITH LINGERING CLOUD COVER MAY HAVE FLURRIES OR A
LIGHT DUSTING.
HIGHS ON FRIDAY WILL STRUGGLE TO REACH FREEZING IN NORTH-CENTRAL
IDAHO AND LOW 20S IN WESTERN MONTANA, AS THE COLDER AIRMASS
SETTLES IN.
SATURDAY THROUGH SUNDAY: THE REGION WILL REMAIN UNDER THE
INFLUENCE OF THE COOLER AIRMASS. WHILE NOT A BRUTAL ARCTIC
OUTBREAK (THE CORE OF THE COLDEST AIR REMAINS WELL TO OUR EAST
OVER THE DAKOTAS), TEMPERATURES WILL RUN 5 TO 10 DEGREES BELOW
NORMAL. HIGHS WILL GENERALLY BE IN THE 20S WITH LOWS IN THE SINGLE
DIGITS TO TEENS. THE FLOW ALOFT TURNS NORTHERLY/NORTHWESTERLY,
KEEPING CHANCES FOR OROGRAPHIC LIGHT SNOW SHOWERS IN THE FORECAST
FOR THE MOUNTAINS, BUT WIDESPREAD VALLEY PRECIPITATION IS NOT
EXPECTED.
MONDAY THROUGH WEDNESDAY: FORECAST CONFIDENCE DECREASES
SIGNIFICANTLY HEADING INTO NEXT WEEK. MODELS ARE STRUGGLING TO
RESOLVE THE INTERACTION BETWEEN A POTENTIAL PACIFIC TROUGH MOVING
INLAND AND THE LINGERING COLD AIR OVER THE CONTINENT.
SCENARIO A (WETTER): SOME ENSEMBLE MEMBERS SUGGEST THE PACIFIC
SYSTEM COULD OVERRIDE THE COLD AIR, LEADING TO AN OVERRUNNING
PRECIPITATION EVENT (SNOW) TUESDAY INTO WEDNESDAY.
SCENARIO B (DRIER): RECENT DETERMINISTIC RUNS AND A CLUSTER OF
ENSEMBLES KEEP THE HIGH PRESSURE RIDGE STRONGER, KEEPING THE
NORTHERN ROCKIES DRY AND COOL.
CURRENT NBM (NATIONAL BLEND OF MODELS) GUIDANCE LEANS TOWARD THE
DRIER SOLUTION, KEEPING POPS (PROBABILITY OF PRECIPITATION)
GENERALLY LOW (20-30%) FOR THE START OF THE WEEK.
AVIATION
PRIMARY AVIATION CONCERN REMAINS PERSISTENT MVFR TO
LOCALIZED IFR STRATUS ACROSS NORTH-CENTRAL IDAHO AND NORTHWEST
MONTANA THROUGH THE PERIOD. HIGH PRESSURE AND INVERSIONS ARE
TRAPPING LOW- LEVEL MOISTURE, KEEPING MOUNTAIN OBSCURATIONS
PREVALENT ACROSS THE CABINET, MISSION, AND GLACIER RANGES. IN
CONTRAST, KMSO AND SOUTHERN TERMINALS (KBTM/KHRF/KSMN) ARE
CURRENTLY VFR, THOUGH A WINDOW OF STAGNANT, HAZIER AIR MAY ALLOW
FOR MVFR CEILINGS TO DEVELOP AT KMSO BETWEEN 15Z AND 19Z. THE
PATTERN SHIFTS ABRUPTLY THIS EVENING (02Z-06Z) AS A MODIFIED
ARCTIC FRONT CROSSES THE DIVIDE. THIS BOUNDARY WILL INTRODUCE
MODERATE LOW- LEVEL TURBULENCE AND GUSTY EASTERLY WINDS,
PARTICULARLY THROUGH HELLGATE CANYON (KMSO) AND BAD ROCK CANYON
(KGPI). WHILE THESE WINDS WILL EFFECTIVELY SCOUR OUT VALLEY
INVERSIONS/STRATUS, THEY WILL BE ACCOMPANIED BY LOWER CEILINGS AND
POTENTIAL LIGHT SNOW OR FLURRIES NEAR THE DIVIDE AND GLACIER
REGION.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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