022
FXUS65 KMSO 201957
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1257 PM MST TUE JAN 20 2026
DISCUSSION
KEY MESSAGES:
- STRONG VALLEY INVERSIONS WILL PERSIST FOR SEVERAL MORE DAYS
- COLDEST TEMPERATURES THIS FORECAST PERIOD FRIDAY INTO SATURDAY
- UNCERTAINTY IN THE FORECAST PAST SATURDAY
A CONTINUATION OF A PERSISTENT PATTERN OF DRY HIGH PRESSURE IS
EXPECTED THROUGH THE WEEKEND. LOWER VALLEYS CAN EXPECT MORNING FOG
AND LOW STRATUS, WHILE HIGHER VALLEYS WILL LIKELY BREAK OUT OF
VALLEY INVERSIONS EACH DAY.
TEMPERATURES WILL SLOWLY COOL, TO A FEW DEGREES BELOW NORMAL FOR
THIS TIME OF YEAR, FRIDAY THROUGH SATURDAY MORNING. THIS WILL BE
DUE TO AN ARCTIC AIR MASS EAST OF THE CONTINENTAL DIVIDE SEEPING
INTO WESTERN MONTANA. THIS AIR MASS IS ORIGINATING FROM
THE CONTINENTAL ARCTIC, WHICH SIMPLY MEANS IT WILL BE COLD AND
GENERALLY DRY. THAT WON'T RULE OUT A LIGHT SHOWER OR FLURRY AS THE
COLD FRONT MOVES THROUGH.
SATURDAY ONWARD THE FORECAST HAS CONSIDERABLE UNCERTAINTY. WHILE
THE NBM, WHICH IS THE STARTING POINT OF OUR FORECAST, IS LOCKED
INTO A STRONG RIDGE OF HIGH PRESSURE REDEVELOPING. THERE IS A
SMALL PERCENTAGE OF OUTLIER MODELS THAT HAVE PRECIPITATION MONDAY
INTO TUESDAY, WITH A TEMPERATURE PROFILE THAT WOULD SUGGEST SNOW
FOR MOST ELEVATIONS. THESE OUTLIERS WHEN AVERAGED OUT AGAINST THE
DRIER MODELS, LEAVE A FORECAST OF SLIGHT CHANCE OR 25% OR LESS FOR
PRECIPITATION, WIDESPREAD ACROSS OUR REGION. SOMETHING TO WATCH
AS THE MODELS COME BETTER INTO FOCUS. AI MODELING, WHICH IS NOT
PART OF THE NBM, IS PREDICTING A LIGHT PRECIPITATION EVENT.
AVIATION
LOW STRATUS AND FOG LINGERS ACROSS MOST OF NORTHWEST
MONTANA (NORTH OF HIGHWAY 200) AND IN THE LOWER ELEVATIONS OF
NORTH CENTRAL IDAHO, INCLUDING THE CAMAS PRAIRIE IN IDAHO. THESE
AREAS WILL LIKELY SEE LITTLE CHANGE IN CONDITIONS, OTHER THAN THAT
THE STRATUS DECK MAY LOWER WITH TIME THIS EVENING AND OVERNIGHT
AS MORE STABLE CONDITIONS DEVELOP ALOFT. THIS MAY BE MOST
PROMINENT FOR AIRFIELD KGPI BETWEEN 21/0400Z AND 21/1500Z. THE
REST OF WESTERN MONTANA AND NORTH CENTRAL IDAHO WILL LIKELY
CONTINUE TO SEE GENERALLY CLEAR SKIES. THERE IS SOME QUESTION ON
HOW THINGS WILL EVOLVE SPECIFICALLY FOR KMSO. RECENT DRYING IN THE
BOUNDARY LAYER MAKES FOG UNLIKELY. HOWEVER, WITH LOW STRATUS TO
THE NORTH OVER THE MISSION VALLEY AND TO OUR WEST NEAR SAINT
REGIS AND PLAINS, THERE IS SOME RISK THAT STRATUS WILL SPREAD INTO
KMSO AFTER 21/0600Z. CONFIDENCE IN THIS OCCURRING IS LOW, BUT
WILL BE MONITORED FOR FUTURE FORECASTS. A WEAK EAVE OF ENERGY
MOVING THROUGH WESTERN MONTANA TOMORROW MORNING (21/1500Z) MAY
DECREASE STABILITY ENOUGH TO LIFT THE STRATUS DECK SLIGHTLY IN
NORTHWEST MONTANA, THOUGH LIKELY WILL NOT SCOUR THE STRATUS OUT.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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