044
FXUS65 KMSO 171905
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1205 PM MST SUN NOV 17 2024
DISCUSSION
KEY MESSAGES:
- TONIGHT THERE WILL BE ANOTHER ROUND OF MODERATE SNOW FOR A FEW
HOURS AS THE COLD FRONT PASSES, ESPECIALLY IN NORTHWEST MONTANA.
- ENSEMBLES ARE SHOWING INCREASING CHANCES OF SNOW NEXT WEEKEND
WITH MOST UNCERTAINTY AROUND THE TIMING.
THE REGION REMAINS IN THE WARM SECTOR AHEAD OF AN APPROACHING COLD
FRONT TODAY. ALSO, THERE'S A LOT OF MOISTURE AHEAD OF THAT FRONT
CAUSING PRECIPITATION. MOST OF THE LIFT, WHICH ENHANCES THE
PRECIPITATION, IS DUE TO THE SOUTHWESTERLY WINDS RUNNING INTO THE
MOUNTAINS. AS A RESULT, MOST OF THE PRECIPITATION IS IN THE
MOUNTAINS AND NEARBY. TONIGHT A COLD FRONT WILL MOVE THROUGH FROM
THE NORTHWEST AND CAUSE EVEN MORE LIFT, SO WE CAN EXPECT AN
INCREASE IN PRECIPITATION OVERNIGHT. THE COLD FRONT WILL BRING
SOME COOLER AIR AND ALSO SINCE IT'S COMING AT NIGHT WHEN IT'S
ALREADY COOLER, WE EXPECT SNOW LEVELS TO BE DOWN TO THE VALLEY
LEVEL ACROSS MOST OF WESTERN MONTANA. WITH SNOW ACCUMULATION
EXPECTED ON THE ROADS TONIGHT, WE'VE ISSUED SEVERAL WINTER WEATHER
ADVISORIES.
ALONG WITH THE FRONT THERE IS THE POSSIBILITY OF SNOW SQUALLS
TONIGHT. THE MAIN IMPACT FROM THESE WILL BE A BRIEF, HOUR OR LESS
PERIOD WITH MUCH LOWER VISIBILITY DUE TO MODERATE TO HEAVY SNOW
RATES WITH WIND. WE EXPECT LOW VISIBILITY WILL BE THE MAIN IMPACT,
BUT HIGH ELEVATION AREAS LIKE GEORGETOWN LAKE HAVE BEEN COLD
ENOUGH RECENTLY TO HAVE A COLD GROUND TEMPERATURE, ALLOWING FOR
RAPID SNOW ACCUMULATION AND VERY SLICK CONDITIONS WITH ANY SNOW
SQUALLS. WE EXPECT THIS TO HAVE MINIMAL IMPACTS DUE TO THE TIME OF
NIGHT THAT THE FRONT WILL COME THROUGH, BUT IF YOU ARE OUT AND
ABOUT IN WEST CENTRAL OR SOUTHWEST MONTANA TONIGHT, BE AWARE OF
THE POTENTIAL FOR HAZARDOUS DRIVING CONDITIONS.
THROUGH MID-WEEK THE PATTERN REMAINS ACTIVE WITH PERIODS OF
MOUNTAIN SHOWERS AND OTHERS OF CLEARING. BY THURSDAY, WARM, MOIST
SOUTHWEST FLOW SETS UP AHEAD OF THE NEXT SYSTEM AND THERE'S AN
INCREASE IN PRECIPITATION WITH SNOW LEVELS RISING ABOVE 6,000FT.
THERE'S A LOT OF UNCERTAINTY WITH THE NEXT SYSTEM. ENSEMBLES AGREE
WELL ON THE TRANSITION TO SOUTHWEST FLOW ON THURSDAY, BUT WHAT
HAPPENS AFTER THAT IS MORE UNCERTAIN. MANY ENSEMBLES MEMBERS BRING
A BACK DOOR COLD FRONT ACROSS THE CONTINENTAL DIVIDE, BUT THE
TIMING IN RECENT ENSEMBLES VARIES FROM FRIDAY THROUGH SUNDAY FOR
THE TIMING. THERE IS ALSO A WIDE RANGE OF POSSIBILITIES FOR THE
INTENSITY OF THE COLD AIR AND HOW FAR WEST IT GOES. DUE TO THE
WIDE RANGE OF THE TIMING IN THE ENSEMBLES, IT'S DIFFICULT TO GIVE
A PROBABILITY FOR WHETHER THE COLD AIR WILL CROSS THE DIVIDE, BUT
USING CLUSTERS IT LOOKS LIKE A ROUGHLY 40% CHANCE THAT IT WILL. IN
ANY CASE, THE JET STREAM WILL MOVE WELL SOUTH OF THE REGION BY
EARLY NEXT WEEK SO WE CAN EXPECT A COOL DOWN.
AVIATION
THE REMNANTS OF AN ATMOSPHERIC RIVER CONTINUE TO
STREAM OVER THE REGION TODAY CAUSING WIDESPREAD CEILINGS AND
MOUNTAIN OBSCURATIONS. WE HAD SOME SNOW REACH THE VALLEYS OF
NORTHWEST MONTANA LAST NIGHT, AND WE EXPECT ANOTHER ROUND TONIGHT
AS A COLD FRONT USHERS THE ATMOSPHERIC RIVER OUT OF THE REGION.
MODERATE TO HEAVY SNOW IS POSSIBLE FOR UP TO AN HOUR AS THE FRONT
PASSES, ESPECIALLY FOR TERMINAL KBTM. EXPECT MVFR TO VFR
CONDITIONS THROUGH THE NIGHT AT MOST AREA TERMINALS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL 11 AM MST MONDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...KOOTENAI/CABINET REGION...
LOWER CLARK FORK REGION...WEST GLACIER REGION.
ID...WINTER WEATHER ADVISORY UNTIL 10 AM PST MONDAY FOR NORTHERN
CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER MOUNTAINS.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page