747
FXUS65 KMSO 192041
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
141 PM MST TUE NOV 19 2024
DISCUSSION
KEY MESSAGES:
- ACTIVE WEATHER WITH LOW TO MODERATE IMPACTS WILL CONTINUE
THROUGH THIS WEEK CAUSING NEARLY CONTINUOUS SNOW IN THE MOUNTAINS
- AN ATMOSPHERIC RIVER WILL BRING AMPLE MOISTURE TO THE MOUNTAINS
OF CENTRAL IDAHO AND NORTHWEST MONTANA WEDNESDAY THROUGH
FRIDAY.
- THERE IS LOW CONFIDENCE FOR ARCTIC AIR TO BREACH THE CONTINENTAL
DIVIDE OF NORTHWEST MONTANA ON SUNDAY.
VISIBLE SATELLITE IMAGERY THIS AFTERNOON IS SHOWING A RATHER
IMPRESSIVE LOW PRESSURE CIRCULATION OFF THE COAST OF THE PACIFIC
NORTHWEST. MOST RECENT ANALYSIS IS ESTIMATING A CENTRAL PRESSURE
OF ABOUT 960 MB, WHICH IS ABOUT AS LOW AS THAT OF A CATEGORY 2 OR
3 HURRICANE. THIS SEMI-STATIONARY CIRCULATION WILL PUSH PACIFIC
MOISTURE ONSHORE, AND EVENTUALLY INTO THE NORTHERN ROCKIES THROUGH
THE WEEKEND. TEMPERATURES WILL STAY LOW ENOUGH FOR PRECIPITATION
TO FALL IN THE FORM OF SNOW WITH THE EXCEPTION OF THE LOWEST
VALLEYS IN CENTRAL IDAHO THROUGH EARLY THURSDAY. SNOW WILL BEGIN
OVERNIGHT TONIGHT IN NORTH-CENTRAL IDAHO AND WESTERN MONTANA.
WINTER WEATHER ADVISORIES WILL GO INTO EFFECT FOR WEDNESDAY
MORNING. LOOKOUT, LOLO, AND LOST TRAIL PASSES WILL ALL SEE ANOTHER
FEW INCHES OF SNOW BY MIDDAY. SNOW WILL SPREAD EAST, AFFECTING
MARIAS PASS AND EASTERN FLATHEAD COUNTY LATER IN THE DAY.
AFTER A SHORT BREAK ON WEDNESDAY AFTERNOON, SNOW WILL CONTINUE.
HOWEVER, SOUTHWESTERLY UPPER LEVEL FLOW WILL BRING IN WARMER AIR,
RAISING SNOW LEVELS. THE FORECAST CHALLENGE FOR THIS SYSTEM WILL
BE TRYING TO NAIL DOWN THE ELEVATION OF THE RAIN-SNOW LINE. SOUTH
OF ABOUT I-90, THE SNOW LEVEL WILL RISE TO ABOUT 6,000 FEET BY
THURSDAY NIGHT. NORTHWEST MONTANA WILL SEE SNOW LEVELS STAY A
LITTLE LOWER, 4000-5000 FEET, FOR MUCH OF THAT REGION. COLDER AIR
FROM THE EAST SIDE OF THE DIVIDE SHOULD KEEP SNOW LEVELS AT
3000-4000 FEET ALONG THE DIVIDE. DESPITE RISING SNOW LEVELS,
MOUNTAIN PRECIPITATION WILL BE IMPRESSIVE THROUGH FRIDAY. THE
MAJORITY OF CLEARWATER COUNTY, ALONG WITH THE MOUNTAINS ON THE
MONTANA/IDAHO BORDER, IS EXPECTED TO RECEIVE BETWEEN 1 TO 3
INCHES OF LIQUID PRECIPITATION DURING THIS TIME FRAME. THE
REMAINDER OF NORTHWEST MONTANA AND NORTH CENTRAL IDAHO ARE
EXPECTED TO EXPERIENCE 0.5 TO 2 INCHES OF PRECIPITATION. LEMHI
COUNTY AND SOUTHWEST MONTANA WILL RECEIVE THE LEAST AMOUNT AS
TOTALS WILL RANGE FROM A FEW HUNDREDTHS TO HALF OF INCH. THE
MOUNTAINS OF NORTHWEST MONTANA, INCLUDING LOOKOUT AND MARIAS
PASSES, SHOULD EXPECT TO RECEIVE A FOOT OR TWO OF NEW SNOWFALL
DURING THIS EVENT.
THE TROUGH SHIFTS NORTH OVER THE WEEKEND. AS IT DOES, SOME
ENSEMBLE SOLUTIONS ARE SHOWING MORE COLD AIR BREACHING THE
CONTINENTAL DIVIDE FROM THE EAST. THIS SCENARIO WOULD DROP
TEMPERATURES ACROSS FLATHEAD COUNTY. CONFIDENCE ON THE ARRIVAL OF
THIS COLD FRONT REMAINS QUITE LOW.
AVIATION
WEATHER THIS AFTERNOON WILL REMAIN MOSTLY DRY. EXPECT
INCREASING CLOUDS OVERNIGHT AS PACIFIC MOISTURE MAKES ITS WAY INTO
THE NORTHERN ROCKIES. SNOW WILL IMPACT THE HIGHER TERRAIN BY EARLY
WEDNESDAY MORNING. LOWERING CEILINGS WILL OBSCURE TERRAIN,
ESPECIALLY ALONG THE CLEARWATER, BITTERROOT, AND CABINET RANGES.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY FROM 5 AM TO 11 AM MST WEDNESDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...KOOTENAI/CABINET REGION.
WINTER WEATHER ADVISORY FROM 11 AM WEDNESDAY TO 11 AM MST
THURSDAY FOR WEST GLACIER REGION.
WINTER WEATHER ADVISORY FROM 5 AM WEDNESDAY TO 11 AM MST
THURSDAY FOR LOWER CLARK FORK REGION.
ID...WINTER WEATHER ADVISORY FROM 4 AM TO 10 AM PST WEDNESDAY FOR
NORTHERN CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER
MOUNTAINS.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page