082
FXUS65 KMSO 201101
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
401 AM MST WED NOV 20 2024
DISCUSSION
KEY MESSAGES:
- AN ATMOSPHERIC RIVER WILL BRING AMPLE MOISTURE TO THE MOUNTAINS
OF CENTRAL IDAHO AND NORTHWEST MONTANA TODAY THROUGH SATURDAY.
- ACTIVE WEATHER THIS WEEKEND INTO NEXT WEEK.
THE MOISTURE ASSOCIATED WITH THE ATMOSPHERIC RIVER IS STARTING TO
PUSH INTO REGION THIS MORNING. THIS STEADY STREAM OF MOISTURE IS
STILL ANTICIPATED TO LAST THROUGH SATURDAY BRINGING SIGNIFICANT
PRECIPITATION TOTALS TO THE MAJORITY OF THE NORTHERN ROCKIES,
ESPECIALLY ALONG THE MONTANA/IDAHO BORDER. SNOW LEVELS WILL START
OFF FAIRLY LOW THIS MORNING ALLOWING MOST LOCATIONS TO START OFF
AS SNOW THEN QUICKLY TRANSITION OVER TO RAIN AS SNOW LEVELS RISE.
NORTH CENTRAL IDAHO INTO NORTHWEST MONTANA ARE STILL EXPECTED TO
RECEIVE 1 TO 3 INCHES OF MOISTURE DURING THIS EVENT. WHILE LEMHI
COUNTY INTO SOUTHWEST MONTANA GET AROUND A TENTH TO 1 INCH OF
MOISTURE. THE MOUNTAINS ACROSS NORTH CENTRAL IDAHO UP INTO
NORTHWEST MONTANA SHOULD ANTICIPATE 10 TO 20 INCHES OF SNOW
ACCUMULATION, INCLUDING LOOKOUT AND MARIAS PASSES.
A COLD FRONT PUSHES THROUGH THE NORTHERN ROCKIES ON SATURDAY
CAUSING THE MOISTURE PLUME TO MOVE OFF TO THE EAST WHILE SNOW
LEVELS DROP BACK DOWN TO MOST VALLEY FLOORS BY SUNDAY MORNING.
THE UPPER LEVEL FLOW BECOME WESTERLY TO NORTHWESTERLY SUNDAY
THROUGH MID NEXT WEEK. THIS FLOW PATTERN WILL BE CONDUCIVE TO WEAK
DISTURBANCES MOVING THROUGH THE NORTHERN ROCKIES. THE LATEST MODEL
RUNS ARE ONLY SHOWING A 13% CHANCE FOR ARCTIC AIR MAKING ITS WAY
OVER THE CONTINENTAL DIVIDE ON SUNDAY. THE MOST PROBABLE SOLUTION
IS FOR THE ARCTIC AIR TO SLIDE DOWN EAST OF THE DIVIDE INTO
CENTRAL MONTANA.
AVIATION
THE ATMOSPHERIC RIVER WILL CONTINUE TO MOVE INTO THE
NORTHERN ROCKIES TODAY CAUSING WIDESPREAD PRECIPITATION ALONG WITH
LOWERING CEILINGS. SNOW LEVELS WILL BE QUITE LOW DURING THE ONSET
OF PRECIPITATION SO SNOW IS EXPECTED DOWN TO MOST VALLEYS. THE
SNOW LEVELS WILL BE STEADILY RISING OVER THE NEXT 24-48 HOURS.
MOUNTAINS AND PASSES ARE EXPECTED TO BE OBSCURED THE MAJORITY OF
THE TIME.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL 11 AM MST THIS MORNING FOR
BITTERROOT/SAPPHIRE MOUNTAINS...KOOTENAI/CABINET REGION.
WINTER WEATHER ADVISORY FROM 11 AM THIS MORNING TO 11 AM MST
THURSDAY FOR WEST GLACIER REGION.
WINTER WEATHER ADVISORY UNTIL 11 AM MST THURSDAY FOR LOWER CLARK
FORK REGION.
ID...WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR
NORTHERN CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER
MOUNTAINS.
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