An impressively moist weather system and associated cold front moved across north central Idaho and western Montana. Intense lift due to the passing cold front and an upper level jet produced areas of heavy snow.
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The episode as NWS MSO wrote it up.
An impressively moist weather system and associated cold front moved across north central Idaho and western Montana. Intense lift due to the passing cold front and an upper level jet produced areas of heavy snow.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Missoula, MT wrote its last area forecast discussion before the first event at Mar 13, 2:03 PM MST, 10 hours 57 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MISSOULA MT 303 PM MDT SUN MAR 13 2011 ...A MOIST AND MILD SYSTEM IS EXPECTED TO IMPACT NORTH CENTRAL IDAHO AND WESTERN MONTANA STARTING TUESDAY THROUGH WEDNESDAY... .DISCUSSION... REMAINDER OF TODAY THROUGH MONDAY NIGHT...THE FIRST OF SEVERAL PACIFIC SYSTEMS WILL SPREAD CLOUDS AND PRECIPITATION INTO NORTH THE REGION THIS EVENING AND TONIGHT. WARM TEMPERATURES WILL KEEP SNOW LEVELS ELEVATED NEAR 5000 FEET...KEEPING SNOWFALL ABOVE PASS LEVELS. AS A COLD FRONT TRACKS ACROSS THE REGION EARLY MONDAY MORNING...SNOW LEVELS WILL RAPIDLY LOWER TO AROUND 3500 FEET AND RESULT IN A QUICK BURST OF SNOW OVER LOOKOUT AND LOLO PASSES. SLUSHY AND SNOW COVERED ROADS MAY IMPACT MOUNTAIN PASS TRAVEL DURING THE MORNING COMMUTE. UNSTABLE CONDITIONS UNDER AN UPPER LEVEL TROUGH WILL CONTINUE SHOWER ACTIVITY MONDAY. BANDING POTENTIAL IN THE AFTERNOON COULD RESULT IN LOCALIZED AREAS OF HEAVY SHOWERS. TEMPERATURES NEAR SEASONAL LEVELS WILL LIMIT ANY SNOW ACCUMULATIONS ON GRASSY SURFACES AND MELT ON ROADWAYS. ADDITIONAL SNOW ACCUMULATIONS OVER PASSES SHOULD BE MINIMAL WITH TRAVEL INCONVENIENCES POSSIBLE MONDAY EVENING. TIGHTENING SURFACE PRESSURE GRADIENT AHEAD OF THE APPROACHING SYSTEM HAS INCREASED SOUTH WINDS IN THE LOWER HELLS CANYON/GRANGEVILLE. BREEZY CONDITIONS ARE EXPECTED TO PERSIST IN THIS REGION THROUGH THE NIGHT...WITH GUSTS PEAKING AROUND 45 MPH WITH THE PASSAGE OF A COLD FRONT EARLY MONDAY MORNING. GUSTS OF 25 TO 35 MPH CAN BE ANTICIPATED WITH THE FRONT ACROSS WESTERN MONTANA AND LEMHI COUNTY IDAHO. BREEZY WINDS WILL PERSIST MONDAY UNDER UNSTABLE CONDITIONS. TUESDAY AND WEDNESDAY...HIGH PRESSURE WILL QUICKLY SHIFT TO THE EAST ON TUESDAY AND A STRONG SOUTHWESTERLY JET WILL TAKE ITS PLACE. THE MOISTURE TRANSPORT DURING THE TIME FRAME IS HIGH FOR THIS TIME OF YEAR AND THAT COUPLED WITH IMPRESSIVE LIFT SHOULD PRODUCE EFFICIENT PRECIPITATION. DEEP LIFT AT THIS TIME SHOULD OVERCOME DOWNSLOPING AFFECTS WITH MOST EVERY LOCATION HAVING A GOOD CHANCE FOR EITHER RAIN OR SNOW. A WARMING SOUTHERLY SURFACE GRADIENT WILL RAISE SNOW LEVELS TO AROUND 5000 FEET DURING THE MAIN FOCUS TIME FOR PRECIP...WHICH IS LATE TUESDAY THROUGH WEDNESDAY MORNING. ELEVATIONS ABOVE 5000 FEET WILL HAVE ENOUGH MOISTURE THAT ONE TO TWO FEET OF SNOWFALL IS POSSIBLE BY LATE WEDNESDAY. ELEVATIONS BELOW 500O FEET WILL MAINLY HAVE RAIN. MOST OF THE LOW ELEVATIONS OF NORTHWEST MONTANA HAVE ONE TO OVER TWO FEET OF SNOW CURRENTLY ON THE GROUND. SOME OF THIS SNOW WILL MELT AS ABOVE FREEZING TEMPERATURES WILL LAST FOR A 36 HOUR PERIOD. RAIN FALLING ON SNOW WILL CAUSE ADDITIONAL MELTING. THE LOCATIONS WITH HIGH AMOUNTS OF SNOW ON THE GROUND HAVE THE ABILITY TO ABSORB THE RAIN...BUT PONDING OF WATER MAY STILL BE AN ISSUE AT LOWER ELEVATIONS AND FAST ACTING STREAMS AND CREEKS WILL LIKELY SHOW RISES. AFTER THE COLD FRONT PASSES...DROPPING SNOW LEVELS ARE EXPECTED WEDNESDAY AFTERNOON AND INSTABILITY SNOW SHOWERS WILL BECOME WIDESPREAD THROUGH EVENING. THURSDAY THROUGH SUNDAY...LONG RANGE MODELS CONTINUE TO BE IN AGREEMENT DEVELOPING A CLOSED LOW OFF OF THE WEST COAST. THIS WILL OPEN UP AND THE LONGWAVE TROF WILL PUSH INLAND BY NEXT WEEKEND. MOIST SOUTHERLY FLOW AND PIECES OF ENERGY BRANCHING OFF THIS FEATURE WILL MOVE THROUGH THE NORTHERN ROCKIES PRODUCING DAILY SHOWERS...ESPECIALLY IN THE MOUNTAINS. EXPECT TEMPERATURES NEAR. && .AVIATION...A TIGHTENING SURFACE PRESSURE GRADIENT AHEAD OF APPROACHING SYSTEM HAS INCREASED SOUTH WINDS OVER NORTH CENTRAL IDAHO AND WEST CENTRAL/SOUTHWEST MONTANA AND WILL PERSIST THROUGH EARLY EVENING. KBTM/KMSO/KSMN CAN EXPECT INCREASED SOUTH WINDS BETWEEN 12/2000Z-13/0300Z. THE CAMAS PRAIRIE WILL SEE WIND GUSTS TO 30 KNOTS THIS AFTERNOON WITH SOME HIGHER GUSTS ASSOCIATED A THE PASSING COLD FRONT LATE TONIGHT...AROUND 14/0900Z. UNSTABLE CONDITIONS ON MONDAY WILL ALLOW SHOWERS AND BREEZY CONDITIONS TO PERSIST THROUGH THE DAY AND SHOULD DIMINISH AFTER SUNSET. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...NONE. ID...NONE. && SHORT TERM/AVIATION...DEROSA LONG TERM....KITSMILLER/RPN
The national radar mosaic for the moment the first event began.
1 heavy snow. Local standard time, as filed.
Lolo Pass received 3 inches of snow in 2 hours and Lost trail pass received 3 inches of snow in 2 hours. Whiteout conditions were also reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2011Every state in 2011This day in weather historyWarnings in Montana, March 2011
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 284777.