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.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
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 14, 1:50 AM PST, 1 hour 10 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
350 AM MDT MON MAR 14 2011
.DISCUSSION...AN IMPRESSIVELY MOIST WEATHER SYSTEM AND ASSOCIATED
COLD FRONT IS CURRENTLY MAKING ITS WAY THROUGH NORTH CENTRAL IDAHO
AND WESTERN MONTANA THIS MORNING. INTENSE LIFT DUE TO THE PASSING
COLD FRONT AND AN UPPER LEVEL JET IS PRODUCING IMPRESSIVE
PRECIPITATION AMOUNTS IN NORTHWEST MONTANA AND NORTH CENTRAL
IDAHO THIS HOUR. HOURLY PRECIPITATION AMOUNTS OF 0.25 TO 0.3 INCHES
HAVE BEEN MEASURED IN NORTH CENTRAL IDAHO. SNOW LEVELS REMAIN AT
ABOUT 4500 TO 5000 FEET...ALLOWING HEAVY SNOW ACCUMULATIONS TO
FALL ON BOTH LOOKOUT AND LOLO PASSES IN A RATHER SHORT AMOUNT OF
TIME. HAVE ISSUED WINTER WEATHER PRODUCTS FOR THESE TWO PASSES DUE
TO INTENSE SNOW CAUSING HAZARDOUS TRAVEL THROUGH THE MORNING
HOURS. PRECIPITATION INTENSITY IS EXPECTED TO DECREASE THROUGH THE
MORNING AS THE FRONT MOVES SOUTHEASTWARD AND OUT OF THE AREA.
HOWEVER...LINGERING MOISTURE AND INSTABILITY WILL KEEP WIDESPREAD
CONVECTIVE SHOWERS AROUND THROUGH THE DAY. WITH LOWERING SNOW
LEVELS BEHIND THE FRONT AND THE CONVECTIVE NATURE OF PRECIPITATION
THIS AFTERNOON...EVEN SOME OF THE VALLEY LOCATIONS...PARTICULARLY
ACROSS NORTHWEST MONTANA COULD SEE A LIGHT DUSTING OF SNOW BY THIS
AFTERNOON. SOUTHWEST TO WEST WINDS WILL CONTINUE THROUGH THE DAY
ACROSS MUCH OF THE REGION AND BECOME QUITE GUSTY THROUGH THE
AFTERNOON. HOWEVER...THE STRONGEST WINDS SHOULD BE RIGHT ALONG THE
FRONT THIS MORNING AND THEN DISSIPATE SLIGHTLY AFTER FRONTAL
PASSAGE.
A WEAK RIDGE OF HIGH PRESSURE WILL BRING A BRIEF RESPITE IN
PRECIPITATION BY THIS EVENING. WITH CLEARING SKIES...MANY OF THE
VALLEY LOCATIONS WILL SEE PATCHY FOG DEVELOP BY TOMORROW MORNING.
ANOTHER VERY MOIST PACIFIC WEATHER SYSTEM WILL IMPACT THE NORTHERN
ROCKIES TUESDAY AFTERNOON THROUGH WEDNESDAY. A SIMILAR SCENARIO TO
THE WEATHER SYSTEM CURRENTLY AFFECTING THE AREA IS EXPECTED.
ABUNDANT MOISTURE WILL COMBINE WITH A VERY DYNAMIC SYSTEM
TO PRODUCE WIDESPREAD PRECIPITATION...MODERATE TO HEAVY AT TIMES.
SNOW LEVELS WILL AGAIN START AT ABOUT 5000 FEET...BRINGING RAIN
TO THE LOWER ELEVATIONS AND HEAVY SNOW ONCE AGAIN TO THE HIGHER
TERRAIN AND MOUNTAIN PASSES. ONE TO TWO FEET OF NEW SNOW IS NOT
OUT OF THE QUESTION IN THE HIGHER TERRAIN BY WEDNESDAY
AFTERNOON...ESPECIALLY ON WEST FACING SLOPES. TRAVEL IMPACTS ARE
ONCE AGAIN LIKELY TO MOUNTAIN PASSES AND THUS ADDITIONAL WINTER
WEATHER PRODUCTS MAY BE NECESSARY. SNOW LEVELS WILL DROP DOWN TO
ALL BUT THE LOWEST VALLEY LOCATIONS BY WEDNESDAY
AFTERNOON...BRINGING ANOTHER POTENTIAL FOR A LIGHT DUSTING OF SNOW
IN THE VALLEYS BY WEDNESDAY AFTERNOON.
ANOTHER CONCERN WITH THIS VERY MOIST SYSTEM WILL BE FROM THE
COMBINATION OF MELTING SNOW (BELOW 5000 FEET) COMBINING WITH
POTENTIALLY HEAVY RAIN TO BRING RISES IN AREA SMALL STREAMS.
PONDING OF WATER WILL ALSO BE POSSIBLE IN URBAN AREAS. NOT
FLOODING IS CURRENTLY EXPECTED AND WILL LIKELY BE MORE OF A
NUISANCE HOWEVER THIS SCENARIO SHOULD CONTINUE TO BE
MONITORED...PARTICULARLY FOR FORECASTED CHANGES IN PRECIPITATION
AMOUNTS.
WEDNESDAY NIGHT THROUGH MONDAY...A CLOSED LOW DEVELOPS OFF THE
PACIFIC COAST AND MOVES SLOWLY ACROSS THE REGION. AS IT MOVES TO THE
EAST A WARM AND MOIST SOUTH TO SOUTHWEST FLOW WILL SET UP OVER
WESTERN MONTANA AND NORTH CENTRAL IDAHO. WITH WEAK DISTURBANCES
MOVING OVER THE REGION EACH DAY...EXPECT TO SEE SOME FORM OF
PRECIPITATION THROUGH THE PERIOD...MAINLY OVER THE MOUNTAINS.
TEMPERATURES SHOULD REMAIN NEAR NORMAL READINGS.
&&
.AVIATION...A VERY MOIST PACIFIC WEATHER SYSTEM AND ASSOCIATED
COLD FRONT WILL BRING WIDESPREAD...LOCALLY HEAVY PRECIPITATION TO
WESTERN MONTANA AND NORTH CENTRAL IDAHO THIS MORNING. THIS WILL
RESULT IN WIDESPREAD TERRAIN OBSCURATIONS AND PERIODICALLY LOWERED
VISIBILITY. PRECIPITATION IS EXPECTED TO DECREASE IN INTENSITY
BEHIND THE COLD FRONT BY MID MORNING...HOWEVER RAIN AND SNOW
SHOWERS WILL REMAIN THROUGH THE AFTERNOON...PARTICULARLY IN THE
HIGHER TERRAIN. SOUTHWEST TO WEST WINDS WILL REMAIN OVER THE
REGION THROUGH THIS AFTERNOON....ESPECIALLY OVER THE HIGHER
TERRAIN.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING UNTIL NOON MDT TODAY FOR LOLO PASS.
WINTER WEATHER ADVISORY UNTIL NOON MDT TODAY FOR I-90 LOOKOUT
PASS TO HAUGAN.
ID...WINTER STORM WARNING UNTIL 11 AM PDT THIS MORNING FOR LOLO PASS.
&&
SHORT TERM...PALLISTER
LONG TERM....KOLATA
AVIATION...PALLISTERThe national radar mosaic for the moment the first event began.
1 heavy snow. Local standard time, as filed.
Lolo Pass experienced whiteout conditions when 3 inches of snow between 3 am and 6 am.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2011Every state in 2011This day in weather historyWarnings in Idaho, 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: 284774.