Cold air was trapped in the valleys of north central Idaho as a strong Pacific storm system moved over the region. This system had abundent moisture with waves of energy moving across Idaho.
Every event with a place to put it; 2 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.
Cold air was trapped in the valleys of north central Idaho as a strong Pacific storm system moved over the region. This system had abundent moisture with waves of energy moving across Idaho. The weather associated with this system covered a wide range of types, from freezing rain to heavy snow and a mixture of rain and snow, along with another blast of freezing rain.
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 Jan 12, 3:32 AM PST, 5 hours 28 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
432 AM MST WED JAN 12 2011
...A WINTRY MIX OF PRECIPITATION TODAY THROUGH THURSDAY.
.DISCUSSION...THE FIRST OF SEVERAL PACIFIC STORM SYSTEMS IS
ENTERING THE NORTHERN IDAHO PANHANDLE AND NORTHWEST MONTANA.
THE MAIN IMPACTS FROM THIS STORM WILL BE:
STRONG SOUTHERLY WINDS IN THE GRANGEVILLE/CAMAS PRAIRIE AREA TODAY.
HEAVY MOUNTAIN SNOWS THROUGH THURSDAY...PRODUCING DIFFICULT TRAVEL
OVER LOLO...LOOKOUT AND MARIAS PASSES.
A MIX OF SNOW/RAIN AND FREEZING RAIN IN THE VALLEYS OF WEST
CENTRAL/NORTHWEST MONTANA AND NORTH CENTRAL IDAHO TODAY THROUGH
THURSDAY MORNING.
PERIODS OF HEAVY SNOW WILL OCCUR IN THE MOUNTAINS TODAY THROUGH
FRIDAY NIGHT WITH SIGNIFICANT ACCUMULATIONS EXPECTED. TRAVEL OVER
LOLO...LOOKOUT AND MARIAS PASSES WILL BECOME DIFFICULT AT TIMES
LATER THIS MORNING THROUGH THURSDAY. IN THE VALLEYS TODAY...SNOW
WILL BEGIN IN NORTHWEST MONTANA EARLY THIS MORNING AND THE
VALLEYS OF WEST CENTRAL MONTANA BY MID TO LATE MORNING.
THE FORECAST BECOMES INCREASINGLY COMPLEX THIS AFTERNOON IN
VALLEY LOCATIONS OF NORTH CENTRAL ID/NORTHWEST AND WEST CENTRAL
MONTANA. THIS IS DUE TO AN INFLUX OF WARMER AIR WHICH WILL PRODUCE
A TRANSITION FROM SNOW TO RAIN OVER THE NEXT 36 HOURS. THE
CHALLENGE IS DETERMINING WHAT TYPE OF PRECIPITATION AND WHEN IT
WILL OCCUR. COLD AIR NEAR THE SURFACE WILL BE SLOWER TO MODIFY...
WHILE THE ATMOSPHERE WARMS ALOFT AT A GREATER PACE. THERE WILL BE
A TRANSITION FROM ALL SNOW TO ALL RAIN AT MOST VALLEY
LOCATIONS...WITH A STRONG POTENTIAL FOR FREEZING RAIN AND
SNOW/RAIN MIX DURING THIS TRANSITIONAL PERIOD. IT APPEARS NOW THAT
PRECIP WILL BE ALL SNOW THIS MORNING WITH THE TRANSITION OR THE
MIX OF SNOW/RAIN/FREEZING RAIN OCCURRING THIS AFTERNOON THROUGH
NOON ON THURSDAY. AN EXCEPTION WILL BE IN THE FLATHEAD VALLEY
WHERE PRECIP WILL REMAIN ALL SNOW THROUGH THE ENTIRE AFTERNOON AND
NOT TRANSITIONING UNTIL THIS EVENING...THUS HIGHER SNOW AMOUNTS
ARE EXPECTED.
WINTER WEATHER HIGHLIGHTS FOCUS ON SNOW...FOLLOWED BY AN EPISODE
OF FREEZING RAIN CREATING HAZARDOUS TRAVEL FOR VALLEY LOCATIONS.
THURSDAY AND FRIDAY...WARM AIR WILL CONTINUE TO MOVE INTO THE
REGION. HOW SUCCESSFUL THE AIR WILL BE IN INFILTRATING THE
VALLEYS WILL DETERMINE WHETHER OR NOT RAIN OR FREEZING RAIN WILL
BE SEEN ACROSS NORTHWEST MONTANA. THE SUB-FREEZING AIR IN THE
VALLEYS SHOULD BE SCOURED OUT BY FRIDAY AFTERNOON...ALLOWING MOST
VALLEYS TO TURN OVER TO ALL RAIN.
SATURDAY THROUGH EARLY NEXT WEEK...A STEADY CONVEYOR BELT OF
PACIFIC SYSTEMS WILL BRING CONTINUED PRECIPITATION TO THE
NORTHERN ROCKIES. MOUNTAINS WILL SEE PERIODS OF ACCUMULATING SNOW
WITH VALLEYS EXPERIENCING INTERMITTENT PRECIPITATION DURING THIS
TIME. VALLEY TEMPERATURES ARE EXPECTED TO REMAIN WARM...WITH
RAINFALL DURING THE DAY AND EITHER SNOW OR A RAIN/SNOW MIX DURING
THE NIGHTTIME HOURS. THE MAIN CONCERN IS THE POTENTIAL FOR WET
SURFACES TO REFREEZE EACH EVENING THROUGH MID-MORNING AS
TEMPERATURES COOL BELOW 32 DEGREES...CREATING TRAVEL HAZARDS DUE
TO SLICK ROADWAYS.
&&
.AVIATION...CONDITIONS WILL STEADILY DETERIORATE IN THE NORTHERN
ROCKIES TODAY...ESPECIALLY IN NORTHWEST MONTANA...AS SNOW SPREADS
ACROSS THE REGION. STRONG WEST WINDS WILL DEVELOP AND STRENGTHEN
THROUGH THE DAY...CREATING TURBULENT CONDITIONS AND POTENTIALLY LOW
LEVEL WIND SHEAR. ALL AREA TERMINALS WILL BE IMPACTED TO VARYING
DEGREES BY ACCUMULATING SNOW...WIND...REDUCED VISIBILITIES AND LOW
CEILINGS OVER THE NEXT 24 HOURS. KSMN AND KBTM WILL EXPERIENCE THE
STRONGER WINDS TODAY AROUND 12/1800Z...BUT PRECIPITATION AND
LOWERED CEILINGS/VISIBILITIES SHOULD HOLD OFF UNTIL LATE THIS
AFTERNOON. FREEZING RAIN IS ALSO POSSIBLE AT KMSO AND KGPI THIS
AFTERNOON THROUGH THURSDAY MORNING...HOWEVER THE EXACT TIMING AND
DURATION WILL BE DIFFICULT TO DETERMINE. TERRAIN WILL BECOME
OBSCURED ACROSS THE NORTHERN ROCKIES LATE THIS MORNING THROUGH
THURSDAY.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY FROM 11 AM THIS MORNING TO 8 AM MST
THURSDAY MISSOULA/BITTERROOT VALLEYS.
WINTER STORM WARNING UNTIL 5 PM MST THURSDAY KOOTENAI/CABINET
REGION...LOWER CLARK FORK REGION.
WINTER STORM WARNING UNTIL 11 AM MST THURSDAY FLATHEAD/MISSION
VALLEYS.
WINTER STORM WARNING UNTIL 5 PM MST THURSDAY WEST GLACIER REGION.
WINTER STORM WARNING UNTIL 5 PM MST THURSDAY FOR LOLO PASS.
WINTER WEATHER ADVISORY FROM 11 AM THIS MORNING TO 11 AM MST
THURSDAY POTOMAC/SEELEY LAKE REGION.
ID...WINTER WEATHER ADVISORY UNTIL 4 AM PST THURSDAY NORTHERN
CLEARWATER MOUNTAINS.
WIND ADVISORY FROM 7 AM THIS MORNING TO 7 PM PST THIS EVENING
FOR GRANGEVILLE AND VICINITY.
&&
SHORT TERM...RPN
LONG TERM....DEROSA
AVIATION...DEROSAThe national radar mosaic for the moment the first event began.
1 heavy snow, 1 winter storm. Local standard time, as filed.
Observer in Powell Idaho measured 8.5 inches of snow.
Chains were required on Highway 12 over Lolo Pass.
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, January 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: 274626, 274629.