A tight surface pressure gradient with an associated strong cold front produce very strong winds across Lemhi county Idaho.
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The episode as NWS MSO wrote it up.
A tight surface pressure gradient with an associated strong cold front produce very strong winds across Lemhi county Idaho.
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 Feb 12, 10:24 PM MST, 2 hours 47 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MISSOULA MT
1024 PM MST SAT FEB 12 2011
.UPDATE...INCLUDED NORTHWEST MONTANA IN A HIGH WIND WARNING AND
FLATHEAD VALLEY/MISSION VALLEY/LOWER CLARK FORK REGION IN A WIND
ADVISORY.
&&
.DISCUSSION...SPOTTER REPORTS AND OBSERVATIONS HAVE BEEN RECEIVED
OF STRONG WIND GUSTS IN EXCESS OF 50 TO 60 MPH IN LOCATIONS OF
NORTHWEST MONTANA...SPECIFICALLY IN AND AROUND THE LIBBY AREA.
WITH WINDS EXPECTED TO INTENSIFY OVERNIGHT...A HIGH WIND WARNING
HAS BEEN ISSUED FOR NORTHWEST MONTANA. SOUTH TO SOUTHWEST WINDS
SHOULD CONTINUE TO INCREASE OVERNIGHT AND THEN SUBSIDE BY MORNING.
SIMILAR OBSERVATIONS...THOUGH NOT AS QUITE AS STRONG...HAVE BEEN
REPORTED ACROSS THE FLATHEAD/MISSION VALLEYS AS WELL AS THROUGH
THE LOWER CLARK FORK REGION. AS A RESULT...HAVE INCLUDED THESE
AREAS IN A WIND ADVISORY THROUGH SUNDAY MORNING.
&&
.AVIATION...A STRONG SURFACE PRESSURE GRADIENT FROM THE SOUTH
ALONG WITH A PASSING UPPER LEVEL DISTURBANCE WILL COMBINE TO
INCREASE WINDS ACROSS THE REGION OVERNIGHT. THE ONLY MAIN
TERMINAL LIKELY EXEMPTED FROM THIS WILL BE KSMN WHERE COOL AIR AT
THE SURFACE IS MAINTAINING STABILITY. ELSEWHERE EXPECT WINDS TO
PEAK TONIGHT...GENERALLY INCREASING INTO THE 20 TO 30 MPH RANGE
WITH GUSTS TO NEAR 40 MPH THROUGH EARLY SUNDAY MORNING. THE
DISTURBANCE WILL ALSO PRODUCE PRECIPITATION...MAINLY IN THE FORM
OF RAIN...THEN A MIX OF RAIN AND SNOW. REDUCED VISIBILITIES AND
CEILINGS ARE POSSIBLE.
&&
PREV DISCUSSION... /ISSUED 214 PM MST SAT FEB 12 2011/
.INCREASING WINDS TONIGHT...
.SNOW AND BLOWING SNOW POSSIBLE OVER THE PASSES...
DISCUSSION...AN UPPER LEVEL RIDGE OVER THE REGION WILL CONTINUE
TO FLATTEN THIS EVENING AS A FAST MOVING DISTURBANCE PASSES. A
SOUTHERLY PRESSURE GRADIENT WILL CONTINUE TO STRENGTHEN IN ADVANCE
OF THIS SYSTEM...AND THUS WINDS WILL BECOME MORE WIDESPREAD AND
INTENSIFY. THE DISTURBANCE WILL DROP OVER THE NORTHERN ROCKIES
AROUND MIDNIGHT. THIS WILL HAVE TWO PRIMARY IMPACTS. THE FIRST IS
TO FURTHER ENHANCE THE WINDY CONDITIONS AS THIS SYSTEM WILL BE
ACCOMPANIED BY STRONG WINDS IN THE MID AND UPPER LEVELS. SOME OF
THIS ENERGY WILL MIX TO THE SURFACE. THE SECOND IMPACT WILL BE THE
POTENTIAL FOR SNOW AND BLOWING SNOW IN THE MOUNTAINS...MAINLY FROM
THE BITTERROOTS NORTH THROUGH NORTHWEST MONTANA. ACTUAL
ACCUMULATIONS WILL NOT BE IMPRESSIVE...BUT DRIVING CONDITIONS OVER
LOOKOUT...LOLO...AND MARIAS PASSES MAY BE DIFFICULT AT TIMES LATE
TONIGHT. SNOW LEVELS WILL START OUT ABOVE THE PASSES THIS
EVENING...BUT THEN DROP BELOW PASS LEVEL AFTER THE DISTURBANCE PASSES.
MOST VALLEYS WILL REMAIN ABOVE FREEZING TONIGHT DUE TO THE VERY
MILD STARTING CONDITIONS EARLY THIS EVENING FOLLOWED BY CONTINUED
MIXING DUE TO THE DISTURBANCE AND PERSISTENT WINDS.
THE SURFACE PRESSURE GRADIENT AND WINDS ALOFT WILL BE DECREASING
IN STRENGTH SUNDAY...BUT WILL STILL YIELD BREEZY WINDS THROUGH
MUCH OF THE DAY. OTHERWISE ANOTHER RIDGE OF HIGH PRESSURE WILL
DEVELOP SUNDAY AND PERSIST THROUGH MIDDAY MONDAY. HOWEVER...BY
LATE MONDAY THE RIDGE WILL MOVE WELL EAST OF THE ROCKIES ALLOWING
A MORE MOIST SOUTHWEST FLOW OVER THE REGION. TEMPERATURES SUNDAY
AND MONDAY WILL NOT BE AS WARM AS TODAY...BUT REMAIN ABOVE NORMAL
FOR MID FEBRUARY.
AS A TROUGH MOVES INTO THE PACIFIC NORTHWEST ON TUESDAY A VERY
MOIST AND WARM SOUTHERLY FLOW WILL REMAIN OVER WESTERN MONTANA AND
NORTH CENTRAL IDAHO. MODELS BRING A STRONG 140 KT JET STREAK
ACROSS THE REGION...ALONG WITH A SURFACE COLD FRONT WHICH COULD
COMBINE TO PRODUCE STRONG GUSTY WINDS AND SOME HEAVY
PRECIPITATION. AFTER THE COLD FRONT MOVES TO THE EAST THE REST OF
THE EXTENDED FORECAST HAS COOLER TEMPERATURES ALONG WITH SOME
SNOWFALL MAINLY OVER THE HIGHER MOUNTAINS.
AVIATION...A STRONG SURFACE PRESSURE GRADIENT FROM THE SOUTH
ALONG WITH A PASSING UPPER LEVEL DISTURBANCE OVERNIGHT WILL
COMBINE TO INCREASE WINDS ACROSS THE REGION. THE ONLY MAIN
TERMINAL LIKELY EXEMPTED FROM THIS WILL BE KSMN WHERE COOL AIR AT
THE SURFACE IS MAINTAINING STABILITY. ELSEWHERE EXPECT WINDS TO
PEAK LATER THIS EVENING AND GENERALLY BE IN THE 20 TO 30 MPH RANGE
WITH GUSTS TO NEAR 40 MPH THROUGH EARLY SUNDAY MORNING. THE
DISTURBANCE WILL ALSO PRODUCE PRECIPITATION...MAINLY RAIN THIS
EVENING...THEN A MIX OF RAIN AND SNOW LATE TONIGHT. REDUCED
VISIBILITIES AND CEILINGS ARE POSSIBLE MAINLY LATE TONIGHT.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...HIGH WIND WARNING UNTIL 5 AM MST SUNDAY BUTTE/BLACKFOOT REGION...
KOOTENAI/CABINET REGION.
WIND ADVISORY UNTIL 5 AM MST SUNDAY FLATHEAD/MISSION VALLEYS...
LOWER CLARK FORK REGION...MISSOULA/BITTERROOT VALLEYS.
WINTER WEATHER ADVISORY UNTIL 11 AM MST SUNDAY WEST GLACIER
REGION.
ID...WIND ADVISORY UNTIL 8 AM PST SUNDAY FOR GRANGEVILLE AND VICINITY.
WIND ADVISORY UNTIL 8 AM PST SUNDAY FOR THE CAMAS PRAIRIE AND
HIGHWAY 95 BETWEEN WHITE BIRD AND RIGGINS.
&&
SHORT TERM...ALLEGRETTO
LONG TERM....WHITMORE
AVIATION...ALLEGRETTOThe national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
The Salmon RAWS on a hill above the city of Salmon recorded a gust to 54 mph, at an elevation of 5100 feet.
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, February 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: 280087.