Abnormally warm temperatures caused increased snow melt over much of western Montana, with many rivers and small streams running at or slightly above normal. Some minor damage was reported along Fifer Creek in southwest Montana.
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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.
Abnormally warm temperatures caused increased snow melt over much of western Montana, with many rivers and small streams running at or slightly above normal. Some minor damage was reported along Fifer Creek in southwest Montana.
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 May 31, 2:53 AM MST, 9 hours 7 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MISSOULA MT 353 AM MDT SUN MAY 31 2009 .DISCUSSION...THE FLAT RIDGE OVER THE NORTHERN ROCKIES WILL CONTINUE TODAY ALONG WITH WARM TEMPERATURES. INSTABILITY...AND THUS THE THREAT OF ISOLATED TO SCATTERED CONVECTIVE SHOWERS AND THUNDERSTORMS...WILL BE FOCUSED OVER LEMHI COUNTY AND SOUTHWEST MONTANA...AND TO A LESSER EXTENT ALONG THE NORTHERN CONTINENTAL DIVIDE. MID AND HIGHER CLOUDS WILL BE A BIT MORE PREVALENT OVER THE REGION TODAY...AND THIS COULD KEEP US A COUPLE DEGREES COOLER THAN YESTERDAY. ON MONDAY A SYSTEM WILL DROP OUT OF ALBERTA INTO THE UPPER PLAINS. THIS WILL BRING SOMEWHAT COOLER AIR INTO CENTRAL MONTANA...AND IT IS EXPECTED TO SPILL INTO WESTERN MONTANA AS WELL. THE GREATEST TEMPERATURE IMPACT WILL BE ALONG THE DIVIDE...BUT MOST OF MONTANA WILL BE 10 TO 15 DEGREES COOLER MONDAY. COOLING IN IDAHO WILL BE MORE MODEST. THE INVADING COOLER AIR MASS WILL ALSO CREATE A EASTERLY SURFACE WIND. LATE DAY INSTABILITY WILL STILL BE AN ISSUE...BUT WILL BE SHUNTED EVEN FARTHER SOUTH. LONGER RANGE FORECAST MODELS ARE COMING INTO BETTER AGREEMENT WITH THE DEVELOPMENT OF A BLOCKING PATTERN THROUGH THE MAJORITY OF NEXT WEEK. VARIANCE OBSERVED BETWEEN THE GFS ENSEMBLE MEMBERS HAS DECREASED WITH THE MAJORITY OF SOLUTIONS CENTERED UPON THE MEAN PATTERN THROUGH THURSDAY. AND THIS MEAN ALONG WITH THE GFS OPERATIONAL SOLUTION ALSO ARE IN DECENT AGREEMENT WITH THE ECMWF. THUS CONFIDENCE IN THE EXTENDED FORECAST IS HIGHER THAN YESTERDAY. OVERALL THE PATTERN IS QUITE SIMILAR EACH DAY. WEAK SOUTHWESTERLY FLOW WILL REMAIN IN PLACE OVER THE WESTERN UNITED STATES THROUGH THE MAJORITY OF NEXT WEEK PUMPING SUBTROPICAL MOISTURE ACROSS THE INTER- MOUNTAIN WEST DUE TO A STALLED...CUT OFF LOW PRESSURE SYSTEM OFF THE CALIFORNIA COAST. WITH A STRONG RIDGE OF HIGH PRESSURE LOCATED DIRECTLY NORTH OF THIS LOW REACHING FAR INTO THE GULF OF ALASKA AND A LARGE AREA OF LOW PRESSURE EAST OF HUDSON BAY PRODUCING A BROAD TROUGH THROUGH CENTRAL CANADA...WESTERN MONTANA AND CENTRAL IDAHO WILL FALL UNDER A REGION OF EXTREMELY WEAK FLOW ALOFT. DIURNAL CONVECTION WILL BE PRESENT EACH DAY...PREDOMINANTLY SOUTH OF THE MISSOULA VALLEY. CONVECTION MAY CREEP NORTH OF MISSOULA...ESPECIALLY LATE IN THE WEEK. BUT THIS WILL ALL HINGE UPON UNPREDICTABLE WOBBLES IN THE CUT OFF LOW OF CALIFORNIA. AS THE WEEK PROGRESSES...THE UPPER LEVEL FLOW WILL ALSO BECOME WEAKER CAUSING ANY STORMS WHICH DEVELOP TO BE VERY SLOW MOVING PRODUCING THE POTENTIAL THREAT FOR LOCALLY HEAVY RAINFALL THURSDAY AND FRIDAY OVER CENTRAL IDAHO AND SOUTHWEST MONTANA. TEMPERATURES WILL BE VERY TRICKY NEXT WEEK AS CLOUD COVER AND PRECIPITATION ARE LIKELY TO IMPACT BOTH MAXIMUM AND MINIMUM VALUES. PERSISTENT CLEAR SKIES WILL PRODUCE CONTINUED WARM ABOVE NORMAL TEMPERATURES ACROSS NORTHWEST MONTANA WHILE CENTRAL IDAHO AND SOUTHWEST MONTANA MAY ACTUALLY EXPERIENCE NEAR NORMAL TEMPERATURES DUE TO INCREASED CLOUD COVER AND PRECIPITATION. HOWEVER AREAS IN THESE LOCATIONS CAN ALSO EXPECT ABOVE NORMAL TEMPERATURES WHEN CLOUDS AND PRECIPITATION ARE LACKING. AT THIS TIME FORECAST MODELS ARE NOT GIVING ANY RELIABLE INDICATION AS TO WHEN THIS PATTERN WILL CEASE. && .AVIATION...THE FLAT RIDGE WILL CONTINUE OVER THE REGION...SO EXPECT SIMILAR CONDITIONS TODAY AS WERE OBSERVED SATURDAY. LATE DAY CONVECTION IS POSSIBLE AT ALL LOCATIONS...BUT THE BEST INSTABILITY WILL STILL RESIDE OVER LEMHI COUNTY AND SOUTHWEST MONTANA. ANY THUNDERSTORM ACTIVITY SHOULD RAPIDLY DIE AFTER DARK. THE INSTABILITY WILL AGAIN ALLOW WESTERLY FLOW TO MIX TO THE SURFACE IN THE AFTERNOON. && .HYDROLOGY...AREA STREAMS...PARTICULARLY THE BITTERROOT RIVER...WILL CONTINUE TO RUN HIGH TODAY DUE TO SNOW MELT. WILL KEEP THE FLOOD WATCH OUT FOR THE BITTERROOT THIS MORNING AS ALL FORECAST POINTS CONTINUE TO RUN ABOVE THE ACTION STAGE. HOWEVER...LATEST RIVER FORECASTS ARE SUGGESTING THE RIVER MAY CREST BELOW FLOOD STAGE LATER TODAY. THE NORTH FORK OF THE FLATHEAD RIVER AT POLEBRIDGE HAS ALSO SEEN A SIGNIFICANT RISE IN THE PAST COUPLE DAYS...BUT IT TOO IS EXPECTED TO CREST BELOW FLOOD STAGE. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...NONE. ID...NONE. && SHORT TERM...WHITMORE LONG TERM....DICKERSON AVIATION...WHITMORE
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE MISSOULA MT 208 PM MDT SAT MAY 30 2009 MTZ003-310300- FLATHEAD/MISSION VALLEYS- 208 PM MDT SAT MAY 30 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST MONTANA. .DAY ONE...THIS AFTERNOON AND TONIGHT INCREASING FLOW ALOFT AND AN UNSTABLE AIR MASS WILL RESULT IN BREEZY WEST WINDS ACROSS FLATHEAD LAKE FROM MID AFTERNOON THROUGH EARLY EVENING. WIND GUSTS WILL FREQUENTLY HIT 25 MPH AND MAY BRIEFLY REGISTER AROUND 30 MPH AT TIMES. BOATERS SHOULD BE PREPARED FOR CHOPPY SURFACE CONDITIONS THROUGH THE AFTERNOON AND EVENING. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY NO HAZARDOUS WEATHER IS EXPECTED. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Basement flooding was reported by the DES Coordinator in two homes along Fifer Creek on Hemlock Street in Anaconda.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2009Every state in 2009This day in weather historyWarnings in Montana, May 2009
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: 166058.