Moderate to heavy rain showers transitioned over to snow by early in the evening on the 9th. Heavy wet snow Saturday night also caused many trees to break under the pressure of the sudden weight.
Every event with a place to put it; 5 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 BOU wrote it up.
Moderate to heavy rain showers transitioned over to snow by early in the evening on the 9th. Heavy wet snow Saturday night also caused many trees to break under the pressure of the sudden weight. Tree damage ranged from minor to significant, with old growth trees losing large limbs and new trees sustaining fatal damage. Power outages affected about 43,350 Xcel Energy customers in metro Denver. The Intermountain Rural Electric Association also reported about 1,000 power outages in the Strasburg areas. In the high country, CDOT shut down Interstate 70 between the Eisenhower Tunnel and Silverthorne due to multiple crashes.
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 Denver/Boulder, CO wrote its last area forecast discussion before the first event at May 9, 8:48 AM MST, 3 hours 19 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER/BOULDER CO 948 AM MDT SAT MAY 9 2015 .UPDATE... ISSUED AT 943 AM MDT SAT MAY 9 2015 BIG CONCERNS REGARDING THE CHANGEOVER TO SNOW TONIGHT. EXPECT THIS WILL HAPPEN EARLY IN THE EVENING WITH THE MDLS DEVELOPING SOME MODERATE TO HEAVY SNOW OVERNIGHT. WE HAVE ISSUED A WINTER STORM WATCH FOR THE FRONT RANGE FOOTHILLS...URBAN CORRIDOR AND MOST OF THE NORTHEAST PLAINS FROM 9 PM TONIGHT THROUGH TO 9 AM SUNDAY MORNING. A LITTLE UNUSUAL TO HAVE A WATCH...BUT STILL UNCERTAIN AS TO WHERE THE HEAVY BANDS WILL SET UP. WL UPDATE THE HIGHLIGHT WITH THE AFTERNOON PACKAGE. ALSO HAVE INCLUDED LOGAN COUNTY IN THE FLASH FLOOD WATCH. SOME ROAD CLOSURES ALREADY WITH SOME OF THE HEAVY RAIN/RUNOFF THIS MORNING. UPDATE ISSUED AT 745 AM MDT SAT MAY 9 2015 WITH ALL THE ONGOING SHOWERS AND THUNDERSTORMS HAVE STARTED THE FLASH FLOOD WATCH THIS MORNING INSTEAD OF NOON TODAY. WILL BE BUMPING ALL THE POPS UP THIS MORNING AS WELL. MAY ALSO ADJUST THE GRIDS TO MOVE UP THE CHANGEOVER TO SNOW...AFTER MIDNIGHT...FOR THE URBAN CORRIDOR. && .SHORT TERM...(TODAY THROUGH TONIGHT ) ISSUED AT 430 AM MDT SAT MAY 9 2015 THE STAGE HAS BEEN SET FOR A REALLY LONG DAY TODAY AND TONIGHT. AREAS OF HEAVY RAIN YESTERDAY AFTERNOON AND OVERNIGHT HAVE KEPT SOIL MOISTURE CONDITIONS NEAR SATURATION ALONG THE I-25 CORRIDOR AND EASTWARD ONTO THE PLAINS. BANDS OF SHOWERS OVER ELBERT AND MORGAN COUNTIES OVERNIGHT ADDED TO THE RAINS THAT FELL ACROSS JEFFERSON...BOULDER AND WELD COUNTIES LAST EVENING. AND TODAY...THE LATE SEASON UPPER LOW WILL BE APPROACHING SOUTHERN COLORADO WITH EVEN STRONGER DYNAMIC FORCING THAN WE HAD YESTERDAY. SHOWERS ARE ALREADY DEVELOPING OVER PUEBLO AND EL PASO COUNTIES...WITH THEIR SIGHTS SET ON THE I-25 CORRIDOR AND ADJACENT PLAINS. MULTIPLE WAVES OF SHOWERS ARE EXPECTED THROUGH THE DAY AND THIS EVENING AS THE UPPER LOW MOVES INTO SOUTHERN COLORADO BY EVENING. AT THE SURFACE...A DEEPENING SURFACE LOW OVER SOUTHEAST COLORADO WILL HELP TO REINFORCE EASTERLY TO SOUTHEASTERLY WINDS AT LOW LEVELS. DEW POINTS WILL BE IN THE LOWER 50S AS MOISTURE FROM KANSAS IS ADVECTED INTO THE REGION. IN ADDITION TO THE LOCALLY HEAVY RAIN...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE EAST-CENTRAL PART OF THE STATE. THE PRESENCE OF THE VERTICALLY STACKED SURFACE AND UPPER LEVEL LOWS WILL MAKE SUPERCELLS WITH SHORT-LIVED FUNNEL CLOUDS OR TORNADOES A POSSIBILITY. MODEL QPF FORECASTS INDICATE THAT FROM ONE TO TWO INCHES OF RAIN IS POSSIBLE ACROSS MUCH OF THE FORECAST AREA BY THIS EVENING. FLASH FLOOD GUIDANCE VALUES ARE GENERALLY IN THE 1.0 TO 1.4 INCH PER HOUR RANGE DUE TO THE SATURATED SOIL CONDITIONS. WILL BE REPLACING THE FLOOD ADVISORY AND AREAL FLOOD WARNINGS WITH A FLASH FLOOD WATCH THAT EXTENDS FROM THE FOOTHILLS EASTWARD TO WASHINGTON AND LINCOLN COUNTIES. HEAVY RAIN SHOWERS ARE GOING TO PRODUCE RAPID HYDROLOGIC RESPONSES IN CREEKS AND RIVERS AS WELL AS FLOODING PROBLEMS IN MORE URBAN AREAS. THE FLASH FLOOD WATCH WILL BE IN EFFECT FROM NOON THROUGH 9 PM. LATER TONIGHT...THE COLD AIR ASSOCIATED WITH THE UPPER LOW WILL DROP TEMPERATURES ENOUGH FOR THE SNOW LEVEL TO DROP DOWN TO 6000 FEET OR LESS. IN THE MOUNTAINS...THE COPIOUS MOISTURE AND COLD TEMPERATURES WILL COMBINE FOR HEAVY SNOW ACCUMULATIONS FROM LATE THIS AFTERNOON THROUGH THE NIGHT. UP TO A FOOT OF NEW SNOW IS EXPECTED OVER THE HIGHEST ELEVATIONS. WILL UPGRADE THE WINTER STORM WATCH TO A WINTER STORM WARNING TO COVER THIS SITUATION. ON THE PLAINS...SNOW ACCUMULATIONS OF A COUPLE INCHES WILL BE POSSIBLE...DEPENDING ON WHEN RAIN CHANGES OVER TO SNOW. .LONG TERM...(SUNDAY THROUGH FRIDAY) ISSUED AT 430 AM MDT SAT MAY 9 2015 THE UPPER LEVEL STORM SYSTEM WILL BE NR THE CO/KS/NE BORDER AREA BY 12Z AND THEN MOVE INTO NCNTRL NE BY LATE AFTN. QG ASCENT WILL GRADUALLY SHIFT NE OF THE AREA AS WELL DURING THE MORNING HOURS WITH PCPN ENDING BY MID MORNING ALONG THE FRONT RANGE AND BY NOON OVER THE FAR ERN PLAINS. THERE IS STILL SOME POTENTIAL FOR HEAVIER SNOW OVER PORTIONS OF THE PLAINS THRU MID MORNING BEFORE THE PCPN SHIFTS AWAY FM THE AREA. IN ADDITION GUSTY NLY WINDS WILL BE IN PLACE AS WELL WHICH WILL CREATE VERY POOR VISIBILITIES IN OPEN AREAS. IN THE MTNS THERE WILL BE FAVORABLE OROGRAPHICS THRU THE DAY HOWEVER MOISTURE SHOULD BEGIN TO DECREASE BY AFTN. ADDITIONAL ACCUMULATIONS SHOULD BE MANLY ON THE LIGHT SIDE. AS FOR HIGHS ON SUN READINGS WILL STAY MAINLY IN THE 40S OVER NERN CO. BY MON A FLAT UPPER LEVEL RIDGE WILL BUILD OVER THE AREA WITH MAINLY DRY CONDITIONS. ENOUGH MOISTURE MAY LINGER IN THE MTNS FOR SOME WDLY SCT SHOWERS. TEMPS WILL REMAIN COOL OVER NERN CO AS READINGS ONLY RISE INTO THE 50S FOR AFTN HIGHS. ON TUE THE FLOW ALOFT WILL BECOME MORE SWLY AS SFC LOW PRES DEVELOPS FM CNTRL WY INTO CNTRL CO. THIS WILL ALLOW FOR INCREASE IN LOW LVL MOISTURE OVER NERN CO BY AFTN IN SELY FLOW. OVERALL THERE WILL BE ENOUGH INSTABILITY BY AFTN TO MENTION SOME WDLY SCT TSTMS. TEMPS SHOULD FINALLY RISE BACK TO SEASONAL LEVELS OVER NERN CO. ON WED THE FLOW ALOFT WILL REMAIN SWLY AS SFC LOW PRES EXTENDS FM CNTRL WY INTO ERN CO. LOW LVL MOISTURE WILL CONTINUE TO INCREASE OVER NERN CO IN SELY FLOW WITH HIGHER CAPES. OVERALL WILL CONTINUE WITH A CHC OF TSTMS OVER THE PLAINS. IN THE MTNS ENOUGH MOISTURE WILL EXIST FOR AT LEAST SOME WDLY SCT TSTMS. HIGHS ON WED WILL RISE INTO THE UPPER 60S TO LOWER 70S OVER NERN CO. BY THU SWLY FLOW ALOFT WILL REMAIN OVER THE AREA. THE GFS SHOWS A DISTURBANCE MOVING ACROSS THE AREA WHILE THE ECMWF DOES NOT. AT THIS POINT WILL KEEP IN A SLIGHT CHC IN ALL AREAS FOR THE AFTN AND EVENING HOURS. IN ADDITION THE GFS SHOWS A WK FNT MOVING INTO NERN CO WHILE THE ECMWF DOES NOT. FOR NOW WILL KEEP HIGHS SIMILAR TO WED ACROSS NERN CO. BY FRI AN UPPER LEVEL TROUGH WILL DVLP OVER THE GREAT BASIN WITH SWLY FLOW REMAINING OVER THE AREA. THUS WILL KEEP IN A SLIGHT CHC OF TSTMS OVER THE AREA WITH TEMPS NEAR SEASONAL LEVELS. && .AVIATION...(FOR THE TAFS THROUGH 18Z SUNDAY MORNING) ISSUED AT 745 AM MDT SAT MAY 9 2015 LOW CEILINGS AND PERIODS OF RAIN WILL DOMINATE THE FORECAST TODAY. THE RAIN COULD BE HEAVY AT TIMES ALONG WITH SOME EMBEDDED THUNDERSTORMS. IFR CONDITIONS WILL BE THE RULE WITH ONLY TEMPORARY IMPROVEMENT BETWEEN PASSING RAIN SHOWERS. TEMPERATURES WILL REMAIN WARM ENOUGH FOR RAIN INTO THE MID-EVENING. AFTER ABOUT 10 PM...TEMPERATURES WILL BE COOLING OFF AND A MIX OF RAIN AND SNOW IS EXPECTED. SOMETIME AFTER MIDNIGHT THE PRECIPITATION MAY CHANGE TO ALL SNOW WITH ONE OR TWO INCHES OF ACCUMULATION BY SUNRISE. STILL ASSESSING THE POTENTIAL FOR MORE SNOW ON SUNDAY MORNING. && .HYDROLOGY... ISSUED AT 751 AM MDT SAT MAY 9 2015 A PERFECT STORM...SO TO SPEAK...AS HEAVY RAIN IS EXPECTED TO FALL ON ALREADY SATURATED SOILS. RIVER RESPONSES TO THE HEAVY RAIN WILL BE RAPID...WITH RIVERS...CREEKS AND STREAMS ALREADY RUNNING CLOSE TO BANKFULL CONDITIONS. THE FLASH FLOOD WATCH WILL HIGHLIGHT THE FACT THAT IT IS NOT GOING TO TAKE MUCH RAIN TO CAUSE PROBLEMS. HEAVY RAIN WILL BE POSSIBLE FROM THE FOOTHILLS WHERE UPSLOPE FORCING WILL BE STRONGEST OUT ACROSS THE PLAINS WHERE MANY AREAS HAVE SEEN PERIODS OF HEAVY RAIN OVER THE LAST COUPLE DAYS. TOO MUCH WATER AND NOWHERE TO STORE IT. A FLOOD WARNING FOR THE SOUTH PLATTE RIVER FROM GREELEY OUT TO THE NORTHEAST CORNER OF THE STATE WILL BE IN EFFECT FOR THE NEXT FEW DAYS. SOME FLASH FLOOD WARNING ALREADY ISSUED THIS MORNING SO HAVE ALREADY STARTED THE FLASH FLOOD WATCH FOR MUCH OF THE AREA THIS MORNING. && .BOU WATCHES/WARNINGS/ADVISORIES... FLASH FLOOD WATCH UNTIL 9 PM MDT THIS EVENING FOR COZ035-036- 038>049. WINTER STORM WATCH FROM 9 PM MDT THIS EVENING THROUGH SUNDAY MORNING FOR COZ035-036-038>046-048-049. WINTER STORM WARNING UNTIL 6 AM MDT SUNDAY FOR COZ033-034. && UPDATE...COOPER SHORT TERM...DANKERS LONG TERM...RPK AVIATION...COOPER HYDROLOGY...DANKERS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DENVER/BOULDER CO 1109 AM MDT SAT MAY 9 2015 COZ030>051-101715- JACKSON COUNTY BELOW 9000 FEET- WEST JACKSON AND WEST GRAND COUNTIES ABOVE 9000 FEET- GRAND AND SUMMIT COUNTIES BELOW 9000 FEET- SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/ NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET- SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/ GILPIN/CLEAR CREEK/SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET-LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET- JEFFERSON AND WEST DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR CREEK/NORTHEAST PARK COUNTIES BELOW 9000 FEET- CENTRAL AND SOUTHEAST PARK COUNTY- LARIMER COUNTY BELOW 6000 FEET/NORTHWEST WELD COUNTY- BOULDER AND JEFFERSON COUNTIES BELOW 6000 FEET/WEST BROOMFIELD COUNTY- NORTH DOUGLAS COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE COUNTIES/EAST BROOMFIELD COUNTY- ELBERT/CENTRAL AND EAST DOUGLAS COUNTIES ABOVE 6000 FEET- NORTHEAST WELD COUNTY-CENTRAL AND SOUTH WELD COUNTY-MORGAN COUNTY- CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES- NORTH AND NORTHEAST ELBERT COUNTY BELOW 6000 FEET/NORTH LINCOLN COUNTY- SOUTHEAST ELBERT COUNTY BELOW 6000 FEET/SOUTH LINCOLN COUNTY- LOGAN COUNTY-WASHINGTON COUNTY-SEDGWICK COUNTY-PHILLIPS COUNTY- 1109 AM MDT SAT MAY 9 2015 ...NUMEROUS FLOOD AND FLASH FLOOD WARNINGS AND WATCHES IN EFFECT ACROSS NORTHEAST COLORADO TODAY AND THIS EVENING... ...WINTER STORM WARNING IN THE MOUNTAINS THIS AFTERNOON AND TONIGHT... ...WINTER STORM WATCH IN THE FOOTHILLS...URBAN CORRIDOR AND ADJACENT PLAINS 9 PM THIS EVENING THROUGH SUNDAY MORNING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL COLORADO. .DAY ONE...TODAY AND TONIGHT A STRONG STORM SYSTEM APPROACHING COLORADO TODAY WILL CREATE A RANGE OF HAZARDOUS WEATHER SITUATIONS THROUGH TONIGHT. THE COOL AND WET WEATHER OF THE PAST WEEK HAS BROUGHT SOIL MOISTURE LEVELS TO NEAR SATURATION AND HAS RAISED RIVER LEVELS TO NEAR BANKFULL. RAIN SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE APPROACHING STORM SYSTEM ARE CAUSING RIVERS TO APPROACH OR EXCEED FLOOD STAGES. THE HEAVIER RAIN SHOWERS MAY ALSO CAUSE FLASH FLOODING AT TIMES. A FLASH FLOOD WATCH IS IN EFFECT THROUGH THIS EVENING FROM THE FRONT RANGE FOOTHILLS EASTWARD ACROSS THE NORTHEAST COLORADO PLAINS. RESIDENTS SHOULD BE ALERT FOR FLOODING PROBLEMS. IN ADDITION...RAIN SHOWERS IN THE FOOTHILLS BELOW 7 THOUSAND FEET MAY CAUSE THE RELEASE OF ROCK OR MUD SLIDES IN THE FOOTHILL CANYONS. THESE ROCK SLIDES CAN OCCUR WITH LITTLE WARNING. ON THE FAR EASTERN PLAINS THERE IS ALSO A THREAT OF SEVERE THUNDERSTORMS TODAY AS MOIST AND UNSTABLE AIR IS BEING DRAWN INTO THE STATE FROM KANSAS. THE VERTICAL WIND SHEAR PROFILE IS GOING TO MAKE IT POSSIBLE FOR SOME THUNDERSTORMS OVER LINCOLN AND WASHINGTON COUNTIES TO BECOME SEVERE...PRODUCING LARGE HAIL AND TORNADOES. THE SNOW LEVEL WILL BE AROUND 7000 FEET THIS AFTERNOON AND WILL LOWER TO 5000 FEET TONIGHT AS COLD AIR BEHIND THE STORM SYSTEM INTRUDES FROM THE NORTH. AREAS STORM TOTALS OF 8 TO 16 INCHES ABOVE 9 THOUSAND FEET. IN THE FRONT RANGE FOOTHILLS...URBAN CORRIDOR AND ADJACENT PLAINS...RAIN WILL CHANGE QUICKLY OVER TO SNOW THIS AFTERNOON AND EVENING. A WINTER STORM WATCH IS IN EFFECT FOR THE FRONT RANGE FOOTHILLS...URBAN CORRIDOR AND NORTHEAST PLAINS FROM 9 PM THIS EVENING THROUGH SUNDAY MORNING. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY SNOW WILL CONTINUE OVER NE COLORADO SUNDAY MORNING INTO THE EARLY AFTERNOON BEFORE TAPERING OFF FROM SOUTH TO NORTH SUNDAY EVENING. TOTAL ACCUMULATIONS OF 5 TO 10 INCHES WILL BE POSSIBLE OVER THE PLAINS BY SUNDAY AFTERNOON. GUSTY NORTH WINDS UP TO 40 MPH MAY PRODUCE POOR VISIBILITIES IN OPEN AREAS THROUGH THE MORNING HOURS. BY EARLY AFTERNOON CONDITIONS WILL SLOWLY IMPROVE OVER NORTHEAST COLORADO. IN THE MOUNTAINS PERIODS OF SNOW WILL LINGER THROUGH THE AFTERNOON HOURS WITH ADDITIONAL ACCUMULATIONS OF 2 TO 4 INCHES WITH STORM TOTAL OF 8 TO 16 INCHES. A DRYING TREND IS EXPECTED FOR MONDAY AND TUESDAY HOWEVER A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS MAY RETURN BY WEDNESDAY. TEMPERATURES WILL GRADUALLY RETURN TO SEASONAL NORMALS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NECESSARY THIS AFTERNOON FOR REPORTS OF SEVERE WEATHER ON THE FAR EASTERN PLAINS AND REPORTS OF FLOODING OR FLASH FLOODING IN AREAS THAT EXPERIENCE HEAVY RAIN.
The national radar mosaic for the moment the first event began.
5 winter storm. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2015Every state in 2015This day in weather historyWarnings in Colorado, May 2015
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: 566106, 566107, 566108, 566109, 566110.