Thunderstorms moving through southwest Colorado produced rainfall amounts in excess of an inch in portions of La Plata County.
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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 GJT wrote it up.
Thunderstorms moving through southwest Colorado produced rainfall amounts in excess of an inch in portions of La Plata County.
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 Grand Junction, CO wrote its last area forecast discussion before the first event at Aug 18, 9:58 AM MST, 3 hours 7 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO 1058 AM MDT SAT AUG 18 2012 .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 321 AM MDT SAT AUG 18 2012 TODAY...A VORT MAX MOVED FROM NW TO SE AND THROUGH THE AREA LAST NIGHT BRINGING DRIER AIR TO MUCH OF WESTERN CO AND EASTERN UT. THE UPPER RIDGE WAS SHIFTED SLIGHTLY WEST...WITH THE MAIN MOISTURE TRACK THROUGH NRN AZ AND NV. WV SATELLITE SHOWS THE SHEAR AXIS WILL HANG AROUND THE FOUR CORNERS...THUS THE ABAJOS... LA SALS... AND SAN JUAN MTS WILL SEE ISOLATED THUNDERSTORMS THIS AFTERNOON. TONIGHT AND SUNDAY...WILL KEEP A MENTION OF THUNDERSTORMS ALONG THE CENTRAL DIVIDE TO THE SAN JUANS AND VICINITY THIS EVENING AS MOISTURE POOLED AHEAD OF A BACKDOOR COLD FRONT THAT DROPPED DOWN ERN CO DURING THE DAY. RIDGE AXIS FROM AZ TO THE NRN ROCKIES MOSTLY HOT AND DRY DAY ON SUNDAY WITH THE RIDGE AXIS TO OUR WEST...THOUGH ISOLATED AFTERNOON STORMS WILL BE POSSIBLE OVER THE SAN JUANS. MID-LEVEL CLOUDS INCREASING FROM THE WEST BY LATE SUNDAY AFTERNOON. .LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) ISSUED AT 321 AM MDT SAT AUG 18 2012 SUNDAY NIGHT THROUGH MONDAY NIGHT...RIDGE AXIS REMAINS TO OUR WEST THROUGH MONDAY. AN EMBEDDED SHORTWAVE MOVES OVER/THROUGH THE RIDGE LATE SUNDAY NIGHT AND MONDAY...CROSSING ID/WY AND JUST CLIPPING THE NORTH. MID-LEVEL CLOUDS SPREAD ACROSS THE FORECAST AREA SUNDAY NIGHT AND GRADUALLY LOWER BY MONDAY MORNING. FORECAST SOUNDINGS SHOW THE BEST MOISTURE IN THE 600-400 MB LAYER...WITH PRECIPITABLE WATER VALUES TOPPING 0.70 INCH BY MONDAY MORNING. BEST UPWARD FORCING SEEN IN THE OMEGA AND Q-G FIELDS ALSO INDICATED ABOUT THIS TIME...THOUGH WITH THE ATMOSPHERE ALSO PRETTY STABLE WILL KEEP JUST A SLIGHT CHANCE OF SHOWERS/STORMS IN THE FORECAST MONDAY MORNING. MODELS SHOW MID-LEVEL DRYING BEGINNING MONDAY AFTERNOON BEHIND THE SHORTWAVE...SO MAY SEE SOME IMPROVEMENT IN CONVECTIVE INSTABILITY SHOULD ENOUGH SUN AND SURFACE HEATING DEVELOP. DRYING AND CLEARING FROM THE NW CONTINUE MONDAY NIGHT. TUESDAY THROUGH FRIDAY...THE RIDGE AXIS IS PROJECTED TO MOVE OVER THE AREA TUE AFTERNOON...WITH INCREASING SW FLOW AND MOISTURE WEST OF THE RIDGELINE. TUESDAY NIGHT THE GFS SHOWS A MODERATELY STRONG SHORTWAVE TROUGH MOVING FROM THE PACNW TO THE NORTHERN ROCKIES AND PICKING UP THE MOISTURE PLUME. AS THIS SHORTWAVE MOVES INTO MONTANA ...THE MONSOONAL MOISTURE PLUME MOVES EAST. BY NOON WED...THE MOISTURE AXIS IS PROJECTED OVER WESTERN CO. THE CHANCE OF RAIN SHOULD INCREASE ACROSS THE AREA WED. THE MOISTURE AND SCATTERED PCPN SHOULD CLEAR THE AREA TO THE EAST WED NIGHT...WITH SIGNIFICANTLY DRIER AIR OVER THE AREA THU THROUGH FRIDAY. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 1057 AM MDT SAT AUG 18 2012 HAZY CONDITIONS WILL PERSIST OVER THE REGION THROUGH SUNDAY WITH ISOLATED AFTERNOON AND EVENING THUNDERSTORMS FAVORING THE CENTRAL AND SOUTHERN MOUNTAINS. THE THUNDERSTORMS WILL PRODUCE GUSTY OUTFLOW WINDS TO NEAR 50 MPH. OTHERWISE...VFR CONDITIONS WILL PREVAIL. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...NONE. UT...NONE. && SHORT TERM...CC/JAD LONG TERM...CC/JAD AVIATION...JDC
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
The national radar mosaic for the moment the first event began.
1 heavy rain. Local standard time, as filed.
Over an inch of rainfall was measured within just 20 minutes. Only minor flooding was reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2012Every state in 2012This day in weather historyWarnings in Colorado, August 2012
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: 479527.