Heavy rain from thunderstorms caused flash flooding and closed Highway 180 north of Alpine until debris could be cleared from the road.
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The episode as NWS FGZ wrote it up.
Heavy rain from thunderstorms caused flash flooding and closed Highway 180 north of Alpine until debris could be cleared from the road.
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 Flagstaff, AZ wrote its last area forecast discussion before the first event at Aug 20, 9:18 AM MST, 3 hours 12 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE FLAGSTAFF AZ 918 AM MST MON AUG 20 2012 .SYNOPSIS...A MOIST AND UNSTABLE AIR MASS WILL REMAIN OVER ARIZONA FOR THE NEXT SEVERAL DAYS BRINGING DAILY SHOWERS AND THUNDERSTORMS TO THE REGION. && DISCUSSION...UNSETTLED WEATHER WILL PERSIST ACROSS THE REGION THROUGH FRIDAY...WITH SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS EXPECTED EACH AFTERNOON AND EVENING. A SLIGHTLY FLATTER RIDGE IS IN PLACE ACROSS THE AREA TODAY WITH THE UPPER LEVEL HIGH CENTERED OVER SOUTHERN/CENTRAL AZ. THE RESULTING FLOW OVER NORTHERN AZ IS WESTERLY. PLENTY OF MOISTURE AVAILABLE TODAY AS INDICATED BY 1.00 INCH PW IN THIS MORNINGS FGZ SOUNDING...WITH SATELLITE BLENDED TOTAL PRECIPITABLE WATER IMAGERY INDICATING NEAR 1.50 INCHES SOUTH OF THE RIM. MOSTLY CLEAR SKIES FROM THE RIM SOUTHWARD THIS MORNING WILL ALLOW AMPLE HEATING AND DAYTIME INSTABILITY TO FUEL SCATTERED SHOWERS AND THUNDERSTORMS. CONVECTIVE DEVELOPMENT WILL BE DELAYED NORTH OF THIS AREA DUE TO MORNING CLOUD COVER. STORM MOTION WILL GENERALLY BE WEST TO EAST ABOUT 10-20 MPH...THOUGH WITHOUT STRONGER WINDS ALOFT STORMS WILL ALSO BE OUTFLOW DRIVEN. HEAVY RAIN AND MOSTLY SMALL HAIL REMAIN THE PRIMARY THREATS TODAY. THE UPPER LEVEL HIGH PRESSURE CENTER IS FORECAST TO SHIFT OVER SOUTHERN NEW MEXICO BY MID-WEEK...A SOUTHERLY FLOW WILL DEVELOP ACROSS ARIZONA AND MOVE DEEPER MOISTURE NORTHWARD BY WEDNESDAY. THE CHANCE FOR THUNDERSTORMS WILL INCREASE FOR MOST AREAS WEDNESDAY/THURSDAY. THERE IS STILL SOME UNCERTAINTY IN THE TIMING AND TRACK OF A WEAK WEST COAST TROUGH THAT IS FORECAST TO PASS THROUGH THE GREAT BASIN AND NORTHERN ARIZONA POSSIBLY WEDNESDAY AND THURSDAY. THE ADDED MOISTURE AND INSTABILITY AND WEAK LARGE SCALE LIFT ASSOCIATED WITH THE TROUGH COULD PRODUCE WIDESPREAD PRECIPITATION DURING THIS TIME PERIOD...LOCALIZED HEAVY RAIN IS POSSIBLE. ACCORDING TO THE GFS AND ECMWF...AFTER THE THE TROUGH PASSES THROUGH THE REGION SATURDAY AND SUNDAY...BOTH MODELS ARE INDICATING A DRYING TREND WITH AT LEAST 20 TO 30 PERCENT CHANCES OF PRECIP IN THE FORECAST...WITH GENERALLY LIGHT WINDS...AND NEAR NORMAL TEMPERATURES. && .AVIATION...FOR THE 18Z PACKAGE...SCT-NMRS SHRA/TSRA WILL DEVELOP TODAY ACROSS MOST OF NORTHERN ARIZONA. MVFR/IFR CONDITIONS WITH HEAVY RAIN AND HAIL ARE LIKELY WITH THE STRONGER STORMS. EXPECT STORM COVERAGE TO DECREASE AFTER 03Z. AVIATION DISCUSSION NOT UPDATED FOR AMENDMENTS. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC.........MCS/TC AVIATION.......RR FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT WEATHER.GOV/FLAGSTAFF
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE FLAGSTAFF AZ 935 AM MST MON AUG 20 2012 AZZ004>018-037>040-210700- KAIBAB PLATEAU-MARBLE AND GLEN CANYONS-GRAND CANYON COUNTRY- COCONINO PLATEAU-YAVAPAI COUNTY MOUNTAINS- NORTHEAST PLATEAUS AND MESAS HWY 264 NORTHWARD-CHINLE VALLEY- CHUSKA MOUNTAINS AND DEFIANCE PLATEAU- LITTLE COLORADO RIVER VALLEY IN COCONINO COUNTY- LITTLE COLORADO RIVER VALLEY IN NAVAJO COUNTY- LITTLE COLORADO RIVER VALLEY IN APACHE COUNTY- WESTERN MOGOLLON RIM-EASTERN MOGOLLON RIM-WHITE MOUNTAINS- NORTHERN GILA COUNTY-YAVAPAI COUNTY VALLEYS AND BASINS- OAK CREEK AND SYCAMORE CANYONS-BLACK MESA AREA- NORTHEAST PLATEAUS AND MESAS SOUTH OF HWY 264- 935 AM MST MON AUG 20 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL ARIZONA...NORTH CENTRAL ARIZONA...NORTHEAST ARIZONA AND WEST CENTRAL ARIZONA. .DAY ONE...TODAY AND TONIGHT DEEP MOISTURE COVERS NEARLY ALL OF NORTHERN ARIZONA TODAY. SCATTERED THUNDERSTORMS ARE EXPECTED TO INITIALLY DEVELOP OVER THE HIGHER TERRAIN...AND MOVE INTO THE LOWER ELEVATIONS LATER THIS AFTERNOON AND TONIGHT. THE PRIMARY THREATS ARE FREQUENT LIGHTNING...HEAVY RAIN...SMALL HAIL AND STRONG GUSTY WINDS. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY A MOIST AND UNSTABLE AIR MASS WILL REMAIN ACROSS ARIZONA FOR THE NEXT SEVERAL DAYS. EXPECT SHOWERS AND THUNDERSTORMS TO DEVELOP EACH DAY. SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BECOME MORE WIDESPREAD WEDNESDAY AND THURSDAY WITH AN INCREASED THREAT OF LOCALLY HEAVY RAIN. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1108 AM MST MON AUG 20 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0130 AM FLASH FLOOD LEES FERRY 36.87N 111.59W
08/20/2012 COCONINO AZ USGS
4 FOOT RISE IN LESS THAN 30 MINUTES MEASURED ON PARIA
RIVER
&&
EVENT NUMBER FGZ1200087
DJOThe Flagstaff radar (KFSX), 205 km away, was scanning. The volume nearest the first event began at 19:30 UTC.
1 flash flood. Local standard time, as filed.
Heavy rain fell for 30 minutes northwest of Alpine. Three feet of water covered a country road. Highway 180 was also closed until the water receded and the debris was cleared.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2012Every state in 2012This day in weather historyWarnings in Arizona, 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: 410959.