A strong cold front pushed through the Pacific Northwest on August 29th aiding the development of showers and thunderstorms including large hail and gusty winds.
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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 BOI wrote it up.
A strong cold front pushed through the Pacific Northwest on August 29th aiding the development of showers and thunderstorms including large hail and gusty winds.
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 Boise, ID wrote its last area forecast discussion before the first event at Aug 29, 7:31 PM MST, 44 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BOISE ID 831 PM MDT SAT AUG 29 2009 .DISCUSSION...THUNDERSTORMS DEVELOPED RAPIDLY LATE THIS AFTERNOON AND EARLY EVENING AHEAD OF COLD FRONT WHICH WAS APPROACHING FROM THE NW. AT 02Z THE FRONT EXTENDED FROM JUST EAST OF HELLS CANYON SSWWD TO CENTRAL MALHEUR COUNTY/OREGON. STRONGEST CELLS WERE IN PAYETTE ...GEM...AND SRN VALLEY COUNTIES. THESE LIKELY CONTAINED LARGE HAIL AND HEAVY RAIN. CELLS WERE MOVING NEWD 30-35 MPH. MORE STORMS FORMED IN THE OWYHEE MOUNTAINS AND MOVED NEWD INTO THE TREASURE VALLEY. THESE WERE HEADED FOR THE BOISE MOUNTAINS. AS THE COLD FRONT PUSHES SEWD...THUNDERSTORMS ARE EXPECTED TO DEVELOP PROGRESSIVELY EASTWARD IN THE SWRN IDAHO HIGHLANDS...THEN WRN MAGIC VALLEY AND CAMAS PRAIRIE. CONDITIONS WILL IMPROVE TO THE WEST OF THE COLD FRONT...WHICH WILL PASS THROUGH THE TREASURE VALLEY BETWEEN 9 PM AND 10 PM MDT. SEE PREVIOUS DISCUSSION FOR A DISCUSSION OF THE CLOSED UPPER LOW NOW MOVING IN FROM THE NW. CURRENT FORECAST LOOKS GOOD...NO UPDATES AT THIS TIME. && .AVIATION...SCATTERED SHOWERS AND THUNDERSTORMS WILL PERSIST ACROSS BAKER COUNTY OREGON AND SW IDAHO THROUGH MIDNIGHT MDT. EXPECT AREAS OF MVFR CEILINGS AND LOCAL IFR VISIBILITIES IN HEAVY RAIN - HAIL ALSO POSSIBLE WITH THESE STORMS. THUNDERSTORMS BASES 7K TO 9K FT MSL WITH TOPS TO 40K FT. SCATTERED SHOWERS WILL CONTINUE /OVER SW IDAHO/ AFTER MIDNIGHT. LIGHT TO MODERATE SURFACE WINDS WITH GUSTY AND ERRATIC WINDS IN THE VICINITY OF STORMS. && .PREV DISCUSSION... SHORT TERM...COMPACT BUT VIGOROUS UPPER LOW CONTINUES TO MOVE SOUTHEAST TOWARD OUR AREA. AS OF 2PM MDT CONVECTION HAS NOT DEVELOPED...BUT CONVECTIVE TEMPERATURES AND INSTABILITY IS JUST NOW BEING REACHED. THUS...WE ARE LOOKING AT A LATE DAY AND EVENING EVENT OVER NORTHEAST OREGON AND THE WEST CENTRAL MOUNTAINS WHILE DRY AND MORE STABLE CONDITIONS EXIST WELL SOUTH OF THE LOW IN THE SNAKE VALLEY AND SE OREGON HIGHLANDS. MODELS IN GOOD AGREEMENT IN MOVING THE LOW SOUTHEAST WITH THE CENTER OVER SOUTHWEST IDAHO BY 12Z SUNDAY MORNING. THIS POSITION WILL KEEP THE BEST DYNAMICS AND MOISTURE ON ITS EASTERN AND NORTHERN FLANKS. MODEL QPF ALSO AGREES WITH THIS AND DEPICTS A QPF BULLSEYE OF MORE THAN ONE HALF INCH OVER THE CENTRAL IDAHO MOUNTAINS SUNDAY MORNING. SYSTEM IS VERY WOUND UP...THUS WRAP AROUND MOISTURE IS FORECAST TO COME BACK WEST THEN SOUTHWARD BY SUNDAY NIGHT AND MONDAY MORNING. HAVE ADDED LIMITED ENHANCED WORDING TO ISOLATED STORMS OVER BAKER COUNTY THIS EVENING...BUT IN COORD WITH WFO PDT AND SPC...FEELING IS THAT THREAT IS WELL BELOW SEVERE LEVELS WITH ONLY LIMITED COVERAGE. HIGH POPS CONTINUE OVER THE NORTHERN MOUNTAINS TONIGHT THROUGH SUNDAY WHERE A COOL DAY WITH WETTING RAINS IS LIKELY. HAVE GONE WITH ONLY SCATTERED POPS TO THE SOUTH OVER THE SNAKE VALLEY WITH A DRY SLOT DEPICTED ON THE SOUTH SIDE OF THE LOW. EVEN DRIER CONDITIONS EXIST IN SOUTHEAST OREGON WHERE UPPER LOW WILL HAVE VERY LITTLE EFFECT OTHER THAN INCREASED WINDS. LOW STALLS OUT UNDERNEATH THE RIDGE SUNDAY...THUS SYSTEM WILL BE SLOW TO DEPART AND PREVENT RAPID CLEARING. HAVE ACCOUNTED FOR THIS BY KEEPING CLOUDS AND SHOWERS AROUND LONGER INTO MONDAY. WARM AND DRIER CONDITIONS IN EASTERN OREGON UNDER WESTERLY FLOW MONDAY WELL WEST OF THE SLOWLY DEPARTING UPPER LOW. LONG TERM...MONDAY NIGHT THROUGH SATURDAY...A BLEND OF THE GFS/GFS ENSEMBLE MEAN AND EC WAS FAVORED THIS PACKAGE. UPPER AIR PATTERN STARTS OFF COOL WITH A FILLING UPPER LOW IN MONTANA MONDAY NIGHT/TUESDAY. A WARMING TREND IS INDICATED IN ITS WAKE WHICH LEVELS OFF MID-WEEK. THIS IS DUE TO AN UPPER HIGH CENTER OVER TX/4-CORNERS EARLY IN THE PERIOD WHICH IS EXPECTED TO EXPAND NORTH/NW INTO NV/ID-OREGON MID-WEEK. GFS AND ITS ENSEMBLE MEAN ARE MORE AMPLIFIED THAN THE EC BY THURSDAY WITH THE 12Z OPERATIONAL GFS HAVING ITS OFFSHORE LOW WELL SOUTH OF THE EC/GFS ENSEMBLE POSITION. FAVORED AN EC/ENSEMBLE BLEND FOR FRIDAY-SUNDAY. EITHER WAY LOWERING HEIGHTS POSE A HIGHER THAN CLIMO RISK OF HIGH ELEVATION AFTERNOON SHOWERS OR THUNDERSTORMS BKE-MYL-IDAHO CITY. LATE WEEK COLD FROPA TIMING STILL HINTS AT FRIDAY WITH COOLING SAT/SUN. THE LATTER FORECAST AS THE EC/ENSEMBLE SHIFT THE UPPER HIGH BACK TO TEXAS AND BRING BROAD TROUGHING INTO WA-OREGON WITH NEAR TO BELOW CLIMO HEIGHTS IN SW FLOW ALOFT OVER THE REGION FRIDAY-NEXT WEEKEND. PRECIPITATION IN THE MEDIUM TO LONG TERM PERIOD LOOKS TO BE NEAR ZERO IN THE SOUTHERN VALLEYS/MOUNTAINS SOUTH OF THE SNAKE RIVER AND MINIMAL PRECIPITATION FROM EAST-CENTRAL OREGON THE WEST CENTRAL AND BOISE MOUNTAINS. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...NONE. OR...NONE. && WEATHER.GOV/BOISE DISCUSSION...LC AVIATION.....MT PREV SHORT TERM...GS PREV LONG TERM....VM/BB
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE BOISE ID 605 AM MDT SAT AUG 29 2009 IDZ011>016-028>030-ORZ061>064-301215- WEST CENTRAL MOUNTAINS-LOWER TREASURE VALLEY ID-BOISE MOUNTAINS- UPPER TREASURE VALLEY-SOUTHWEST HIGHLANDS-WESTERN MAGIC VALLEY- CAMAS PRAIRIE-OWYHEE MOUNTAINS-SOUTHERN TWIN FALLS COUNTY- HARNEY COUNTY-BAKER COUNTY-MALHEUR COUNTY- LOWER TREASURE VALLEY OR- 605 AM MDT SAT AUG 29 2009 /505 AM PDT SAT AUG 29 2009/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL IDAHO...SOUTHWEST IDAHO...WEST CENTRAL IDAHO...NORTHEAST OREGON AND SOUTHEAST OREGON. .DAY ONE...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE BOISE ID 739 PM MDT SAT AUG 29 2009 IDZ011>013-300230- ADAMS ID-VALLEY ID-BOISE ID-PAYETTE ID-WASHINGTON ID-GEM ID- 739 PM MDT SAT AUG 29 2009 THE NATIONAL WEATHER SERVICE IN BOISE HAS ISSUED A SIGNIFICANT WEATHER ADVISORY FOR... NORTHEASTERN GEM COUNTY IN SOUTHWEST IDAHO... NORTHEASTERN PAYETTE COUNTY IN SOUTHWEST IDAHO... SOUTHEASTERN WASHINGTON COUNTY IN SOUTHWEST IDAHO... SOUTHEASTERN ADAMS COUNTY IN WEST CENTRAL IDAHO... NORTHWESTERN BOISE COUNTY IN WEST CENTRAL IDAHO... AND SOUTHWESTERN VALLEY COUNTY IN WEST CENTRAL IDAHO... UNTIL 830 PM MDT. AT 737 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM NEAR OLA...MOVING NORTHEAST AT 35 MPH. HAIL UP TO ONE-HALF INCH IN DIAMETER IS EXPECTED WITH THIS STORM... ALONG WITH HEAVY RAIN AND FREQUENT DANGEROUS LIGHTNING. THE THUNDERSTORM WILL BE NEAR... OLA AROUND 740 PM MDT... HIGH VALLEY AROUND 745 PM MDT... DODSON PASS AROUND 750 PM MDT... SAGE HEN RESERVOIR AROUND 755 PM MDT... GRANITE PEAK AND FOUR BIT SUMMIT AROUND 805 PM MDT... CASCADE AROUND 820 PM MDT. LIGHTNING IS ONE OF NATURES NUMBER ONE KILLERS. TAKE SHELTER INSIDE A BUILDING OR VEHICLE WHEN THUNDERSTORMS APPROACH. LIGHTNING CAN OCCUR 15 MILES OR MORE AWAY FROM THE CENTER OF A STORM. IF YOU CAN HEAR THUNDER...YOU ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING. LAT...LON 4486 11616 4465 11553 4399 11628 4412 11656 TIME...MOT...LOC 0139Z 205DEG 31KT 4421 11629 LRC
The Boise radar (KCBX), 28 km away, was scanning. The volume nearest the first event began at 03:14 UTC.
1 hail. Local standard time, as filed.
A trained spotter in Nampa, Idaho reported three quarter inch hail.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2009Every state in 2009This day in weather historyWarnings in Idaho, August 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: 193138.