An useasonably moist atmosphere coupled with strong daytime heating and a disturbance dropping south from British Columbia led to numerous heavy thunderstorms during the afternoon of August 4th. Slow to nearly stationary storms produced rainfall rates between one to two inches per hour leading to multiple debris flows and areas of flash flooding.
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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 OTX wrote it up.
An useasonably moist atmosphere coupled with strong daytime heating and a disturbance dropping south from British Columbia led to numerous heavy thunderstorms during the afternoon of August 4th. Slow to nearly stationary storms produced rainfall rates between one to two inches per hour leading to multiple debris flows and areas of flash flooding.
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 Spokane, WA wrote its last area forecast discussion before the first event at Aug 4, 1:13 PM PST, 42 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPOKANE WA 213 PM PDT Sun Aug 4 2013 .SYNOPSIS... Summer weather will return to the Inland Northwest as a warming trend continues this week. The northern mountains and upper Columbia Basin may see some showers and thunderstorms through Monday, but drier weather is expected for mid week. There is better chance of thunderstorms returning for the area by Friday and into the weekend. && .DISCUSSION... Tonight and Monday...An upper level short wave trough over southern British Columbia this afternoon will track southeast into Northeast Washington and the North Idaho Panhandle overnight tonight into Monday. Afternoon heating...abundant low level moisture...and weak lift from this approaching trough will continue to produce scattered showers and thunderstorms over the northern mountains, and East Slopes of the Cascades through this evening. Some of this convection may spill off the mountains into the Wenatchee area and Okanogan Valley. The forecast becomes a little more difficult overnight. Weak lift moving across the area and some mid level instability with 700-500mb theta e lapse rates may result in isolated showers persisting overnight mainly in the same areas as this evening. With 700-500mb most unstable CAPE's less than 100 J/KG lightning is not expected overnight. Exception is over the Blue Mountains, Lewiston area, and Camas Prairie. A wave coming out of Central Oregon this evening tracks into these areas overnight into Monday morning with NAM showing 200-300 J/KG of elevated CAPE which combined with some lift could spark isolated thunderstorms. With these storms fast moving rainfall amounts would be light. On Monday the best instability will be over far Northeast Washington and North Idaho with the short wave trough passing through during peak heating. Scattered showers and thunderstorms will increase in the late morning and afternoon in this area. Elsewhere mainly isolated coverage of showers and thunderstorms is expected...confined mostly to the high terrain. JW Monday night through Wednesday night: The pesky upper level disturbance will slide east Monday night while high pressure builds into western Washington and across the Cascades. Isolated showers and thunderstorms will still be found across the Idaho Panhandle mountains Monday evening but will quickly diminish overnight. A high pressure ridge will pump up over the Pacific NW for Tuesday through Wednesday with a southerly flow and drier and warmer weather. Summer conditions will return with temperatures rising above seasonal normals through mid week. There will be minor disturbances that will need to be monitored, both to the north and to the south of the ridge. To the north, the storm track will lie across central BC into Alberta and a couple disturbances will track over the ridge and flatten it. This may may lead to a slight chance of convection near the Canadian border by Wednesday and into Wednesday night. Meanwhile to the south, the southerly flow on the back side of the ridge will pump monsoon moisture northward. This moisture will spread over Oregon by Wednesday. /rfox. Thursday through Friday Morning...The ridge should be holding in place for much of the Inland Northwest. This should keep temperatures around from what we experience on Wednesday. Moisture associated with the low pressure center that will be off the northern California coast will have to be watched, but it looks it will hold off at during this time frame. Will keep pops very low for this period, with the exception of the far northeast Washington mountains into the mountains of the Idaho panhandle. A shortwave moving south through Alberta should provide enough lift for some showers and isolated thunderstorms to develop. These would likely remain over the higher terrain, leaving the lower elevations dry. ty Friday afternoon through Sunday...Model agreement is good regarding the overall flow regime featuring a weakening upper low over northern California shifting northward into Oregon as it weakens further by next weekend. The forecast area lays to the north of this upper low and will be in a sort of dead zone between the upper low tot he south and a weak ridgy/westerly flow to the north. A surface thermal trough will continue to be well established over the Columbia Basin through the period. This augers fro continued warm and summer-like temperatures...probably above normal but not record breaking. The air mass will also become increasingly moist and sensibly muggy as the weekend approaches as a Pacific/Monsoonal composite moisture feed wells up from the south into the region under the southerly flow wrapping around the upper low. Thus...in addition to being warm and increasingly humid (for this part of the country at least) this heat and moisture will lead to gradually increasing surface based CAPE values every afternoon for an overall increase in thunderstorm potential as the week wears on...probably pretty much confined to the mountains on Friday but becoming more active and spreading into the valleys and basin Saturday and Sunday with the largest threat on Sunday as the remnants of the upper low may add some weak upper level forcing to the mix. /Fugazzi && .AVIATION... 18Z TAFS...Conditions will start off VFR this morning with light winds, but convection will quickly develop especially between 21z-03z over the northern and Cascade mountains. Surface based showers with a mid level cloud deck will spread from the northern Cascades to the Spokane/Coeur d'Alene area this evening and decrease overnight. /rfox && .PRELIMINARY POINT TEMPS/POPS... Spokane 60 84 62 88 63 89 / 10 20 10 0 10 10 Coeur d'Alene 55 82 57 87 57 89 / 10 20 20 0 10 10 Pullman 50 85 53 89 53 89 / 10 10 10 0 10 10 Lewiston 62 93 64 97 64 97 / 20 20 0 0 10 10 Colville 52 85 55 92 56 95 / 20 20 10 0 10 10 Sandpoint 49 80 52 84 52 88 / 20 40 20 0 10 10 Kellogg 54 81 56 84 56 88 / 10 30 20 0 10 10 Moses Lake 59 92 63 96 63 96 / 20 10 0 0 10 10 Wenatchee 64 91 67 96 67 96 / 20 10 0 0 10 10 Omak 60 91 62 97 63 97 / 20 20 10 0 10 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SPOKANE WA 503 AM PDT SUN AUG 4 2013 IDZ001>004-026-027-WAZ031>038-041>044-051215- NORTHERN PANHANDLE-COEUR D'ALENE AREA-IDAHO PALOUSE- CENTRAL PANHANDLE MOUNTAINS-LEWISTON AREA- LEWIS AND SOUTHERN NEZ PERCE COUNTIES-NORTHEAST BLUE MOUNTAINS- LOWER GARFIELD AND ASOTIN COUNTIES-WASHINGTON PALOUSE- MOSES LAKE AREA-UPPER COLUMBIA BASIN-SPOKANE AREA- NORTHEAST MOUNTAINS-OKANOGAN HIGHLANDS-WENATCHEE AREA- EAST SLOPES NORTHERN CASCADES-OKANOGAN VALLEY-WATERVILLE PLATEAU- 503 AM PDT SUN AUG 4 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH IDAHO... NORTH CENTRAL IDAHO...CENTRAL WASHINGTON...EAST CENTRAL WASHINGTON...NORTH CENTRAL WASHINGTON...NORTHEAST WASHINGTON AND SOUTHEAST WASHINGTON. .DAY ONE...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE SPOKANE WA 1256 PM PDT SUN AUG 4 2013 WAZ042-042030- OKANOGAN WA- 1256 PM PDT SUN AUG 4 2013 THE NATIONAL WEATHER SERVICE IN SPOKANE HAS ISSUED A SIGNIFICANT WEATHER ADVISORY FOR... NORTH CENTRAL OKANOGAN COUNTY IN NORTH CENTRAL WASHINGTON UNTIL 130 PM PDT AT 1249 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 20 MILES SOUTHWEST OF OROVILLE..MOVING SOUTHEAST AT 5 MPH. HAIL UP TO THE SIZE OF PENNIES IS EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN. LOCATIONS IMPACTED INCLUDE... RURAL NORTHERN OKANOGAN COUNTY... RURAL CENTRAL OKANOGAN COUNTY... THIS STORM MAY INTENSIFY...SO BE CERTAIN TO MONITOR LOCAL RADIO AND TV STATIONS...AS WELL AS LOCAL CABLE TV OUTLETS...FOR ADDITIONAL INFORMATION AND POSSIBLE WARNINGS FROM THE NATIONAL WEATHER SERVICE. LAT...LON 4879 11961 4867 11978 4880 11989 4887 11980 TIME...MOT...LOC 1956Z 300DEG 4KT 4879 11980 FUGAZZI
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE SPOKANE WA 226 PM PDT SUN AUG 4 2013 WAZ042-042215- OKANOGAN WA- 226 PM PDT SUN AUG 4 2013 THE NATIONAL WEATHER SERVICE IN SPOKANE HAS ISSUED A SIGNIFICANT WEATHER ADVISORY FOR... CENTRAL OKANOGAN COUNTY IN NORTH CENTRAL WASHINGTON UNTIL 315 PM PDT AT 217 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 17 MILES NORTHWEST OF OMAK..MOVING SOUTHEAST AT 5 MPH. HAIL UP TO THE SIZE OF PENNIES IS EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN. LOCATIONS IMPACTED INCLUDE... CONCONULLY... IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A STURDY BUILDING. LAT...LON 4861 11964 4846 11978 4853 11992 4862 11983 TIME...MOT...LOC 2126Z 304DEG 5KT 4856 11979 MJF
The national radar mosaic for the moment the first event began.
2 debris flow. Local standard time, as filed.
Conconully was pounded by heavy rain for almost two hours leading to backed up culverts and mudslides. One slide was two to three feet deep on Lake Street. A second slide was two feet deep on Sinlahekin Road. Three houses on Silver Street had some minor water damage.
Heavy rain across the 2012 Peavine Canyon Burn Scar resulted in a large debris flow down Number One Canyon Road into southwestern portions of Wenatchee. Upwards of eight inches of mud filled yards, basements, and garages of homes along the road. Witnesses described a wall of water, mud, rocks, branches, and tree limbs coming down Number One Canyon Road with the sound of rocks scraping the road. The debris flow reached the intersection of Lars Lane and Number One Canyon Road. There were no injuries.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2013Every state in 2013This day in weather historyWarnings in Washington, August 2013
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: 472030, 458259.