Slow moving showers and thunderstorms rotating around a large area of low pressure over the Pacific Northwest caused some flash flooding issues. Incidents of note include water over roadways and entering some basements of homes in the Nine Mile Falls area of Spokane as well as water and debris flowing across 291 between Francis Boulevard and Rifle Club Road.
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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.
Slow moving showers and thunderstorms rotating around a large area of low pressure over the Pacific Northwest caused some flash flooding issues. Incidents of note include water over roadways and entering some basements of homes in the Nine Mile Falls area of Spokane as well as water and debris flowing across 291 between Francis Boulevard and Rifle Club 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 Spokane, WA wrote its last area forecast discussion before the first event at May 21, 1:25 PM PST, 1 hour 12 minutes earlier.
Area Forecast Discussion National Weather Service Spokane WA 225 PM PDT SAT MAY 21 2016 .SYNOPSIS... Showers with isolated evening thunderstorms are expected tonight mainly across Eastern Washington and north Idaho. Cooler than average conditions will continue Sunday with the most concentrated precipitation expected over the Idaho Panhandle. The cool and showery weather pattern is expected to continue through the week especially over the mountainous portions of the Inland Northwest. && .DISCUSSION... Tonight and Sunday...A large closed low over NE Oregon this afternoon will move quickly towards the northeast into southern Alberta by early Sunday morning. For this evening with the low over NE Oregon...bands of showers will continue to move into the region with the greatest focus over SE Washington, the Spokane area, and Idaho Panhandle given closer proximity to low center. Also clearing this morning allowed for increased heating and allowed instability to increase across these areas with CAPE values of 300-700 J/KG. This will continue to produce isolated thunderstorms through early this evening. Overnight as the low moves into NW Montana and then into southern Alberta early Sunday a significant band of wrap around moisture on the back side of the low will produce a steady rain over the Idaho Panhandle. Models show the potential for as much as 1-2 inches of rain in the north Idaho Panhandle...which includes places like Bonners Ferry and Sandpoint. Low level upslope into the mountains could produce even precip totals...falling as snow above 6k-7k feet. Cloud cover and rain in these areas will hold temperatures down on Sunday with highs only reaching the lower to mid 50s. Some of this wrap around precip will likely reach portions of NE Washington including the Spokane area as well as the Central Panhandle Mountains but amounts will likely be light...except for Pend Oreille county...northern Shoshone county...and NE Spokane county where models show up to an inch of rain may fall. As the low moves into southern Alberta Sunday...pressure gradients tighten across the area with breezy west-southwest winds expected to develop by late morning across the Wenatchee area, Columbia Basin, Palouse, and Spokane area. JW Sunday night through Thursday...The cool and unsettled weather pattern will continue through this portion of the forecast, but not quite as wet and cool as this past weekend. The closed low will move into Alberta Sunday night, with ample moisture expected to wrap around the exiting low. This will keep a good chance for showers across mainly the northern mountains and the Panhandle both Monday and Tuesday. Split flow on Tuesday night and Wednesday will bring a brief respite for the precipitation. This will be followed by another upper level low Thursday. Sunday night through Tuesday...As mentioned above the trough will eject into Alberta Sunday and Sunday night. The models are similar in showing a couple of robust waves wrapping around the main low and back into central WA. This will also pull ample moisture back into the region. The best chance for rain will be across the northern mountains and the eastern half of the forecast area. Moderate to heavy precipitation is expected from about Lake Roosevelt and east to the Montana border. As the low moves away from the region the chance for precipitation will decrease rapidly from the west, but remain high across the northeast zones. Surface heating Tuesday afternoon and lingering low and mid level moisture will result in scattered showers and some isolated thunderstorms across most of the northern mountains. QPF amounts for the western zones will be a couple hundredths with the basin getting skunked. The QPF amounts will increase rapidly from west to east. The Okanogan Highlands could see around a quarter of an inch but the northeast mountains and the north Panhandle mountains could see 1.0 to 1.20 inches of rain from Sunday night through Tuesday afternoon. This will likely result in streams and small rivers rising, but remaining below action stage. Temperatures will be on the increase but remain below seasonal averages. Tuesday night and early Wednesday...the models are showing a split flow across the region with no forcing mechanism. Isolated mountain showers will be possible overnight. Good surface heating combined with lingering low level moisture will destabilize the atmosphere enough to support mountain showers and isolated thunderstorms Wednesday afternoon and evening. Temperatures will warm to right around seasonal normals. Thursday...Some differences begin to show up Wednesday night and Thursday, but it looks like another closed low will move in from the northwest on Thursday for more mountain showers. Tobin Friday through Saturday: Another low pressure system will impact the area descending from British Columbia Friday and into the weekend. Models diverge on the placement of this low at the moment, with the GFS keeping it off the Oregon coast while the Euro sets up over central Idaho through the weekend. Either way, will keep a chance of showers in the forecast Fri and Sat afternoon, especially for the northern and panhandle mountains. Could see some thunder with these showers, given ample CAPE during the afternoon and evening hours. /BWilliams && .AVIATION... 18Z TAFS: Another disturbance rotation around a large low pressure system over Oregon will move into SE Washington and N Idaho this afternoon and tonight bringing numerous showers. CIGS should gradually rise this afternoon with prevailing CIGS VFR although under heavier showers MVFR conditions are possible. Elsewhere showers will be more isolated/scattered in nature and decreasing this evening with the loss of daytime heating. Isolated thunderstorms are also expected...but with low confidence of impacting any of the TAF sites did not include in the TAF's. Some of the rain will wrap around the back side of the low into NE WA/N Idaho overnight into Sunday morning as the low tracks into NW Montana and Alberta...which may bring lowering CIGS to KGEG/KSFF/KCOE. As the low tracks NE of the area Sunday morning pressure gradients increase, with breezy SW winds developing in some areas. JW && .PRELIMINARY POINT TEMPS/POPS... Spokane 46 60 45 60 47 65 / 50 60 30 50 10 30 Coeur d'Alene 45 55 45 58 46 62 / 80 80 40 70 30 50 Pullman 44 57 44 59 45 62 / 60 30 10 20 10 20 Lewiston 47 64 49 66 50 68 / 50 10 10 20 10 30 Colville 47 64 45 62 45 68 / 50 60 70 70 20 40 Sandpoint 46 53 44 56 44 61 / 90 100 80 90 50 60 Kellogg 43 50 41 52 42 57 / 90 90 50 80 60 60 Moses Lake 49 71 47 69 47 73 / 20 10 10 10 10 10 Wenatchee 50 70 51 69 52 73 / 10 0 10 20 10 10 Omak 47 70 48 67 48 72 / 20 10 30 40 10 20 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. &&
Hazardous Weather Outlook National Weather Service SPOKANE WA 547 AM PDT SAT MAY 21 2016 IDZ001-004-027-WAZ031-037-038-041>043-221300- NORTHERN PANHANDLE-CENTRAL PANHANDLE MOUNTAINS- LEWIS AND SOUTHERN NEZ PERCE COUNTIES-NORTHEAST BLUE MOUNTAINS- NORTHEAST MOUNTAINS-OKANOGAN HIGHLANDS-WENATCHEE AREA- EAST SLOPES NORTHERN CASCADES-OKANOGAN VALLEY- 547 AM PDT SAT MAY 21 2016 This Hazardous Weather Outlook is for portions of North Idaho... North Central Idaho...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...SUNDAY THROUGH FRIDAY The weather pattern across the Inland NW will provide continued opportunities for showers and thunderstorms...along with occasional periods of steadier rain. Brief heavy rain and small hail and occasional lightning will be possible through the weekend. The risk for flooding or debris flows on recent burn scars exists...but the overall potential looks low at this time. IDZ002-003-026-WAZ032>036-044-221300- COEUR D'ALENE AREA-IDAHO PALOUSE-LEWISTON AREA- LOWER GARFIELD AND ASOTIN COUNTIES-WASHINGTON PALOUSE- MOSES LAKE AREA-UPPER COLUMBIA BASIN-SPOKANE AREA- WATERVILLE PLATEAU- 547 AM PDT SAT MAY 21 2016 This Hazardous Weather Outlook is for portions of North Idaho... North Central Idaho...Central Washington...East Central Washington...Northeast Washington and Southeast Washington. .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.
The Spokane radar (KOTX), 12 km away, was scanning. The volume nearest the first event began at 22:38 UTC.
2 flash flood. Local standard time, as filed.
A member of the public reported water over roadways and entering basements of some homes in and near Nine Mile Falls, WA.
An NWS Employee reported water and debris flowing across highway 291 between West Francis Avenue and Weest Rifle Club Road up in the northwest portion of Spokane, WA.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2016Every state in 2016This day in weather historyWarnings in Washington, May 2016
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: 625409, 625408.